metro-buck: check validity of segments

Reviewed By: davidaurelio

Differential Revision: D6496312

fbshipit-source-id: 586dc8d9f64d13cfddaf6bfe768e8f7b3442561a

Author: Jean Lauliac

Libraries/Utilities/asyncRequire.js

@@ -13,6 +13,8 @@
 
 'use strict';
 
+const dynamicRequire: number => mixed = (require: $FlowFixMe);
+
 /**
  * The bundler must register the dependency properly when generating a call to
  * `asyncRequire`, that allows us to call `require` dynamically with confidence
@@ -24,7 +26,7 @@ function asyncRequire(moduleID: number): Promise<mixed> {
       const {segmentId} = (require: $FlowFixMe).unpackModuleId(moduleID);
       return loadSegment(segmentId);
     })
-    .then(() => require.call(null, (moduleID: $FlowFixMe)));
+    .then(() => dynamicRequire(moduleID));
 }
 
 let segmentLoaders = new Map();
@@ -45,6 +47,10 @@ function loadSegment(segmentId: number): Promise<void> {
     if (segmentId === 0) {
       return;
     }
+    if (typeof global.__BUNDLE_DIGEST__ !== 'string') {
+      throw IncorrectBundleSetupError();
+    }
+    const globalDigest = global.__BUNDLE_DIGEST__;
     let segmentLoader = segmentLoaders.get(segmentId);
     if (segmentLoader != null) {
       return segmentLoader;
@@ -61,6 +67,19 @@ function loadSegment(segmentId: number): Promise<void> {
         }
         resolve();
       });
+    }).then(() => {
+      const metaModuleId = (require: $FlowFixMe).packModuleId({
+        segmentId,
+        localId: 0,
+      });
+      const metaModule = dynamicRequire(metaModuleId);
+      const digest: string =
+        typeof metaModule === 'object' && metaModule != null
+          ? (metaModule.BUNDLE_DIGEST: $FlowFixMe)
+          : 'undefined';
+      if (digest !== globalDigest) {
+        throw new IncompatibleSegmentError(globalDigest, digest);
+      }
     });
     segmentLoaders.set(segmentId, segmentLoader);
     return segmentLoader;
@@ -76,4 +95,27 @@ class FetchSegmentNotAvailableError extends Error {
   }
 }
 
+class IncorrectBundleSetupError extends Error {
+  constructor() {
+    super(
+      'To be able to use split segments, the bundler must define a global ' +
+        'constant `__BUNDLE_DIGEST__` that identifies the bundle uniquely.',
+    );
+  }
+}
+asyncRequire.IncorrectBundleSetupError = IncorrectBundleSetupError;
+
+class IncompatibleSegmentError extends Error {
+  constructor(globalDigest, segmentDigest) {
+    super(
+      'The split segment that is being loaded has been built from a ' +
+        'different version of the code than the main segment. Or, the ' +
+        'bundler is setting up the module #0 of the segment incorrectly. ' +
+        `The global digest is \`${globalDigest}\` while the segment is ` +
+        `\`${segmentDigest}\`.`,
+    );
+  }
+}
+asyncRequire.IncompatibleSegmentError = IncompatibleSegmentError;
+
 module.exports = asyncRequire;