Enable parallelization of @embroider/macros in non-Embroider builds

packages/macros/src/ember-addon-main.ts

@@ -82,18 +82,34 @@ export = {
       // MacrosConfig.astPlugins is static because in classic ember-cli, at this
       // point there's not yet an appInstance, so we defer getting it and
       // calling setConfig until our included hook.
-      let { plugins, setConfig } = MacrosConfig.astPlugins((this as any).parent.root);
+      let { plugins, setConfig, getConfigForPlugin } = MacrosConfig.astPlugins((this as any).parent.root);
       this.setMacrosConfig = setConfig;
       plugins.forEach((plugin, index) => {
+        let name = `@embroider/macros/${index}`;
+        let baseDir = join(__dirname, '..');
+        let projectRoot = (this as any).parent.root;
+
         registry.add('htmlbars-ast-plugin', {
-          name: `@embroider/macros/${index}`,
+          name,
           plugin,
-          baseDir() {
-            return join(__dirname, '..');
+          parallelBabel: {
+            requireFile: join(__dirname, 'glimmer', 'ast-transform.js'),
+            buildUsing: 'buildPlugin',
+            params: {
+              name,
+              get configs() {
+                return getConfigForPlugin();
+              },
+              methodName: index === 0 ? 'makeSecondTransform' : 'makeFirstTransform',
+              projectRoot: projectRoot,
+              baseDir,
+            },
           },
+          baseDir: () => baseDir,
         });
       });
     }
   },
+
   options: {},
 };

packages/macros/src/glimmer/ast-transform.ts

@@ -5,6 +5,23 @@ import { maybeAttrs } from './macro-maybe-attrs';
 import { macroIfBlock, macroIfExpression, macroIfMustache } from './macro-condition';
 import { failBuild } from './fail-build';
 
+export function buildPlugin(params: {
+  name: string;
+  baseDir: string;
+  projectRoot: string;
+  methodName: string;
+  configs: any;
+}) {
+  return {
+    name: params.name,
+    plugin:
+      params.methodName === 'makeFirstTransform'
+        ? makeFirstTransform({ userConfigs: params.configs, baseDir: params.projectRoot })
+        : makeSecondTransform(),
+    baseDir: () => params.baseDir,
+  };
+}
+
 export function makeFirstTransform(opts: { userConfigs: { [packageRoot: string]: unknown }; baseDir?: string }) {
   function embroiderFirstMacrosTransform(env: {
     syntax: { builders: any };
@@ -97,7 +114,6 @@ export function makeFirstTransform(opts: { userConfigs: { [packageRoot: string]:
 export function makeSecondTransform() {
   function embroiderSecondMacrosTransform(env: { syntax: { builders: any } }) {
     let scopeStack: string[][] = [];
-
     return {
       name: '@embroider/macros/second',
 

packages/macros/src/macros-config.ts

@@ -260,7 +260,11 @@ export default class MacrosConfig {
     return [join(__dirname, 'babel', 'macros-babel-plugin.js'), opts];
   }
 
-  static astPlugins(owningPackageRoot?: string): { plugins: Function[]; setConfig: (config: MacrosConfig) => void } {
+  static astPlugins(owningPackageRoot?: string): {
+    plugins: Function[];
+    setConfig: (config: MacrosConfig) => void;
+    getConfigForPlugin(): any;
+  } {
     let configs: MacrosConfig | undefined;
     let plugins = [
       makeFirstTransform({
@@ -279,7 +283,14 @@ export default class MacrosConfig {
     function setConfig(c: MacrosConfig) {
       configs = c;
     }
-    return { plugins, setConfig };
+    function getConfigForPlugin() {
+      if (!configs) {
+        throw new Error(`Bug: @embroider/macros ast-transforms were not plugged into a MacrosConfig`);
+      }
+
+      return configs.userConfigs;
+    }
+    return { plugins, setConfig, getConfigForPlugin };
   }
 
   private mergerFor(pkgRoot: string) {

tests/scenarios/macro-test.ts

@@ -39,12 +39,13 @@ appScenarios
       });
 
       test(`yarn test`, async function (assert) {
-        let result = await app.execute(`yarn test`);
+        let result = await app.execute(`cross-env THROW_UNLESS_PARALLELIZABLE=1 yarn test`);
         assert.equal(result.exitCode, 0, result.output);
       });
 
       test(`CLASSIC=true yarn test`, async function (assert) {
-        let result = await app.execute(`cross-env CLASSIC=true yarn test`);
+        // throw_unless_parallelizable is enabled to ensure that @embroider/macros is parallelizable
+        let result = await app.execute(`cross-env THROW_UNLESS_PARALLELIZABLE=1 CLASSIC=true yarn test`);
         assert.equal(result.exitCode, 0, result.output);
       });
     });