add cache to efficiently lookup CodegenModel in csharp codegen

Author: ivan_leb

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

@@ -116,6 +116,9 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen {
     // A cache to efficiently lookup schema `toModelName()` based on the schema Key
     private final Map<String, String> schemaKeyToModelNameCache = new HashMap<>();
 
+    // A cache to efficiently lookup CodegenModel `fromModel(codegenModelName, parentModelSchema)` based on the pair of model name and schema
+    private final Map<Map.Entry<String, Schema>, CodegenModel> codegenModelNameAndSchemaKeyToCodegenModelCache = new HashMap<>();
+
     public AbstractCSharpCodegen() {
         super();
 
@@ -1703,6 +1706,17 @@ public String toModelTestFilename(String name) {
         return toModelName(name) + "Tests";
     }
 
+    protected CodegenModel getCodegenModel(String codegenModelName, Schema schema){
+       var key = new AbstractMap.SimpleEntry<>(codegenModelName, schema);
+       if(codegenModelNameAndSchemaKeyToCodegenModelCache.containsKey(key)){
+           return codegenModelNameAndSchemaKeyToCodegenModelCache.get(key);
+       }
+
+       CodegenModel model = super.fromModel(codegenModelName, schema);
+       codegenModelNameAndSchemaKeyToCodegenModelCache.put(key, model);
+       return model;
+    }
+
     public void setNullableReferenceTypes(final Boolean nullReferenceTypesFlag) {
         this.nullReferenceTypesFlag = nullReferenceTypesFlag;
         additionalProperties.put("nullableReferenceTypes", nullReferenceTypesFlag);

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

@@ -436,7 +436,7 @@ public CodegenModel fromModel(String name, Schema model) {
         if (allDefinitions != null && codegenModel != null && codegenModel.parent != null) {
             final Schema<?> parentModel = allDefinitions.get(toModelName(codegenModel.parent));
             if (parentModel != null) {
-                final CodegenModel parentCodegenModel = super.fromModel(codegenModel.parent, parentModel);
+                final CodegenModel parentCodegenModel = getCodegenModel(codegenModel.parent, parentModel);
                 if (codegenModel.hasEnums) {
                     codegenModel = this.reconcileInlineEnums(codegenModel, parentCodegenModel);
                 }

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

@@ -380,7 +380,7 @@ public CodegenModel fromModel(String name, Schema model) {
         if (allDefinitions != null && codegenModel != null && codegenModel.parent != null) {
             final Schema parentModel = allDefinitions.get(toModelName(codegenModel.parent));
             if (parentModel != null) {
-                final CodegenModel parentCodegenModel = super.fromModel(codegenModel.parent, parentModel);
+                final CodegenModel parentCodegenModel = getCodegenModel(codegenModel.parent, parentModel);
                 if (codegenModel.hasEnums) {
                     codegenModel = this.reconcileInlineEnums(codegenModel, parentCodegenModel);
                 }