Use Babel directly

Simplify test and helper file precompilation. Remove alternate Babel
options resolution, at the cost of false cache positives.

Fixes #1732
Fixes #1667
Fixes #1789

api.js

@@ -10,9 +10,9 @@ const debounce = require('lodash.debounce');
 const Bluebird = require('bluebird');
 const getPort = require('get-port');
 const arrify = require('arrify');
+const makeDir = require('make-dir');
 const ms = require('ms');
-const babelConfigHelper = require('./lib/babel-config');
-const CachingPrecompiler = require('./lib/caching-precompiler');
+const babelPipeline = require('./lib/babel-pipeline');
 const Emittery = require('./lib/emittery');
 const RunStatus = require('./lib/run-status');
 const AvaFiles = require('./lib/ava-files');
@@ -37,6 +37,8 @@ class Api extends Emittery {
 
 		this.options = Object.assign({match: []}, options);
 		this.options.require = resolveModules(this.options.require);
+
+		this._precompiler = null;
 	}
 
 	run(files, runtimeOptions) {
@@ -117,11 +119,10 @@ class Api extends Emittery {
 					}
 				});
 
-				// Set up a fresh precompiler for each test run.
 				return emittedRun
 					.then(() => this._setupPrecompiler())
 					.then(precompilation => {
-						if (!precompilation) {
+						if (!precompilation.precompileFile) {
 							return null;
 						}
 
@@ -132,11 +133,13 @@ class Api extends Emittery {
 						return new AvaFiles({cwd: this.options.resolveTestsFrom}).findTestHelpers().then(helpers => {
 							return {
 								cacheDir: precompilation.cacheDir,
-								map: files.concat(helpers).reduce((acc, file) => {
+								map: [...files, ...helpers].reduce((acc, file) => {
 									try {
 										const realpath = fs.realpathSync(file);
-										const hash = precompilation.precompiler.precompileFile(realpath);
-										acc[realpath] = hash;
+										const cachePath = precompilation.precompileFile(realpath);
+										if (cachePath) {
+											acc[realpath] = cachePath;
+										}
 									} catch (err) {
 										throw Object.assign(err, {file});
 									}
@@ -204,31 +207,23 @@ class Api extends Emittery {
 	}
 
 	_setupPrecompiler() {
+		if (this._precompiler) {
+			return this._precompiler;
+		}
+
 		const cacheDir = this.options.cacheEnabled === false ?
 			uniqueTempDir() :
 			path.join(this.options.projectDir, 'node_modules', '.cache', 'ava');
 
-		return this._buildBabelConfig(cacheDir).then(result => {
-			return result ? {
-				cacheDir,
-				precompiler: new CachingPrecompiler({
-					path: cacheDir,
-					getBabelOptions: result.getOptions,
-					babelCacheKeys: result.cacheKeys
-				})
-			} : null;
-		});
-	}
-
-	_buildBabelConfig(cacheDir) {
-		if (this._babelConfigPromise) {
-			return this._babelConfigPromise;
-		}
+		// Ensure cacheDir exists
+		makeDir.sync(cacheDir);
 
-		const compileEnhancements = this.options.compileEnhancements !== false;
-		const promise = babelConfigHelper.build(this.options.projectDir, cacheDir, this.options.babelConfig, compileEnhancements);
-		this._babelConfigPromise = promise;
-		return promise;
+		const {projectDir, babelConfig, compileEnhancements} = this.options;
+		this._precompiler = {
+			cacheDir,
+			precompileFile: babelPipeline.build(projectDir, cacheDir, babelConfig, compileEnhancements !== false)
+		};
+		return this._precompiler;
 	}
 
 	_computeForkExecArgv() {

docs/recipes/babel.md

@@ -2,14 +2,12 @@
 
 Translations: [Français](https://github.com/avajs/ava-docs/blob/master/fr_FR/docs/recipes/babel.md)
 
-AVA uses [Babel 7](https://babeljs.io) so you can use the latest JavaScript syntax in your tests. We do this by compiling test and helper files using our [`@ava/stage-4`](https://github.com/avajs/babel-preset-stage-4) preset. We also use a [second preset](https://github.com/avajs/babel-preset-transform-test-files) to enable [enhanced assertion messages](../../readme#enhanced-assertion-messages) and detect improper use of `t.throws()` assertions.
+AVA uses [Babel 7](https://babeljs.io) so you can use the latest JavaScript syntax in your tests. We do this by compiling test and helper files using our [`@ava/stage-4`](https://github.com/avajs/babel-preset-stage-4) preset. We also use a [second preset, `@ava/transform-test-files`](https://github.com/avajs/babel-preset-transform-test-files) to enable [enhanced assertion messages](../../readme#enhanced-assertion-messages) and detect improper use of `t.throws()` assertions.
 
-By default our Babel pipeline is applied to test and helper files ending in `.js`. If your project uses Babel then we'll automatically compile these files using your project's Babel configuration.
+By default our Babel pipeline is applied to test and helper files ending in `.js`. If your project uses Babel then we'll automatically compile these files using your project's Babel configuration. The `@ava/transform-helper-files` preset is applied first, and the `@ava/stage-4` last.
 
 If you are using Babel for your source files then you must also [configure source compilation](#compile-sources).
 
-AVA only looks for Babel configuration files in your project directory. That is, `.babelrc` or `.babelrc.js` files next to your `package.json` file, or the `package.json` file itself.
-
 ## Customize how AVA compiles your test files
 
 You can override the default Babel configuration AVA uses for test file compilation in `package.json`. For example, the configuration below adds support for JSX syntax and stage 3 features:
@@ -29,6 +27,16 @@ You can override the default Babel configuration AVA uses for test file compilat
 
 All `.babelrc` options are allowed inside the `testOptions` object.
 
+## Reset AVA's cache
+
+AVA caches the compiled test and helper files. It automatically recompiles these files when you change them, however it can't detect updates of your Babel plugins and presets, or changes to your Babel configuration files.
+
+Instead run the following to reset AVA's cache when you change the configuration or update plugins or presets:
+
+```console
+$ npx ava --reset-cache
+```
+
 ## Make AVA skip your project's Babel options
 
 You may not want AVA to use your project's Babel options, for example if your project is relying on Babel 6. You can set the `babelrc` option to `false`:
@@ -65,6 +73,8 @@ You can disable AVA's stage-4 preset:
 
 Note that this *does not* stop AVA from compiling your test files using Babel.
 
+You **must** disable the preset by configuring it in the `testOptions`. AVA will still apply the preset if you configure it in other files (for instance a `.babelrc` file). This is [due to a Babel issue](https://github.com/babel/babel/issues/7920).
+
 ## Preserve ES module syntax
 
 By default AVA's stage-4 preset will convert ES module syntax to CommonJS. This can be disabled:
@@ -83,6 +93,8 @@ By default AVA's stage-4 preset will convert ES module syntax to CommonJS. This
 }
 ```
 
+You **must** configure the preset in the `testOptions` in order to preserve the ES module syntax. AVA will still apply the preset if you configure it in other files (for instance a `.babelrc` file). This is [due to a Babel issue](https://github.com/babel/babel/issues/7920).
+
 You'll have to use the [`esm`](https://github.com/standard-things/esm) module so that AVA can still load your test files. [See our recipe for details](./es-modules.md).
 
 ## Disable AVA's Babel pipeline