[go] fix: explode object query parameters

modules/openapi-generator/src/main/resources/go/client.mustache

@@ -191,10 +191,14 @@ func parameterAddToHeaderOrQuery(headerOrQueryParams interface{}, keyPrefix stri
 				for i:=0;i<lenIndValue;i++ {
 					var arrayValue = indValue.Index(i)
 					var keyPrefixForCollectionType = keyPrefix
+					var styleForElement = style
 					if style == "deepObject" {
 						keyPrefixForCollectionType = keyPrefix + "[" + strconv.Itoa(i) + "]"
+					} else if style == "form" {
+						// only the parameter's own map is flattened; a map inside an array keeps its bracketed path
+						styleForElement = ""
 					}
-					parameterAddToHeaderOrQuery(headerOrQueryParams, keyPrefixForCollectionType, arrayValue.Interface(), style, collectionType)
+					parameterAddToHeaderOrQuery(headerOrQueryParams, keyPrefixForCollectionType, arrayValue.Interface(), styleForElement, collectionType)
 				}
 				return
 
@@ -206,13 +210,36 @@ func parameterAddToHeaderOrQuery(headerOrQueryParams interface{}, keyPrefix stri
 				iter := indValue.MapRange()
 				for iter.Next() {
 					k,v := iter.Key(), iter.Value()
-					parameterAddToHeaderOrQuery(headerOrQueryParams, fmt.Sprintf("%s[%s]", keyPrefix, k.String()), v.Interface(), style, collectionType)
+					var keyPrefixForMapEntry = fmt.Sprintf("%s[%s]", keyPrefix, k.String())
+					var styleForMapEntry = style
+					if style == "form" {
+						// form style: one query parameter per entry, keyed by the property name; anything nested keeps its bracketed path
+						keyPrefixForMapEntry = k.String()
+						styleForMapEntry = ""
+						// a nil entry, or a nil item of a list entry, is left out rather than sent as "null"
+						entry, ok := parameterValueIndirect(v)
+						if !ok {
+							continue
+						}
+						if entry.Kind() == reflect.Slice {
+							for i := 0; i < entry.Len(); i++ {
+								if element, ok := parameterValueIndirect(entry.Index(i)); ok {
+									parameterAddToHeaderOrQuery(headerOrQueryParams, keyPrefixForMapEntry, element.Interface(), styleForMapEntry, collectionType)
+								}
+							}
+							continue
+						}
+					}
+					parameterAddToHeaderOrQuery(headerOrQueryParams, keyPrefixForMapEntry, v.Interface(), styleForMapEntry, collectionType)
 				}
 				return
 
 			case reflect.Interface:
 				fallthrough
 			case reflect.Ptr:
+				if v.IsNil() {
+					return
+				}
 				parameterAddToHeaderOrQuery(headerOrQueryParams, keyPrefix, v.Elem().Interface(), style, collectionType)
 				return
 
@@ -247,6 +274,18 @@ func parameterAddToHeaderOrQuery(headerOrQueryParams interface{}, keyPrefix stri
 	}
 }
 
+// parameterValueIndirect unwraps interfaces and pointers down to the value they hold,
+// reporting false when that value is nil
+func parameterValueIndirect(v reflect.Value) (reflect.Value, bool) {
+	for v.Kind() == reflect.Interface || v.Kind() == reflect.Ptr {
+		if v.IsNil() {
+			return v, false
+		}
+		v = v.Elem()
+	}
+	return v, v.IsValid()
+}
+
 // helper for converting interface{} parameters to json strings
 func parameterToJson(obj interface{}) (string, error) {
 	jsonBuf, err := json.Marshal(obj)

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

@@ -141,6 +141,35 @@ public void testPrimitiveTypeInOneOf() throws IOException {
         TestUtils.assertFileNotContains(modelFile, "dst.int32");
     }
 
+    @Test(description = "Verify form style query parameters explode an object instead of bracketing it")
+    public void testExplodedObjectQueryParameter() throws IOException {
+        File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("go")
+                .setInputSpec("src/test/resources/3_0/exploded-object-query-param.yaml")
+                .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+        DefaultGenerator generator = new DefaultGenerator();
+        List<File> files = generator.opts(configurator.toClientOptInput()).generate();
+        files.forEach(File::deleteOnExit);
+
+        TestUtils.assertFileContains(Paths.get(output + "/client.go"),
+                "keyPrefixForMapEntry = k.String()",
+                "if !ok { continue } if entry.Kind() == reflect.Slice {",
+                "case reflect.Ptr: if v.IsNil() { return }",
+                "styleForElement = \"\"");
+
+        // the api passes the declared style through
+        Path api = Paths.get(output + "/api_default.go");
+        TestUtils.assertFileContains(api,
+                "parameterAddToHeaderOrQuery(localVarQueryParams, \"filter\", r.filter, \"form\", \"\")",
+                "parameterAddToHeaderOrQuery(localVarQueryParams, \"typedFilter\", r.typedFilter, \"form\", \"\")",
+                "parameterAddToHeaderOrQuery(localVarQueryParams, \"deepFilter\", r.deepFilter, \"deepObject\", \"\")",
+                "parameterAddToHeaderOrQuery(localVarQueryParams, \"flatFilter\", r.flatFilter, \"form\", \"\")");
+    }
+
     @Test
     public void testNullableComposition() throws IOException {
         File output = Files.createTempDirectory("test").toFile();

modules/openapi-generator/src/test/resources/3_0/exploded-object-query-param.yaml

@@ -0,0 +1,49 @@
+openapi: 3.0.3
+info:
+  title: Exploded object query parameters
+  description: >
+    Object typed query parameters under form/explode (as a free-form object and as a typed map), deepObject, and form without explode. The free-form variant matters because it is flagged isMap but not isContainer.
+  version: 1.0.0
+servers:
+  - url: localhost:8080
+paths:
+  /items:
+    get:
+      operationId: listItems
+      parameters:
+        # style and explode both left out, so the form/true defaults apply: every entry
+        # becomes its own parameter, keyed by the property name alone.
+        - in: query
+          name: filter
+          schema:
+            type: object
+        # the same, but declared as a map rather than as a free-form object
+        - in: query
+          name: typedFilter
+          schema:
+            type: object
+            additionalProperties:
+              type: string
+        # deepObject nests each entry under the parameter name: deepFilter[key]=value
+        - in: query
+          name: deepFilter
+          style: deepObject
+          explode: true
+          schema:
+            type: object
+        # form without explode keeps a single parameter carrying the whole object
+        - in: query
+          name: flatFilter
+          style: form
+          explode: false
+          schema:
+            type: object
+      responses:
+        '200':
+          description: a list of items
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  type: string