Fix sourceMap flow annotations by making them nullable

Reviewed By: mjesun

Differential Revision: D5755671

fbshipit-source-id: 19be8475b1f1b54bc55b64a1de4b8a446e125c65

packages/metro-bundler/src/Bundler/index.js

@@ -110,8 +110,8 @@ export type PostProcessModules = (
 
 export type PostMinifyProcess = ({
   code: string,
-  map: MappingsMap,
-}) => {code: string, map: MappingsMap};
+  map: ?MappingsMap,
+}) => {code: string, map: ?MappingsMap};
 
 export type PostProcessBundleSourcemap = ({
   code: Buffer | string,

packages/metro-bundler/src/JSTransformer/index.js

@@ -93,8 +93,8 @@ class Transformer {
   minify: (
     filename: string,
     code: string,
-    sourceMap: MappingsMap,
-  ) => Promise<{code: string, map: MappingsMap}>;
+    sourceMap: ?MappingsMap,
+  ) => Promise<{code: string, map: ?MappingsMap}>;
 
   constructor(
     transformModulePath: string,

packages/metro-bundler/src/Resolver/index.js

@@ -32,8 +32,8 @@ import type {GlobalTransformCache} from '../lib/GlobalTransformCache';
 type MinifyCode = (
   filePath: string,
   code: string,
-  map: MappingsMap,
-) => Promise<{code: string, map: MappingsMap}>;
+  map: ?MappingsMap,
+) => Promise<{code: string, map: ?MappingsMap}>;
 
 type ContainsTransformerOptions = {+transformer: JSTransformerOptions};
 
@@ -225,7 +225,7 @@ class Resolver {
     resolutionResponse: ResolutionResponse<Module, T>,
     module: Module,
     name: string,
-    map: MappingsMap,
+    map: ?MappingsMap,
     code: string,
     meta?: {
       dependencyOffsets?: Array<number>,
@@ -263,8 +263,8 @@ class Resolver {
   }: {
     path: string,
     code: string,
-    map: MappingsMap,
-  }): Promise<{code: string, map: MappingsMap}> {
+    map: ?MappingsMap,
+  }): Promise<{code: string, map: ?MappingsMap}> {
     return this._minifyCode(path, code, map);
   }