[DefaultGenerator] consider referenced headers (#863)

Author: Matthieu Berthomé

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

@@ -2260,7 +2260,7 @@ public CodegenOperation fromOperation(String path,
             for (String key : operation.getResponses().keySet()) {
                 ApiResponse response = operation.getResponses().get(key);
                 addProducesInfo(openAPI, response, op);
-                CodegenResponse r = fromResponse(key, response);
+                CodegenResponse r = fromResponse(openAPI, key, response);
                 r.hasMore = true;
                 if (r.baseType != null &&
                         !defaultIncludes.contains(r.baseType) &&
@@ -2329,7 +2329,7 @@ public CodegenOperation fromOperation(String path,
                         op.returnTypeIsPrimitive = true;
                     }
                 }
-                addHeaders(methodResponse, op.responseHeaders);
+                addHeaders(openAPI, methodResponse, op.responseHeaders);
             }
         }
 
@@ -2506,11 +2506,12 @@ public boolean isParameterNameUnique(CodegenParameter p, List<CodegenParameter>
     /**
      * Convert OAS Response object to Codegen Response object
      *
+     * @param openAPI    a OAS object representing the spec
      * @param responseCode HTTP response code
      * @param response     OAS Response object
      * @return Codegen Response object
      */
-    public CodegenResponse fromResponse(String responseCode, ApiResponse response) {
+    public CodegenResponse fromResponse(OpenAPI openAPI, String responseCode, ApiResponse response) {
         CodegenResponse r = CodegenModelFactory.newInstance(CodegenModelType.RESPONSE);
         if ("default".equals(responseCode)) {
             r.code = "0";
@@ -2527,7 +2528,7 @@ public CodegenResponse fromResponse(String responseCode, ApiResponse response) {
         if (response.getExtensions() != null && !response.getExtensions().isEmpty()) {
             r.vendorExtensions.putAll(response.getExtensions());
         }
-        addHeaders(response, r.headers);
+        addHeaders(openAPI, response, r.headers);
         r.hasHeaders = !r.headers.isEmpty();
 
         if (r.schema != null) {
@@ -3073,12 +3074,15 @@ protected List<Map<String, Object>> toExamples(Map<String, Object> examples) {
      * @param response   API response
      * @param properties list of codegen property
      */
-    private void addHeaders(ApiResponse response, List<CodegenProperty> properties) {
+    private void addHeaders(OpenAPI openAPI, ApiResponse response, List<CodegenProperty> properties) {
         if (response.getHeaders() != null) {
             for (Map.Entry<String, Header> headers : response.getHeaders().entrySet()) {
-                CodegenProperty cp = fromProperty(headers.getKey(), headers.getValue().getSchema());
-                cp.setDescription(escapeText(headers.getValue().getDescription()));
-                cp.setUnescapedDescription(headers.getValue().getDescription());
+                String description = headers.getValue().getDescription();
+                // follow the $ref
+                Header header = ModelUtils.getReferencedHeader(openAPI, headers.getValue());
+                CodegenProperty cp = fromProperty(headers.getKey(), header.getSchema());
+                cp.setDescription(escapeText(description));
+                cp.setUnescapedDescription(description);
                 properties.add(cp);
             }
         }

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

@@ -512,8 +512,8 @@ public CodegenProperty fromProperty(String name, Schema p) {
     }
 
     @Override
-    public CodegenResponse fromResponse(String responseCode, ApiResponse resp) {
-        final CodegenResponse response = super.fromResponse(responseCode, resp);
+    public CodegenResponse fromResponse(OpenAPI openAPI, String responseCode, ApiResponse resp) {
+        final CodegenResponse response = super.fromResponse(openAPI, responseCode, resp);
         if (response.dataType != null) {
             addEncoderAndDecoder(response.vendorExtensions, response.dataType, response.isMapContainer, response.primitiveType);
         }

modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java

@@ -20,6 +20,7 @@
 import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.Operation;
 import io.swagger.v3.oas.models.PathItem;
+import io.swagger.v3.oas.models.headers.Header;
 import io.swagger.v3.oas.models.media.ArraySchema;
 import io.swagger.v3.oas.models.media.BinarySchema;
 import io.swagger.v3.oas.models.media.BooleanSchema;
@@ -670,4 +671,25 @@ public static Schema getAdditionalProperties(Schema schema) {
         return null;
     }
 
