Check explicitly for invalid model type in C#

Please see #510 for more details. This is a fix particularly for C#
generation.

aas_core_codegen/csharp/jsonization/_generate.py

@@ -23,6 +23,7 @@
     INDENT2 as II,
     INDENT3 as III,
     INDENT4 as IIII,
+    INDENT5 as IIIII,
 )
 
 
@@ -381,6 +382,9 @@ def _generate_from_method_for_class(
 
     blocks.append(Stripped(args_init_writer.getvalue()))
 
+    if cls.serialization.with_model_type:
+        blocks.append(Stripped("string? modelType = null;"))
+
     # endregion
 
     # region Switch on property name
@@ -419,11 +423,42 @@ def _generate_from_method_for_class(
         return None, errors
 
     if cls.serialization.with_model_type:
+        model_type = naming.json_model_type(cls.name)
+
         cases.append(
             Stripped(
-                """\
+                f"""\
 case "modelType":
-    continue;"""
+{I}{{
+{II}if (keyValue.Value == null)
+{II}{{
+{III}error = new Reporting.Error(
+{IIII}"Expected a model type, but got null");
+{III}return null;
+{II}}}
+{II}modelType = DeserializeImplementation.StringFrom(
+{III}keyValue.Value,
+{III}out error);
+{II}if (error != null)
+{II}{{
+{III}error.PrependSegment(
+{IIII}new Reporting.NameSegment(
+{IIIII}"modelType"));
+{III}return null;
+{II}}}
+
+{II}if (modelType != "{model_type}")
+{II}{{
+{III}error = new Reporting.Error(
+{IIII}"Expected the model type '{model_type}', " +
+{IIII}$"but got {{modelType}}");
+{III}error.PrependSegment(
+{IIII}new Reporting.NameSegment(
+{IIIII}"modelType"));
+{III}return null;
+{II}}}
+{II}break;
+{I}}}"""
             )
         )
 
@@ -482,6 +517,19 @@ def _generate_from_method_for_class(
 
     blocks.append(Stripped(required_check_writer.getvalue()))
 
+    if cls.serialization.with_model_type:
+        blocks.append(
+            Stripped(
+                f"""\
+if (modelType == null)
+{{
+{I}error = new Reporting.Error(
+{II}"Required property \\"modelType\\" is missing");
+{I}return null;
+}}"""
+            )
+        )
+
     # endregion
 
     # region Pass in arguments to the constructor

aas_core_codegen/naming.py

@@ -79,6 +79,11 @@ def json_property(identifier: Identifier) -> Identifier:
 @ensure(
     lambda result: "_" not in result
 ) # This post-condition avoids naming conflicts with prefixing in the JSON schema.
+@ensure(
+    lambda result: '"' not in result and "'" not in result and '\\' not in result
+    # This post-condition simplifies a lot of generator code since we can simply in-line
+    # the model type in strings.
+)
 # fmt: on
 def json_model_type(identifier: Identifier) -> Identifier:
     """