LibJS: Add static initializers to classes

4 files changed, 134 insertions, 13 deletions

diff --git a/Userland/Libraries/LibJS/AST.cpp b/Userland/Libraries/LibJS/AST.cpp
index f74a1d2ea3..806157e4b1 100644
--- a/Userland/Libraries/LibJS/AST.cpp
+++ b/Userland/Libraries/LibJS/AST.cpp
@@ -1244,6 +1244,18 @@ ThrowCompletionOr<ClassElement::ClassValue> ClassField::class_element_evaluation
     };
 }
 
+// 15.7.11 Runtime Semantics: ClassStaticBlockDefinitionEvaluation, https://tc39.es/ecma262/#sec-runtime-semantics-classstaticblockdefinitionevaluation
+ThrowCompletionOr<ClassElement::ClassValue> StaticInitializer::class_element_evaluation(Interpreter& interpreter, GlobalObject& global_object, Object& home_object) const
+{
+    auto* lexical_environment = interpreter.vm().running_execution_context().lexical_environment;
+
+    // Note: The function bodyFunction is never directly accessible to ECMAScript code.
+    auto* body_function = ECMAScriptFunctionObject::create(global_object, "", *m_function_body, {}, 0, lexical_environment, FunctionKind::Regular, true, false, m_contains_direct_call_to_eval, false);
+    body_function->set_home_object(&home_object);
+
+    return ClassValue { normal_completion(body_function) };
+}
+
 Value ClassExpression::execute(Interpreter& interpreter, GlobalObject& global_object) const
 {
     InterpreterNodeScope node_scope { interpreter, *this };
@@ -1364,8 +1376,10 @@ ThrowCompletionOr<Value> ClassExpression::class_definition_evaluation(Interprete
 
     prototype->define_direct_property(vm.names.constructor, class_constructor, Attribute::Writable | Attribute::Configurable);
 
+    using StaticElement = Variant<ClassElement::ClassFieldDefinition, ECMAScriptFunctionObject*>;
+
     Vector<ClassElement::ClassFieldDefinition> instance_fields;
-    Vector<ClassElement::ClassFieldDefinition> static_fields;
+    Vector<StaticElement> static_elements;
 
     // FIXME: Do things with private methods, and fields here
     for (auto const& element : m_elements) {
@@ -1375,12 +1389,16 @@ ThrowCompletionOr<Value> ClassExpression::class_definition_evaluation(Interprete
 
         if (auto* class_field_definition_ptr = element_value.get_pointer<ClassElement::ClassFieldDefinition>()) {
             if (element.is_static())
-                static_fields.append(move(*class_field_definition_ptr));
+                static_elements.append(move(*class_field_definition_ptr));
             else
                 instance_fields.append(move(*class_field_definition_ptr));
+        } else if (element.class_element_kind() == ClassElement::ElementKind::StaticInitializer) {
+            // We use Completion to hold the ClassStaticBlockDefinition Record.
+            VERIFY(element_value.has<Completion>() && element_value.get<Completion>().has_value());
+            auto element_object = element_value.get<Completion>().value();
+            VERIFY(is<ECMAScriptFunctionObject>(element_object.as_object()));
+            static_elements.append(static_cast<ECMAScriptFunctionObject*>(&element_object.as_object()));
         }
-
-        // FIXME: Else if element is class static block
     }
 
     vm.running_execution_context().lexical_environment = environment;
@@ -1393,18 +1411,23 @@ ThrowCompletionOr<Value> ClassExpression::class_definition_evaluation(Interprete
     for (auto& field : instance_fields)
         class_constructor->add_field(field.name, field.initializer);
 
-    for (auto& field : static_fields) {
-        Value field_value = js_undefined();
-        if (field.initializer)
-            field_value = TRY(interpreter.vm().call(*field.initializer, class_constructor_value));
-
-        // FIXME: Handle private static fields
+    for (auto& element : static_elements) {
+        TRY(element.visit(
+            [&](ClassElement::ClassFieldDefinition const& field) -> ThrowCompletionOr<void> {
+                Value field_value = js_undefined();
+                if (field.initializer)
+                    field_value = TRY(call(global_object, field.initializer, class_constructor_value));
 
-        TRY(class_constructor->create_data_property_or_throw(field.name, field_value));
+                TRY(class_constructor->create_data_property_or_throw(field.name, field_value));
+                return {};
+            },
+            [&](ECMAScriptFunctionObject* static_block_function) -> ThrowCompletionOr<void> {
+                // We discard any value returned here.
+                TRY(call(global_object, static_block_function, class_constructor_value));
+                return {};
+            }));
     }
 
-    // FIXME: Run static initializers
-
     return Value(class_constructor);
 }
 
