Metadata-Version: 2.1
Name: javascripthon
Version: 0.11
Summary: Javascript for refined palates: a Python 3 to ES6 Javascript translator
Home-page: https://github.com/azazel75/metapensiero.pj
Author: Alberto Berti
Author-email: alberto@arstecnica.it
License: GPLv3+
Description: .. -*- coding: utf-8 -*-
        .. :Project:  metapensiero.pj -- readme
        .. :Created:  mar 01 mar 2016 15:52:36 CET
        .. :Author:   Alberto Berti <alberto@metapensiero.it>
        .. :License:  GNU General Public License version 3 or later
        ..
        
        ======================================================
        JavaScripthon: a Python 3 to ES6 JavaScript translator
        ======================================================
        
        .. image:: https://gitlab.com/metapensiero/metapensiero.pj/badges/master/pipeline.svg
           :target: https://gitlab.com/metapensiero/metapensiero.pj/commits/master
           :align: left
           :alt: tests status
        
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           :target: https://gitlab.com/metapensiero/metapensiero.pj/commits/master
           :align: left
           :alt: tests coverage
        
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           :alt: Join the chat at https://gitter.im/javascripthon/Lobby
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        .. figure:: http://s3.amazonaws.com/fossbytes.content/wp-content/uploads/2016/04/Javascripthon-python-js-converter.jpg
           :alt: JavaScripthon
           :align: left
           :width: 750px
        
           ..
        
           (image courtesy of `fossBytes`__)
        
           __ http://fossbytes.com/javascripthon-a-simple-python-to-es6-javascript-translator/
        
        
        It is based on previous work by `Andrew Schaaf <andrew@andrewschaaf.com>`_.
        
         :author: Alberto Berti
         :contact: alberto@metapensiero.it
         :license: GNU General Public License version 3 or later
        
        .. contents:: Table of Contents
           :backlinks: top
        
        Introduction
        ------------
        
        JavaScripthon is a small and simple Python 3.5+ translator to JavaScript which
        aims to be able to translate most of the Python's core semantics without
        providing a full python-in-js environment, as most existing translators do. It
        tries to emit code which is simple to read and check. It does so by switching
        to ES6 construct when possible/required. This allows to simplify the needs of
        polyfills for many of the expected Python behaviors.
        
        It is designed to be the first step in a pipeline that translates your Pyhton
        code into something that a browser can understand. Usually it is used with
        tools like `BabelJS`__ and `Webpack`__ to prepare the final bundle that will
        be served to the browser. The steps from the source code to the bundle are the
        following:
        
        1) JavaScripthon converts your Python 3.5+ code to ES6 JavaScript modules;
        2) the BabelJS loader (configured inside Webpack or standalone) translates the
           ES6 JavaScript to ES5 so that the browser can understand it;
        3) Webpack parses the resulting source code and packages your source code with
           its dependencies by analyzing ``import`` statements and emits a
           ``bundle.js`` ready to be served to the browser.
        
        Along this process the corresponding `source maps`__ are read and integrated at
        every step, allowing you to place breakpoints on your original Python source
        files when working with the developer tools of your browser.
        
        An example of such setup is provided in the ``examples`` directory.
        
        __ http://babeljs.io/
        __ http://webpack.github.io/
        __ http://blog.teamtreehouse.com/introduction-source-maps
        
        
        In addition to that, you can choose to do most these steps without using
        external JS tools. It comes with an `embedded js interpreter`__ that loads a
        standalone version of BabelJS and converts your code to ES5 JavaScript without
        the need to install anything else. In fact most of the the test you can find
        in ``tests/test_evaljs.py`` use the embedded interpreter to dual evaluate the
        source code (one time in Python, one time in JavaScript) and simply check that
        the results are the same.
        
        __ https://github.com/amol-/dukpy
        
        Thanks to that, JavaScripthon can also be used as a server-side library to
        translate single functions or classes that you want your browser to load and
        evaluate.
        
        The interface with the JS world is completely flat, just import the modules
        or use the expected globals (``window``, ``document``, etc...) as you
        would do in JavaScript.
        
        Brief list of the supported Python semantics
        --------------------------------------------
        
        The fact that JavaScripthon doesn't *reinvent the wheel* by reimplementing in
        Python many of the features available with JavaScript translators/transpilers
        allows it to be lean while implementing quite a decent set of the core Python
        semanticts. These are, briefly:
        
        * Misc
        
          - list slices;
          - list's ``append()``;
          - dict's ``copy()``, ``update()``;
          - ``len()``;
          - ``print()``;
          - ``str()``;
          - ``type(instance)``;
          - ``yield`` and ``yield from``;
          - ``async`` and ``await``;
          - ``import`` and ``from...import`` to use any JS module (see `import
            statements`_);
          - ``callable()``;
          - ``hasattr()``, ``getattr()``, ``setattr()``;
          - template literals with ``tmpl('a string with ${substitution}')``;
          - simple Python 3.6+ `f-strings`_ (see `Strings`_);
          - template literals and tagged_templates (see `Strings`_);
          - names starting with ``d_`` and ``dd_`` will have that part replaced with
            ``$`` and ``$$``, respectively;
          - names ending with an underscore will have it removed. Useful for example
            with the AVA ES6 test runner which has a check named ``is``;
          - ``__instancecheck__`` to ``[Symbol.hasInstance]``;
          - ``int`` to ``parseInt``;
          - ``float`` to ``parseFloat``;
          - dictionary keys are unanbiguous when ES6 translation is
            enabled. For example the following code gets translated correctly:
        
            .. code:: python
        
               a = 'foo'
               d = {a: 1}
               print(d[a])
        
            prints ``1`` in both Python and JavaScript, while it prints
            ``undefined`` when translated and evaluated in JavaScript without
            ES6.
        
