Kevin Curtis wrote:
> In May there was some discussion on the possibility of a standardized
> format for the ECMAScript AST in JSON/JsonML.
>
> The V8 engine has an option (in bleeding_edge) where the internal AST
> tree can be output to JsonML for debugging purposes:
> ./shell_g --print_json_ast <file.js>
>
> This is V8's internal AST type, which necessarily includes some
> implementation-specific artifacts. That said, the V8 AST is very
> nearly straight out of the ECMA 262 spec, so it's pretty generic.
> (Note: it's an initial version e.g doesn't recur into switch statement
> cases). It could be useful as an input as to what a standard JSON AST
> should look like. (Which, i guess, ECMAScript engines could support as
> an new, additional format to any existing AST serialization formats).
The Jacaranda parser (not released yet) also produces a JsonML AST.
Below is the same example for comparison, also with Jacaranda-specific
artefacts removed.
> Here's an example - with some V8 artefact's removed for clarity. Note:
> the script gets wrapped in a FunctionLiteral and VariableProxy ==
> Identifier.
>
> --- source ---
>
> x = 1;
> if (x > 0) {
> y = x + 2;
> print(y);
> }
["SEQ", {},
["EXPRSTMT", {},
["=", {},
["REF", {"name":"x"}],
["NUMBER", {"MV":1}]]],
["if", {},
[">", {},
["REF", {"name":"x"}],
["NUMBER", {"MV":0}]],
["{", {},
["SEQ", {},
["EXPRSTMT", {},
["=", {},
["REF", {"name":"y"}],
["+", {},
["REF", {"name":"x"}],
["NUMBER", {"MV":2}]]],
["EXPRSTMT", {},
["(", {},
["REF", {"name":"print"}],
["ARGS", {},
["REF", {"name":"y"}]]]]]]]]
> --- AST JsonML ---
>
> ["FunctionLiteral",
> {"name":""},
> ["ExpressionStatement",
> ["Assignment",
> {"op":"ASSIGN"},
> ["VariableProxy",
> {"name":"x"}
> ],
> ["Literal",
> {"handle":1}
> ]
> ]
> ],
> ["IfStatement",
> ["CompareOperation",
> {"op":"GT"},
> ["VariableProxy",
> {"name":"x"}
> ],
> ["Literal",
> {"handle":0}
> ]
> ],
> ["Block",
> ["ExpressionStatement",
> ["Assignment",
> {"op":"ASSIGN"},
> ["VariableProxy",
> {"name":"y"}
> ],
> ["BinaryOperation",
> {"op":"ADD"},
> ["VariableProxy",
> {"name":"x"}
> ],
> ["Literal",
> {"handle":2}
> ]
> ]
> ]
> ],
> ["ExpressionStatement",
> ["Call",
> ["VariableProxy",
> {"name":"print"}
> ],
> ["VariableProxy",
> {"name":"y"}
> ]
> ]
> ]
> ],
> ["EmptyStatement"]
> ]
> ]
>
> 3
--
David-Sarah Hopwood ⚥ http://davidsarah.livejournal.com
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