User-controlled babel config

packages/compat/babel.js

@@ -0,0 +1 @@
+module.exports = require('./src/babel');

packages/compat/package.json

@@ -12,6 +12,7 @@
   "author": "Edward Faulkner",
   "main": "src/index.js",
   "files": [
+    "babel.js",
     "src/**/*.js",
     "src/**/*.d.ts",
     "src/**/*.js.map"
@@ -36,7 +37,8 @@
     "@types/yargs": "^17.0.3",
     "assert-never": "^1.1.0",
     "babel-import-util": "^2.0.0",
-    "babel-plugin-ember-template-compilation": "^2.1.1",
+    "babel-plugin-debug-macros": "^1.0.2",
+    "babel-plugin-ember-template-compilation": "^2.3.0",
     "babel-plugin-syntax-dynamic-import": "^6.18.0",
     "babylon": "^6.18.0",
     "bind-decorator": "^1.0.11",

packages/compat/src/audit.ts

@@ -1,4 +1,4 @@
-import { existsSync, readFileSync, readJSONSync } from 'fs-extra';
+import { readFileSync, readJSONSync } from 'fs-extra';
 import { join, resolve as resolvePath, dirname } from 'path';
 import type { AppMeta, ResolverOptions } from '@embroider/core';
 import { explicitRelative, hbsToJS, locateEmbroiderWorkingDir, Resolver, RewrittenPackageCache } from '@embroider/core';
@@ -122,15 +122,6 @@ export class Audit {
     }
 
     let audit = new this(options.app, options);
-    if (options['reuse-build']) {
-      if (!audit.meta.babel.isParallelSafe) {
-        throw new BuildError(
-          `You can't use the ${chalk.red(
-            '--reuse-build'
-          )} option because some of your babel or HBS plugins are non-serializable`
-        );
-      }
-    }
     return audit.run();
   }
 
@@ -153,19 +144,20 @@ export class Audit {
 
   @Memoize()
   private get babelConfig() {
-    // Depending on how the app builds, the babel config is not at the same location
-    let embroiderLocation = join(locateEmbroiderWorkingDir(this.originAppRoot), '_babel_config_.js');
-    let config = existsSync(embroiderLocation)
-      ? // eslint-disable-next-line @typescript-eslint/no-require-imports
-        require(embroiderLocation)
-      : // eslint-disable-next-line @typescript-eslint/no-require-imports
-        require(join(this.movedAppRoot, this.meta.babel.filename));
-
-    config = Object.assign({}, config);
-    config.plugins = config.plugins.filter((p: any) => !isMacrosPlugin(p));
-
-    config.ast = true;
-    return config;
+    let origCwd = process.cwd();
+    process.chdir(this.originAppRoot);
+    try {
+      // eslint-disable-next-line @typescript-eslint/no-require-imports
+      let config = require(join(this.originAppRoot, 'babel.config.cjs'));
+
+      config = Object.assign({}, config);
+      config.plugins = config.plugins.filter((p: any) => !isMacrosPlugin(p));
+
+      config.ast = true;
+      return config;
+    } finally {
+      process.chdir(origCwd);
+    }
   }
 
