Sync Java core duplicate discriminator fix

.chronus/changes/fix-java-duplicate-inherited-discriminators-2026-09-02.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-java"
+---
+
+Avoid duplicate inherited discriminator fields in generated Java models.

packages/typespec-java/core-commit.json

@@ -1 +1 @@
-{ "sha": "890cad64c70072aacf01c8e540a26fb676fa6abe" }
+{ "sha": "a61e90890abb32806dba1efa87f6d4f0aae8bf29" }

packages/typespec-java/emitter-tests/src/test/java/tsptest/discriminatoredgecases/DiscriminatorRegressionTests.java

@@ -0,0 +1,51 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package tsptest.discriminatoredgecases;
+
+import com.azure.core.util.BinaryData;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import tsptest.discriminatoredgecases.models.RegressionAncestorOrdinaryPropertyMaskingAssistant;
+import tsptest.discriminatoredgecases.models.RegressionAncestorOrdinaryPropertyMaskingBase;
+import tsptest.discriminatoredgecases.models.RegressionDuplicateRepeatedInheritedDiscriminatorAssistant;
+import tsptest.discriminatoredgecases.models.RegressionDuplicateRepeatedInheritedDiscriminatorBase;
+import tsptest.discriminatoredgecases.models.RegressionSuperclassConstructorPropagationAssistant;
+import tsptest.discriminatoredgecases.models.RegressionSuperclassConstructorPropagationBase;
+
+public class DiscriminatorRegressionTests {
+
+    @Test
+    public void duplicateRepeatedInheritedDiscriminatorHasOneCanonicalRepresentation() {
+        String json = "{\"type\":\"message\",\"role\":\"assistant\"}";
+
+        RegressionDuplicateRepeatedInheritedDiscriminatorBase model
+            = BinaryData.fromString(json).toObject(RegressionDuplicateRepeatedInheritedDiscriminatorBase.class);
+
+        Assertions.assertInstanceOf(RegressionDuplicateRepeatedInheritedDiscriminatorAssistant.class, model);
+        Assertions.assertEquals(json, BinaryData.fromObject(model).toString());
+    }
+
+    @Test
+    public void canonicalDiscriminatorMasksAncestorOrdinaryProperty() {
+        String json = "{\"type\":\"message\",\"role\":\"assistant\"}";
+
+        RegressionAncestorOrdinaryPropertyMaskingBase model
+            = BinaryData.fromString(json).toObject(RegressionAncestorOrdinaryPropertyMaskingBase.class);
+
+        Assertions.assertInstanceOf(RegressionAncestorOrdinaryPropertyMaskingAssistant.class, model);
+        Assertions.assertEquals(json, BinaryData.fromObject(model).toString());
+    }
+
+    @Test
+    public void canonicalDiscriminatorSuppliesSuperclassConstructor() {
+        String json = "{\"type\":\"message\",\"role\":\"assistant\"}";
+
+        RegressionSuperclassConstructorPropagationBase model
+            = BinaryData.fromString(json).toObject(RegressionSuperclassConstructorPropagationBase.class);
+
+        Assertions.assertInstanceOf(RegressionSuperclassConstructorPropagationAssistant.class, model);
+        Assertions.assertEquals("message", model.getType());
+    }
+
+}

packages/typespec-java/emitter-tests/src/test/java/tsptest/responseheaders/ResponseHeadersTests.java

@@ -8,6 +8,7 @@
 import com.azure.core.test.http.MockHttpResponse;
 import java.time.OffsetDateTime;
 import java.time.ZoneOffset;
+import java.util.Map;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 import reactor.core.publisher.Mono;
@@ -25,7 +26,9 @@ private ResponseHeadersClient createClient(HttpHeaders responseHeaders) {
     public void testResponseHeadersAsModel() {
         HttpHeaders responseHeaders = new HttpHeaders().set(HttpHeaderName.ETAG, "\"0x8D9\"")
             .set(HttpHeaderName.fromString("x-resource-count"), "42")
-            .set(HttpHeaderName.LAST_MODIFIED, "Mon, 26 Aug 2022 14:38:00 GMT");
+            .set(HttpHeaderName.LAST_MODIFIED, "Mon, 26 Aug 2022 14:38:00 GMT")
+            .set(HttpHeaderName.fromString("X-Ms-Meta-key1"), "value1")
+            .set(HttpHeaderName.fromString("x-ms-meta-key2"), "value2");
 
         ResponseHeaderOpsGetResourceMetadataHeaders headers = createClient(responseHeaders).getResourceMetadata();
 