        .. _f-strings: https://docs.python.org/3.6/reference/lexical_analysis.html#f-strings
        
        * Comparisons (see section `Simple stuff`_ for the details)
        
          - most of the basics;
          - ``isinstance()`` and ``issubclass()``;
          - ``element in container`` for use with lists, objects, strings and the new
            ES6 collections like ``Map``, ``Set`` and so on;
          - identity checks: ``foo is bar``;
          - chained comparisons like ``x < y <= z``;
        
        * Statements (see section `Simple stuff`_ and `for statement`_ for the
          details)
        
          - ``if...elif...else``;
          - ``while`` loop;
          - ``for`` over list, over range, over plain js objects, over iterables (JS
            iterables);
          - ``try...except...finally`` with pythonesque behavior (see
            `try...except...finally statement`_ section for the details);
          - ``assert`` statement;
        
        * Functions (see `Functions`_ section)
        
          - standard functions, generator functions, async functions;
          - parameters defaults;
          - keyword parameters;
          - parameters accumulators (``*args`` and ``**kwargs``), with some
            restrictions;
          - functions in methods are usually converted to "arrow functions" (the new
            ES6 syntax like ``(foo, bar) => foo * bar;``) because they automatically
            keep ``this`` from the enclosing scope. Appending ``_fn`` to a function
            declaration will force the translation to a normal function;
        
        * Classes (see `Classes`_ section)
        
          - single inheritance;
          - Exception classes for use with ``except`` statement;
          - class decorators and method decorators;
          - property descriptors;
          - special handling of ``property`` and ``classmethod`` descriptors;
          - async methods, generator methods;
          - non-function body members (i.e. ``member_of_class_Foo = bar``);
        
        License
        -------
        
        This package is covered by the `GNU General Public License version
        3 or later`__. The code produced by it (i.e. the transpiled
        JavaScript) is *your* code, and *you* are free to choose whatever
        license you like. The only ``runtime`` that exists is the file
        `snippets.py`__ from which some utility functions are picked when
        necessary and transpiled together with your code. While it's
        distributed with the same license as the other source code, in its
        *transpiled* form will have the license you choose.
        
        So, to summarize, the license of the this tool is GPL, but it doesn't
        extends to the products of this tool, on which you are free to decide.
        
        __ https://www.gnu.org/licenses/gpl.html
        __ https://github.com/azazel75/metapensiero.pj/blob/master/src/metapensiero/pj/snippets.py
        
        Installation
        ------------
        
        Python 3.5 is required because Python's AST has changed between 3.4
        and 3.5 and as of now supporting multiple Python versions is not one
        of my priorities.
        
        To install the package execute the following command::
        
          $ pip install javascripthon
        
        or, if you want install it from sources::
        
          $ git clone https://github.com/azazel75/metapensiero.pj
          $ pip install -r metapensiero.pj/requirements.txt
          $ pip install metapensiero.pj
        
        Usage
        -----
        
        To *compile* or *transpile* a python source module, use the
        commandline:
        
        .. code:: bash
        
          $ python -m metapensiero.pj source.py
        
        or:
        
        .. code:: bash
        
          $ python -m metapensiero.pj -5 source.py
        
        to transpile.
        
        A ``pj`` console script is also automatically installed:
        
        .. code:: bash
        
        
          $ pj --help
          usage: pj [-h] [--disable-es6] [--disable-stage3] [-5] [--transform-runtime]
                    [-o OUTPUT] [-d] [--pdb] [-s STRING] [-e]
                    [file [file ...]]
        
          A Python 3.5+ to ES6 JavaScript compiler
        
          positional arguments:
            file                  Python source file(s) or directory(ies) to convert.
                                  When it is a directory it will be converted
                                  recursively
        
          optional arguments:
            -h, --help            show this help message and exit
            --disable-es6         Disable ES6 features during conversion (Ignored if
                                  --es5 is specified)
            --disable-stage3      Disable ES7 stage3 features during conversion
            -5, --es5             Also transpile to ES5 using BabelJS.
            --transform-runtime   Add trasform runtime as plugin during transpile
            -o OUTPUT, --output OUTPUT
                                  Output file/directory where to save the generated code
            -d, --debug           Enable error reporting
            --pdb                 Enter post-mortem debug when an error occurs
            -s STRING, --string STRING
                                  Convert a string, useful for small snippets. If the
                                  string is '-' will be read from the standard input.
            -e, --eval            Evaluate the string supplied with the -s using the
                                  embedded interpreter and return the last result. This
                                  will convert the input string with all the extensions
                                  enabled (comparable to adding the '-5' option) and so
                                  it will take some time because of BabelJS load times.
        
        This offers many ways to test the framework, both the string conversion and
        the evaluation using the embedded JavaScript interpreter are very handy. For
        example:
        
        .. code:: bash
        
          $ pj -s '"foo" if True else "bar"'
          (true ? "foo" : "bar");
        
        and evaluating the same statement:
        
        .. code:: bash
        
          $ pj -s '"foo" if True else "bar"' -e
          foo
        
        You can even try more fancy ES6 features, like destructuring assignment:
        
        .. code:: bash
        
           $ pj -s "a, b, c = (2, 3, 5) \na+b+c" -e
           10
        
        Reporting Bugs
        --------------
        
        The main development repository is the one on gitlab__, the one on
        github is just a mirror so please report issues and feature requests
        there__.
        
        __ https://gitlab.com/metapensiero/metapensiero.pj
        __ https://gitlab.com/metapensiero/metapensiero.pj/issues
        
        Conversions Rosetta Stone
        -------------------------
        
        Here is a brief list of examples of the conversions the tool applies,
        just some, but not all.
        
