Add test for overriding default_value while there is a value

This should not be done anywhere since the default_value won't have any effect then. We disregard CuraEngine's command line method here but that's infeasible with those profiles anyway.

Done during Turbo Testing & Tooling.

tests/Settings/TestDefinitionContainer.py

@@ -1,18 +1,17 @@
 # Copyright (c) 2019 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+import json  # To check files for unnecessarily overridden properties.
+import os
+import os.path
 import pytest #This module contains automated tests.
+from typing import Any, Dict
+import uuid
 
 import UM.Settings.ContainerRegistry #To create empty instance containers.
 import UM.Settings.ContainerStack #To set the container registry the container stacks use.
 from UM.Settings.DefinitionContainer import DefinitionContainer #To check against the class of DefinitionContainer.
 
-
-
-import os
-import os.path
-import uuid
-
 from UM.Resources import Resources
 Resources.addSearchPath(os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "resources")))
 
@@ -51,4 +50,62 @@ def assertIsDefinitionValid(definition_container, path, file_name):
             assert metadata[0]["platform"] in all_meshes
 
         if "platform_texture" in metadata[0]:
-            assert metadata[0]["platform_texture"] in all_images
+            assert metadata[0]["platform_texture"] in all_images
+
+##  Tests whether setting values are not being hidden by parent containers.
+#
+#   When a definition container defines a "default_value" but inherits from a
+#   definition that defines a "value", the "default_value" is ineffective. This
+#   test fails on those things.
+@pytest.mark.parametrize("file_name", machine_filepaths)
+def test_validateOverridingDefaultValue(file_name):
+    definition_path = os.path.join(os.path.dirname(__file__), "..", "..", "resources", "definitions", file_name)
+    with open(definition_path, encoding = "utf-8") as f:
+        doc = json.load(f)
+
+    if "inherits" not in doc:
+        return  # We only want to check for documents where the inheritance overrides the children. If there's no inheritance, this can't happen so it's fine.
+    if "overrides" not in doc:
+        return  # No settings are being overridden. No need to check anything.
+    parent_settings = getInheritedSettings(doc["inherits"])
+    for key, val in doc["overrides"].items():
+        if "value" in parent_settings[key]:
+            assert "default_value" not in val, "Unnecessary default_value in {file_name}".format(file_name = file_name)  # If there is a value in the parent settings, then the default_value is not effective.
+
+def getInheritedSettings(definition_id: str) -> Dict[str, Any]:
+    definition_path = os.path.join(os.path.dirname(__file__), "..", "..", "resources", "definitions", definition_id + ".def.json")
+    with open(definition_path, encoding = "utf-8") as f:
+        doc = json.load(f)
+    result = {}
+
+    if "inherits" in doc:  # Recursive inheritance.
+        result.update(getInheritedSettings(doc["inherits"]))
+    if "settings" in doc:
+        result.update(flattenSettings(doc["settings"]))
+    if "overrides" in doc:
+        result = merge_dicts(result, doc["overrides"])
+
+    return result
+
+def flattenSettings(settings) -> Dict[str, Any]:
+    result = {}
+    for entry, contents in settings.items():
+        if "children" in contents:
+            result.update(flattenSettings(contents["children"]))
+            del contents["children"]
+        result[entry] = contents
+    return result
+
+def merge_dicts(base: Dict[str, Any], overrides: Dict[str, Any]) -> Dict[str, Any]:
+    result = {}
+    result.update(base)
+    for key, val in overrides.items():
+        if key not in result:
+            result[key] = val
+            continue
+
+        if hasattr(result[key], "__getitem__") and hasattr(val, "__getitem__"):  # Duck typing of dicts. Also works with JSON documents for sure.
+            result[key] = merge_dicts(result[key], val)
+        else:
+            result[key] = val
+    return result