@@ -1689,6 +1712,12 @@ void ClassField::dump(int indent) const
     }
 }
 
+void StaticInitializer::dump(int indent) const
+{
+    ASTNode::dump(indent);
+    m_function_body->dump(indent + 1);
+}
+
 void StringLiteral::dump(int indent) const
 {
     print_indent(indent);
diff --git a/Userland/Libraries/LibJS/AST.h b/Userland/Libraries/LibJS/AST.h
index be7806a4f0..774e34df74 100644
--- a/Userland/Libraries/LibJS/AST.h
+++ b/Userland/Libraries/LibJS/AST.h
@@ -1013,6 +1013,7 @@ public:
     enum class ElementKind {
         Method,
         Field,
+        StaticInitializer,
     };
 
     virtual ElementKind class_element_kind() const = 0;
@@ -1023,6 +1024,7 @@ public:
         ECMAScriptFunctionObject* initializer { nullptr };
     };
 
+    // We use the Completion also as a ClassStaticBlockDefinition Record.
     using ClassValue = Variant<ClassFieldDefinition, Completion>;
     virtual ThrowCompletionOr<ClassValue> class_element_evaluation(Interpreter&, GlobalObject&, Object& home_object) const = 0;
 
@@ -1082,6 +1084,25 @@ private:
     RefPtr<Expression> m_initializer;
 };
 
+class StaticInitializer final : public ClassElement {
+public:
+    StaticInitializer(SourceRange source_range, NonnullRefPtr<FunctionBody> function_body, bool contains_direct_call_to_eval)
+        : ClassElement(source_range, true)
+        , m_function_body(move(function_body))
+        , m_contains_direct_call_to_eval(contains_direct_call_to_eval)
+    {
+    }
+
+    virtual ElementKind class_element_kind() const override { return ElementKind::StaticInitializer; }
+    virtual ThrowCompletionOr<ClassValue> class_element_evaluation(Interpreter&, GlobalObject&, Object& home_object) const override;
+
+    virtual void dump(int indent) const override;
+
+private:
+    NonnullRefPtr<FunctionBody> m_function_body;
+    bool m_contains_direct_call_to_eval { false };
+};
+
 class SuperExpression final : public Expression {
 public:
     explicit SuperExpression(SourceRange source_range)
diff --git a/Userland/Libraries/LibJS/Parser.cpp b/Userland/Libraries/LibJS/Parser.cpp
index 06e866f284..03fecfd13b 100644
--- a/Userland/Libraries/LibJS/Parser.cpp
+++ b/Userland/Libraries/LibJS/Parser.cpp
@@ -97,6 +97,11 @@ public:
         return scope_pusher;
     }
 
+    static ScopePusher static_init_block_scope(Parser& parser, ScopeNode& node)
+    {
+        return ScopePusher(parser, &node, true);
+    }
+
     void add_declaration(NonnullRefPtr<Declaration> declaration)
     {
         if (declaration->is_lexical_declaration()) {
@@ -957,6 +962,24 @@ NonnullRefPtr<ClassExpression> Parser::parse_class_expression(bool expect_class_
                     break;
                 }
                 property_key = create_ast_node<StringLiteral>({ m_state.current_token.filename(), rule_start.position(), position() }, name);
+            } else if (match(TokenType::CurlyOpen) && is_static) {
+                auto static_start = push_start();
+                consume(TokenType::CurlyOpen);
+
+                auto static_init_block = create_ast_node<FunctionBody>({ m_state.current_token.filename(), rule_start.position(), position() });
+
+                TemporaryChange break_context_rollback(m_state.in_break_context, false);
+                TemporaryChange continue_context_rollback(m_state.in_continue_context, false);
+                TemporaryChange function_context_rollback(m_state.in_function_context, false);
+                TemporaryChange generator_function_context_rollback(m_state.in_generator_function_context, false);
+                TemporaryChange in_class_field_initializer_rollback(m_state.in_class_field_initializer, true);
+
+                ScopePusher static_init_scope = ScopePusher::static_init_block_scope(*this, *static_init_block);
+                parse_statement_list(static_init_block);
+
+                consume(TokenType::CurlyClose);
+                elements.append(create_ast_node<StaticInitializer>({ m_state.current_token.filename(), static_start.position(), position() }, move(static_init_block), static_init_scope.contains_direct_call_to_eval()));
+                continue;
             } else {
                 expected("property key");
             }
diff --git a/Userland/Libraries/LibJS/Tests/classes/class-static-initializers.js b/Userland/Libraries/LibJS/Tests/classes/class-static-initializers.js
new file mode 100644
index 0000000000..feb7afe76c
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/classes/class-static-initializers.js
@@ -0,0 +1,48 @@
+test("basic functionality", () => {
+    var called = false;
+    class A {
+        static {
+            expect(called).toBeFalse();
+            expect(this.name).toBe("A");
+            called = true;
+        }
+    }
+
+    expect(called).toBeTrue();
+    new A();
+    expect(called).toBeTrue();
+});
+
+test("called in order", () => {
+    var i = 0;
+    class A {
+        static {
+            expect(i).toBe(0);
+            i++;
+        }
+
+        static method() {
+            return 2;
+        }
+
+        static {
+            expect(i).toBe(1);
+            i++;
+        }
+    }
+
+    expect(i).toBe(2);
+    new A();
+    expect(i).toBe(2);
+});
+
+test("correct this", () => {
+    var thisValue = null;
+    class A {
+        static {
+            thisValue = this;
+        }
+    }
+
+    expect(thisValue).toBe(A);
+});