LibJS: Stop tracking whether execution context is strict mode or not

awesomekling · awesomekling · commit fdb85a330ed5 · 2025-10-29T21:20:10.000+01:00
This was only used for basic testing, and forced us to plumb this flag
flag in a bunch of places.
diff --git a/Libraries/LibJS/Bytecode/Interpreter.cpp b/Libraries/LibJS/Bytecode/Interpreter.cpp
@@ -249,9 +249,6 @@ ThrowCompletionOr<Value> Interpreter::run(Script& script_record, GC::Ptr<Environ
 
     // 8. Set the PrivateEnvironment of scriptContext to null.
 
-    // NOTE: This isn't in the spec, but we require it.
-    script_context->is_strict_mode = script_record.is_strict_mode();
-
     // 9. Suspend the currently running execution context.
     // 10. Push scriptContext onto the execution context stack; scriptContext is now the running execution context.
     TRY(vm.push_execution_context(*script_context, {}));
diff --git a/Libraries/LibJS/Runtime/AbstractOperations.cpp b/Libraries/LibJS/Runtime/AbstractOperations.cpp
@@ -723,9 +723,6 @@ ThrowCompletionOr<Value> perform_eval(VM& vm, Value x, CallerMode strict_caller,
     // 28. Set evalContext's PrivateEnvironment to privateEnv.
     eval_context->private_environment = private_environment;
 
-    // NOTE: This isn't in the spec, but we require it.
-    eval_context->is_strict_mode = strict_eval;
-
     // 29. Push evalContext onto the execution context stack; evalContext is now the running execution context.
     TRY(vm.push_execution_context(*eval_context, {}));
 
diff --git a/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp b/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp
@@ -689,9 +689,6 @@ void ECMAScriptFunctionObject::make_method(Object& home_object)
 // 10.2.1.1 PrepareForOrdinaryCall ( F, newTarget ), https://tc39.es/ecma262/#sec-prepareforordinarycall
 void ECMAScriptFunctionObject::prepare_for_ordinary_call(VM& vm, ExecutionContext& callee_context, Object* new_target)
 {
-    // Non-standard
-    callee_context.is_strict_mode = is_strict_mode();
-
     // 1. Let callerContext be the running execution context.
     // 2. Let calleeContext be a new ECMAScript code execution context.
 
diff --git a/Libraries/LibJS/Runtime/ExecutionContext.cpp b/Libraries/LibJS/Runtime/ExecutionContext.cpp
@@ -125,7 +125,6 @@ NonnullOwnPtr<ExecutionContext> ExecutionContext::copy() const
     copy->program_counter = program_counter;
     copy->function_name = function_name;
     copy->this_value = this_value;
-    copy->is_strict_mode = is_strict_mode;
     copy->executable = executable;
     copy->arguments_offset = arguments_offset;
     copy->passed_argument_count = passed_argument_count;
diff --git a/Libraries/LibJS/Runtime/ExecutionContext.h b/Libraries/LibJS/Runtime/ExecutionContext.h
@@ -95,7 +95,6 @@ struct JS_API ExecutionContext {
 
     u32 arguments_offset { 0 };
     u32 passed_argument_count { 0 };
-    bool is_strict_mode { false };
 
     Span<Value> arguments;
 
diff --git a/Libraries/LibJS/Runtime/NativeFunction.cpp b/Libraries/LibJS/Runtime/NativeFunction.cpp
@@ -151,9 +151,6 @@ ThrowCompletionOr<Value> NativeFunction::internal_call(ExecutionContext& callee_
     //       calling async_block_start which goes through a NativeFunction here.
     callee_context.private_environment = caller_context.private_environment;
 
-    // NOTE: This is a LibJS specific hack for NativeFunction to inherit the strictness of its caller.
-    callee_context.is_strict_mode = caller_context.is_strict_mode;
-
     // </8.> --------------------------------------------------------------------------
 
