fix(golang): make object values nullable when specified

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

@@ -394,7 +394,23 @@ public String getTypeDeclaration(Schema p) {
             return "[]" + typDecl;
         } else if (ModelUtils.isMapSchema(p)) {
             Schema inner = ModelUtils.getAdditionalProperties(p);
-            return getSchemaType(p) + "[string]" + getTypeDeclaration(unaliasSchema(inner));
+            if (inner != null) {
+                inner = unaliasSchema(inner);
+            }
+            String typDecl;
+            if (inner != null) {
+                typDecl = getTypeDeclaration(inner);
+            } else {
+                typDecl = "interface{}";
+            }
+
+            // when nullable and the type of the map isn't nullable already (maps, slices, ...): make it a pointer
+            if (inner != null && Boolean.TRUE.equals(inner.getNullable()) && !typDecl.startsWith("map") && !typDecl.startsWith("[]")) {
+                typDecl = "*" + typDecl;
+            }
+
+            return getSchemaType(p) + "[string]" + typDecl;
+
         }
 
         //return super.getTypeDeclaration(p);

modules/openapi-generator/src/test/java/org/openapitools/codegen/go/AbstractGoCodegenTest.java

@@ -119,6 +119,35 @@ public void getTypeDeclarationTest() {
         ModelUtils.setGenerateAliasAsModel(false);
         defaultValue = codegen.getTypeDeclaration(schema);
         Assert.assertEquals(defaultValue, "map[string]interface{}");
+
+        // Create object schema with nullable set to false
+        ModelUtils.setGenerateAliasAsModel(false);
+        schema = new ObjectSchema().additionalProperties(new StringSchema().nullable(false));
+        defaultValue = codegen.getTypeDeclaration(schema);
+        Assert.assertEquals(defaultValue, "map[string]string");
+
+        // Create object schema with nullable set to true
+        ModelUtils.setGenerateAliasAsModel(false);
+        schema = new ObjectSchema().additionalProperties(new StringSchema().nullable(true));
+        defaultValue = codegen.getTypeDeclaration(schema);
+        Assert.assertEquals(defaultValue, "map[string]*string");
+
+        // slice in object schema is no pointer, even if nullable (slices are already nullable by default in Golang)
+        ModelUtils.setGenerateAliasAsModel(false);
+        schema = new ObjectSchema().additionalProperties(new ArraySchema().nullable(true).items(new IntegerSchema().format("int32")));
+        defaultValue = codegen.getTypeDeclaration(schema);
+        Assert.assertEquals(defaultValue, "map[string][]int32");
+
+        // map in nested object schema is no pointer, even if nullable (maps are already nullable by default in Golang)
+        ModelUtils.setGenerateAliasAsModel(false);
+        schema = new ObjectSchema().additionalProperties(new ObjectSchema().nullable(true));
+        defaultValue = codegen.getTypeDeclaration(schema);
+        Assert.assertEquals(defaultValue, "map[string]map[string]interface{}");
+
+        // nested object schema with nullable set to true (maps itself are already nullable by default in Golang, so no pointer type needed there)
+        schema = new ObjectSchema().additionalProperties(new ObjectSchema().nullable(true).additionalProperties(new StringSchema().nullable(true)));
+        defaultValue = codegen.getTypeDeclaration(schema);
+        Assert.assertEquals(defaultValue, "map[string]map[string]*string");
     }
 
     @Test(description = "test that os import is added for array of binary parameters in operations")