fix: enhance error handling for missing __datafusion_table_provider__ in UDTF example

Author: kosiew

examples/table_capsule_failure.py

@@ -4,7 +4,8 @@
 
 This example mirrors how advanced integrations unwrap ``Table`` instances via the
 ``__datafusion_table_provider__`` PyCapsule. The refactor that removed this method
-means user-defined table functions returning ``Table`` now raise ``NotImplementedError``.
+means user-defined table functions returning ``Table`` now raise ``NotImplementedError``
+and the script prints the resulting error message instead of crashing.
 """
 
 from __future__ import annotations
@@ -16,6 +17,7 @@ def main() -> None:
     """Register a Python table UDTF that returns a ``Table`` and trigger it."""
 
     ctx = SessionContext()
+    failing_table = Table(ctx.sql("SELECT 1 AS value"))
 
     @udtf("capsule_dependent")
     def capsule_dependent_udtf() -> Table:
@@ -24,13 +26,21 @@ def capsule_dependent_udtf() -> Table:
         # Prior to the refactor the wrapper exposed ``__datafusion_table_provider__``
         # so this conversion succeeded. Without it the runtime raises a
         # ``NotImplementedError`` complaining about the missing attribute.
-        return Table(ctx.sql("SELECT 1 AS value"))
+        return failing_table
 
     ctx.register_udtf(capsule_dependent_udtf)
 
     # Executing the UDTF now fails because ``Table`` no longer exposes the
     # ``__datafusion_table_provider__`` helper that PyTableFunction expects.
-    ctx.sql("SELECT * FROM capsule_dependent()").collect()
+    try:
+        ctx.sql("SELECT * FROM capsule_dependent()").collect()
+    except NotImplementedError as err:
+        # Document the regression by surfacing the missing capsule attribute
+        # instead of crashing with a panic inside the execution engine.
+        print(
+            "capsule_dependent() failed due to missing __datafusion_table_provider__: "
+            f"{err}"
+        )
 
 
 if __name__ == "__main__":