Make the scope bag an object instead of an array

Now that the scope bag is a `Record<string, unknown>`, the lexical symbol
names are always carried alongside their values. This eliminates the need
for the `lexicalSymbols` slot in the wire format block (previously only
available when `debugSymbols` was enabled) and allows `meta()` to derive
`lexical` names and `scopeValues` directly from the scope object's keys
and values.

See also: upstream PR emberjs#21224, PR emberjs#21068.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: NullVoxPopuli

packages/@glimmer-workspace/integration-tests/lib/compile.ts

@@ -24,17 +24,16 @@ export function createTemplate(
 ): TemplateFactory {
   options.locals = options.locals ?? Object.keys(scopeValues ?? {});
   let [block, usedLocals] = precompileJSON(templateSource, options);
-  let reifiedScopeValues = usedLocals.map((key) => scopeValues[key]);
-
-  if ('emit' in options && options.emit?.debugSymbols) {
-    block.push(usedLocals);
-  }
+  let reifiedScope: Record<string, unknown> | null =
+    usedLocals.length > 0
+      ? Object.fromEntries(usedLocals.map((key) => [key, scopeValues[key]]))
+      : null;
 
   let templateBlock: SerializedTemplateWithLazyBlock = {
     id: String(templateId++),
     block: JSON.stringify(block),
     moduleName: options.meta?.moduleName ?? '(unknown template module)',
-    scope: reifiedScopeValues.length > 0 ? () => reifiedScopeValues : null,
+    scope: reifiedScope ? () => reifiedScope! : null,
     isStrictMode: options.strictMode ?? false,
   };
 

packages/@glimmer-workspace/integration-tests/test/compiler/compile-options-test.ts

@@ -57,7 +57,7 @@ module('[glimmer-compiler] precompile', ({ test }) => {
       ...WireFormat.Statement[],
     ];
 
-    assert.deepEqual(wire.scope?.(), [hello]);
+    assert.deepEqual(wire.scope?.(), { hello });
 
     assert.deepEqual(
       componentNameExpr,
@@ -84,7 +84,7 @@ module('[glimmer-compiler] precompile', ({ test }) => {
       ...WireFormat.Statement[],
     ];
 
-    assert.deepEqual(wire.scope?.(), [f]);
+    assert.deepEqual(wire.scope?.(), { f });
     assert.deepEqual(
       componentNameExpr,
       [SexpOpcodes.GetLexicalSymbol, 0, ['hello']],
@@ -218,7 +218,7 @@ module('[glimmer-compiler] precompile', ({ test }) => {
       _wire = compile(`{{this.message}}`, ['this'], (source) => eval(source));
     }).call(target);
     let wire = _wire!;
-    assert.deepEqual(wire.scope?.(), [target]);
+    assert.deepEqual(wire.scope?.(), { 'this': target });
     assert.deepEqual(wire.block[0], [
       [SexpOpcodes.Append, [SexpOpcodes.GetLexicalSymbol, 0, ['message']]],
     ]);

packages/@glimmer/compiler/lib/compiler.ts

@@ -123,9 +123,8 @@ export function precompile(
 ): TemplateJavascript {
   const [block, usedLocals] = precompileJSON(source, options);
 
-  if ('emit' in options && options.emit?.debugSymbols && usedLocals.length > 0) {
-    block.push(usedLocals);
-  }
+  // lexical symbol names are now carried by the scope object itself (as keys),
+  // so we no longer need to push them into the wire format block for debug symbols.
 
   const moduleName = options.meta?.moduleName;
   const idFn = options.id || defaultId;
@@ -148,7 +147,10 @@ export function precompile(
   let stringified = JSON.stringify(templateJSONObject);
 
   if (usedLocals.length > 0) {
-    const scopeFn = `()=>[${usedLocals.join(',')}]`;
+    const scopeEntries = usedLocals.map((l) =>
+      l === 'this' ? '"this":this' : l
+    );
+    const scopeFn = `()=>({${scopeEntries.join(',')}})`;
 
     stringified = stringified.replace(`"${SCOPE_PLACEHOLDER}"`, scopeFn);
   }

packages/@glimmer/interfaces/lib/compile/wire-format/api.d.ts

@@ -373,7 +373,6 @@ export type SerializedTemplateBlock = [
   statements: Statements.Statement[],
   locals: string[],
   upvars: string[],
-  lexicalSymbols?: string[],
 ];
 
 /**
@@ -397,7 +396,7 @@ export interface SerializedTemplateWithLazyBlock {
   id?: Nullable<string>;
   block: SerializedTemplateBlockJSON;
   moduleName: string;
-  scope?: (() => unknown[]) | undefined | null;
+  scope?: (() => Record<string, unknown>) | undefined | null;
   isStrictMode: boolean;
 }
 

packages/@glimmer/interfaces/lib/template.d.ts

@@ -18,7 +18,7 @@ export interface LayoutWithContext {
   readonly block: SerializedTemplateBlock;
   readonly moduleName: string;
   readonly owner: Owner | null;
-  readonly scope: (() => unknown[]) | undefined | null;
+  readonly scope: (() => Record<string, unknown>) | undefined | null;
   readonly isStrictMode: boolean;
 }
 

packages/@glimmer/opcode-compiler/lib/opcode-builder/helpers/shared.ts

@@ -106,15 +106,16 @@ export function CompilePositional(
 }
 
 export function meta(layout: LayoutWithContext): BlockMetadata {
-  let [, locals, upvars, lexicalSymbols] = layout.block;
+  let [, locals, upvars] = layout.block;
+  let scopeRecord = layout.scope?.() ?? null;
 
   return {
     symbols: {
       locals,
       upvars,
-      lexical: lexicalSymbols,
+      lexical: scopeRecord ? Object.keys(scopeRecord) : undefined,
     },
-    scopeValues: layout.scope?.() ?? null,
+    scopeValues: scopeRecord ? Object.values(scopeRecord) : null,
     isStrictMode: layout.isStrictMode,
     moduleName: layout.moduleName,
     owner: layout.owner,

packages/internal-test-helpers/lib/compile.ts

@@ -24,12 +24,15 @@ export default function compile(
 ): TemplateFactory {
   options.locals = options.locals ?? Object.keys(scopeValues ?? {});
   let [block, usedLocals] = precompileJSON(templateSource, compileOptions(options));
-  let reifiedScopeValues = usedLocals.map((key) => scopeValues[key]);
+  let reifiedScope: Record<string, unknown> | null =
+    usedLocals.length > 0
+      ? Object.fromEntries(usedLocals.map((key) => [key, scopeValues[key]]))
+      : null;
 
   let templateBlock: SerializedTemplateWithLazyBlock = {
     block: JSON.stringify(block),
     moduleName: options.moduleName ?? options.meta?.moduleName ?? '(unknown template module)',
-    scope: reifiedScopeValues.length > 0 ? () => reifiedScopeValues : null,
+    scope: reifiedScope ? () => reifiedScope! : null,
     isStrictMode: options.strictMode ?? false,
   };