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LibJS: Implement Function.prototype.toString() according to the spec

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That's an old yak :^)
No, past me, AST nodes do not need to learn to stringify themselves.
This is now massively simplified by using the [[SourceText]] internal
slot.

Also updates a bunch of tests that are incorrect due to the old
implementation not being spec compliant, and add plenty more.
This commit is contained in:
Linus Groh 2022-01-18 23:50:53 +00:00
parent 1ee7e97e24
commit 7d521b7c7c
3 changed files with 166 additions and 59 deletions
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64
Userland/Libraries/LibJS/Runtime/FunctionPrototype.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2020-2021, Linus Groh <linusg@serenityos.org>
* Copyright (c) 2020-2022, Linus Groh <linusg@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -94,50 +94,30 @@ JS_DEFINE_NATIVE_FUNCTION(FunctionPrototype::call)
// 20.2.3.5 Function.prototype.toString ( ), https://tc39.es/ecma262/#sec-function.prototype.tostring
JS_DEFINE_NATIVE_FUNCTION(FunctionPrototype::to_string)
{
auto* this_object = TRY(vm.this_value(global_object).to_object(global_object));
if (!this_object->is_function())
return vm.throw_completion<TypeError>(global_object, ErrorType::NotAnObjectOfType, "Function");
String function_name;
String function_parameters;
String function_body;
// 1. Let func be the this value.
auto function_value = vm.this_value(global_object);
if (is<ECMAScriptFunctionObject>(this_object)) {
auto& function = static_cast<ECMAScriptFunctionObject&>(*this_object);
StringBuilder parameters_builder;
auto first = true;
for (auto& parameter : function.formal_parameters()) {
// FIXME: Also stringify binding patterns.
if (auto* name_ptr = parameter.binding.get_pointer<FlyString>()) {
if (!first)
parameters_builder.append(", ");
first = false;
parameters_builder.append(*name_ptr);
if (parameter.default_value) {
// FIXME: See note below
parameters_builder.append(" = TODO");
}
}
}
function_name = function.name();
function_parameters = parameters_builder.build();
// FIXME: ASTNodes should be able to dump themselves to source strings - something like this:
// auto& body = static_cast<ECMAScriptFunctionObject*>(this_object)->body();
// function_body = body.to_source();
function_body = " ???";
} else {
// This is "implementation-defined" - other engines don't include a name for
// ProxyObject and BoundFunction, only NativeFunction - let's do the same here.
if (is<NativeFunction>(this_object))
function_name = static_cast<NativeFunction&>(*this_object).name();
function_body = " [native code]";
// If func is not a function, let's bail out early. The order of this step is not observable.
if (!function_value.is_function()) {
// 5. Throw a TypeError exception.
return vm.throw_completion<TypeError>(global_object, ErrorType::NotAnObjectOfType, "Function");
}
auto function_source = String::formatted(
"function {}({}) {{\n{}\n}}",
function_name.is_null() ? "" : function_name,
function_parameters.is_null() ? "" : function_parameters,
function_body);
return js_string(vm, function_source);
auto& function = function_value.as_function();
// 2. If Type(func) is Object and func has a [[SourceText]] internal slot and func.[[SourceText]] is a sequence of Unicode code points and ! HostHasSourceTextAvailable(func) is true, then
if (is<ECMAScriptFunctionObject>(function)) {
// a. Return ! CodePointsToString(func.[[SourceText]]).
return js_string(vm, static_cast<ECMAScriptFunctionObject&>(function).source_text());
}
// 3. If func is a built-in function object, return an implementation-defined String source code representation of func. The representation must have the syntax of a NativeFunction. Additionally, if func has an [[InitialName]] internal slot and func.[[InitialName]] is a String, the portion of the returned String that would be matched by NativeFunctionAccessor[opt] PropertyName must be the value of func.[[InitialName]].
if (is<NativeFunction>(function))
return js_string(vm, String::formatted("function {}() {{ [native code] }}", static_cast<NativeFunction&>(function).name()));
// 4. If Type(func) is Object and IsCallable(func) is true, return an implementation-defined String source code representation of func. The representation must have the syntax of a NativeFunction.
// NOTE: ProxyObject, BoundFunction, WrappedFunction
return js_string(vm, "function () { [native code] }");
}
// 20.2.3.6 Function.prototype [ @@hasInstance ] ( V ), https://tc39.es/ecma262/#sec-function.prototype-@@hasinstance