From a411cab939d764da8dba284223d2756ef30b1afb Mon Sep 17 00:00:00 2001
From: Alitzel Mendez <6895254+AlitzelMendez@users.noreply.github.com>
Date: Fri, 15 Nov 2024 12:02:49 -0800
Subject: [PATCH] No matching versions found (#1838)

issue: https://github.com/Azure/typespec-azure/issues/1647
---
 ...orest-version-error-2024-10-14-17-31-30.md |  7 +++++
 packages/typespec-autorest/src/emit.ts        |  6 +++-
 packages/typespec-autorest/src/lib.ts         |  7 +++++
 .../typespec-autorest/test/versioning.test.ts | 28 ++++++++++++++++++-
 4 files changed, 46 insertions(+), 2 deletions(-)
 create mode 100644 .chronus/changes/fix-autorest-version-error-2024-10-14-17-31-30.md

diff --git a/.chronus/changes/fix-autorest-version-error-2024-10-14-17-31-30.md b/.chronus/changes/fix-autorest-version-error-2024-10-14-17-31-30.md
new file mode 100644
index 0000000000..d606e76c98
--- /dev/null
+++ b/.chronus/changes/fix-autorest-version-error-2024-10-14-17-31-30.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-autorest"
+---
+
+Emit error `@azure-tools/typespec-autorest/no-matching-version-found` when the version option is used and does not match any versions of the service.
diff --git a/packages/typespec-autorest/src/emit.ts b/packages/typespec-autorest/src/emit.ts
index a6877fada4..372f4a5af4 100644
--- a/packages/typespec-autorest/src/emit.ts
+++ b/packages/typespec-autorest/src/emit.ts
@@ -17,7 +17,7 @@ import {
 } from "@typespec/compiler";
 import { resolveInfo } from "@typespec/openapi";
 import { buildVersionProjections } from "@typespec/versioning";
-import { AutorestEmitterOptions, getTracer } from "./lib.js";
+import { AutorestEmitterOptions, getTracer, reportDiagnostic } from "./lib.js";
 import {
   AutorestDocumentEmitterOptions,
   getOpenAPIForService,
@@ -128,6 +128,10 @@ export async function getAllServicesAtAllVersions(
       (v) => !options.version || options.version === v.version,
     );
 
+    if (versions.length === 0) {
+      reportDiagnostic(program, { code: "no-matching-version-found", target: service.type });
+    }
+
     if (versions.length === 1 && versions[0].version === undefined) {
       let projectedProgram;
       if (versions[0].projections.length > 0) {
diff --git a/packages/typespec-autorest/src/lib.ts b/packages/typespec-autorest/src/lib.ts
index 30e1e7170f..aa56def8b2 100644
--- a/packages/typespec-autorest/src/lib.ts
+++ b/packages/typespec-autorest/src/lib.ts
@@ -353,6 +353,13 @@ export const $lib = createTypeSpecLibrary({
         default: paramMessage`Authentication "${"authType"}" is not a known authentication by the openapi3 emitter, it will be ignored.`,
       },
     },
+    "no-matching-version-found": {
+      severity: "error",
+      messages: {
+        default:
+          "The emitter did not emit any files because the specified version option does not match any versions of the service.",
+      },
+    },
   },
   emitter: {
     options: EmitterOptionsSchema as JSONSchemaType<AutorestEmitterOptions>,
diff --git a/packages/typespec-autorest/test/versioning.test.ts b/packages/typespec-autorest/test/versioning.test.ts
index b1a5b341ac..18be51171b 100644
--- a/packages/typespec-autorest/test/versioning.test.ts
+++ b/packages/typespec-autorest/test/versioning.test.ts
@@ -1,7 +1,8 @@
+import { expectDiagnostics } from "@typespec/compiler/testing";
 import { deepStrictEqual, strictEqual } from "assert";
 import { describe, expect, it } from "vitest";
 import { OpenAPI2Document } from "../src/openapi2-document.js";
-import { openApiFor } from "./test-host.js";
+import { diagnoseOpenApiFor, openApiFor } from "./test-host.js";
 
 describe("typespec-autorest: versioning", () => {
   it("if version enum is referenced only include current member and mark it with modelAsString: true", async () => {
@@ -269,4 +270,29 @@ describe("typespec-autorest: versioning", () => {
       required: ["jsonProp1", "jsonProp2", "prop3"],
     });
   });
+
+  it("emit diagnostics when version option is used an doesn't match the versions of the service", async () => {
+    const diagnostics = await diagnoseOpenApiFor(
+      `
+@versioned(Versions)
+@service
+namespace DemoService;
+
+enum Versions {
+  v1,
+  v2,
+}
+
+model A {}
+    `,
+      { version: "v3" },
+    );
+    expectDiagnostics(diagnostics, [
+      {
+        code: "@azure-tools/typespec-autorest/no-matching-version-found",
+        message:
+          "The emitter did not emit any files because the specified version option does not match any versions of the service.",
+      },
+    ]);
+  });
 });