Inline requires: Flow-type plugin and tests

Summary:
Ahead of making some changes/enhancements to `inline-requires-plugin`, make it type-safe.

Changelog: Internal

Reviewed By: vzaidman

Differential Revision: D61869704

fbshipit-source-id: 8d61d22fcffd66a28d4860dc596d4b22f685f977

flow-typed/npm/babel-plugin-tester_v6.x.x.js

@@ -0,0 +1,37 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict
+ * @format
+ */
+
+// Partial typings for babel-plugin-tester. Add APIs as you need them.
+
+declare module 'babel-plugin-tester' {
+  import typeof * as Babel from '@babel/core';
+  import type {BabelCoreOptions, PluginObj} from '@babel/core';
+
+  declare type PluginTesterOptions<TOpts = mixed, TState = mixed> = {
+    babelOptions?: BabelCoreOptions,
+    plugin: (babel: Babel) => PluginObj<TState>,
+    pluginOptions?: TOpts,
+    tests: $ReadOnly<{
+      [title: string]: $ReadOnly<{
+        code: string,
+        output?: string,
+        error?: string,
+        snapshot?: boolean,
+        ...
+      }>,
+    }>,
+  };
+
+  declare function pluginTester<TOpts = mixed, TState = mixed>(
+    opts: PluginTesterOptions<TOpts, TState>,
+  ): void;
+
+  declare module.exports: typeof pluginTester;
+}

packages/metro-transform-plugins/src/__tests__/inline-requires-plugin-test.js

@@ -5,18 +5,20 @@
  * LICENSE file in the root directory of this source tree.
  *
  * @format
+ * @flow strict-local
  */
 
-/* eslint-disable max-len */
-
 'use strict';
 
+import type {PluginOptions, State} from '../inline-requires-plugin';
+
 const inlineRequiresPlugin = require('../inline-requires-plugin');
 const validateOutputAst = require('./validateOutputAst');
 const babel = require('@babel/core');
 const pluginTester = require('babel-plugin-tester');
+const nullthrows = require('nullthrows');
 
-pluginTester({
+pluginTester<PluginOptions, State>({
   babelOptions: {
     babelrc: false,
     configFile: false,
@@ -246,17 +248,25 @@ pluginTester({
 });
 
 describe('inline-requires', () => {
-  const transform = (source, options) =>
-    babel.transform(source.join('\n'), {
+  const transform = (
+    source: $ReadOnlyArray<string>,
+    options?: $ReadOnly<{...}>,
+  ) =>
+    babel.transformSync(source.join('\n'), {
       ast: true,
       compact: true,
       plugins: [
+        // $FlowFixMe[untyped-import] @babel/plugin-transform-modules-commonjs
         [require('@babel/plugin-transform-modules-commonjs'), {strict: false}],
         [inlineRequiresPlugin, options],
       ],
     });
 
-  const compare = (input, output, options) => {
+  const compare = (
+    input: $ReadOnlyArray<string>,
+    output: $ReadOnlyArray<string>,
+    options?: $ReadOnly<{...}>,
+  ) => {
     expect(transform(input, options).code).toBe(
       transform(output, options).code,
     );
@@ -293,16 +303,19 @@ describe('inline-requires', () => {
 
   it('should remove loc information from nodes', function () {
     const ast = transform(['var x = require("x"); x']).ast;
-    const expression = ast.program.body[0].expression;
+    expect(ast).not.toBeNull();
+    const expression = nullthrows(ast).program.body[0].expression;
 
-    function expectNoLocation(node) {
+    function expectNodeWithNoLocation(maybeNode: ?BabelNode) {
+      expect(maybeNode).not.toBeNull();
+      const node = nullthrows(maybeNode);
       expect(node.start).toBeUndefined();
       expect(node.end).toBeUndefined();
       expect(node.loc).toBeUndefined();
     }
 
-    expectNoLocation(expression);
-    expectNoLocation(expression.arguments[0]);
+    expectNodeWithNoLocation(expression);
+    expectNodeWithNoLocation(nullthrows(expression?.arguments)[0]);
   });
 
   it('should not emit duplicate nodes', function () {
@@ -311,6 +324,6 @@ describe('inline-requires', () => {
       'foo.bar()',
       'foo.baz()',
     ]).ast;
-    validateOutputAst(ast);
+    validateOutputAst(nullthrows(ast));
   });
 });

packages/metro-transform-plugins/src/__tests__/validateOutputAst.js

@@ -3,19 +3,24 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict
  */
 
 'use strict';
 
 const t = require('@babel/types');
 
-module.exports = function validateOutputAst(ast) {
-  const seenNodes = new Set();
+module.exports = function validateOutputAst(ast: BabelNode) {
+  const seenNodes = new Set<BabelNode>();
   t.traverseFast(ast, function enter(node) {
     if (seenNodes.has(node)) {
-      throw new Error('Found a duplicate node in the output, which can cause'
-        + ' undefined behavior in Babel.');
+      throw new Error(
+        'Found a duplicate node in the output, which can cause' +
+          ' undefined behavior in Babel.',
+      );
     }
     seenNodes.add(node);
-  })
-}
+  });
+};