     // 9. Push calleeContext onto the execution context stack; calleeContext is now the running execution context.
@@ -204,9 +201,6 @@ ThrowCompletionOr<GC::Ref<Object>> NativeFunction::internal_construct(ExecutionC
     callee_context.lexical_environment = caller_context.lexical_environment;
     callee_context.variable_environment = caller_context.variable_environment;
 
-    // NOTE: This is a LibJS specific hack for NativeFunction to inherit the strictness of its caller.
-    callee_context.is_strict_mode = caller_context.is_strict_mode;
-
     // </8.> --------------------------------------------------------------------------
 
     // 9. Push calleeContext onto the execution context stack; calleeContext is now the running execution context.
diff --git a/Libraries/LibJS/Runtime/ShadowRealm.cpp b/Libraries/LibJS/Runtime/ShadowRealm.cpp
@@ -342,9 +342,6 @@ NonnullOwnPtr<ExecutionContext> get_shadow_realm_context(Realm& shadow_realm, bo
     // 10. Set context's PrivateEnvironment to null.
     context->private_environment = nullptr;
 
-    // Non-standard
-    context->is_strict_mode = strict_eval;
-
     // 11. Return context.
     return context;
 }
diff --git a/Libraries/LibJS/Script.cpp b/Libraries/LibJS/Script.cpp
@@ -25,18 +25,15 @@ Result<GC::Ref<Script>, Vector<ParserError>> Script::parse(StringView source_tex
     if (parser.has_errors())
         return parser.errors();
 
-    bool strict_mode = script->is_strict_mode();
-
     // 3. Return Script Record { [[Realm]]: realm, [[ECMAScriptCode]]: script, [[HostDefined]]: hostDefined }.
-    return realm.heap().allocate<Script>(realm, filename, move(script), host_defined, strict_mode);
+    return realm.heap().allocate<Script>(realm, filename, move(script), host_defined);
 }
 
-Script::Script(Realm& realm, StringView filename, NonnullRefPtr<Program> parse_node, HostDefined* host_defined, bool strict_mode)
+Script::Script(Realm& realm, StringView filename, NonnullRefPtr<Program> parse_node, HostDefined* host_defined)
     : m_realm(realm)
     , m_parse_node(move(parse_node))
     , m_filename(filename)
     , m_host_defined(host_defined)
-    , m_strict_mode(strict_mode)
 {
 }
 
diff --git a/Libraries/LibJS/Script.h b/Libraries/LibJS/Script.h
@@ -46,10 +46,8 @@ class JS_API Script final : public Cell {
     HostDefined* host_defined() const { return m_host_defined; }
     StringView filename() const LIFETIME_BOUND { return m_filename; }
 
-    [[nodiscard]] bool is_strict_mode() const { return m_strict_mode; }
-
 private:
-    Script(Realm&, StringView filename, NonnullRefPtr<Program>, HostDefined*, bool strict_mode);
+    Script(Realm&, StringView filename, NonnullRefPtr<Program>, HostDefined*);
 
     virtual void visit_edges(Cell::Visitor&) override;
 
@@ -60,8 +58,6 @@ class JS_API Script final : public Cell {
     // Needed for potential lookups of modules.
     ByteString m_filename;
     HostDefined* m_host_defined { nullptr }; // [[HostDefined]]
-
-    bool m_strict_mode { false };
 };
 
 }
diff --git a/Libraries/LibJS/SourceTextModule.cpp b/Libraries/LibJS/SourceTextModule.cpp
@@ -709,9 +709,6 @@ ThrowCompletionOr<void> SourceTextModule::execute_module(VM& vm, GC::Ptr<Promise
     ExecutionContext* module_context = nullptr;
     ALLOCATE_EXECUTION_CONTEXT_ON_NATIVE_STACK(module_context, registers_and_constants_and_locals_count, 0);
 
-    // NOTE: This is not in the spec but we require it.
-    module_context->is_strict_mode = true;
-
     // 2. Set the Function of moduleContext to null.
 