        Simple stuff
        ~~~~~~~~~~~~
        
        .. list-table:: Most are obvious
          :header-rows: 1
        
          * - Python
            - JavaScript
        
          * - .. code:: python
        
                x < y <= z < 5
        
            - .. code:: javascript
        
                ((x < y) && (y <= z) && (z < 5))
        
          * - .. code:: python
        
        
                def foo():
                    return [True, False, None, 1729,
                            "foo", r"foo\bar", {}]
        
            - .. code:: javascript
        
                function foo() {
                    return [true, false, null, 1729,
                            "foo", "foo\\bar", {}];
                }
        
        
          * - .. code:: python
        
                while len(foo) > 0:
                    print(foo.pop())
        
            - .. code:: javascript
        
                while ((foo.length > 0)) {
                    console.log(foo.pop());
                }
        
        
          * - .. code:: python
        
                if foo > 0:
                    ....
                elif foo < 0:
                    ....
                else:
                    ....
        
            - .. code:: javascript
        
                if ((foo > 0)) {
                    ....
                } else {
                    if ((foo < 0)) {
                        ....
                    } else {
                        ....
                    }
                }
        
        
          * - .. code:: python
        
                str(x)
        
            - .. code:: javascript
        
                x.toString()
        
          * - .. code:: python
        
                yield foo
                yield from foo
        
            - .. code:: javascript
        
                yield foo
                yield* foo
        
        
        Then there are special cases. Here you can see some of these
        conversions. JavaScripthon cannot do a full trace of the sources, so
        some shortcuts are taken about the conversion of some core, specific
        Python's semantics. For example Python's ``self`` is always converted
        to JavaScript's ``this``, no matter where it's found. Or ``len(foo)``
        is always translated to ``foo.length``. Albeit this an API specific of
        just some objects (Strings, Arrays, etc...), it is considered wide
        adopted and something the user may consider obvious.
        
        The rules of thumb to treat things especially are:
        
        * Is it possible to think of a conversion that covers most of the use
          cases?
        
        * Is ts possible to find a convention widely used on the Python world
          to express this special case?
        
        .. list-table:: There are special cases
          :header-rows: 1
        
          * - Python
            - JavaScript
        
          * - .. code:: python
        
                ==
        
            - .. code:: javascript
        
                ===
        
          * - .. code:: python
        
                !=
        
            - .. code:: javascript
        
                !==
        
          * - .. code:: python
        
                2**3
        
            - .. code:: javascript
        
                Math.pow(2, 3)
        
          * - .. code:: python
        
                'docstring'
        
            - .. code:: javascript
        
                /* docstring */
        
          * - .. code:: python
        
                self
        
            - .. code:: javascript
        
                this
        
          * - .. code:: python
        
                len(...)
        
            - .. code:: javascript
        
                (...).length
        
          * - .. code:: python
        
                print(...)
        
            - .. code:: javascript
        
                console.log(...)
        
          * - .. code:: python
        
                isinstance(x, y)
                isinstance(x, (y, z))
        
            - .. code:: javascript
        
                (x instanceof y)
                (x instanceof y || x instanceof z)
        
          * - .. code:: python
        
                typeof(x)
        
            - .. code:: javascript
        
                (typeof x)
        
          * - .. code:: python
        
                type(x)
        
            - .. code:: javascript
        
                Object.getPrototypeOf(x)
        
          * - .. code:: python
        
                FirstCharCapitalized(...)
                new(any_function(...))
        
            - .. code:: javascript
        
                new FirstCharCapitalized(...)
                new any_function(...)
        
          * - .. code:: python
        
                foo in bar
        
            - .. code:: javascript
        
                var _pj;
                function _pj_snippets(container) {
                    function in_es6(left, right) {
                        if (((right instanceof Array) || ((typeof right) === "string"))) {
                            return (right.indexOf(left) > (- 1));
                        } else {
                            if (((right instanceof Map) || (right instanceof Set)
                                || (right instanceof WeakMap)
                                || (right instanceof WeakSet))) {
                                return right.has(left);
                            } else {
                                return (left in right);
                            }
                        }
                    }
                    container["in_es6"] = in_es6;
                    return container;
                }
                _pj = {};
                _pj_snippets(_pj);
                _pj.in_es6(foo, bar);
        
          * - .. code:: python
        
                foo[3:]
                foo[:3]
        
            - .. code:: javascript
        
                foo.slice(3);
                foo.slice(0, 3);
        
          * - .. code:: python
        
                list(foo).append(bar)
        
            - .. code:: javascript
        
                foo.push(bar);
        
          * - .. code:: python
        
                dict(foo).update(bar)
        
            - .. code:: javascript
        
                Object.assign(foo, bar);
        
          * - .. code:: python
        
                dict(foo).copy()
        
            - .. code:: javascript
        
                Object.assign({}, foo);
        
        
        ``for`` statement
        ~~~~~~~~~~~~~~~~~
        
        The ``for`` statement by default is translated as if the object of the
        cycle is a list but has two special cases:
        
        
        .. list-table:: ``for`` loops
          :header-rows: 1
        
          * - Python
            - JavaScript
            - notes
        
          * - .. code:: python
        
                for el in dict(a_dict):
                    print(el)
        
            - .. code:: javascript
        
                var _pj_a = a_dict;
                for (var el in _pj_a) {
                    if (_pj_a.hasOwnProperty(el)) {
                        console.log(el);
                    }
                }
        
            - With this kind of loop if you use ``dict(a_dict, True)`` the check on
              ``hasOwnProperty()`` will not be added, so the loop will include
              *inherited* (and *enumerable*) properties.
        
          * - .. code:: python
        
                for el in an_array:
                    print(el)
        
            - .. code:: javascript
        
                for (var el, _pj_c = 0, _pj_a = an_array, _pj_b = _pj_a.length;
                      (_pj_c < _pj_b); _pj_c += 1) {
                    el = _pj_a[_pj_c];
                    console.log(el);
                }
        
            -
        
          * - .. code:: python
        
                for i in range(5):
                    print(i)
        
            - .. code:: javascript
        
                for (var i = 0, _pj_a = 5; (i < _pj_a); i += 1) {
                    console.log(i);
                }
        
            -
        
          * - .. code:: python
        
                for el in iterable(a_set):
                    print(el)
        
            - .. code:: javascript
        
                var _pj_a = a_set;
                for (var el of  _pj_a) {
                    console.log(el);
                }
        
            - This will loop over all the iterables, like instances of ``Array``,
              ``Map``, ``Set``, etc. **but not over normal objects**.
        
