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LibJS: Introduce NativeJavaScriptBackedFunction

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This hosts the ability to compile and run JavaScript to implement
native functions. This is particularly useful for any native function
that is not a normal function, for example async functions such as
Array.fromAsync, which require yielding.

These functions are not allowed to observe anything from outside their
environment. Any global identifiers will instead be assumed to be a
reference to an abstract operation or a constant. The generator will
inject the appropriate bytecode if the name of the global identifier
matches a known name. Anything else will cause a code generation error.
This commit is contained in:
Luke Wilde 2025-11-06 19:00:36 +00:00 • committed by Andreas Kling
parent 899c6ebffc
commit a63b0cfaba
Notes: github-actions[bot] 2025-11-30 10:56:11 +00:00
21 changed files with 412 additions and 52 deletions
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34
Libraries/LibJS/Runtime/NativeFunction.cpp
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@ -9,6 +9,7 @@
#include <LibJS/Bytecode/Interpreter.h>
#include <LibJS/Runtime/FunctionEnvironment.h>
#include <LibJS/Runtime/NativeFunction.h>
#include <LibJS/Runtime/NativeJavaScriptBackedFunction.h>
#include <LibJS/Runtime/Realm.h>
#include <LibJS/Runtime/Value.h>
@ -127,8 +128,21 @@ ThrowCompletionOr<Value> NativeFunction::internal_call(ExecutionContext& callee_
// 8. Perform any necessary implementation-defined initialization of calleeContext.
callee_context.this_value = this_argument;
callee_context.lexical_environment = caller_context.lexical_environment;
callee_context.variable_environment = caller_context.variable_environment;
if (function_environment_needed()) {
// 7. Let localEnv be NewFunctionEnvironment(F, newTarget).
auto local_environment = new_function_environment(as<NativeJavaScriptBackedFunction>(*this), nullptr);
local_environment->ensure_capacity(function_environment_bindings_count());
// 8. Set the LexicalEnvironment of calleeContext to localEnv.
callee_context.lexical_environment = local_environment;
// 9. Set the VariableEnvironment of calleeContext to localEnv.
callee_context.variable_environment = local_environment;
} else {
callee_context.lexical_environment = caller_context.lexical_environment;
callee_context.variable_environment = caller_context.variable_environment;
}
// Note: Keeping the private environment is probably only needed because of async methods in classes
// calling async_block_start which goes through a NativeFunction here.
callee_context.private_environment = caller_context.private_environment;
@ -169,8 +183,20 @@ ThrowCompletionOr<GC::Ref<Object>> NativeFunction::internal_construct(ExecutionC
// 7. Set the ScriptOrModule of calleeContext to null.
// Note: This is already the default value.
callee_context.lexical_environment = caller_context.lexical_environment;
callee_context.variable_environment = caller_context.variable_environment;
if (function_environment_needed()) {
// 7. Let localEnv be NewFunctionEnvironment(F, newTarget).
auto local_environment = new_function_environment(as<NativeJavaScriptBackedFunction>(*this), nullptr);
local_environment->ensure_capacity(function_environment_bindings_count());
// 8. Set the LexicalEnvironment of calleeContext to localEnv.
callee_context.lexical_environment = local_environment;
// 9. Set the VariableEnvironment of calleeContext to localEnv.
callee_context.variable_environment = local_environment;
} else {
callee_context.lexical_environment = caller_context.lexical_environment;
callee_context.variable_environment = caller_context.variable_environment;
}
// </8.> --------------------------------------------------------------------------