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LibJS: Tweak generated source in 'new Function()' to match ES 2015 spec

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ES 5(.1) described parsing of the function body string as:

https://www.ecma-international.org/ecma-262/5.1/#sec-15.3.2.1

7. If P is not parsable as a FormalParameterList[opt] then throw a SyntaxError exception.
8. If body is not parsable as FunctionBody then throw a SyntaxError exception.

We implemented it as building the source string of a complete function
and feeding that to the parser, with the same outcome. ES 2015+ does
exactly that, but with newlines at certain positions:

https://tc39.es/ecma262/#sec-createdynamicfunction

16. Let bodyString be the string-concatenation of 0x000A (LINE FEED), ? ToString(bodyArg), and 0x000A (LINE FEED).
17. Let prefix be the prefix associated with kind in Table 49.
18. Let sourceString be the string-concatenation of prefix, " anonymous(", P, 0x000A (LINE FEED), ") {", bodyString, and "}".

This patch updates the generated source string to match these
requirements. This will make certain edge cases work, e.g.
'new Function("-->")', where the user supplied input must be placed on
its own line to be valid syntax.
This commit is contained in:
Linus Groh 2020-10-29 18:11:35 +00:00 • committed by Andreas Kling
parent bed270ca47
commit a10d09faba
3 changed files with 16 additions and 8 deletions
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2
Libraries/LibJS/Runtime/FunctionConstructor.cpp
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@ -81,7 +81,7 @@ Value FunctionConstructor::construct(Function&)
if (vm.exception())
return {};
}
auto source = String::formatted("function anonymous({}) {{ {} }}", parameters_source, body_source);
auto source = String::formatted("function anonymous({}\n) {{\n{}\n}}", parameters_source, body_source);
auto parser = Parser(Lexer(source));
auto function_expression = parser.parse_function_node<FunctionExpression>();
if (parser.has_errors()) {