🎬 : Improved file uploader and camera input to call its on_change han…

…dler only when necessary (#4270)

* Add __eq__ method to UploadedFile, to be able to compare different UploadedFile instances with same FileRec.
We need that change to prevent `on_change` call for file_uploader on rerun.

lib/streamlit/uploaded_file_manager.py

@@ -50,6 +50,11 @@ def __init__(self, record: UploadedFileRec):
         self.type = record.type
         self.size = len(record.data)
 
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, UploadedFile):
+            return NotImplemented
+        return self.id == other.id
+
     def __repr__(self) -> str:
         return util.repr_(self)
 

lib/tests/streamlit/file_uploader_test.py

@@ -123,7 +123,7 @@ def test_unique_uploaded_file_instance(self, get_file_recs_patch):
         file1: UploadedFile = st.file_uploader("a", accept_multiple_files=False)
         file2: UploadedFile = st.file_uploader("b", accept_multiple_files=False)
 
-        self.assertNotEqual(file1, file2)
+        self.assertNotEqual(id(file1), id(file2))
 
         # Seeking in one instance should not impact the position in the other.
         file1.seek(2)

lib/tests/streamlit/state/session_state_test.py

@@ -305,22 +305,7 @@ def test_file_uploader_serde(self, get_file_recs_patch):
         get_file_recs_patch.return_value = file_recs
 
         uploaded_file = st.file_uploader("file_uploader", key="file_uploader")
-
-        # We can't use check_roundtrip here as the return_value of a
-        # file_uploader widget isn't a primitive value, so comparing them
-        # using == checks for reference equality.
-        session_state = get_session_state()
-        metadata = session_state.get_metadata_by_key("file_uploader")
-        serializer = metadata.serializer
-        deserializer = metadata.deserializer
-
-        file_after_serde = deserializer(serializer(uploaded_file), "")
-
-        assert uploaded_file.id == file_after_serde.id
-        assert uploaded_file.name == file_after_serde.name
-        assert uploaded_file.type == file_after_serde.type
-        assert uploaded_file.size == file_after_serde.size
-        assert uploaded_file.read() == file_after_serde.read()
+        check_roundtrip("file_uploader", uploaded_file)
 
     def test_multiselect_serde(self):
         multiselect = st.multiselect(