react-native: prefer custom source extensions over default extensions

Reviewed By: mjesun

Differential Revision: D7066617

fbshipit-source-id: cdde7451cb817d62d6705071752fce0686cf04dc

Author: Jean Lauliac

local-cli/bundle/buildBundle.js

@@ -100,7 +100,7 @@ async function buildBundle(
     providesModuleNodeModules: providesModuleNodeModules,
     resetCache: args.resetCache,
     reporter: new TerminalReporter(terminal),
-    sourceExts: defaultSourceExts.concat(sourceExts),
+    sourceExts: sourceExts.concat(defaultSourceExts),
     transformCache: TransformCaching.useTempDir(),
     transformModulePath: transformModulePath,
     watch: false,

local-cli/server/runServer.js

@@ -187,7 +187,7 @@ function getPackagerServer(args, config, reporter) {
     providesModuleNodeModules: providesModuleNodeModules,
     reporter,
     resetCache: args.resetCache,
-    sourceExts: defaultSourceExts.concat(args.sourceExts),
+    sourceExts: args.sourceExts.concat(defaultSourceExts),
     transformModulePath: transformModulePath,
     transformCache: TransformCaching.useTempDir(),
     verbose: args.verbose,