@@ -35,6 +38,7 @@ public void testResponseHeadersAsModel() {
         Assertions.assertEquals(42, headers.getResourceCount());
         Assertions.assertEquals(OffsetDateTime.of(2022, 8, 26, 14, 38, 0, 0, ZoneOffset.UTC),
             headers.getLastModified());
+        Assertions.assertEquals(Map.of("key1", "value1", "key2", "value2"), headers.getMetadata());
     }
 
     @Test

packages/typespec-java/emitter-tests/tsp/discriminator-edge-cases.tsp

@@ -1,8 +1,10 @@
 import "@typespec/rest";
+import "@typespec/xml";
 import "@azure-tools/typespec-azure-core";
 import "@azure-tools/typespec-client-generator-core";
 
 using TypeSpec.Http;
+using TypeSpec.Xml;
 using Azure.Core;
 using Azure.ClientGenerator.Core;
 
@@ -28,6 +30,91 @@ model GrandChildWithRequiredProperty extends ChildWithRequiredPropertyAsDiscrimi
   discriminator: "aValue";
 }
 
+@usage(Usage.output)
+@access(Access.public)
+@discriminator("type")
+model RegressionDuplicateRepeatedInheritedDiscriminatorBase {
+  type: string;
+}
+
+@discriminator("role")
+model RegressionDuplicateRepeatedInheritedDiscriminatorMessage
+  extends RegressionDuplicateRepeatedInheritedDiscriminatorBase {
+  type: "message";
+  role: string;
+}
+
+model RegressionDuplicateRepeatedInheritedDiscriminatorAssistant
+  extends RegressionDuplicateRepeatedInheritedDiscriminatorMessage {
+  type: "message";
+  role: "assistant";
+}
+
+model RegressionAncestorOrdinaryPropertyMaskingRoot {
+  type?: string;
+}
+
+@usage(Usage.output)
+@access(Access.public)
+@discriminator("type")
+model RegressionAncestorOrdinaryPropertyMaskingBase
+  extends RegressionAncestorOrdinaryPropertyMaskingRoot {}
+
+@discriminator("role")
+model RegressionAncestorOrdinaryPropertyMaskingMessage
+  extends RegressionAncestorOrdinaryPropertyMaskingBase {
+  type: "message";
+  role: string;
+}
+
+model RegressionAncestorOrdinaryPropertyMaskingAssistant
+  extends RegressionAncestorOrdinaryPropertyMaskingMessage {
+  role: "assistant";
+}
+
+model RegressionSuperclassConstructorPropagationRoot {
+  type: string;
+}
+
+@usage(Usage.output)
+@access(Access.public)
+@discriminator("type")
+model RegressionSuperclassConstructorPropagationBase
+  extends RegressionSuperclassConstructorPropagationRoot {}
+
+@discriminator("role")
+model RegressionSuperclassConstructorPropagationMessage
+  extends RegressionSuperclassConstructorPropagationBase {
+  type: "message";
+  role: string;
+}
+
+model RegressionSuperclassConstructorPropagationAssistant
+  extends RegressionSuperclassConstructorPropagationMessage {
+  role: "assistant";
+}
+
+@usage(Usage.output)
+@access(Access.public)
+@name("NestedDiscriminatorBase")
+@discriminator("type")
+model NestedDiscriminatorBase {
+  @attribute type: string;
+}
+
+@name("NestedDiscriminatorMessage")
+@discriminator("role")
+model NestedDiscriminatorMessage extends NestedDiscriminatorBase {
+  @attribute type: "message";
+  @attribute role: string;
+}
+
+@name("NestedDiscriminatorAssistant")
+model NestedDiscriminatorAssistant extends NestedDiscriminatorMessage {
+  @attribute type: "message";
+  @attribute role: "assistant";
+}
+
 model GrandChildWithAnotherDiscriminator extends ChildWithAnotherDiscriminator {
   differentDiscriminator: "anotherValue";
 }

packages/typespec-java/emitter-tests/tsp/response-headers.tsp

@@ -7,6 +7,10 @@ using Azure.ClientGenerator.Core;
 @service(#{ title: "ResponseHeaders" })
 namespace TspTest.ResponseHeaders;
 
+model MetadataHeaders {
+  @header("x-ms-meta") metadata?: string;
+}
+
 @route("/response-headers")
 interface ResponseHeaderOp {
   // HEAD operation with significant response headers but no response body.
@@ -28,7 +32,11 @@ interface ResponseHeaderOp {
 
     // optional header, with mixed-case header name
     @header("Last-Modified") lastModified?: utcDateTime;
+
+    ...MetadataHeaders;
   };
 }
 
 @@clientOption(ResponseHeaderOp.getResourceMetadata, "responseHeadersAsModel", true, "java");
+@@alternateType(MetadataHeaders.metadata, Record<string>, "java");
+@@clientOption(MetadataHeaders.metadata, "collectionHeaderPrefix", "x-ms-meta-", "java");