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LibJS: Allow let and const to create locals in global code

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This is actually safe everywhere but in the topmost program scope.
For web compatibility reasons, we have to flush all top-level bindings
to the environment, in case a subsequent separate <script> program
comes looking for them.
This commit is contained in:
Andreas Kling 2024-06-13 21:31:31 +02:00 committed by Andreas Kling
parent 0aa8cb7dac
commit 9d21d88374
Notes: sideshowbarker 2024-07-17 03:00:02 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/LadybirdBrowser/ladybird/commit/9d21d88374
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/165
2 changed files with 27 additions and 13 deletions
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36
Userland/Libraries/LibJS/Parser.cpp
View file

@ -351,12 +351,24 @@ public:
continue;
if (!identifier_group.captured_by_nested_function && !identifier_group.used_inside_with_statement) {
auto function_scope = last_function_scope();
if (!function_scope || m_screwed_by_eval_in_scope_chain) {
if (m_screwed_by_eval_in_scope_chain)
continue;
auto local_scope = last_function_scope();
if (!local_scope) {
// NOTE: If there is no function scope, we are in a *descendant* of the global program scope.
// While we cannot make `let` and `const` into locals in the topmost program scope,
// as that would break expected web behavior where subsequent <script> elements should see
// lexical bindings created by earlier <script> elements, we *can* promote them in descendant scopes.
// Of course, global `var` bindings can never be made into locals, as they get hoisted to the topmost program scope.
if (identifier_group.declaration_kind == DeclarationKind::Var)
continue;
// Add these locals to the top-level scope. (We only produce one executable for the entire program
// scope, so that's where the locals have to be stored.)
local_scope = m_top_level_scope;
}
auto local_variable_index = function_scope->m_node->add_local_variable(identifier_group_name);
auto local_variable_index = local_scope->m_node->add_local_variable(identifier_group_name);
for (auto& identifier : identifier_group.identifiers)
identifier->set_local_variable_index(local_variable_index);
}
@ -421,7 +433,7 @@ public:
return m_scope_level != ScopeLevel::ScriptTopLevel;
}
void register_identifier(NonnullRefPtr<Identifier> id)
void register_identifier(NonnullRefPtr<Identifier> id, Optional<DeclarationKind> declaration_kind = {})
{
if (auto maybe_identifier_group = m_identifier_groups.get(id->string()); maybe_identifier_group.has_value()) {
maybe_identifier_group.value().identifiers.append(id);
@ -429,6 +441,7 @@ public:
m_identifier_groups.set(id->string(), IdentifierGroup {
.captured_by_nested_function = false,
.identifiers = { id },
.declaration_kind = declaration_kind,
});
}
}
@ -495,6 +508,7 @@ private:
bool used_inside_scope_with_eval { false };
bool might_be_variable_in_lexical_scope_in_named_function_assignment { false };
Vector<NonnullRefPtr<Identifier>> identifiers;
Optional<DeclarationKind> declaration_kind;
};
HashMap<DeprecatedFlyString, IdentifierGroup> m_identifier_groups;
@ -3273,24 +3287,24 @@ RefPtr<BindingPattern const> Parser::parse_binding_pattern(Parser::AllowDuplicat
return pattern;
}
RefPtr<Identifier const> Parser::parse_lexical_binding()
RefPtr<Identifier const> Parser::parse_lexical_binding(Optional<DeclarationKind> declaration_kind)
{
auto binding_start = push_start();
if (match_identifier()) {
return create_identifier_and_register_in_current_scope({ m_source_code, binding_start.position(), position() }, consume_identifier().DeprecatedFlyString_value());
return create_identifier_and_register_in_current_scope({ m_source_code, binding_start.position(), position() }, consume_identifier().DeprecatedFlyString_value(), declaration_kind);
}
if (!m_state.in_generator_function_context && match(TokenType::Yield)) {
if (m_state.strict_mode)
syntax_error("Identifier must not be a reserved word in strict mode ('yield')");
return create_identifier_and_register_in_current_scope({ m_source_code, binding_start.position(), position() }, consume().DeprecatedFlyString_value());
return create_identifier_and_register_in_current_scope({ m_source_code, binding_start.position(), position() }, consume().DeprecatedFlyString_value(), declaration_kind);
}
if (!m_state.await_expression_is_valid && match(TokenType::Async)) {
if (m_program_type == Program::Type::Module)
syntax_error("Identifier must not be a reserved word in modules ('async')");
return create_identifier_and_register_in_current_scope({ m_source_code, binding_start.position(), position() }, consume().DeprecatedFlyString_value());
return create_identifier_and_register_in_current_scope({ m_source_code, binding_start.position(), position() }, consume().DeprecatedFlyString_value(), declaration_kind);
}
return {};
@ -3329,7 +3343,7 @@ NonnullRefPtr<VariableDeclaration const> Parser::parse_variable_declaration(IsFo
}
target = pattern.release_nonnull();
} else if (auto lexical_binding = parse_lexical_binding()) {
} else if (auto lexical_binding = parse_lexical_binding(declaration_kind)) {
check_identifier_name_for_assignment_validity(lexical_binding->string());
if ((declaration_kind == DeclarationKind::Let || declaration_kind == DeclarationKind::Const) && lexical_binding->string() == "let"sv)
syntax_error("Lexical binding may not be called 'let'");
@ -5145,11 +5159,11 @@ Parser::ForbiddenTokens Parser::ForbiddenTokens::forbid(std::initializer_list<To
template NonnullRefPtr<FunctionExpression> Parser::parse_function_node(u16, Optional<Position> const&);
template NonnullRefPtr<FunctionDeclaration> Parser::parse_function_node(u16, Optional<Position> const&);
NonnullRefPtr<Identifier const> Parser::create_identifier_and_register_in_current_scope(SourceRange range, DeprecatedFlyString string)
NonnullRefPtr<Identifier const> Parser::create_identifier_and_register_in_current_scope(SourceRange range, DeprecatedFlyString string, Optional<DeclarationKind> declaration_kind)
{
auto id = create_ast_node<Identifier const>(range, string);
if (m_state.current_scope_pusher)
m_state.current_scope_pusher->register_identifier(const_cast<Identifier&>(*id));
m_state.current_scope_pusher->register_identifier(const_cast<Identifier&>(*id), declaration_kind);
return id;
}

4
Userland/Libraries/LibJS/Parser.h
View file

@ -96,7 +96,7 @@ public:
};
NonnullRefPtr<VariableDeclaration const> parse_variable_declaration(IsForLoopVariableDeclaration is_for_loop_variable_declaration = IsForLoopVariableDeclaration::No);
RefPtr<Identifier const> parse_lexical_binding();
[[nodiscard]] RefPtr<Identifier const> parse_lexical_binding(Optional<DeclarationKind> = {});
NonnullRefPtr<UsingDeclaration const> parse_using_declaration(IsForLoopVariableDeclaration is_for_loop_variable_declaration = IsForLoopVariableDeclaration::No);
NonnullRefPtr<Statement const> parse_for_statement();
@ -347,7 +347,7 @@ private:
}
};
NonnullRefPtr<Identifier const> create_identifier_and_register_in_current_scope(SourceRange range, DeprecatedFlyString string);
[[nodiscard]] NonnullRefPtr<Identifier const> create_identifier_and_register_in_current_scope(SourceRange range, DeprecatedFlyString string, Optional<DeclarationKind> = {});
NonnullRefPtr<SourceCode const> m_source_code;
Vector<Position> m_rule_starts;