+    public static Header getReferencedHeader(OpenAPI openAPI, Header header) {
+        if (header != null && StringUtils.isNotEmpty(header.get$ref())) {
+            String name = getSimpleRef(header.get$ref());
+            Header referencedheader = getHeader(openAPI, name);
+            if (referencedheader != null) {
+                return referencedheader;
+            }
+        }
+        return header;
+    }
+
+    public static Header getHeader(OpenAPI openAPI, String name) {
+        if (name == null) {
+            return null;
+        }
+
+        if (openAPI != null && openAPI.getComponents() != null && openAPI.getComponents().getHeaders() != null) {
+            return openAPI.getComponents().getHeaders().get(name);
+        }
+        return null;
+    }
 }

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

@@ -31,18 +31,12 @@
 import io.swagger.v3.oas.models.media.Schema;
 import io.swagger.v3.oas.models.media.StringSchema;
 import io.swagger.v3.oas.models.parameters.RequestBody;
+import io.swagger.v3.oas.models.responses.ApiResponse;
 import io.swagger.v3.parser.core.models.ParseOptions;
 import io.swagger.v3.parser.util.SchemaTypeUtil;
 
-import org.openapitools.codegen.ClientOptInput;
-import org.openapitools.codegen.CodegenConstants;
-import org.openapitools.codegen.CodegenModel;
-import org.openapitools.codegen.CodegenOperation;
-import org.openapitools.codegen.CodegenParameter;
-import org.openapitools.codegen.CodegenProperty;
-import org.openapitools.codegen.MockDefaultGenerator;
+import org.openapitools.codegen.*;
 import org.openapitools.codegen.MockDefaultGenerator.WrittenTemplateBasedFile;
-import org.openapitools.codegen.TestUtils;
 import org.openapitools.codegen.config.CodegenConfigurator;
 import org.openapitools.codegen.languages.JavaClientCodegen;
 import org.openapitools.codegen.utils.ModelUtils;
@@ -305,6 +299,20 @@ public void testGeneratePing() throws Exception {
         output.deleteOnExit();
     }
 
+    @Test
+    public void testReferencedHeader() {
+        final OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/3_0/issue855.yaml", null, new ParseOptions()).getOpenAPI();
+        JavaClientCodegen codegen = new JavaClientCodegen();
+
+        ApiResponse ok_200 = openAPI.getComponents().getResponses().get("OK_200");
+        CodegenResponse response = codegen.fromResponse(openAPI, "200", ok_200);
+
+        Assert.assertEquals(1, response.headers.size());
+        CodegenProperty header = response.headers.get(0);
+        Assert.assertEquals("UUID", header.dataType);
+        Assert.assertEquals("Request", header.baseName);
+    }
+
     @Test
     public void testFreeFormObjects() {
         final OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/3_0/issue796.yaml", null, new ParseOptions()).getOpenAPI();

modules/openapi-generator/src/test/resources/3_0/issue855.yaml

@@ -0,0 +1,29 @@
+openapi: 3.0.1
+info:
+  title: Issue 855 example
+  version: 1.0.0
+components:
+  headers:
+    Request:
+      description: ID of the request, unique to the call, as determined by the initiating party.
+      required: true
+      example: "99391c7e-ad88-49ec-a2ad-99ddcb1f7721"
+      schema:
+        type: string
+        format: uuid
+
+  responses:
+    OK_200:
+      description: OK
+      headers:
+        Request:
+          $ref: "#/components/headers/Request"
+
+paths:
+  /ping:
+    get:
+      summary: Get Payment Information
+      description: Returns the content of a payment object
+      responses:
+        '200':
+          $ref: "#/components/responses/OK_200"