more comments, slightly different test

Signed-off-by: Yee Hing Tong <[email protected]>

flytekit/core/type_engine.py

@@ -287,8 +287,12 @@ def _serialize_flyte_type(self, python_val: T, python_type: Type[T]):
                 lv = TypeEngine.to_literal(FlyteContext.current_context(), v, field_type, None)
                 # dataclass_json package will extract the "path" from FlyteFile, FlyteDirectory, and write it to a
                 # JSON which will be stored in IDL. The path here should always be a remote path, but sometimes the
-                # path in FlyteFile and FlyteDirectory could be a local path. Therefore, We reset the python value here,
+                # path in FlyteFile and FlyteDirectory could be a local path. Therefore, reset the python value here,
                 # so that dataclass_json can always get a remote path.
+                # In other words, the file transformer has special code that handles the fact that if remote_source is
+                # set, then the real uri in the literal should be the remote source, not the path (which may be an
+                # auto-generated random local path). To be sure we're writing the right path to the json, use the uri
+                # as determined by the transformer.
                 if issubclass(field_type, FlyteFile) or issubclass(field_type, FlyteDirectory):
                     python_val.__setattr__(f.name, field_type(path=lv.scalar.blob.uri))
 

tests/flytekit/unit/core/test_flyte_file.py

@@ -407,3 +407,28 @@ def test_file_guess():
     fft = transformer.guess_python_type(lt)
     assert issubclass(fft, FlyteFile)
     assert fft.extension() == ""
+
+
+def test_flyte_file_in_dyn():
+    @task
+    def t1(path: str) -> FlyteFile:
+        return FlyteFile(path)
+
+    @dynamic
+    def dyn(fs: FlyteFile):
+        t2(ff=fs)
+
+    @task
+    def t2(ff: FlyteFile) -> os.PathLike:
+        assert ff.remote_source == "s3://somewhere"
+        assert "/tmp/flyte/" in ff.path
+
+        return ff.path
+
+    @workflow
+    def wf(path: str) -> os.PathLike:
+        n1 = t1(path=path)
+        dyn(fs=n1)
+        return t2(ff=n1)
+
+    assert "/tmp/flyte/" in wf(path="s3://somewhere").path