        Functions
        ~~~~~~~~~
        
        Functions are very well supported. This should be obvious, you can say. Really
        it is not so simple, if we mean functions in their broader meaning, including
        the  *async functions* and *generator functions*.
        
        .. list-table:: The various types of functions at play
          :header-rows: 1
        
          * - Python
            - JavaScript
            - notes
        
          * - .. code:: python
        
                def foo(a, b, c):
                    pass
        
            - .. code:: javascript
        
                function foo(a, b, c) {
                }
        
            - Normal functions
        
          * - .. code:: python
        
                def foo(a, b, c):
                    for i in range(a, b, c):
                        yield i
        
                for i in iterable(foo(0, 5, 2)):
                    print(i)
        
            - .. code:: javascript
        
                function* foo(a, b, c) {
                    for ... { // loop control omitted for brevity
                        yield i;
                    }
                }
        
                for (var i of foo(0, 5, 2)) {
                    console.log(i);
                }
        
            - Generator functions. They return an iterable and to correctly loop over
              it you should use the ``iterable(...)`` call, so that the Python's
              ``for...in`` will be converted into a ``for...of``
        
          * - .. code:: python
        
                async def foo(a, b, c):
                    await some_promise_based_async
        
        
            - .. code:: javascript
        
                async function foo(a, b, c) {
                    await some_promised_base_async;
                }
        
            - Async functions. They make use of the new ``Promise`` class, which is
              also available.
        
        
        Function's args and call parameters
        +++++++++++++++++++++++++++++++++++
        
        Parmeters defaults and keyword parameters are supported and so is ``*foo``
        accumulator, which is translated into the ES6 rest expression (``...foo``).
        
        The only caveat is that JS support for keyword args sucks, so you will have to
        **remember to fill in all the arguments before specifying keywords**.
        
        On function definitions, ``**kwargs`` is supported if it's alone, i.e. without
        either keyword arguments or ``*args``.
        
        .. list-table:: function's args and call parameters
          :header-rows: 1
        
          * - Python
            - JavaScript
        
          * - .. code:: python
        
                def foo(a=2, b=3, *args):
                    pass
        
            - .. code:: javascript
        
                function foo(a = 2, b = 3, ...args) {
                }
        
          * - .. code:: python
        
                def bar(c, d, *, zoo=2):
                    pass
        
            - .. code:: javascript
        
                function bar(c, d, {zoo = 2}={}) {
                }
        
          * - .. code:: python
        
                foo(5, *a_list)
        
            - .. code:: javascript
        
                foo(5, ...a_list);
        
          * - .. code:: python
        
                bar('a', 'b', zoo=5, another='c')
        
            - .. code:: javascript
        
                bar("a", "b", {zoo: 5, another: "c"});
        
          * - .. code:: python
        
                def zoo(e, **kwargs):
                    print(kwargs['bar'])
        
            - .. code:: javascript
        
                function zoo(e, kwargs = {}) {
                    console.log(kwargs['bar'])
                }
        
          * - .. code:: python
        
                zoo(4, bar=6)
        
            - .. code:: javascript
        
                zoo(4, {bar: 6})
        
        Classes
        ~~~~~~~
        
        Classes are translated to ES6 classes as much as they can support. This means:
        
        * no direct support multi-class inheritance, you have to come up with your own
          solution for now. Many established frameworks support this in a way or
          another so just use those facilities for now. I've read of some attempts,
          see for example the suggestion on `Mozilla developer`__ or the other about
          `simple mixins`__ on ``Exploring ES6``.
        
        * external implementation for class-level non assignment members. Assignment
          members are those on the body of a class which are defined with: ``a_label =
          an_expression`` like:
        
          .. code:: python
        
            class Foo:
        
                bar = 'zoo' # or any kind of expression
        
          These members are removed from the translated body and submitted to a
          snippet of code that will run after class creation in JS land. This serves
          two purposes: if the value is *simple*, i.e. it isn't an instance of
          ``Object``, it will be setup as a *data descriptor*, and it will work mostly
          like you are used to in Python. The most noticeable caveat is that it will
          not be accessible through the class as it is in Python, you will have to
          access the class' *prototype*, so in the case above i mean
          ``Foo.prototype.bar``.
        
          The other purpose is to check for *accessor descriptors*. If the value on
          the right side of the assignment implements a ``get`` function, it will be
          installed as a property as-is, and its *get* and *set* members will be used
          to manage the value with the ``bar`` name.
        
        * external implementation for method decorators whose name is different from
          ``property`` or ``classmethod`` (more on these later on), because these are
          already supported by the ES6 class notation.
        
        * external implementation for class decorators. One caveat here is that the
          return value of the decorator has always to be a function with a prototype:
          unfortunately a ``new`` statement seems not to be *delegable* in any way. So
          for example a class decorator implemented like the following:
        
          .. code:: python
        
            def test_class_deco():
        
                counter = 0
        
                def deco(cls):
                    def wrapper(self, *args):
                        counter += 1 # side effect
                        return cls(*args)
                    return wrapper
        
                @deco
                class Foo:
                    pass
        
          will never work. This will work instead:
        
          .. code:: python
        
            def deco(cls):
                def wrapper(self, *args):
                    counter += 1 # side effect
                    return cls.prototype.constructor.call(self, *args)
                wrapper.prototype = cls.prototype
                return wrapper
        
          So either return the original class or setup the wrapper appropriately.
        
