From 64f2319d8c878a65d1a53f7a13961c88bd9c1e27 Mon Sep 17 00:00:00 2001
From: Jose Manuel Heredia Hidalgo <joheredi@microsoft.com>
Date: Mon, 27 Jan 2025 16:29:03 -0800
Subject: [PATCH 1/2] Add option to enable semantic walker to visit derived
 models

---
 packages/compiler/src/core/semantic-walker.ts |  11 ++
 .../compiler/test/semantic-walker.test.ts     | 104 +++++++++++++++++-
 2 files changed, 114 insertions(+), 1 deletion(-)

diff --git a/packages/compiler/src/core/semantic-walker.ts b/packages/compiler/src/core/semantic-walker.ts
index 693313c692..7b0e9d3761 100644
--- a/packages/compiler/src/core/semantic-walker.ts
+++ b/packages/compiler/src/core/semantic-walker.ts
@@ -27,6 +27,10 @@ export interface NavigationOptions {
    * Skip non instantiated templates.
    */
   includeTemplateDeclaration?: boolean;
+  /**
+   * Visit derived types.
+   */
+  visitDerivedTypes?: boolean;
 }
 
 export interface NamespaceNavigationOptions {
@@ -253,6 +257,13 @@ function navigateModelType(model: Model, context: NavigationContext) {
   if (model.indexer && model.indexer.value) {
     navigateTypeInternal(model.indexer.value, context);
   }
+
+  if (context.options.visitDerivedTypes) {
+    for (const derived of model.derivedModels) {
+      navigateModelType(derived, context);
+    }
+  }
+
   context.emit("exitModel", model);
 }
 
diff --git a/packages/compiler/test/semantic-walker.test.ts b/packages/compiler/test/semantic-walker.test.ts
index 8d35b1c883..ce86966de3 100644
--- a/packages/compiler/test/semantic-walker.test.ts
+++ b/packages/compiler/test/semantic-walker.test.ts
@@ -17,15 +17,23 @@ import {
 import {
   getProperty,
   navigateProgram,
+  navigateType,
   navigateTypesInNamespace,
 } from "../src/core/semantic-walker.js";
-import { TestHost, createTestHost } from "../src/testing/index.js";
+import {
+  BasicTestRunner,
+  TestHost,
+  createTestHost,
+  createTestRunner,
+} from "../src/testing/index.js";
 
 describe("compiler: semantic walker", () => {
   let host: TestHost;
+  let runner: BasicTestRunner;
 
   beforeEach(async () => {
     host = await createTestHost();
+    runner = await createTestRunner();
   });
 
   function createCollector(customListener?: SemanticNodeListener) {
@@ -138,6 +146,100 @@ describe("compiler: semantic walker", () => {
     return result;
   }
 
+  it("finds derived models", async () => {
+    const { Bird } = (await runner.compile(`
+      namespace Test;
+
+      @discriminator("kind")
+      @test 
+      model Bird {
+        kind: string;
+        wingspan: int32;
+      }
+
+      model SeaGull extends Bird {
+        kind: "seagull";
+      }
+
+      model Sparrow extends Bird {
+        kind: "sparrow";
+      }
+
+      model Goose extends Bird {
+        kind: "goose";
+      }
+
+      model Eagle extends Bird {
+        kind: "eagle";
+        friends?: Bird[];
+        hate?: Record<Bird>;
+        partner?: Bird;
+      }
+      `)) as { Bird: Model };
+
+    const visitedModels: Model[] = [];
+    navigateType(
+      Bird,
+      {
+        model(model) {
+          visitedModels.push(model);
+        },
+      },
+      { includeTemplateDeclaration: false, visitDerivedTypes: true },
+    );
+
+    const expectedModels = ["Bird", "SeaGull", "Sparrow", "Goose", "Eagle"];
+    strictEqual(
+      expectedModels.every((element) => visitedModels.map((m) => m.name).includes(element)),
+      true,
+    );
+  });
+
+  it("doesn't visit derived models without the option", async () => {
+    const { Bird } = (await runner.compile(`
+      namespace Test;
+
+      @discriminator("kind")
+      @test 
+      model Bird {
+        kind: string;
+        wingspan: int32;
+      }
+
+      model SeaGull extends Bird {
+        kind: "seagull";
+      }
+
+      model Sparrow extends Bird {
+        kind: "sparrow";
+      }
+
+      model Goose extends Bird {
+        kind: "goose";
+      }
+
+      model Eagle extends Bird {
+        kind: "eagle";
+        friends?: Bird[];
+        hate?: Record<Bird>;
+        partner?: Bird;
+      }
+      `)) as { Bird: Model };
+
+    const visitedModels: Model[] = [];
+    navigateType(
+      Bird,
+      {
+        model(model) {
+          visitedModels.push(model);
+        },
+      },
+      { visitDerivedTypes: false },
+    );
+
+    strictEqual(visitedModels.length, 1);
+  });
+
   it("finds models", async () => {
     const result = await runNavigator(`
       model Foo {

From 117510f01a36219ad5e9f41546b5c187394c2662 Mon Sep 17 00:00:00 2001
From: Jose Manuel Heredia Hidalgo <joheredi@microsoft.com>
Date: Mon, 27 Jan 2025 16:30:11 -0800
Subject: [PATCH 2/2] Add change description

---
 ...er-semantic-walker-derived-models-2025-0-27-16-29-58.md | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 .chronus/changes/feature-compiler-semantic-walker-derived-models-2025-0-27-16-29-58.md

diff --git a/.chronus/changes/feature-compiler-semantic-walker-derived-models-2025-0-27-16-29-58.md b/.chronus/changes/feature-compiler-semantic-walker-derived-models-2025-0-27-16-29-58.md
new file mode 100644
index 0000000000..4767aff027
--- /dev/null
+++ b/.chronus/changes/feature-compiler-semantic-walker-derived-models-2025-0-27-16-29-58.md
@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@typespec/compiler"
+---
+
+Add option for semantic walker to visit model derived types
\ No newline at end of file