Provided Externs and Generated Externs Equally Applied (#50)

* Ensure provided externs are leveraged
* Ensure transformer externs are not overwritten by provided externs
* Remove pasted type
* Messaging for tests to clarify purpose

Author: kristoferbaxter

package-lock.json

@@ -80,23 +80,26 @@ export default function(
   transforms: Array<Transform> | null,
 ): [CompileOptions, string] {
   const mapFile = sync('');
-  const externs = (compileOptions: CompileOptions): Array<string> => {
-    if ('externs' in compileOptions) {
-      switch (typeof compileOptions.externs) {
-        case 'boolean':
-          return [];
-        case 'string':
-          return [compileOptions.externs as string];
-        default:
-          return compileOptions.externs as Array<string>;
-      }
+  let externs: Array<string> = [];
+
+  if ('externs' in compileOptions) {
+    switch (typeof compileOptions.externs) {
+      case 'boolean':
+        externs = [];
+        break;
+      case 'string':
+        externs = [compileOptions.externs as string];
+        break;
+      default:
+        externs = compileOptions.externs as Array<string>;
+        break;
     }
 
-    return [];
-  };
+    delete compileOptions.externs;
+  }
 
   const options = {
-    ...defaults(outputOptions, externs(compileOptions), transforms),
+    ...defaults(outputOptions, externs, transforms),
     ...compileOptions,
     js: sync(code),
     create_source_map: mapFile,

src/options.ts

@@ -0,0 +1,2 @@
+/** @externs */
+var x = '';

test/closure-config/fixtures/externs.js

@@ -0,0 +1,56 @@
+/**
+ * Copyright 2018 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 test from 'ava';
+import compile from '../../transpile/options';
+import path from 'path';
+import fs from 'fs';
+import util from 'util';
+const readFile = util.promisify(fs.readFile);
+
+const PROVIDED_EXTERN = path.resolve('test', 'closure-config', 'fixtures', 'externs.js');
+const IIFE_TRANSFORM_EXTERN_CONTENT = '/** @externs */ function wrapper(){}';
+
+const IifeTransform = class {
+  // Transforms have a public method `extern` that generates an extern
+  // if one is needed for the transform.
+  
+  // This test ensures the externs created by transforms are passed to
+  // closure compiler when the caller also passes externs.
+  extern() {
+    return IIFE_TRANSFORM_EXTERN_CONTENT;
+  }
+};
+
+test('when rollup configuration specifies externs, extern is leveraged', async t => {
+  t.plan(3);
+
+  const compilerOptionsExterns = compile({
+    externs: PROVIDED_EXTERN,
+  }, {
+    format: 'iife',
+    name: 'wrapper',
+  }, 'var x = 1;', [new IifeTransform()])[0].externs;
+
+  t.is(compilerOptionsExterns.length, 2);
+  t.true(compilerOptionsExterns.includes(PROVIDED_EXTERN));
+
+  // While we can use the path for the provided extern, we need to inspect the content of 
+  // the other extern to ensure it is the generated extern.
+  // Externs are passed as filepaths to Closure Compiler.
+  const fileContent = await readFile(compilerOptionsExterns.filter(path => path !== PROVIDED_EXTERN)[0], 'utf8');
+  t.true(fileContent === IIFE_TRANSFORM_EXTERN_CONTENT);
+});

test/closure-config/rollup-config-externs.js

@@ -0,0 +1,31 @@
+/**
+ * Copyright 2018 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 {generator, ESM_OUTPUT} from '../generator';
+const path = require('path');
+
+const EXTERNS = path.resolve('test', 'provided-externs', 'fixtures', 'class.externs.js');
+
+generator('provided-externs', 'class', [ESM_OUTPUT], {
+  default: {
+    externs: EXTERNS
+  },
+  advanced: {
+    externs: EXTERNS,
+    compilation_level: 'ADVANCED_OPTIMIZATIONS',
+    language_out: 'ECMASCRIPT_2015',
+  }
+});

test/provided-externs/class.js

@@ -0,0 +1 @@
+class a{constructor(b){this.a=b}console(){console.log(this.a)}}var Exported=a;export{Exported};

test/provided-externs/fixtures/class.esm.advanced.js

@@ -0,0 +1 @@
+class a{constructor(b){this.name_=b}console(){console.log(this.name_)}}var Exported=a;export{Exported};

test/provided-externs/fixtures/class.esm.default.js

@@ -0,0 +1,16 @@
+/** @externs */
+
+/**
+ * @constructor @struct
+ */
+var Exported = class {
+  /** 
+   * @param {!string} name
+   */
+  constructor(name) {}
+
+  /** 
+   * @return {string}
+   */
+  console() {}
+}

test/provided-externs/fixtures/class.externs.js

@@ -0,0 +1,18 @@
+export class Exported {
+  /** 
+   * @param {!string} name 
+   */
+  constructor(name) {
+    /**
+     * @private {!string}
+     */
+    this.name_ = name;
+  }
+
+  /**
+   * @return {string}
+   */
+  console() {
+    console.log(this.name_);
+  }
+}