        
        __ https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes#Mix-ins
        __ http://exploringjs.com/es6/ch_classes.html#_simple-mixins
        
        
        Methods can be functions or async-functions although the latters aren't
        officially supported yet by the JavaScript specification. You can disable them
        adding a ``--disable-stage3`` to the command line utility.
        
        Python`s ``super()`` calls are converted accordingly to the type of
        their surrounding method: ``super().__init__(foo)`` becomes
        ``super(foo)`` in constructors.
        
        Functions inside methods are translated to arrow functions so that
        they keep the ``this`` of the surrounding method.
        
        ``@property`` and ``@a_property.setter`` are translated to ES6 properties.
        
        Methods decorated with ``@classmethod`` are translated to ``static`` methods.
        
        Special methods ``__str__`` and ``__len__`` are translated to
        ``toString()`` method and ``get length()`` property, respectively.
        
        Arrow method expression to retain the ``this`` at method level aren't
        implemented yet.
        
        
        .. list-table:: Classes
          :header-rows: 1
        
          * - Python
            - JavaScript
        
          * - .. code:: python
        
                class Foo(bar):
                    def __init__(self, zoo):
                        super().__init__(zoo)
        
        
                    def meth(self, zoo):
                        super().meth(zoo)
                        def cool(a, b, c):
                            print(self.zoo)
        
        
                    async def something(self, a_promise):
                        result = await a_promise
        
                    def generator_method(self):
                        yield something
        
                    @property
                    def foo(self):
                        return self._foo
        
        
                    @foo.setter
                    def foo(self, value):
                        self._foo = value
        
        
                    @classmethod
                    def bar(self, val):
                        do_something()
        
        
                    def __len__(self):
                        return 1
        
        
                    def __str__(self):
                        return 'Foo instance'
        
            - .. code:: javascript
        
                class Foo extends bar {
                    constructor(zoo) {
                        super(zoo);
                    }
        
                    meth(zoo) {
                        super.meth(zoo);
                        var cool;
                        cool = (a, b, c) => {
                            console.log(this.zoo);
                        };
                    }
        
                    async something(a_promise) {
                        var result;
                        result = await a_promise;
                    }
        
                    * generator_method() {
                        yield something;
                    }
        
                    get foo() {
                        return this._foo;
                    }
        
                    set foo(value) {
                        self._foo = value;
                    }
        
                    static bar(val) {
                        do_something()
                    }
        
                    get length() {
                        return 1;
                    }
        
                    toString() {
                        return "Foo instance";
                    }
                }
        
        Only direct descendants of ``Exception`` are threated especially, but
        just for them to be meaningful in JS land and to be detectable with
        ``instanceof`` in catch statements.
        
        
        .. list-table:: Exceptions
          :header-rows: 1
        
          * - Python
            - JavaScript
        
          * - .. code:: python
        
                class MyError(Exception):
                    pass
        
                raise MyError("An error occurred")
        
            - .. code:: javascript
        
                function MyError(message) {
                    this.name = "MyError";
                    this.message = (message || "Custom error MyError");
                    if (((typeof Error.captureStackTrace) === "function")) {
                        Error.captureStackTrace(this, this.constructor);
                    } else {
                        this.stack = new Error(message).stack;
                    }
                }
                MyError.prototype = Object.create(Error.prototype);
                MyError.prototype.constructor = MyError;
                throw new MyError("An error occurred");
        
        
        ``try...except...finally`` statement
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        
        The conversion of this statement is mostly obvious with the only
        exception of the ``except`` part: it translates to a ``catch`` part
        containing one ``if`` statement for each non catchall ``except``. If a
        catchall ``except`` isn't present, the error will be re-thrown, to mimic
        Python's behavior.
        
        .. list-table:: ``try...catch...finally`` statement
          :header-rows: 1
        
          * - Python
            - JavaScript
        
          * - .. code:: python
        
                try:
                    foo.bar()
                except MyError:
                    recover()
                except MyOtherError:
                    recover_bad()
                finally:
                    foo.on_end()
        
            - .. code:: javascript
        
                try {
                    foo.bar();
                } catch(e) {
                    if ((e instanceof MyError)) {
                        recover();
                    } else {
                        if ((e instanceof MyOtherError)) {
                            recover_bad()
                        } else {
                            throw e;
                        }
                    }
                } finally {
                    foo.on_end();
                }
        
        
        ``import`` statements
        ~~~~~~~~~~~~~~~~~~~~~
        
        ``import`` and ``from ... import`` statements are converted to ES6
        imports, and the declaration of an ``__all__`` member on the module
        top level is translated to ES6 named exports.
        
        .. list-table:: import and exports
          :header-rows: 1
        
          * - Python
            - JavaScript
        
          * - .. code:: python
        
                import foo, bar
                import foo.bar as b
                from foo.bar import hello as h, bye as bb
                from ..foo.zoo import bar
                from . import foo
                from .foo import bar
        
                from foo__bar import zoo
        
                from __foo.zoo import bar
        
                from foo import __default__ as bar
        
                from __globals__ import test_name
        
                # this should not trigger variable definition
                test_name = 2
        
                # this instead should do it
                test_foo = True
        
                __all__ = ['test_name', 'test_foo']
                __default__ = 'test_name'
        
            - .. code:: javascript
        
                var test_foo;
        
                import * as foo from 'foo';
                import * as bar from 'bar';
                import * as b from 'foo/bar';
                import {hello as h, bye as bb} from 'foo/bar';
                import {bar} from '../foo/zoo';
                import * as foo from './foo';
                import {bar} from './foo';
        
                import {zoo} from 'foo-bar';
        
                import {bar} from '@foo/zoo';
        
                import bar from 'foo';
        
                test_name = 2;
                test_foo = true;
        
                export {test_name, test_foo};
                export default test_name;
        
        About JS **default** ``export`` and ``import``
        ++++++++++++++++++++++++++++++++++++++++++++++
        
