Bugfix: Pydantic deserialization for FlyteFile and FlyteDirectory

flytekit/types/directory/types.py

@@ -176,10 +176,25 @@ def serialize_flyte_dir(self) -> Dict[str, str]:
         )
         return {"path": lv.scalar.blob.uri}
 
+    def _was_initialized_via_init(self) -> bool:
+        """Check if object was initialized via __init__ or deserialized by Pydantic.
+
+        When Pydantic deserializes a FlyteDirectory, it bypasses __init__ and directly
+        sets the 'path' attribute. This means the _downloader and _remote_source attributes
+        won't exist. We use this check to determine if we need to go through the transformer
+        to properly set up these internal attributes.
+
+        Returns:
+            bool: True if __init__ was called (normal initialization), False if created via
+                Pydantic deserialization and needs to pass through transformer.
+        """
+        return hasattr(self, "_downloader") and hasattr(self, "_remote_source")
+
     @model_validator(mode="after")
     def deserialize_flyte_dir(self, info) -> FlyteDirectory:
         if info.context is None or info.context.get("deserialize") is not True:
-            return self
+            if self._was_initialized_via_init():
+                return self
 
         pv = FlyteDirToMultipartBlobTransformer().to_python_value(
             FlyteContextManager.current_context(),

flytekit/types/file/file.py

@@ -193,10 +193,25 @@ def serialize_flyte_file(self) -> Dict[str, typing.Any]:
             out["metadata"] = lv.metadata
         return out
 
+    def _was_initialized_via_init(self) -> bool:
+        """Check if object was initialized via __init__ or deserialized by Pydantic.
+
+        When Pydantic deserializes a FlyteFile, it bypasses __init__ and directly
+        sets the 'path' attribute. This means the _downloader and _remote_source attributes
+        won't exist. We use this check to determine if we need to go through the transformer
+        to properly set up these internal attributes.
+
+        Returns:
+            bool: True if __init__ was called (normal initialization), False if created via
+                Pydantic deserialization and needs to pass through transformer.
+        """
+        return hasattr(self, "_downloader") and hasattr(self, "_remote_source")
+
     @model_validator(mode="after")
     def deserialize_flyte_file(self, info) -> "FlyteFile":
         if info.context is None or info.context.get("deserialize") is not True:
-            return self
+            if self._was_initialized_via_init():
+                return self
 
         pv = FlyteFilePathTransformer().to_python_value(
             FlyteContextManager.current_context(),

tests/flytekit/unit/extras/pydantic_transformer/test_pydantic_basemodel_transformer.py

@@ -1022,3 +1022,109 @@ def mock_resolve_remote_path(flyte_uri: str):
 
     bm_revived = TypeEngine.to_python_value(ctx, lit, BM)
     assert bm_revived.s.literal.uri == "/my/replaced/val"
+
+
+def test_flytefile_pydantic_model_dump_validate_cycle():
+    class BM(BaseModel):
+        ff: FlyteFile
+
+    bm = BM(ff=FlyteFile.from_source("s3://my-bucket/file.txt"))
+
+    assert bm.ff.remote_source == "s3://my-bucket/file.txt"
+
+    bm_dict = bm.model_dump()
+    bm2 = BM.model_validate(bm_dict)
+
+    assert isinstance(bm2.ff, FlyteFile)
+    assert bm2.ff.remote_source == "s3://my-bucket/file.txt"
+
+    bm2_dict = bm2.model_dump()
+    assert bm_dict == bm2_dict
+
+
+def test_flytefile_pydantic_with_local_file(local_dummy_file):
+    class BM(BaseModel):
+        ff: FlyteFile
+
+    bm = BM(ff=FlyteFile(path=local_dummy_file))
+
+    bm_dict = bm.model_dump()
+    bm2 = BM.model_validate(bm_dict)
+
+    assert isinstance(bm2.ff, FlyteFile)
+    assert hasattr(bm2.ff, "_downloader")
+    assert hasattr(bm2.ff, "_remote_source")
+
+    bm2.model_dump()
+
+
+def test_flytefile_pydantic_with_metadata(local_dummy_file):
+    class BM(BaseModel):
+        ff: FlyteFile
+
+    bm = BM(ff=FlyteFile(path=local_dummy_file, metadata={"key": "value"}))
+
+    bm_dict = bm.model_dump()
+    bm2 = BM.model_validate(bm_dict)
+
+    assert isinstance(bm2.ff, FlyteFile)
+    assert hasattr(bm2.ff, "_downloader")
+    assert hasattr(bm2.ff, "_remote_source")
+    assert bm2.ff.metadata == {"key": "value"}
+
+    bm2.model_dump()
+
+
+def test_flytefile_pydantic_direct_dict_validate(local_dummy_file):
+    class BM(BaseModel):
+        ff: FlyteFile
+
+    bm = BM.model_validate({"ff": {"path": local_dummy_file}})
+
+    assert isinstance(bm.ff, FlyteFile)
+    assert hasattr(bm.ff, "_downloader")
+    assert hasattr(bm.ff, "_remote_source")
+
+
+def test_flytedirectory_pydantic_direct_dict_validate(local_dummy_directory):
+    class BM(BaseModel):
+        fd: FlyteDirectory
+
+    bm = BM.model_validate({"fd": {"path": local_dummy_directory}})
+
+    assert isinstance(bm.fd, FlyteDirectory)
+    assert hasattr(bm.fd, "_downloader")
+    assert hasattr(bm.fd, "_remote_source")
+
+
+def test_flytedirectory_pydantic_model_dump_validate_cycle():
+    class BM(BaseModel):
+        fd: FlyteDirectory
+
+    bm = BM(fd=FlyteDirectory.from_source("s3://my-bucket/my-dir"))
+
+    assert bm.fd.remote_source == "s3://my-bucket/my-dir"
+
+    bm_dict = bm.model_dump()
+    bm2 = BM.model_validate(bm_dict)
+
+    assert isinstance(bm2.fd, FlyteDirectory)
+    assert bm2.fd.remote_source == "s3://my-bucket/my-dir"
+
+    bm2.model_dump()
+
+
+def test_flytedirectory_pydantic_with_local_directory(local_dummy_directory):
+    class BM(BaseModel):
+        fd: FlyteDirectory
+
+    bm = BM(fd=FlyteDirectory(path=local_dummy_directory))
+
+    bm_dict = bm.model_dump()
+    bm2 = BM.model_validate(bm_dict)
+
+    assert isinstance(bm2.fd, FlyteDirectory)
+    assert hasattr(bm2.fd, "_downloader")
+    assert hasattr(bm2.fd, "_remote_source")
+
+    bm2.model_dump()