Use babel-generator to regenerate enhanced assertion statements

Fixes #1513.

lib/enhance-assert.js

@@ -1,6 +1,7 @@
 'use strict';
 const concordance = require('concordance');
 const dotProp = require('dot-prop');
+const generate = require('babel-generator').default;
 const concordanceOptions = require('./concordance-options').default;
 
 // When adding patterns, don't forget to add to
@@ -15,31 +16,16 @@ const PATTERNS = [
 	't.notRegex(contents, regex, [message])'
 ];
 
-const isRangeMatch = (a, b) => {
-	return (a[0] === b[0] && a[1] === b[1]) ||
-		(a[0] > b[0] && a[0] < b[1]) ||
-		(a[1] > b[0] && a[1] < b[1]);
-};
-
-const computeStatement = (tokens, range) => {
-	return tokens
-		.filter(token => isRangeMatch(token.range, range))
-		.map(token => token.value === undefined ? token.type.label : token.value)
-		.join('');
-};
-
+const computeStatement = node => generate(node, {quotes: 'single'}).code;
 const getNode = (ast, path) => dotProp.get(ast, path.replace(/\//g, '.'));
 
 const formatter = context => {
 	const ast = JSON.parse(context.source.ast);
-	const tokens = JSON.parse(context.source.tokens);
 	const args = context.args[0].events;
-
 	return args
 		.map(arg => {
-			const range = getNode(ast, arg.espath).range;
-			const statement = computeStatement(tokens, range);
-
+			const node = getNode(ast, arg.espath);
+			const statement = computeStatement(node);
 			const formatted = concordance.format(arg.value, concordanceOptions);
 			return [statement, formatted];
 		})

package.json

@@ -107,6 +107,7 @@
 		"auto-bind": "^1.1.0",
 		"ava-init": "^0.2.0",
 		"babel-core": "^6.17.0",
+		"babel-generator": "^6.26.0",
 		"bluebird": "^3.0.0",
 		"caching-transform": "^1.0.0",
 		"chalk": "^2.0.1",

test/api.js

@@ -371,6 +371,43 @@ function generateTests(prefix, apiCreator) {
 			});
 	});
 
+	test(`${prefix} enhanced assertion formatting necessary whitespace and empty strings`, t => {
+		const expected = [
+			[
+				/foo === '' && '' === foo/,
+				/foo === ''/,
+				/foo/
+			],
+			[
+				/new Object\(foo\) instanceof Object/,
+				/Object/,
+				/new Object\(foo\)/,
+				/foo/
+			],
+			[
+				/\[foo].filter\(item => {\n\s+return item === 'bar';\n}\).length > 0/,
+				/\[foo].filter\(item => {\n\s+return item === 'bar';\n}\).length/,
+				/\[foo].filter\(item => {\n\s+return item === 'bar';\n}\)/,
+				/\[foo]/,
+				/foo/
+			]
+		];
+
+		t.plan(14);
+		const api = apiCreator();
+		return api.run([path.join(__dirname, 'fixture/enhanced-assertion-formatting.js')])
+			.then(result => {
+				t.is(result.errors.length, 3);
+				t.is(result.passCount, 0);
+
+				result.errors.forEach((error, errorIndex) => {
+					error.error.statements.forEach((statement, statementIndex) => {
+						t.match(statement[0], expected[errorIndex][statementIndex]);
+					});
+				});
+			});
+	});
+
 	test(`${prefix} stack traces for exceptions are corrected using a source map file (cache off)`, t => {
 		t.plan(4);
 

test/fixture/enhanced-assertion-formatting.js

@@ -0,0 +1,21 @@
+import test from '../..';
+
+const foo = 'foo';
+
+test('fails with multiple empty string expressions and mixed quotes', t => {
+	// eslint-disable-next-line quotes, yoda
+	t.true(foo === '' && "" === foo);
+});
+
+test('fails with "instanceof" expression', t => {
+	// eslint-disable-next-line no-new-object
+	t.false(new Object(foo) instanceof Object);
+});
+
+test('fails with multiple lines', t => {
+	t.true(
+		[foo].filter(item => {
+			return item === 'bar';
+		}).length > 0
+	);
+});