        If you want to export something as *default export* in your modules,
        declare a ``__default__`` member and assign to it the string of the
        symbol you want to export. To clarify:
        
        .. code:: python
        
          foo = 42
          bar = "hello"
        
          __all__ = ['foo', 'bar']  # foo and bar will be exported as named exports
          __default__ = 'bar'  # bar will also be exported as the *default*
        
        This becomes:
        
        .. code:: javascript
        
          var bar, foo;
        
          foo = 42;
          bar = "hello";
        
          export {foo, bar};
          export default bar;
        
        For what concerns the ``import``, you can import the default export of
        a module using the ``default`` name, as defined by the ES6
        spec. However, as there were some issues reported to me with bundlers
        not supporting the named import of the default export, a special
        ``import`` statement using ``__default__ as name`` has been added that
        directly translates to the more common form of ES6 default import. So:
        
        .. code:: python
        
          from foo import default as bar
          from foo import __default__ as zoo
        
        Translates to:
        
        .. code:: javascript
        
          import {default as bar} from 'foo';
          import zoo from 'foo';
        
        The two imports should work the same, see `exploring js section`__ and
        the linked spec. But if you encounter problems with the former use
        the latter instead. Keep in mind that you cannot mix the
        ``__default__`` import with others (i.e. it needs to be on a line of
        its own) and that you always need to specify an ``... as name ...`` part.
        
        __ http://exploringjs.com/es6/ch_modules.html#sec_importing-exporting-details
        
        Strings
        -------
        
        Javascripthon supports converting Python 3.6+ `f-strings`_ to ES6
        `template literals`_. The expression in the braces gets converted, but
        neither `conversion`__ nor `format_spec`__ are supported: ``f"Value of
        {a}"`` becomes ```Value of ${a}``` and ``f"Value of {self.foo}"``
        becomes ```Value of ${this.foo}```.
        
        .. _template literals: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals
        __ https://docs.python.org/3.6/reference/lexical_analysis.html#grammar-token-conversion
        __ https://docs.python.org/3.6/reference/lexical_analysis.html#grammar-token-format_spec
        
        You can also write *raw* template literals by using the function
        ``tmpl()`` it does only a conversion of the string markers, from those
        used in Python's literal string notation to template literal notation.
        
        There is also the way to express *tagged templates*, template literals
        that are parsed using a provided function. This is done by using the
        function ``__``. So for example:
        
        .. code:: python
        
          __('A template ${string} with foo', bar)
        
        gets translated to:
        
        .. code:: javascript
        
          bar`A template ${string} with foo`
        
        ``bar`` will be executed with the value of ``${string}`` as a
        parameter, see the link for `template literals`_ for help.
        
        Verbatim JS
        -----------
        
        You can intermix Python and JS by using the
        ``JS('Your-JS-code-here')`` marker function. It will not be touched by
        the ES6 transcoder but if you choose to also transpile it to ES5, il
        will be considered by Babel.
        
        
        Examples
        --------
        
        Execute ``make`` inside the ``examples`` directory.
        
        Testing
        -------
        
        To run the tests you should run the following at the package root::
        
          python setup.py test
        
        How to contribute
        -----------------
        
        So you like this project and want to contribute? Good!
        
        These are the terse guidelines::
        
          There are some TODO points in the readme, or even the issue #6 is
          quite simple to fix. Feel free to pick what you like.
        
          The guidelines are to follow PEP8 for coding where possible, so use
          CamelCase for classes and snake_case for variables, functions and
          members, and UPPERCASE for constants.
        
          An exception to this rules are the function names inside
          ``metapensiero.pj.transformations`` subpackage. Those are matched
          against names of the AST objects coming from the ``ast`` module in
          standard lib, so they have to to match even in case.
        
          Try to keep lines lengths under 79 chars, more or less ;-)
        
          The workflow is to fork the project, do your stuff, maybe add a test
          for it and then submit a pull request.
        
          Have fun
        
        Contributing
        ------------
        
        Any contribution is welcome, drop me a line or file a pull request.
        
        External contributions
        ----------------------
        
        * `BrainBacon`__ has made a `JavaScripthon loader`__ for WebPack;
        
        * `icarito`_ has contributed support for JavaScripthon to the
          `python-webpack-loader`__ for WebPack (Every valid JS package has at
          least two implementations! ROTFL);
        
        * `icarito`_ has also `integrated JavaScripthon with Nuxt.js and
          Vue.js`__;
        
        * `chfw`__ has integrated `JavaScripthon into pyecharts`__ to allow
          Python function translation.
        
        .. _icarito: https://github.com/icarito
        __ https://github.com/BrainBacon
        __ https://github.com/Beg-in/javascripthon-loader
        __ https://github.com/martim00/python-webpack-loader
        __ https://nuxt-python.surge.sh/
        __ https://github.com/chfw
        __ https://github.com/pyecharts/pyecharts
        
        Todo
        ----
        
        This is a brief list of what needs to be done:
        
        * refactor the comprehensions conversion to use the snippets facility;
        * refactor snippets rendering to write them as a module and import
          them in the module when tree conversion is enabled;
        * convert ``dict()`` calls to ES6 ``Map`` object creation;
        * convert *set* literals to ES6 ``Set`` objects. Also, update
          "foo in bar" to use bar.has(foo) for sets;
        
        Done
        ----
        
        Stuff that was previously in the todo:
        
        * translate *import* statements to ES6;
        * translate ``__all__`` definition to ES6 module exports;
        * write a command line interface to expose the api;
        * make try...except work again and implement try...finally;
        * convert *async* and *await* to the same proposed features for js
          (see BabelJS documentation);
        * convert argument defaults on functions to ES6;
        * convert call keyword arguments;
        * convert `*iterable` syntax to ES6 destructuring;
        * use arrow functions for functions created in functions;
        * properties to ES6 properties (getter and setter);
        * take advantage of new duckpy features to use a JS execution context
          that lasts multiple calls. This way the BabelJS bootstrap affects
          only the initial execution;
        * class and method decorators;
        * implement *yield*, *yield from* and generator functions;
        * update "foo in bar" to use bar.has(foo) for maps;
        
        
        External documentation
        ----------------------
        
        A good documentation and explanation of ES6 features can be found on
        the book `Exploring ES6`__ by Axel Rauschmayer (donate if you can).
        