     // 3. Set the Realm of moduleContext to module.[[Realm]].
diff --git a/Libraries/LibJS/Tests/builtins/ShadowRealm/ShadowRealm.prototype.evaluate.js b/Libraries/LibJS/Tests/builtins/ShadowRealm/ShadowRealm.prototype.evaluate.js
@@ -15,12 +15,11 @@ describe("normal behavior", () => {
         // Currently uses a plain JS::GlobalObject, i.e. no TestRunnerGlobalObject functions are available on the
         // shadow realm's global object. This may change in the future, update the test accordingly.
         const shadowRealm = new ShadowRealm();
-        expect(shadowRealm.evaluate("globalThis.isStrictMode")).toBeUndefined();
+        expect(shadowRealm.evaluate("globalThis.markAsGarbage")).toBeUndefined();
     });
 
     test("strict mode behavior", () => {
         const shadowRealm = new ShadowRealm();
-        // NOTE: We don't have access to the isStrictMode() test helper inside the shadow realm, see the comment in the test above.
 
         // sloppy mode
         expect(shadowRealm.evaluate("(function() { return !this; })()")).toBe(false);
diff --git a/Libraries/LibJS/Tests/classes/class-strict-mode.js b/Libraries/LibJS/Tests/classes/class-strict-mode.js
diff --git a/Libraries/LibJS/Tests/functions/arrow-functions.js b/Libraries/LibJS/Tests/functions/arrow-functions.js
@@ -110,33 +110,6 @@ test("arrow functions in objects", () => {
     expect(foobar.x.z()).toBe(foobar.x);
 });
 
-test("strict mode propagation", () => {
-    (() => {
-        "use strict";
-        expect(isStrictMode()).toBeTrue();
-
-        (() => {
-            expect(isStrictMode()).toBeTrue();
-        })();
-    })();
-
-    (() => {
-        "use strict";
-        expect(isStrictMode()).toBeTrue();
-    })();
-
-    (() => {
-        expect(isStrictMode()).toBeFalse();
-
-        (() => {
-            "use strict";
-            expect(isStrictMode()).toBeTrue();
-        })();
-
-        expect(isStrictMode()).toBeFalse();
-    })();
-});
-
 test("no prototype", () => {
     let foo = () => {};
     expect(foo).not.toHaveProperty("prototype");
diff --git a/Libraries/LibJS/Tests/functions/function-strict-mode.js b/Libraries/LibJS/Tests/functions/function-strict-mode.js
@@ -1,64 +1,3 @@
-test("non strict-mode by default", () => {
-    expect(isStrictMode()).toBeFalse();
-});
-
-test("use strict with double quotes", () => {
-    "use strict";
-    expect(isStrictMode()).toBeTrue();
-});
-
-// prettier-ignore
-test("use strict with single quotes", () => {
-    'use strict';
-    expect(isStrictMode()).toBeTrue();
-});
-
-// prettier-ignore
-test("use strict with backticks does not yield strict mode", () => {
-    `use strict`;
-    expect(isStrictMode()).toBeFalse();
-});
-
-// prettier-ignore
-test("use strict with single quotes after statement does not yield strict mode code", () => {
-    ;'use strict';
-    expect(isStrictMode()).toBeFalse();
-});
-
-// prettier-ignore
-test("use strict with double quotes after statement does not yield strict mode code", () => {
-    ;"use strict";
-    expect(isStrictMode()).toBeFalse();
-});
-
-test("use strict interrupted by a line continuation does not yield strict mode code", () => {
-    "use \
-strict";
-    expect(isStrictMode()).toBeFalse();
-});
-
-test("strict mode propagates down the scope chain", () => {
-    "use strict";
-    expect(isStrictMode()).toBeTrue();
-    (function () {
-        expect(isStrictMode()).toBeTrue();
-    })();
-});
-
-test("strict mode does not propagate up the scope chain", () => {
-    expect(isStrictMode()).toBeFalse();
-    (function () {
-        "use strict";
-        expect(isStrictMode()).toBeTrue();
-    })();
-    expect(isStrictMode()).toBeFalse();
-});
-
-test('only the string "use strict" yields strict mode code', () => {
-    "use stric";
-    expect(isStrictMode()).toBeFalse();
-});
-
 test("strict mode does not apply global object to |this|", () => {
     "use strict";
     let functionThis;
diff --git a/Libraries/LibJS/Tests/program-non-strict.js b/Libraries/LibJS/Tests/program-non-strict.js
diff --git a/Libraries/LibJS/Tests/program-strict-mode.js b/Libraries/LibJS/Tests/program-strict-mode.js
diff --git a/Libraries/LibJS/Tests/strict-mode-blocks.js b/Libraries/LibJS/Tests/strict-mode-blocks.js
diff --git a/Libraries/LibJS/Tests/use-strict-directive.js b/Libraries/LibJS/Tests/use-strict-directive.js
diff --git a/Tests/LibJS/test-js.cpp b/Tests/LibJS/test-js.cpp

