Support disabling of the Babel pipeline

Set babel=false to disable AVA's default test compilation. *Also* set
compileEnhancements=false to disable the Babel pipeline altogether.

Fixes #1556.

Author: novemberborn

api.js

@@ -57,10 +57,13 @@ class Api extends EventEmitter {
 	}
 
 	_runFile(file, runStatus, execArgv) {
-		const hash = this.precompiler.precompileFile(file);
-		const precompiled = Object.assign({}, this._precompiledHelpers);
-		const resolvedfpath = fs.realpathSync(file);
-		precompiled[resolvedfpath] = hash;
+		const precompiled = {};
+		if (this.precompiler) {
+			Object.assign(precompiled, this._precompiledHelpers);
+			const hash = this.precompiler.precompileFile(file);
+			const resolvedfpath = fs.realpathSync(file);
+			precompiled[resolvedfpath] = hash;
+		}
 
 		const options = Object.assign({}, this.options, {precompiled});
 		if (runStatus.updateSnapshots) {
@@ -120,16 +123,21 @@ class Api extends EventEmitter {
 		const compileEnhancements = this.options.compileEnhancements !== false;
 		return babelConfigHelper.build(this.options.projectDir, cacheDir, this.options.babelConfig, compileEnhancements)
 			.then(result => {
-				this.precompiler = new CachingPrecompiler({
-					path: cacheDir,
-					getBabelOptions: result.getOptions,
-					babelCacheKeys: result.cacheKeys
-				});
+				if (result) {
+					this.precompiler = new CachingPrecompiler({
+						path: cacheDir,
+						getBabelOptions: result.getOptions,
+						babelCacheKeys: result.cacheKeys
+					});
+				}
 			});
 	}
 
 	_precompileHelpers() {
 		this._precompiledHelpers = {};
+		if (!this.precompiler) {
+			return Promise.resolve();
+		}
 
 		// Assumes the tests only load helpers from within the `resolveTestsFrom`
 		// directory. Without arguments this is the `projectDir`, else it's
@@ -138,7 +146,7 @@ class Api extends EventEmitter {
 		// processes, avoiding the need for precompilation.
 		return new AvaFiles({cwd: this.options.resolveTestsFrom})
 			.findTestHelpers()
-			.map(file => { // eslint-disable-line array-callback-return
+			.each(file => { // eslint-disable-line array-callback-return
 				const hash = this.precompiler.precompileFile(file);
 				this._precompiledHelpers[file] = hash;
 			});

docs/recipes/babel.md

@@ -61,6 +61,19 @@ You can disable AVA's stage-4 preset:
 
 Note that this *does not* stop AVA from compiling your test files using Babel.
 
+## Disable AVA's Babel pipeline
+
+You can completely disable AVA's use of Babel:
+
+```json
+{
+	"ava": {
+		"babel": false,
+		"compileEnhancements": false
+	}
+}
+```
+
 ## Use Babel polyfills
 
 AVA lets you write your tests using new JavaScript syntax, even on Node.js versions that otherwise wouldn't support it. However, it doesn't add or modify built-ins of your current environment. Using AVA would, for example, not provide modern features such as `Object.entries()` to an underlying Node.js 6 environment.

lib/babel-config.js

@@ -14,6 +14,10 @@ const syntaxObjectRestSpreadPath = require.resolve('@babel/plugin-syntax-object-
 const transformTestFilesPath = require.resolve('@ava/babel-preset-transform-test-files');
 
 function validate(conf) {
+	if (conf === false) {
+		return null;
+	}
+
 	if (conf === undefined) {
 		return {testOptions: {}};
 	}
@@ -77,6 +81,10 @@ function resolveOptions(baseConfig, cache, envName, optionsFile, verifierFile) {
 }
 
 function build(projectDir, cacheDir, userOptions, compileEnhancements) {
+	if (!userOptions && !compileEnhancements) {
+		return Promise.resolve(null);
+	}
+
 	// Note that Babel ignores empty string values, even for NODE_ENV. Here
 	// default to 'test' unless NODE_ENV is defined, in which case fall back to
 	// Babel's default of 'development' if it's empty.
@@ -102,24 +110,27 @@ function build(projectDir, cacheDir, userOptions, compileEnhancements) {
 	const baseOptions = {
 		babelrc: false,
 		plugins: [],
-		presets: [
-			stage4Path // Always apply the stage-4 preset.
-		]
+		presets: []
 	};
 
-	// By default extend the project's Babel configuration, but allow this to be
-	// disabled through userOptions.
-	if (userOptions.testOptions.babelrc !== false) {
-		baseOptions.babelrc = true;
-	}
-	if (userOptions.testOptions.extends) {
-		baseOptions.extends = userOptions.testOptions.extends;
-	}
+	if (userOptions) {
+		// Always apply the stage-4 preset.
+		baseOptions.presets.push(stage4Path);
 