        __ http://exploringjs.com/es6/
        
        An `extensive documentation`__ about Python's AST objects, very handy.
        
        __ https://greentreesnakes.readthedocs.org/en/latest/
        
        Tools
        -----
        
        Have a look at `ECMAScript 6 Tools`__ by Addy Osmani.
        
        __ https://github.com/addyosmani/es6-tools
        
        To debug *source maps* have a look at `source-map-visualization`__ and
        its `package`__ on npm.
        
        __ https://sokra.github.io/source-map-visualization/
        __ https://www.npmjs.com/package/source-map-visualize
        
        Still i found these links to be helpful:
        
        * `BASE64 VLQ CODEC (COder/DECoder)`__
        * `Testing Source Maps`__
        
        __ http://murzwin.com/base64vlq.html
        __ http://fitzgeraldnick.com/2013/08/02/testing-source-maps.html
        
        Here is an `example`__ of the latter tool showing code generated by
        JavaScripthon, have fun!
        
        __ https://sokra.github.io/source-map-visualization/#base64,ZnVuY3Rpb24gc2ltcGxlX2FsZXJ0KCkgewogICAgd2luZG93LmFsZXJ0KCJIaSB0aGVyZSEiKTsKfQpmdW5jdGlvbiBhdHRhY2hfaGFuZGxlcigpIHsKICAgIHZhciBlbDsKICAgIGVsID0gZG9jdW1lbnQucXVlcnlTZWxlY3RvcigiYnV0dG9uIik7CiAgICBlbC5hZGRFdmVudExpc3RlbmVyKCJjbGljayIsIHNpbXBsZV9hbGVydCk7Cn0KYXR0YWNoX2hhbmRsZXIoKTsKCi8vIyBzb3VyY2VNYXBwaW5nVVJMPWh0bWxfdGVzdC5qcy5tYXAK,eyJtYXBwaW5ncyI6IkFBT0E7SUFDSUEsTUFBQUMsTUFBQSxDQUFhLFdBQWI7QUFESjtBQUdBOztJQUNJQyxLQUFLQyxRQUFBQyxjQUFBLENBQXVCLFFBQXZCO0lBQ0xGLEVBQUFHLGlCQUFBLENBQW9CLE9BQXBCLEVBQTZCQyxZQUE3QjtBQUZKO0FBSUFDLGNBQUEiLCJzb3VyY2VzIjpbImh0bWxfdGVzdC5weSJdLCJ2ZXJzaW9uIjozLCJuYW1lcyI6WyJ3aW5kb3ciLCJ3aW5kb3cuYWxlcnQiLCJlbCIsImRvY3VtZW50IiwiZG9jdW1lbnQucXVlcnlTZWxlY3RvciIsImVsLmFkZEV2ZW50TGlzdGVuZXIiLCJzaW1wbGVfYWxlcnQiLCJhdHRhY2hfaGFuZGxlciJdLCJzb3VyY2VzQ29udGVudCI6WyIjIC0qLSBjb2Rpbmc6IHV0Zi04IC0qLVxuIyA6UHJvamVjdDogIHBqIC0tIHRlc3QgZm9yIGh0bWxcbiMgOkNyZWF0ZWQ6ICAgIG1hciAwMSBtYXIgMjAxNiAyMzo0ODo1MiBDRVRcbiMgOkF1dGhvcjogICAgQWxiZXJ0byBCZXJ0aSA8YWxiZXJ0b0BtZXRhcGVuc2llcm8uaXQ+XG4jIDpMaWNlbnNlOiAgIEdOVSBHZW5lcmFsIFB1YmxpYyBMaWNlbnNlIHZlcnNpb24gMyBvciBsYXRlclxuI1xuXG5kZWYgc2ltcGxlX2FsZXJ0KCk6XG4gICAgd2luZG93LmFsZXJ0KCdIaSB0aGVyZSEnKVxuXG5kZWYgYXR0YWNoX2hhbmRsZXIoKTpcbiAgICBlbCA9IGRvY3VtZW50LnF1ZXJ5U2VsZWN0b3IoJ2J1dHRvbicpXG4gICAgZWwuYWRkRXZlbnRMaXN0ZW5lcignY2xpY2snLCBzaW1wbGVfYWxlcnQpXG5cbmF0dGFjaF9oYW5kbGVyKClcbiJdfQ==,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
        
        
        Notes
        -----
        
        * A `post`__ about proposed solutions to use ES6 classes with
          `Backbone`__. See also the `bug`__ open on github.
        
        __ http://benmccormick.org/2015/07/06/backbone-and-es6-classes-revisited/
        __ http://backbonejs.org
        __ https://github.com/jashkenas/backbone/issues/3560
        
        
        * A `benchmark of ES6 features`__ and `discussion about it`__ on
          hacker's news.
        
        __ https://kpdecker.github.io/six-speed/
        __ https://news.ycombinator.com/item?id=11203183
        
        * A `compatibility table of ES6 features`__ showing completeness of
          support feature by feature.
        
