handle nested maps recurssively

Author: devhl-labs

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java

@@ -770,24 +770,42 @@ protected void patchProperty(Map<String, CodegenModel> enumRefs, CodegenModel mo
 
         property.name = patchPropertyName(model, property.name, null);
 
+        patchNestedMaps(property);
+
+        // HOTFIX: https://github.com/OpenAPITools/openapi-generator/issues/14944
+        if (property.datatypeWithEnum.equals("decimal")) {
+            property.isDecimal = true;
+        }
+    }
+
+    private void patchNestedMaps(CodegenProperty property) {
+        // Process nested types before making any replacements to ensure we have the correct inner type
+        if (property.items != null) {
+            patchNestedMaps(property.items);
+        }
+
         String[] nestedTypes = {"List", "Collection", "ICollection", "Dictionary"};
+        
+        if (property.datatypeWithEnum != null) {
+            String originalType = property.datatypeWithEnum;
+            
+            for (String nestedType : nestedTypes) {
+                // fix incorrect data types for maps of maps
+                if (property.items != null) {
+                    if (property.datatypeWithEnum.contains(", " + nestedType + ">")) {
+                        property.datatypeWithEnum = property.datatypeWithEnum.replace(", " + nestedType + ">", ", " + property.items.datatypeWithEnum + ">");
+                    }
 
-        Arrays.stream(nestedTypes).forEach(nestedType -> {
-            // fix incorrect data types for maps of maps
-            if (property.datatypeWithEnum.contains(", " + nestedType + ">") && property.items != null) {
-                property.datatypeWithEnum = property.datatypeWithEnum.replace(", " + nestedType + ">", ", " + property.items.datatypeWithEnum + ">");
-                property.dataType = property.datatypeWithEnum;
+                    if (property.datatypeWithEnum.contains("<" + nestedType + ">")) {
+                        property.datatypeWithEnum = property.datatypeWithEnum.replace("<" + nestedType + ">", "<" + property.items.datatypeWithEnum + ">");
+                    }
+                }
             }
 
-            if (property.datatypeWithEnum.contains("<" + nestedType + ">") && property.items != null) {
-                property.datatypeWithEnum = property.datatypeWithEnum.replace("<" + nestedType + ">", "<" + property.items.datatypeWithEnum + ">");
+            // Only update dataType if we actually made changes
+            if (!originalType.equals(property.datatypeWithEnum)) {
                 property.dataType = property.datatypeWithEnum;
             }
-        });
-
-        // HOTFIX: https://github.com/OpenAPITools/openapi-generator/issues/14944
-        if (property.datatypeWithEnum.equals("decimal")) {
-            property.isDecimal = true;
         }
     }