bandcamp-dl/bandcamp_dl/jsobj.py

"""
Simple JavaScript/ECMAScript object literal reader
    Only supports object literals wrapped in `var x = ...;` statements, so you
      might want to do read_js_object('var x = %s;' % literal) if it's in another format.

    Requires the slimit <https://github.com/rspivak/slimit> library for parsing.

    Basic constand folding on strings and numbers is done, e.g. "hi " + "there!" reduces to "hi there!",
    and 1+1 reduces to 2.

    Copyright (c) 2013 darkf
    Licensed under the terms of the WTFPL:

        DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                        Version 2, December 2004

        Everyone is permitted to copy and distribute verbatim or modified
        copies of this license document, and changing it is allowed as long
        as the name is changed.

                   DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
          TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

          0. You just DO WHAT THE FUCK YOU WANT TO.
"""

from slimit.parser import Parser
import slimit.ast as ast


def read_js_object(code):
    parser = Parser()

    def visit(node):
        if isinstance(node, ast.Program):
            d = {}
            for child in node:
                if not isinstance(child, ast.VarStatement):
                    raise ValueError("All statements should be var statements")
                key, val = visit(child)
                d[key] = val
            return d
        elif isinstance(node, ast.VarStatement):
            return visit(node.children()[0])
        elif isinstance(node, ast.VarDecl):
            return visit(node.identifier), visit(node.initializer)
        elif isinstance(node, ast.Object):
            d = {}
            for property in node:
                key = visit(property.left)
                value = visit(property.right)
                d[key] = value
            return d
        elif isinstance(node, ast.BinOp):
            # simple constant folding
            if node.op == '+':
                if isinstance(node.left, ast.String) and isinstance(node.right, ast.String):
                    return visit(node.left) + visit(node.right)
                elif isinstance(node.left, ast.Number) and isinstance(node.right, ast.Number):
                    return visit(node.left) + visit(node.right)
                else:
                    raise ValueError("Cannot + on anything other than two literals")
            else:
                raise ValueError("Cannot do operator '{}'".format(node.op))

        elif isinstance(node, ast.String):
            return node.value.strip('"').strip("'")
        elif isinstance(node, ast.Array):
            return [visit(x) for x in node]
        elif isinstance(node, ast.Number) or isinstance(node, ast.Identifier)\
                or isinstance(node, ast.Boolean) or isinstance(node, ast.Null):
            return node.value
        else:
            raise Exception("Unhandled node: {}".format(node))

    return visit(parser.parse(code))


if __name__ == "__main__":
    print(read_js_object("""var foo = {x: 10, y: "hi " + "there!"};
                            var bar = {derp: ["herp", "it", "up", "forever"]};"""))