Replace Handlebars parser with Peggy grammar for @glimmer/syntax

Inlines the former @handlebars/parser package into @glimmer/syntax and
replaces the Jison-generated parser with a Peggy grammar that produces
ASTv1 nodes directly. Drops the runtime simple-html-tokenizer dependency
and deletes the separate handlebars-node-visitors pipeline.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Author: NullVoxPopuli

.github/workflows/ci-jobs.yml

@@ -37,8 +37,6 @@ jobs:
         run: pnpm build:types
       - name: Check internal types
         run: pnpm type-check:internals
-      - name: Check @handlebars/parser types
-        run: pnpm type-check:handlebars
       - name: Check published types
         run: pnpm type-check:types
 
@@ -222,7 +220,7 @@ jobs:
           SHOULD_TRANSPILE_FOR_NODE: true
         run: pnpm build
       - name: test
-        run: pnpm test:node && pnpm --filter "@handlebars/parser" test
+        run: pnpm test:node
 
   blueprint-test:
     name: Blueprint Tests

.github/workflows/glimmer-syntax-prettier-smoke-test.yml

@@ -17,7 +17,6 @@ on:
       - "packages/@glimmer/interfaces/**"
       - "packages/@glimmer/util/**"
       - "packages/@glimmer/wire-format/**"
-      - "packages/@handlebars/parser/**"
   pull_request:
     paths:
       - ".github/workflows/glimmer-syntax-prettier-smoke-test.yml"
@@ -27,7 +26,6 @@ on:
       - "packages/@glimmer/interfaces/**"
       - "packages/@glimmer/util/**"
       - "packages/@glimmer/wire-format/**"
-      - "packages/@handlebars/parser/**"
   workflow_dispatch:
 
 permissions:

.gitignore

@@ -55,3 +55,6 @@ npm-debug.log
 # couple of the files. Once it is, we can switch this over to just ignoring
 # `types/stable` entirely.
 types/stable
+
+# Generated Peggy parser (regenerate with: pnpm build:hbs-parser)
+packages/@glimmer/syntax/lib/hbs-parser/parser.js

.prettierignore

@@ -7,10 +7,11 @@ docs/
 **/smoke-tests/
 **/types/
 **/type-tests/
-packages/@handlebars/**/*.l
-packages/@handlebars/**/*.yy
 CHANGELOG.md
 package.json
 pnpm-lock.yaml
 internal-docs/**/*.md
+packages/@glimmer/syntax/lib/hbs-parser/parser.js
+packages/@glimmer/syntax/lib/parser/html5-named-char-refs.js
+*.peggy
 tracerbench-testing/

eslint.config.mjs

@@ -28,8 +28,7 @@ export default [
       '**/type-tests/',
       'internal-docs/guides/**',
       'packages/@glimmer-workspace/**',
-      'packages/@handlebars/parser/lib/parser.js',
-      'packages/@handlebars/parser/src/**',
+      'packages/@glimmer/syntax/lib/hbs-parser/parser.js',
       'tracerbench-testing/',
     ],
   },
@@ -189,15 +188,6 @@ export default [
       'import/namespace': 'off',
     },
   },
-  {
-    files: ['packages/@handlebars/parser/spec/**/*.js'],
-
-    languageOptions: {
-      globals: {
-        ...globals.mocha,
-      },
-    },
-  },
   {
     files: [
       'packages/*/tests/**/*.[jt]s',

internal-docs/guides/development/build-constraints.md

@@ -137,7 +137,6 @@ The build system has specific rules for what gets inlined vs treated as external
 - TypeScript helper library (`tslib`)
 
 **Always External:**
-- `@handlebars/parser`
 - `simple-html-tokenizer`
 - `babel-plugin-debug-macros`
 - Other `@glimmer/*` packages (to avoid duplication)

package.json

@@ -38,7 +38,9 @@
     "actions-up": "pnpm dlx actions-up",
     "bench": "node ./bin/benchmark.mjs",
     "bench:precompile": "node --expose-gc bin/precompile.bench.mjs",
+    "build:hbs-parser": "peggy --format es --allowed-start-rules Template,ExpressionWithParamsAndHash packages/@glimmer/syntax/lib/hbs-parser/hbs.peggy -o packages/@glimmer/syntax/lib/hbs-parser/parser.js",
     "build:js": "rollup --config",
+    "prepare": "pnpm build:hbs-parser",
     "build:types": "node types/publish.mjs",
     "build": "npm-run-all build:*",
     "docs": "ember ember-cli-yuidoc",
@@ -56,7 +58,6 @@
     "test:browserstack": "node bin/run-browserstack-tests.js",
     "test:wip": "vite build --mode development --minify false && testem ci",
     "type-check:internals": "tsc --noEmit",
-    "type-check:handlebars": "tsc --noEmit --project packages/@handlebars/parser/tsconfig.json",
     "type-check:types": "tsc --noEmit --project type-tests",
     "type-check": "npm-run-all type-check:*"
   },
@@ -126,6 +127,7 @@
     "mitata": "^1.0.34",
     "mocha": "^11.0.0",
     "npm-run-all2": "^8.0.0",
+    "peggy": "^5.1.0",
     "prettier": "^3.5.3",
     "qunit": "^2.19.4",
     "recast": "^0.22.0",

packages/@ember/template-compiler/lib/compile-options.ts

@@ -118,7 +118,10 @@ function buildCompileOptions(_options: EmberPrecompileOptions): EmberPrecompileO
   }
 
   if (options.strictMode) {
-    options.keywords = STRICT_MODE_KEYWORDS;
+    // Include fn/on as keywords for runtime compilation so the strict mode
+    // validation pass allows them. The auto-import-builtins plugin will
+    // rewrite them to __ember_keywords__.fn / __ember_keywords__.on.
+    options.keywords = [...STRICT_MODE_KEYWORDS, 'fn', 'on'];
   }
 
   return options;