Add back assertion on empty resource classes in ResourceCacheGenerator

Currently we're failing to load some images that are present in cache
due to a race condition. I haven't had any luck looking through the code
to see why this happens. I suspect a race of some sort. I'm hoping that
adding the exception back in with additional logging will help me move
forward.

I'm also hoping that this change avoids the worst of the behavior in the
bug by failing only one request, rather than all requests. I may
actually have to revert back to failing all requests if I can detect via
ecatcher that this exception happens but no one reports it.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=209077692

library/src/main/java/com/bumptech/glide/Registry.java

@@ -25,10 +25,13 @@
 import com.bumptech.glide.provider.ResourceDecoderRegistry;
 import com.bumptech.glide.provider.ResourceEncoderRegistry;
 import com.bumptech.glide.util.pool.FactoryPools;
+import java.io.File;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 /**
  * Manages component registration to extend or replace Glide's default loading, decoding, and
@@ -530,17 +533,43 @@ public <Model, TResource, Transcode> List<Class<?>> getRegisteredResourceClasses
     if (result == null) {
       result = new ArrayList<>();
       List<Class<?>> dataClasses = modelLoaderRegistry.getDataClasses(modelClass);
+
+      Map<Class<?>, List<? extends Class<?>>> dataClassToResourceClasses = new HashMap<>();
+      Map<Class<?>, List<Class<Transcode>>> resourceClassToTranscodeClasses = new HashMap<>();
+
       for (Class<?> dataClass : dataClasses) {
         List<? extends Class<?>> registeredResourceClasses =
             decoderRegistry.getResourceClasses(dataClass, resourceClass);
+
+        dataClassToResourceClasses.put(dataClass, registeredResourceClasses);
+
         for (Class<?> registeredResourceClass : registeredResourceClasses) {
-          List<Class<Transcode>> registeredTranscodeClasses = transcoderRegistry
-              .getTranscodeClasses(registeredResourceClass, transcodeClass);
+
+          List<Class<Transcode>> registeredTranscodeClasses =
+              transcoderRegistry.getTranscodeClasses(registeredResourceClass, transcodeClass);
+
+          resourceClassToTranscodeClasses.put(registeredResourceClass, registeredTranscodeClasses);
+
           if (!registeredTranscodeClasses.isEmpty() && !result.contains(registeredResourceClass)) {
             result.add(registeredResourceClass);
           }
         }
       }
+
+      // Throw the exception before populating the cache in the hopes that a subsequent attempt will
+      // succeed and only one request will randomly fail. This is really debugging logic that should
+      // go away when we find the actual cause for b/73882030.
+      if (result.isEmpty() && !File.class.equals(transcodeClass)) {
+        if (dataClasses.isEmpty()) {
+          throw new IllegalStateException("Failed to find any data classes for: " + modelClass);
+        }
+
+        throw new IllegalStateException(
+            "Failed to find any resource or transcode classes for model: " + modelClass
+                + ", data to resource classes: " + dataClassToResourceClasses
+                + ", resource to transcode classes: " + resourceClassToTranscodeClasses);
+      }
+
       modelToResourceClassCache.put(modelClass, resourceClass,
           Collections.unmodifiableList(result));
     }

library/src/main/java/com/bumptech/glide/load/engine/ResourceCacheGenerator.java

@@ -53,9 +53,9 @@ public boolean startNext() {
       // TODO(b/73882030): This case gets triggered when it shouldn't. With this assertion it causes
       // all loads to fail. Without this assertion it causes loads to miss the disk cache
       // unnecessarily
-      // throw new IllegalStateException(
-      //    "Failed to find any load path from " + helper.getModelClass() + " to "
-      //        + helper.getTranscodeClass());
+      throw new IllegalStateException(
+         "Failed to find any load path from " + helper.getModelClass() + " to "
+             + helper.getTranscodeClass());
     }
     while (modelLoaders == null || !hasNextModelLoader()) {
       resourceClassIndex++;