        __ http://kangax.github.io/compat-table/es6/
        
        * `A story`__ about ES6 crazyest stuff... symbols
        
        __ http://blog.keithcirkel.co.uk/metaprogramming-in-es6-symbols/
        
        
        .. -*- coding: utf-8 -*-
        
        Changes
        -------
        
        0.11 (2020-03-30)
        ~~~~~~~~~~~~~~~~~
        
        - update test infrastructure to work with latest ``pytest``;
        - add support for Python 3.7 and 3.8 (thanks to Richard Höchenberger).
        - do not crash when translating source with assignment typehints (
          with the help of Sirenfal)
        
        0.10 (2018-05-12)
        ~~~~~~~~~~~~~~~~~
        
        - use Macropy3 version 1.1.0b2 to avoid issues with Django
        
        0.9 (2018-04-19)
        ~~~~~~~~~~~~~~~~
        
        - add a ``--source-name`` options to be used together with
          ``--inline-map`` when using ``-s``;
        - move main repository to gitlab.com/metapensiero;
        - add support for default export and import;
        - add documentation for the ``JS()`` marker function;
        - refactor of the JS AST nodes;
        - fix path splitting and joining on Windows (thanks to Roman Yakubuk);
        
        0.8 (2017-11-16)
        ~~~~~~~~~~~~~~~~
        
        - add support for ``except`` sections with more than one exception
          type and arbitrary exception variable name. Thanks to @devanlai;
        - dict keys conversion fixes;
        - enable ``--inline-map`` when translating a string with ``-s``;
        
        
        0.7 (2017-09-08)
        ~~~~~~~~~~~~~~~~
        
        - translate dicts unambiguously, using "computed member name form" for
          keys that aren't strings;
        - use ``macropy`` package to deal with some of the translation
          details;
        - translate ``int()`` and ``float()``;
        - fix a bug that prevented BabelJS translation when keyword arguments;
          are present;
        
        0.6 (2017-05-09)
        ~~~~~~~~~~~~~~~~~
        
        - allow to define template literals and tagged templates;
        - define package scopes in imports prepending names with ``__``;
        - translate ``issubclass()``;
        - translate lambdas as arrow functions;
        - translate Python 3.6+ f-strings to ES6 template literals;
        - Add translation for ``__instancecheck__`` to ``[Symbol.hasInstance]``;
        - Sort imports alphabetically;
        
        0.5 (2016-11-23)
        ~~~~~~~~~~~~~~~~
        
        - translate ``tmpl("A string with js ${interpolation}")`` to ES6 template
          literals;
        - preliminary support to translate names like ``d_foo`` and ``dd_bar`` to
          ``$foo`` and ``$$bar``;
        - addded translation of the ``assert`` statement;
        - fixed a bug in ``try...except...finally`` statement when there's no
          ``except`` section;
        - added translation for ``foo is not bar`` that seems to have dedicated ast
          node;
        - if the function is defined in a method but starts with ``fn_`` do not convert
          it to an arrow function. Useful to *not* maintain ``this``;
        - added translation for ``callable`` and ``hasattr/getattr/setattr``;
        - updated for loops to support more than one target, so now its possible to
          write loops like ``for k, v in iterable(a_map):``;
        - updated documentation;
        - added a new cli option ``-s`` to translate source from the command line or
          the standard input;
        - fixed a pair of bugs on sourcemaps;
        - added a new cli option ``--eval`` to also evaluate the produced JavaScript
          using the embedded interpreter;
        - added a new cli option ``--dump-ast`` to print out the ast tree of the
          passed in string;
        - added sorting to the rendered snippets/decorators/assignments so that their
          order does not change at every ricompilation;
        - do not re-declare variables declare in outer scopes;
        
        0.4 (2016-11-15)
        ~~~~~~~~~~~~~~~~
        
        - updated BabelJS to version 6.18.1;
        - allow to import modules with dashes inside by using dunder-inside-words
          notation (``foo__bar`` becomes ``foo-bar``);
        - reuse JavaScript interpreter context to speedup translation;
        - update ``in`` operator to support ES6 collections;
        - added support for method and class decorators;
        - added support for class properties and descriptors;
        - add ``for`` loop over JS iterables;
        - allow to loop over inherited properties;
        - fix a bug on ``type()`` translation;
        - support for ``range()`` steps;
        - add support for generator functions and ``yield`` and ``yield from``
          expressions;
        - optionally load babel-polyfill before evaluating code;
        - fix a bug on sourcemaps having wrong references when there are documentation
          elements;
        - translate ``__get__()`` and ``__set__()`` to to JS equivalents;
        - implement ``dict(foo).update(bar)`` and ``dict(foo).copy``;
        - documentation improvements;
        
        0.3 (2016-04-08)
        ~~~~~~~~~~~~~~~~
        
        - updates to the documentation ( with some fixes made by Hugo Herter,
          Daniel Kopitchinski and ironmaniiith)
        - Translate ``str(x)`` into ``x.toString()``
        - Add support for properties and classmethods
        - Translate ``__len__`` and ``__str__`` methods to ``get length()``
          and ``toString()``
        - Add support for slices syntax to ``.slice()``
        - Fixed two bugs in sourcemaps generation
        - Fixed a bug in the ``inport ... from`` translation
        - Correctly include BabelJS minimized code
        - Fix transpiling of stage3 features
        
        0.2 (2016-03-29)
        ~~~~~~~~~~~~~~~~
        
        - use arrow functions to retain ``this`` were possible
        - translate ``async/await``
        - refactoring of the ``for`` loops
        - add ability to subtranslate pieces of Python code or objects. Used
          to template the creation of ``Exception`` sublasses
        - add support for param defaults and keyword arguments
        - updated documentation
        
        0.1 (2016-03-21)
        ~~~~~~~~~~~~~~~~
        
        - First cut of the features
        
Keywords: JavaScript EcmaScript compilation translation transpiling babel
Platform: UNKNOWN
Classifier: Development Status :: 5 - Production/Stable
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.5
Classifier: Programming Language :: Python :: 3.6
Classifier: Programming Language :: Python :: 3.7
Classifier: Programming Language :: Python :: 3.8
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: GNU General Public License (GPL)
Provides-Extra: dev
Provides-Extra: test
