packager worker: more @flow

Reviewed By: matryoshcow

Differential Revision: D4160528

fbshipit-source-id: 5f43cb47717288c5344c1204cf435ec727ca752e

react-packager/src/JSTransformer/worker/constant-folding.js

@@ -5,10 +5,15 @@
  * This source code is licensed under the BSD-style license found in the
  * LICENSE file in the root directory of this source tree. An additional grant
  * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @flow
  */
+
 'use strict';
 
 const babel = require('babel-core');
+
+import type {Ast, SourceMap} from 'babel-core';
 const t = babel.types;
 
 const Conditional = {
@@ -65,7 +70,11 @@ const plugin = {
   },
 };
 
-function constantFolding(filename, transformResult) {
+function constantFolding(filename: string, transformResult: {
+  ast: Ast,
+  code?: ?string,
+  map: ?SourceMap,
+}) {
   return babel.transformFromAst(transformResult.ast, transformResult.code, {
     filename,
     plugins: [plugin],

react-packager/src/JSTransformer/worker/extract-dependencies.js

@@ -5,7 +5,10 @@
  * This source code is licensed under the BSD-style license found in the
  * LICENSE file in the root directory of this source tree. An additional grant
  * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @flow
  */
+
 'use strict';
 
 const babel = require('babel-core');
@@ -20,7 +23,7 @@ const babylon = require('babylon');
  * dependencies, and an array of offsets to the string literals with module IDs.
  * The index points to the opening quote.
  */
-function extractDependencies(code) {
+function extractDependencies(code: string) {
   const ast = babylon.parse(code);
   const dependencies = new Set();
   const dependencyOffsets = [];

react-packager/src/JSTransformer/worker/inline.js

@@ -5,10 +5,16 @@
  * This source code is licensed under the BSD-style license found in the
  * LICENSE file in the root directory of this source tree. An additional grant
  * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @flow
  */
+
 'use strict';
 
 const babel = require('babel-core');
+const invariant = require('invariant');
+
+import type {Ast, SourceMap} from 'babel-core';
 const t = babel.types;
 
 const React = {name: 'React'};
@@ -145,7 +151,17 @@ function checkRequireArgs(args, dependencyId) {
          t.isNumericLiteral(args[0]) && t.isStringLiteral(args[1], pattern);
 }
 
-function inline(filename, transformResult, options) {
+type AstResult = {
+  ast: Ast,
+  code: ?string,
+  map: ?SourceMap,
+};
+
+function inline(
+  filename: string,
+  transformResult: {ast?: ?Ast, code: string, map: ?SourceMap},
+  options: {},
+): AstResult {
   const code = transformResult.code;
   const babelOptions = {
     filename,
@@ -158,9 +174,12 @@ function inline(filename, transformResult, options) {
     compact: true,
   };
 
-  return transformResult.ast
-      ? babel.transformFromAst(transformResult.ast, code, babelOptions)
-      : babel.transform(code, babelOptions);
+  const result = transformResult.ast
+    ? babel.transformFromAst(transformResult.ast, code, babelOptions)
+    : babel.transform(code, babelOptions);
+  const {ast} = result;
+  invariant(ast != null, 'Missing AST in babel transform results.');
+  return {ast, code: result.code, map: result.map};
 }
 
 inline.plugin = inlinePlugin;

react-packager/src/JSTransformer/worker/minify.js

@@ -5,12 +5,15 @@
  * This source code is licensed under the BSD-style license found in the
  * LICENSE file in the root directory of this source tree. An additional grant
  * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @flow
  */
+
 'use strict';
 
 const uglify = require('uglify-js');
 
-function minify(filename, code, sourceMap) {
+function minify(filename: string, code: string, sourceMap: ?string) {
   const minifyResult = uglify.minify(code, {
     fromString: true,
     inSourceMap: sourceMap,

react-packager/src/JSTransformer/worker/worker.js

@@ -14,9 +14,11 @@
 const constantFolding = require('./constant-folding');
 const extractDependencies = require('./extract-dependencies');
 const inline = require('./inline');
+const invariant = require('invariant');
 const minify = require('./minify');
 
 import type {LogEntry} from '../../Logger/Types';
+import type {Ast, SourceMap} from 'babel-core';
 
 function makeTransformParams(filename, sourceCode, options) {
   if (filename.endsWith('.json')) {
@@ -32,11 +34,17 @@ export type TransformedCode = {
   map?: ?{},
 };
 
-type Transform = (params: {
-  filename: string,
-  sourceCode: string,
-  options: ?{},
-}) => mixed;
+type Transform = (
+  params: {
+    filename: string,
+    sourceCode: string,
+    options: ?{},
+  },
+  callback: (
+    error?: Error,
+    tranformed?: {ast: ?Ast, code: string, map: ?SourceMap},
+  ) => mixed,
+) => void;
 
 export type Options = {transform?: {}};
 
@@ -75,15 +83,18 @@ function transformCode(
       return;
     }
 
+    invariant(
+      transformed != null,
+      'Missing transform results despite having no error.',
+    );
+
     var code, map;
     if (options.minify) {
-      const optimized =
-        constantFolding(filename, inline(filename, transformed, options));
-      code = optimized.code;
-      map = optimized.map;
+      ({code, map} =
+        constantFolding(filename, inline(filename, transformed, options)));
+      invariant(code != null, 'Missing code from constant-folding transform.');
     } else {
-      code = transformed.code;
-      map = transformed.map;
+      ({code, map} = transformed);
     }
 
     if (isJson) {

react-packager/src/lib/SourceMap.js

@@ -11,19 +11,13 @@
 
 'use strict';
 
-type SourceMapBase = {
+import type {SourceMap as BabelSourceMap} from 'babel-core';
+
+export type SourceMap = BabelSourceMap;
+
+export type CombinedSourceMap = {
   version: number,
   file: string,
-};
-
-export type SourceMap = SourceMapBase & {
-  sources: Array<string>,
-  names: Array<string>,
-  mappings: string,
-  sourcesContent: Array<string>,
-};
-
-export type CombinedSourceMap = SourceMapBase & {
   sections: Array<{
     offset: {line: number, column: number},
     map: SourceMap,