F fix compare entities branch2

Summary

This is a fix for #81 (closed) .

Focus

I added a statement analogous to existing statements for datatype and importance that compares the values of the entities.

Test Environment

I added a unit test in test_apiutils.py.

Issue #81 (closed) contains a script for testing it manually.

Check List for the Author

• All automated tests pass
• Reference related Issues
• Up-to-date CHANGELOG.md
• Add type hints in created/changed code
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there spezifications? Are they satisfied?

src/caosdb/apiutils.py

@@ -561,7 +561,23 @@ def getCommitIn(folder):
 COMPARED = ["name", "role", "datatype", "description", "importance"]
 
 
-def compare_entities(old_entity, new_entity):
+def compare_entities(old_entity: Entity, new_entity: Entity):
+    """
+    Compare two entites.
+
+    Return a tuple of dictionaries, the first index belongs to additional information for old
+    entity, the second index belongs to additional information for new entity.
+
+    Additional information means in detail:
+    - Additional parents (a list under key "parents")
+    - Information about properties:
+      - Each property lists either an additional property or a property with a changed:
+        - ... datatype
+        - ... importance or
+        - ... value (not implemented yet)
+        In case of changed information the value listed under the respective key shows the
+        value that is stored in the respective entity.
+    """
     olddiff = {"properties": {}, "parents": []}
     newdiff = {"properties": {}, "parents": []}
 
@@ -623,6 +639,13 @@ def compare_entities(old_entity, new_entity):
                 newdiff["properties"][prop.name]["datatype"] = \
                     matching[0].datatype
 
+            if ((prop.value is not None and
+                    matching[0].value is not None) and
+                    (prop.value != matching[0].value)):
+                olddiff["properties"][prop.name]["value"] = prop.value
+                newdiff["properties"][prop.name]["value"] = \
+                    matching[0].value
+
             if (len(newdiff["properties"][prop.name]) == 0
                     and len(olddiff["properties"][prop.name]) == 0):
                 newdiff["properties"].pop(prop.name)