[GitHub] [beam] TheNeuralBit commented on a change in pull request #12454: [BEAM-10629] KnownBuilderInstances in ExternalTransformRegistrar

[GitBox <gi...@apache.org>]

TheNeuralBit commented on a change in pull request #12454:
URL: https://github.com/apache/beam/pull/12454#discussion_r464726158



##########
File path: sdks/java/expansion-service/src/main/java/org/apache/beam/sdk/expansion/service/ExpansionService.java
##########
@@ -107,39 +107,39 @@
           ImmutableMap.builder();
       for (ExternalTransformRegistrar registrar :
           ServiceLoader.load(ExternalTransformRegistrar.class)) {
-        for (Map.Entry<String, Class<? extends ExternalTransformBuilder<?, ?, ?>>> entry :
-            registrar.knownBuilders().entrySet()) {
+        for (Map.Entry<String, ExternalTransformBuilder<?, ?, ?>> entry :
+            registrar.knownBuilderInstances().entrySet()) {
           String urn = entry.getKey();
-          Class<? extends ExternalTransformBuilder<?, ?, ?>> builderClass = entry.getValue();
+          ExternalTransformBuilder builderInstance = entry.getValue();
           builder.put(
               urn,
               spec -> {
                 try {
                   ExternalTransforms.ExternalConfigurationPayload payload =
                       ExternalTransforms.ExternalConfigurationPayload.parseFrom(spec.getPayload());
-                  return translate(payload, builderClass);
+                  return builderInstance.buildExternal(
+                      payloadToConfig(
+                          payload,
+                          (Class<? extends ExternalTransformBuilder<?, ?, ?>>)
+                              builderInstance.getClass()));
                 } catch (Exception e) {
                   throw new RuntimeException(
                       String.format("Failed to build transform %s from spec %s", urn, spec), e);
                 }
               });
         }
       }
+
       return builder.build();
     }
 
-    private static PTransform<?, ?> translate(
+    Object payloadToConfig(
         ExternalTransforms.ExternalConfigurationPayload payload,
         Class<? extends ExternalTransformBuilder<?, ?, ?>> builderClass)
         throws Exception {
-      Preconditions.checkState(
-          ExternalTransformBuilder.class.isAssignableFrom(builderClass),
-          "Provided identifier %s is not an ExternalTransformBuilder.",
-          builderClass.getName());
-
       Object configObject = initConfiguration(builderClass);
       populateConfiguration(configObject, payload);
-      return buildTransform(builderClass, configObject);

Review comment:
       I think after this change there are no callers to `buildTransform`, can you remove it?

##########
File path: sdks/java/core/src/main/java/org/apache/beam/sdk/expansion/ExternalTransformRegistrar.java
##########
@@ -31,4 +34,27 @@
 
   /** A mapping from URN to an {@link ExternalTransformBuilder} class. */
   Map<String, Class<? extends ExternalTransformBuilder<?, ?, ?>>> knownBuilders();

Review comment:
       There should be a default implementation for this that just returns an empty Map, that way new implementations will only have to override `knownBuilderInstances()`

##########
File path: sdks/java/core/src/main/java/org/apache/beam/sdk/expansion/ExternalTransformRegistrar.java
##########
@@ -31,4 +34,27 @@
 
   /** A mapping from URN to an {@link ExternalTransformBuilder} class. */

Review comment:
       Let's mark this Deprecated and we can remove it down the road.
   ```suggestion
     /** 
      * A mapping from URN to an {@link ExternalTransformBuilder} class.
      *
      * @deprecated Prefer implementing `knownBuilderInstances`. This method will be removed in a future version of Beam.
      */
      @Deprecated
   ```




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