Merge pull request #7473 from webpack/feat/optional-catch-binding

Add support for ECMAScript 2019

lib/Parser.js

@@ -23,7 +23,7 @@ const joinRanges = (startRange, endRange) => {
 const defaultParserOptions = {
 	ranges: true,
 	locations: true,
-	ecmaVersion: 2018,
+	ecmaVersion: 2019,
 	sourceType: "module",
 	onComment: null,
 	plugins: {
@@ -34,6 +34,8 @@ const defaultParserOptions = {
 // regexp to match at lease one "magic comment"
 const webpackCommentRegExp = new RegExp(/(^|\W)webpack[A-Z]{1,}[A-Za-z]{1,}:/);
 
+const EMPTY_ARRAY = [];
+
 const EMPTY_COMMENT_OPTIONS = {
 	options: null,
 	errors: null
@@ -1356,7 +1358,11 @@ class Parser extends Tapable {
 	}
 
 	walkCatchClause(catchClause) {
-		this.inScope([catchClause.param], () => {
+		// Error binding is optional in catch clause since ECMAScript 2019
+		const errorBinding =
+			catchClause.param === null ? EMPTY_ARRAY : [catchClause.param];
+
+		this.inScope(errorBinding, () => {
 			this.prewalkStatement(catchClause.body);
 			this.walkStatement(catchClause.body);
 		});

package.json

@@ -10,7 +10,7 @@
     "@webassemblyjs/wasm-edit": "1.5.11",
     "@webassemblyjs/wasm-opt": "1.5.11",
     "@webassemblyjs/wasm-parser": "1.5.11",
-    "acorn": "^5.0.0",
+    "acorn": "^5.6.2",
     "acorn-dynamic-import": "^3.0.0",
     "ajv": "^6.1.0",
     "ajv-keywords": "^3.1.0",

test/Parser.unittest.js

@@ -618,4 +618,19 @@ describe("Parser", () => {
 			});
 		});
 	});
+
+	describe("optional catch binding support", () => {
+		describe("should accept", () => {
+			const cases = {
+				"optional binding": "try {} catch {}"
+			};
+			Object.keys(cases).forEach(name => {
+				const expr = cases[name];
+				it(name, () => {
+					const actual = Parser.parse(expr);
+					expect(typeof actual).toBe("object");
+				});
+			});
+		});
+	});
 });

test/cases/parsing/optional-catch-binding/index.js

@@ -0,0 +1,5 @@
+import f from "./module";
+
+it("should support optional catch binding", () => {
+	expect(f()).toBe(true);
+});

test/cases/parsing/optional-catch-binding/module.js

@@ -0,0 +1,7 @@
+export default function() {
+	try {
+		throw new Error();
+	} catch {
+		return true;
+	}
+};

test/cases/parsing/optional-catch-binding/test.filter.js

@@ -0,0 +1,9 @@
+const supportsOptionalCatchBinding = require("../../../helpers/supportsOptionalCatchBinding");
+
+module.exports = function(config) {
+	// XXX: Disable this test if UglifyJS is used because it does not support ES 2019
+	if (config.mode === "production") {
+		return false;
+	}
+	return supportsOptionalCatchBinding();
+};

test/helpers/supportsOptionalCatchBinding.js

@@ -0,0 +1,8 @@
+module.exports = function supportsOptionalCatchBinding() {
+	try {
+		eval("try {} catch {}");
+		return true;
+	} catch(e) {
+		return false;
+	}
+};

yarn.lock

@@ -234,9 +234,9 @@ acorn@^4.0.4, acorn@~4.0.2:
   version "4.0.13"
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-4.0.13.tgz#105495ae5361d697bd195c825192e1ad7f253787"
 
-acorn@^5.0.0, acorn@^5.3.0, acorn@^5.5.0:
-  version "5.5.3"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.5.3.tgz#f473dd47e0277a08e28e9bec5aeeb04751f0b8c9"
+acorn@^5.0.0, acorn@^5.3.0, acorn@^5.5.0, acorn@^5.6.2:
+  version "5.6.2"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.6.2.tgz#b1da1d7be2ac1b4a327fb9eab851702c5045b4e7"
 
 ajv-keywords@^2.1.0:
   version "2.1.1"