[GitHub] [beam] robertwb commented on a diff in pull request #24022: Add error reporting for BatchConverter match failure

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

robertwb commented on code in PR #24022:
URL: https://github.com/apache/beam/pull/24022#discussion_r1021950368


##########
sdks/python/apache_beam/typehints/batch.py:
##########
@@ -72,26 +74,36 @@ def estimate_byte_size(self, batch):
     raise NotImplementedError
 
   @staticmethod
-  def register(
-      batch_converter_constructor: Callable[[type, type], 'BatchConverter']):
-    BATCH_CONVERTER_REGISTRY.append(batch_converter_constructor)
-    return batch_converter_constructor
+  def register(*, name: str):
+    def do_registration(
+        batch_converter_constructor: Callable[[type, type], 'BatchConverter']):
+      if name in BATCH_CONVERTER_REGISTRY:
+        raise AssertionError(
+            f"Attempted to register two batch converters with name {name}")
+
+      BATCH_CONVERTER_REGISTRY[name] = batch_converter_constructor
+      return batch_converter_constructor
+
+    return do_registration
 
   @staticmethod
   def from_typehints(*, element_type, batch_type) -> 'BatchConverter':
     element_type = typehints.normalize(element_type)
     batch_type = typehints.normalize(batch_type)
-    for constructor in BATCH_CONVERTER_REGISTRY:
-      result = constructor(element_type, batch_type)
-      if result is not None:
+    errors = {}
+    for name, constructor in BATCH_CONVERTER_REGISTRY.items():
+      try:
+        result = constructor(element_type, batch_type)
+      except TypeError as e:
+        errors[name] = e.args[0]
+      else:
         return result

Review Comment:
   It's fine to just `return constructor(element_type, batch_type)` in the try clause rather than have an else clause here, as the act of returning can't raise a TypeError.



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