Fixed tests + added post compilation transform to ensure single argument arrow functions are not wrapped in parenthesis for their singular argument. (#169)

Author: kristoferbaxter

package.json

@@ -30,7 +30,7 @@
     "acorn": "6.1.1",
     "acorn-dynamic-import": "4.0.0",
     "acorn-walk": "6.1.1",
-    "google-closure-compiler": "20190215.0.1",
+    "google-closure-compiler": "20190325.0.0",
     "magic-string": "0.25.2",
     "temp-write": "3.4.0"
   },

src/transformers/arrow-function.ts

@@ -0,0 +1,60 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Transform, Range, TransformInterface } from '../types';
+import { TransformSourceDescription } from 'rollup';
+import MagicString from 'magic-string';
+import { ArrowFunctionExpression } from 'estree';
+import { parse, walk } from '../acorn';
+
+/**
+ * Closure Compiler will occasionally wrap ArrowFunctionExpression Parameters with additional parenthesis.
+ * e.g (a)=>a.foo() => a=>a.foo()
+ *
+ * @see https://astexplorer.net/#/gist/20d7fbe32292c6c9f303c1d9643885ec/6c97fabca987814cced795b8d3d078094e642264
+ */
+export default class ArrowFunctionTransform extends Transform implements TransformInterface {
+  /**
+   * @param code source to parse, and modify
+   * @return modified input source with computed literal keys
+   */
+  public async postCompilation(code: string): Promise<TransformSourceDescription> {
+    const source = new MagicString(code);
+    const program = parse(code);
+
+    walk.simple(program, {
+      ArrowFunctionExpression(arrowFunction: ArrowFunctionExpression) {
+        const functionRange: Range = arrowFunction.range as Range;
+        const params = arrowFunction.params;
+        if (params.length === 1) {
+          const identifier = params[0];
+          if ('name' in identifier) {
+            const paramRange: Range = params[0].range as Range;
+            if (functionRange[0] !== paramRange[0]) {
+              const bodyRange = arrowFunction.body.range as Range;
+              source.overwrite(functionRange[0], bodyRange[0], `${identifier.name}=>`);
+            }
+          }
+        }
+      },
+    });
+
+    return {
+      code: source.toString(),
+      map: source.generateMap().mappings,
+    };
+  }
+}

src/transformers/imports.ts

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import { Transform } from '../types';
+import { Transform, Range } from '../types';
 import { literalName, importLocalNames } from './parsing-utilities';
 import { TransformSourceDescription } from 'rollup';
 import MagicString from 'magic-string';
@@ -33,7 +33,7 @@ const HEADER = `/**
 
 interface RangedImport {
   type: string;
-  range: [number, number];
+  range: Range;
 }
 
 export default class ImportTransform extends Transform {
@@ -83,7 +83,7 @@ window['${DYNAMIC_IMPORT_REPLACEMENT}'] = ${DYNAMIC_IMPORT_REPLACEMENT};`;
     walk.simple(program, {
       async ImportDeclaration(node: ImportDeclaration) {
         const name = literalName(self.context, node.source);
-        const range: [number, number] = node.range ? [node.range[0], node.range[1]] : [0, 0];
+        const range: Range = node.range ? [node.range[0], node.range[1]] : [0, 0];
         self.importedExternalsSyntax[name] = code.slice(range[0], range[1]);
         source.remove(range[0], range[1]);
 
@@ -127,7 +127,7 @@ window['${DYNAMIC_IMPORT_REPLACEMENT}'] = ${DYNAMIC_IMPORT_REPLACEMENT};`;
     walk.simple(program, {
       Identifier(node: Identifier) {
         if (node.name === DYNAMIC_IMPORT_REPLACEMENT) {
-          const range: [number, number] = node.range ? [node.range[0], node.range[1]] : [0, 0];
+          const range: Range = node.range ? [node.range[0], node.range[1]] : [0, 0];
           source.overwrite(range[0], range[1], DYNAMIC_IMPORT_KEYWORD);
         }
       },

src/transforms.ts

@@ -22,6 +22,7 @@ import ExportTransform from './transformers/exports';
 import ImportTransform from './transformers/imports';
 import StrictTransform from './transformers/strict';
 import ConstTransform from './transformers/const';
+import ArrowFunctionTransform from './transformers/arrow-function';
 import { logSource } from './debug';
 
 /**
@@ -41,6 +42,7 @@ export const createTransforms = (
     new StrictTransform(context, options),
     new ExportTransform(context, options),
     new ImportTransform(context, options),
+    new ArrowFunctionTransform(context, options),
   ];
 };
 

src/types.ts

@@ -42,6 +42,8 @@ export const ALL_EXPORT_DECLARATIONS = [
   EXPORT_ALL_DECLARATION,
 ];
 
+export type Range = [number, number];
+
 export enum ExportClosureMapping {
   NAMED_FUNCTION = 0,
   NAMED_CLASS = 1,
@@ -58,7 +60,7 @@ export interface ExportNameToClosureMapping {
   [key: string]: {
     alias: string | null;
     type: ExportClosureMapping;
-    range: [number, number];
+    range: Range;
   };
 }
 

test/export-transpilation/fixtures/named-constant.esm.advanced.js

@@ -1 +1 @@
-var b=Symbol.for("smth");var isSmth=(a)=>a&&!!a[b];export{isSmth};
+var b=Symbol.for("smth");var isSmth=a=>a&&!!a[b];export{isSmth};

test/export-transpilation/fixtures/named-constant.esm.default.js

@@ -1 +1 @@
-var b=Symbol.for("smth");var isSmth=(a)=>a&&!!a[b];export{isSmth};
+var b=Symbol.for("smth");var isSmth=a=>a&&!!a[b];export{isSmth};

test/export-transpilation/fixtures/named-constant.esm.es5.js

@@ -116,7 +116,9 @@ function generate(shouldFail, category, name, codeSplit, formats, closureFlags)
           const output = await compile(optionKey, format);
 
           t.plan(output.length);
-          output.forEach(result => t.is(result.code, result.minified));
+          for (result of output) {
+            t.is(result.code, result.minified)
+          }
         },
       );
     }

test/generator.js

@@ -1 +1 @@
-'use strict';var wrapper=function(a){a.a=function(a){document.body.innerHTML="hello "+a};return a}({});
+'use strict';var wrapper=function(a){a.a=function(b){document.body.innerHTML="hello "+b};return a}({});