Warn and annotate on metro-file-map cache read error

Summary:
Currently `metro-file-map` will *silently* ignore errors encountered when reading from the configured cache manager, and fall back to a cold crawl.

This adds a console warning and records an annotation to give these error cases more visibility.

In addition, propagate unexpected errors, such as deserialisation failures, from the default `DiskCacheManager`.

Changelog:
**[Fix]** Log warning on unexpected error during `metro-file-map`cache read.

Reviewed By: huntie

Differential Revision: D39514918

fbshipit-source-id: 4569a1ed7f2114307c96c0b5064b367ebd487947

Author: robhogan

packages/metro-file-map/src/cache/DiskCacheManager.js

@@ -68,8 +68,14 @@ export class DiskCacheManager implements CacheManager {
   async read(): Promise<?InternalData> {
     try {
       return deserialize(readFileSync(this._cachePath));
-    } catch {}
-    return null;
+    } catch (e) {
+      if (e?.code === 'ENOENT') {
+        // Cache file not found - not considered an error.
+        return null;
+      }
+      // Rethrow anything else.
+      throw e;
+    }
   }
 
   async write(

packages/metro-file-map/src/index.js

@@ -411,7 +411,15 @@ export default class HasteMap extends EventEmitter {
     this._options.perfLogger?.point('read_start');
     try {
       data = await this._cacheManager.read();
-    } catch {}
+    } catch (e) {
+      this._console.warn(
+        'Error while reading cache, falling back to a full crawl:\n',
+        e,
+      );
+      this._options.perfLogger?.annotate({
+        string: {cacheReadError: e.toString()},
+      });
+    }
     data = data ?? this._createEmptyMap();
     this._options.perfLogger?.point('read_end');