   private get resolverParams(): ResolverOptions {

packages/compat/src/babel.ts

@@ -0,0 +1,158 @@
+import type { PluginItem } from '@babel/core';
+import { existsSync } from 'fs';
+import {
+  locateEmbroiderWorkingDir,
+  ResolverLoader,
+  templateColocationPluginPath,
+  type TemplateColocationPluginOptions,
+} from '@embroider/core';
+import { join } from 'path';
+import type { Transform } from 'babel-plugin-ember-template-compilation';
+import type { Options as ResolverTransformOptions } from './resolver-transform';
+import type { Options as AdjustImportsOptions } from './babel-plugin-adjust-imports';
+
+export interface CompatBabelState {
+  plugins: PluginItem[];
+  templateTransforms: Transform[];
+  babelMacros: PluginItem[];
+  templateMacros: Transform[];
+}
+
+function loadCompatConfig(): CompatBabelState {
+  let compatFile = join(locateEmbroiderWorkingDir(process.cwd()), '_babel_compat_.js');
+  if (existsSync(compatFile)) {
+    // eslint-disable-next-line @typescript-eslint/no-require-imports
+    return require(compatFile);
+  }
+  return {
+    plugins: [],
+    templateTransforms: [],
+    babelMacros: [],
+    templateMacros: [],
+  };
+}
+
+const resolverLoader = new ResolverLoader(process.cwd());
+
+export function pluginsFromV1Addons() {
+  let config = loadCompatConfig();
+  return config.plugins;
+}
+
+export function transformsFromV1Addons() {
+  let config = loadCompatConfig();
+  return config.templateTransforms;
+}
+
+export function looseModeSupport(): Transform {
+  const { resolver } = resolverLoader;
+  let opts: ResolverTransformOptions = {
+    appRoot: resolver.options.appRoot,
+    emberVersion: resolver.options.emberVersion,
+  };
+  return [require.resolve('./resolver-transform'), opts];
+}
+
+export function templateMacros() {
+  let config = loadCompatConfig();
+  return config.templateMacros;
+}
+
+export function babelMacros() {
+  let config = loadCompatConfig();
+  return config.babelMacros;
+}
+
+export function adjustImports() {
+  let pluginConfig: AdjustImportsOptions = {
+    appRoot: resolverLoader.resolver.options.appRoot,
+  };
+  return [require.resolve('./babel-plugin-adjust-imports'), pluginConfig];
+}
+
+export function oldDebugMacros(): PluginItem[] {
+  let debugMacros = require.resolve('babel-plugin-debug-macros');
+  return [
+    [
+      debugMacros,
+      {
+        flags: [
+          {
+            source: '@glimmer/env',
+            flags: {
+              DEBUG: true,
+              CI: false,
+            },
+          },
+        ],
+        debugTools: {
+          isDebug: true,
+          source: '@ember/debug',
+          assertPredicateIndex: 1,
+        },
+        externalizeHelpers: {
+          module: '@ember/debug',
+        },
+      },
+      '@ember/debug stripping',
+    ],
+    [
+      debugMacros,
+      {
+        externalizeHelpers: {
+          module: '@ember/application/deprecations',
+        },
+        debugTools: {
+          isDebug: true,
+          source: '@ember/application/deprecations',
+          assertPredicateIndex: 1,
+        },
+      },
+      '@ember/application/deprecations stripping',
+    ],
+  ];
+}
+
+export function templateColocation(): PluginItem {
+  let colocationOptions: TemplateColocationPluginOptions = {
+    appRoot: resolverLoader.resolver.options.appRoot,
+
+    // This extra weirdness is a compromise in favor of build performance.
+    //
+    // 1. When auto-upgrading an addon from v1 to v2, we definitely want to
+    //    run any custom AST transforms in stage1.
+    //
+    // 2. In general case, AST transforms are allowed to manipulate Javascript
+    //    scope. This means that running transforms -- even when we're doing
+    //    source-to-source compilation that emits handlebars and not wire
+    //    format -- implies changing .hbs files into .js files.
+    //
+    // 3. So stage1 may need to rewrite .hbs to .hbs.js (to avoid colliding
+    //    with an existing co-located .js file).
+    //
+    // 4. But stage1 doesn't necessarily want to run babel over the
+    //    corresponding JS file. Most of the time, that's just an
+    //    unnecessarily expensive second parse. (We only run it in stage1 to
+    //    eliminate an addon's custom babel plugins, and many addons don't
+    //    have any.)
+    //
+    // 5. Therefore, the work of template-colocation gets defered until here,
+    //    and it may see co-located templates named `.hbs.js` instead of the
+    //    usual `.hbs.
+    templateExtensions: ['.hbs', '.hbs.js'],
+
+    // All of the above only applies to auto-upgraded packages that were
+    // authored in v1. V2 packages don't get any of this complexity, they're
+    // supposed to take care of colocating their own templates explicitly.
+    packageGuard: true,
+  };
+  return [templateColocationPluginPath, colocationOptions];
+}
+
+export function babelCompatSupport(): PluginItem[] {
+  return [...babelMacros(), adjustImports(), ...oldDebugMacros(), templateColocation(), ...pluginsFromV1Addons()];
+}
+
+export function templateCompatSupport(): Transform[] {
+  return [...transformsFromV1Addons(), ...templateMacros(), looseModeSupport()];
+}