refactor: is_data_content_block

libs/core/langchain_core/messages/content_blocks.py

@@ -130,7 +130,7 @@ Factory functions offer benefits such as:
 """  # noqa: E501
 
 import warnings
-from typing import Any, Literal, Optional, Union
+from typing import Any, Literal, Optional, Union, get_args, get_type_hints
 from uuid import uuid4
 
 from typing_extensions import NotRequired, TypedDict, TypeGuard
@@ -950,8 +950,24 @@ KNOWN_BLOCK_TYPES = {
 }
 
 
+def _get_data_content_block_types() -> tuple[str, ...]:
+    """Get type literals from DataContentBlock union members dynamically."""
+    data_block_types = []
+
+    for block_type in get_args(DataContentBlock):
+        hints = get_type_hints(block_type)
+        if "type" in hints:
+            type_annotation = hints["type"]
+            if hasattr(type_annotation, "__args__"):
+                # This is a Literal type, get the literal value
+                literal_value = type_annotation.__args__[0]
+                data_block_types.append(literal_value)
+
+    return tuple(data_block_types)
+
+
 def is_data_content_block(block: dict) -> bool:
-    """Check if the content block is a standard data content block.
+    """Check if the provided content block is a standard v1 data content block.
 
     Args:
         block: The content block to check.
@@ -960,20 +976,19 @@ def is_data_content_block(block: dict) -> bool:
         True if the content block is a data content block, False otherwise.
 
     """
-    return block.get("type") in (
-        "audio",
-        "image",
-        "video",
-        "file",
-        "text-plain",
-    ) and any(
+    return block.get("type") in _get_data_content_block_types() and any(
+        # Check if at least one non-type key is present to signify presence of data
         key in block
         for key in (
             "url",
             "base64",
             "file_id",
             "text",
-            "source_type",  # backwards compatibility
+            "source_type",  # for backwards compatibility with v0 content blocks
+            # TODO: should we verify that if source_type is present, at least one of
+            # url, base64, or file_id is also present? Otherwise, source_type could be
+            # present without any actual data? Need to confirm whether this was ever
+            # possible in v0 content blocks in the first place.
         )
     )