Drive all template compilation from babel

Classically, standalone templates got a dedicated preprocessor that had nothing to do with Javascript transpilation.

Later came inline templates that appear inside Javascript. Those were handled as a totally separate code path from the standalone templates. To this day, there are two different code paths for handling these two cases.

But at this point, templates-inside-javascript are the foundational primitive that is aligned with [where Ember is heading](emberjs/rfcs#779), because they have access to Javascript scope and this solves a lot of problems.

We can treat standalone HBS as just a degenerate kind of JS that is easily up-compiled via a pure function, allowing them to go down the Javascript code path and allowing us to drop all the old code path.

This also makes it easier to support new features like [AST transforms that can manipulate Javascript scope](emberjs/babel-plugin-ember-template-compilation#5).

Embroider already [implemented this same pattern](embroider-build/embroider#1010).

Author: ef4

lib/template-compiler-plugin.js

@@ -1,155 +1,38 @@
 'use strict';
 
-const path = require('path');
-const utils = require('./utils');
 const Filter = require('broccoli-persistent-filter');
-const crypto = require('crypto');
-const stringify = require('json-stable-stringify');
-const stripBom = require('strip-bom');
-
-function rethrowBuildError(error) {
-  if (!error) {
-    throw new Error('Unknown Error');
-  }
-
-  if (typeof error === 'string') {
-    throw new Error('[string exception]: ' + error);
-  } else {
-    // augment with location and type information and re-throw.
-    error.type = 'Template Compiler Error';
-    error.location = error.location && error.location.start;
-
-    throw error;
-  }
-}
+const jsStringEscape = require('js-string-escape');
 
 class TemplateCompiler extends Filter {
-  constructor(inputTree, _options, requiresModuleApiPolyfill = true) {
-    let options = _options || {};
-
+  constructor(inputTree, options = {}) {
     if (!('persist' in options)) {
       options.persist = true;
     }
-
     super(inputTree, options);
-
-    this.options = options;
-    this.inputTree = inputTree;
-    this.requiresModuleApiPolyfill = requiresModuleApiPolyfill;
-
-    // TODO: do we need this?
-    this.precompile = this.options.templateCompiler.precompile;
-
-    let { templateCompiler, EmberENV } = options;
-
-    utils.initializeEmberENV(templateCompiler, EmberENV);
   }
 
   baseDir() {
     return __dirname;
   }
 
   processString(string, relativePath) {
-    let srcDir = this.inputPaths[0];
-    let srcName = path.join(srcDir, relativePath);
-
-    try {
-      // we have to reverse these for reasons that are a bit bonkers. the initial
-      // version of this system used `registeredPlugin` from
-      // `ember-template-compiler.js` to set up these plugins (because Ember ~ 1.13
-      // only had `registerPlugin`, and there was no way to pass plugins directly
-      // to the call to `compile`/`precompile`). calling `registerPlugin`
-      // unfortunately **inverted** the order of plugins (it essentially did
-      // `PLUGINS = [plugin, ...PLUGINS]`).
-      //
-      // sooooooo...... we are forced to maintain that **absolutely bonkers** ordering
-      let astPlugins = this.options.plugins ? [...this.options.plugins.ast].reverse() : [];
-
-      let precompiled = this.options.templateCompiler.precompile(stripBom(string), {
-        contents: string,
-        isProduction: this.options.isProduction,
-        moduleName: relativePath,
-        parseOptions: {
-          srcName: srcName,
-        },
-
-        // intentionally not using `plugins: this.options.plugins` here
-        // because if we do, Ember will mutate the shared plugins object (adding
-        // all of the built in AST transforms into plugins.ast, which breaks
-        // persistent caching)
-        plugins: {
-          ast: astPlugins,
-        },
-      });
-
-      if (this.options.dependencyInvalidation) {
-        let plugins = pluginsWithDependencies(this.options.plugins.ast);
-        let dependencies = [];
-        for (let i = 0; i < plugins.length; i++) {
-          let pluginDeps = plugins[i].getDependencies(relativePath);
-          dependencies = dependencies.concat(pluginDeps);
-        }
-        this.dependencies.setDependencies(relativePath, dependencies);
-      }
-
-      if (this.requiresModuleApiPolyfill) {
-        return `export default Ember.HTMLBars.template(${precompiled});`;
-      } else {
-        return `import { createTemplateFactory } from '@ember/template-factory';\n\nexport default createTemplateFactory(${precompiled});`;
-      }
-    } catch (error) {
-      rethrowBuildError(error);
+    return [
+      `import { hbs } from 'ember-cli-htmlbars';`,
+      `export default hbs('${jsStringEscape(string)}', { moduleName: '${jsStringEscape(
+        relativePath
+      )}' });`,
+      '',
+    ].join('\n');
+  }
+
+  getDestFilePath(relativePath) {
+    if (relativePath.endsWith('.hbs')) {
+      return relativePath.replace(/\.hbs$/, '.js');
     }
   }
-
-  _buildOptionsForHash() {
-    let strippedOptions = {};
-
-    for (let key in this.options) {
-      if (key !== 'templateCompiler') {
-        strippedOptions[key] = this.options[key];
-      }
-    }
-
-    strippedOptions._requiresModuleApiPolyfill = this.requiresModuleApiPolyfill;
-
-    return strippedOptions;
-  }
-
-  optionsHash() {
-    if (!this._optionsHash) {
-      let templateCompilerCacheKey = utils.getTemplateCompilerCacheKey(
-        this.options.templateCompilerPath
-      );
-
-      this._optionsHash = crypto
-        .createHash('md5')
-        .update(stringify(this._buildOptionsForHash()), 'utf8')
-        .update(templateCompilerCacheKey, 'utf8')
-        .digest('hex');
-    }
-
-    return this._optionsHash;
-  }
-
-  cacheKeyProcessString(string, relativePath) {
-    return (
-      this.optionsHash() + Filter.prototype.cacheKeyProcessString.call(this, string, relativePath)
-    );
-  }
 }
 