-	// Include object rest spread support for Node.js versions that support it
-	// natively.
-	if (semver.satisfies(process.versions.node, '>= 8.3.0')) {
-		baseOptions.plugins.push(syntaxObjectRestSpreadPath);
+		// By default extend the project's Babel configuration, but allow this to be
+		// disabled through userOptions.
+		if (userOptions.testOptions.babelrc !== false) {
+			baseOptions.babelrc = true;
+		}
+		if (userOptions.testOptions.extends) {
+			baseOptions.extends = userOptions.testOptions.extends;
+		}
+
+		// Include object rest spread support for Node.js versions that support it
+		// natively.
+		if (semver.satisfies(process.versions.node, '>= 8.3.0')) {
+			baseOptions.plugins.push(syntaxObjectRestSpreadPath);
+		}
 	}
 
 	const baseConfig = configManager.createConfig({
@@ -131,7 +142,7 @@ function build(projectDir, cacheDir, userOptions, compileEnhancements) {
 	});
 
 	let intermediateConfig = baseConfig;
-	if (Object.keys(userOptions.testOptions).length > 0) {
+	if (userOptions && Object.keys(userOptions.testOptions).length > 0) {
 		// At this level, babelrc *must* be false.
 		const options = Object.assign({}, userOptions.testOptions, {babelrc: false});
 		// Any extends option has been applied in baseConfig.

test/cli.js

@@ -824,3 +824,43 @@ test('doesn\'t set NODE_ENV when it is set', t => {
 		t.end();
 	});
 });
+
+test('skips test file compilation when babel=false and compileEnhancements=false', t => {
+	execCli(['import.js'], {dirname: 'fixture/no-babel-compilation'}, (err, stdout, stderr) => {
+		t.ok(err);
+		t.match(stderr, /SyntaxError: Unexpected (reserved word|token import)/);
+		t.end();
+	});
+});
+
+test('skips helper file compilation when babel=false and compileEnhancements=false', t => {
+	execCli(['require-helper.js'], {dirname: 'fixture/no-babel-compilation'}, (err, stdout, stderr) => {
+		t.ifError(err);
+		t.match(stderr, /1 passed/);
+		t.end();
+	});
+});
+
+test('no power-assert when babel=false and compileEnhancements=false', t => {
+	execCli(['no-power-assert.js'], {dirname: 'fixture/no-babel-compilation'}, (err, stdout, stderr) => {
+		t.ok(err);
+		t.notMatch(stripAnsi(stderr), /bool\n.*=> false/);
+		t.end();
+	});
+});
+
+test('skips stage-4 transform when babel=false and compileEnhancements=true', t => {
+	execCli(['import.js'], {dirname: 'fixture/just-enhancement-compilation'}, (err, stdout, stderr) => {
+		t.ok(err);
+		t.match(stderr, /SyntaxError: Unexpected (reserved word|token import)/);
+		t.end();
+	});
+});
+
+test('power-assert when babel=false and compileEnhancements=true', t => {
+	execCli(['power-assert.js'], {dirname: 'fixture/just-enhancement-compilation'}, (err, stdout, stderr) => {
+		t.ok(err);
+		t.match(stripAnsi(stderr), /bool\n.*=> false/);
+		t.end();
+	});
+});

test/fixture/just-enhancement-compilation/_helper.js

@@ -0,0 +1 @@
+import dependency from './dependency'; // eslint-disable-line no-unused-vars

test/fixture/just-enhancement-compilation/dependency.js

@@ -0,0 +1 @@
+import dependency from './dependency'; // eslint-disable-line no-unused-vars

test/fixture/just-enhancement-compilation/import.js

@@ -0,0 +1,6 @@
+{
+	"ava": {
+		"babel": false,
+		"compileEnhancements": true
+	}
+}

test/fixture/just-enhancement-compilation/package.json

@@ -0,0 +1,8 @@
+'use strict';
+
+const test = require('../../../');
+
+test(t => {
+	const bool = false;
+	t.true(bool);
+});

test/fixture/just-enhancement-compilation/power-assert.js

@@ -0,0 +1 @@
+import dependency from './dependency'; // eslint-disable-line no-unused-vars

test/fixture/no-babel-compilation/_helper.js

@@ -0,0 +1 @@
+import dependency from './dependency'; // eslint-disable-line no-unused-vars

test/fixture/no-babel-compilation/dependency.js

@@ -0,0 +1,8 @@
+'use strict';
+
+const test = require('../../../');
+
+test(t => {
+	const bool = false;
+	t.true(bool);
+});

test/fixture/no-babel-compilation/import.js

@@ -0,0 +1,6 @@
+{
+	"ava": {
+		"babel": false,
+		"compileEnhancements": false
+	}
+}

test/fixture/no-babel-compilation/no-power-assert.js

@@ -0,0 +1,7 @@
+'use strict';
+
+const test = require('../../../');
+
+test(t => {
+	t.throws(() => require('./_helper'), SyntaxError);
+});