Original file line number	Diff line number	Diff line change
`@@ -689,9 +689,6 @@ void ECMAScriptFunctionObject::make_method(Object& home_object)`
`689`	`689`	`// 10.2.1.1 PrepareForOrdinaryCall ( F, newTarget ), https://tc39.es/ecma262/#sec-prepareforordinarycall`
`690`	`690`	`void ECMAScriptFunctionObject::prepare_for_ordinary_call(VM& vm, ExecutionContext& callee_context, Object* new_target)`
`691`	`691`	`{`
`692`		`- // Non-standard`
`693`		`- callee_context.is_strict_mode = is_strict_mode();`
`694`		`-`
`695`	`692`	`// 1. Let callerContext be the running execution context.`
`696`	`693`	`// 2. Let calleeContext be a new ECMAScript code execution context.`
`697`	`694`
Original file line number	Diff line number	Diff line change
`@@ -342,9 +342,6 @@ NonnullOwnPtr<ExecutionContext> get_shadow_realm_context(Realm& shadow_realm, bo`
`342`	`342`	`// 10. Set context's PrivateEnvironment to null.`
`343`	`343`	`context->private_environment = nullptr;`
`344`	`344`
`345`		`- // Non-standard`
`346`		`- context->is_strict_mode = strict_eval;`
`347`		`-`
`348`	`345`	`// 11. Return context.`
`349`	`346`	`return context;`
`350`	`347`	`}`
Original file line number	Diff line number	Diff line change
`@@ -25,18 +25,15 @@ Result<GC::Ref<Script>, Vector<ParserError>> Script::parse(StringView source_tex`
`25`	`25`	`if (parser.has_errors())`
`26`	`26`	`return parser.errors();`
`27`	`27`
`28`		`- bool strict_mode = script->is_strict_mode();`
`29`		`-`
`30`	`28`	`// 3. Return Script Record { [[Realm]]: realm, [[ECMAScriptCode]]: script, [[HostDefined]]: hostDefined }.`
`31`		`- return realm.heap().allocate<Script>(realm, filename, move(script), host_defined, strict_mode);`
	`29`	`+ return realm.heap().allocate<Script>(realm, filename, move(script), host_defined);`
`32`	`30`	`}`
`33`	`31`
`34`		`-Script::Script(Realm& realm, StringView filename, NonnullRefPtr<Program> parse_node, HostDefined* host_defined, bool strict_mode)`
	`32`	`+Script::Script(Realm& realm, StringView filename, NonnullRefPtr<Program> parse_node, HostDefined* host_defined)`
`35`	`33`	`: m_realm(realm)`
`36`	`34`	`, m_parse_node(move(parse_node))`
`37`	`35`	`, m_filename(filename)`
`38`	`36`	`, m_host_defined(host_defined)`
`39`		`- , m_strict_mode(strict_mode)`
`40`	`37`	`{`
`41`	`38`	`}`
`42`	`39`