 TemplateCompiler.prototype.extensions = ['hbs', 'handlebars'];
 TemplateCompiler.prototype.targetExtension = 'js';
 
-function pluginsWithDependencies(registeredPlugins) {
-  let found = [];
-  for (let i = 0; i < registeredPlugins.length; i++) {
-    if (registeredPlugins[i].getDependencies) {
-      found.push(registeredPlugins[i]);
-    }
-  }
-  return found;
-}
-
 module.exports = TemplateCompiler;

lib/utils.js

@@ -190,34 +190,6 @@ function getTemplateCompiler(templateCompilerPath, EmberENV = {}) {
   return context.module.exports;
 }
 
-function initializeEmberENV(templateCompiler, EmberENV) {
-  if (!templateCompiler || !EmberENV) {
-    return;
-  }
-
-  let props;
-
-  if (EmberENV.FEATURES) {
-    props = Object.keys(EmberENV.FEATURES);
-
-    props.forEach((prop) => {
-      templateCompiler._Ember.FEATURES[prop] = EmberENV.FEATURES[prop];
-    });
-  }
-
-  if (EmberENV) {
-    props = Object.keys(EmberENV);
-
-    props.forEach((prop) => {
-      if (prop === 'FEATURES') {
-        return;
-      }
-
-      templateCompiler._Ember.ENV[prop] = EmberENV[prop];
-    });
-  }
-}
-
 function setup(pluginInfo, options) {
   let projectConfig = options.projectConfig || {};
   let templateCompilerPath = options.templateCompilerPath;
@@ -374,13 +346,9 @@ function setupPlugins(wrappers) {
 
 module.exports = {
   buildOptions,
-  initializeEmberENV,
   setup,
-  makeCacheKey,
   setupPlugins,
   isColocatedBabelPluginRegistered,
   isInlinePrecompileBabelPluginRegistered,
   buildParalleizedBabelPlugin,
-  getTemplateCompiler,
-  getTemplateCompilerCacheKey,
 };

node-tests/addon-test.js

@@ -87,8 +87,11 @@ describe('ember-cli-htmlbars addon', function () {
         yield output.build();
 
         expect(output.read()).to.deep.equal({
-          'hello.js':
-            'export default Ember.HTMLBars.template({"id":"pb4oG9l/","block":"[[[10,0],[12],[1,\\"Hello, World!\\"],[13]],[],false,[]]","moduleName":"hello.hbs","isStrictMode":false});',
+          'hello.js': [
+            `import { hbs } from 'ember-cli-htmlbars';`,
+            `export default hbs('<div>Hello, World!</div>', { moduleName: 'hello.hbs' });`,
+            '',
+          ].join('\n'),
         });
       })
     );