Allow suppressing Python no-client warnings

.chronus/changes/fix-python-no-sdk-clients-suppression-2026-09-02.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/http-client-python"
+---
+
+Allow `no-sdk-clients` warnings to be suppressed by reporting them on the TypeSpec service namespace.

packages/http-client-python/emitter/src/emitter.ts

@@ -1,6 +1,11 @@
 import { createSdkContext } from "@azure-tools/typespec-client-generator-core";
 import type { EmitContext } from "@typespec/compiler";
-import { emitFile, joinPaths, NoTarget } from "@typespec/compiler";
+import {
+  emitFile,
+  joinPaths,
+  listServices,
+  NoTarget,
+} from "@typespec/compiler";
 import pkgJson from "../../package.json" with { type: "json" };
 import { emitCodeModel } from "./code-model.js";
 import {
@@ -92,7 +97,10 @@ function walkThroughNodes(yamlMap: Record<string, any>): Record<string, any> {
           }
         } else if (Array.isArray(current[key])) {
           stack.push(current[key]);
-        } else if (current[key] !== undefined && typeof current[key] === "object") {
+        } else if (
+          current[key] !== undefined &&
+          typeof current[key] === "object"
+        ) {
           stack.push(current[key]);
         }
       }
@@ -164,7 +172,9 @@ export async function $onEmit(context: EmitContext<PythonEmitterOptions>) {
       "========================================= error stack start ================================================";
     const errStackEnd =
       "========================================= error stack end ================================================";
-    const errStack = error.stack ? `\n${errStackStart}\n${error.stack}\n${errStackEnd}` : "";
+    const errStack = error.stack
+      ? `\n${errStackStart}\n${error.stack}\n${errStackEnd}`
+      : "";
     reportDiagnostic(context.program, {
       code: "unknown-error",
       target: NoTarget,
@@ -181,29 +191,33 @@ async function onEmitMain(context: EmitContext<PythonEmitterOptions>) {
   const yamlMap = emitCodeModel(sdkContext);
   const parsedYamlMap = walkThroughNodes(yamlMap);
 
-  // Python emitter requires an SDK client in the TypeSpec
+  // Warn when no SDK clients are present, while still allowing model-only generation.
   if (sdkContext.sdkPackage.clients.length === 0) {
     reportDiagnostic(program, {
       code: "no-sdk-clients",
-      target: NoTarget,
+      target:
+        listServices(program)[0]?.type ??
+        program.getGlobalNamespaceType().models.values().next().value ??
+        program.getGlobalNamespaceType(),
     });
-    return;
   }
 
   const resolvedOptions = sdkContext.emitContext.options;
   const commandArgs: Record<string, string> = {};
   if (resolvedOptions["packaging-files-config"]) {
-    const keyValuePairs = Object.entries(resolvedOptions["packaging-files-config"]).map(
-      ([key, value]) => {
-        return `${key}:${value}`;
-      },
-    );
+    const keyValuePairs = Object.entries(
+      resolvedOptions["packaging-files-config"],
+    ).map(([key, value]) => {
+      return `${key}:${value}`;
+    });
     commandArgs["packaging-files-config"] = keyValuePairs.join("|");
     resolvedOptions["packaging-files-config"] = undefined;
   }
   if (resolvedOptions["keep-pyproject-fields"]) {
     // Flatten the object of enabled fields into a comma-separated list for the generator.
-    const enabledFields = Object.entries(resolvedOptions["keep-pyproject-fields"])
+    const enabledFields = Object.entries(
+      resolvedOptions["keep-pyproject-fields"],
+    )
       .filter(([, value]) => value === true)
       .map(([key]) => key);
     commandArgs["keep-pyproject-fields"] = enabledFields.join(",");
@@ -215,8 +229,11 @@ async function onEmitMain(context: EmitContext<PythonEmitterOptions>) {
     commandArgs[key] = value;
   }
   if (resolvedOptions["generate-packaging-files"]) {
-    commandArgs["package-mode"] = sdkContext.arm ? "azure-mgmt" : "azure-dataplane";
-    commandArgs["keep-setup-py"] = resolvedOptions["keep-setup-py"] === true ? "true" : "false";
+    commandArgs["package-mode"] = sdkContext.arm
+      ? "azure-mgmt"
+      : "azure-dataplane";
+    commandArgs["keep-setup-py"] =
+      resolvedOptions["keep-setup-py"] === true ? "true" : "false";
   }
   if (sdkContext.arm === true) {
     commandArgs["azure-arm"] = "true";

packages/http-client-python/emitter/src/lib.ts

@@ -180,10 +180,10 @@ const libDef = {
       },
     },
     "no-sdk-clients": {
-      severity: "error",
+      severity: "warning",
       messages: {
         default:
-          "The Python emitter did not find any SDK clients in this TypeSpec program. The current Python generator expects at least one client/service to generate code.",
+          "The Python emitter did not find any SDK clients in this TypeSpec program. No client code will be generated (models can still be emitted). Suppress this warning if this is expected.",
       },
     },
     "browser-runtime-load-failed": {

packages/http-client-python/emitter/test/emitter.test.ts

@@ -0,0 +1,62 @@
+import { expectDiagnostics, t } from "@typespec/compiler/testing";
+import { mkdtemp, readFile, rm } from "fs/promises";
+import { tmpdir } from "os";
+import { join } from "path";
+import { expect, it } from "vitest";
+import { EmitterTester } from "./test-host.js";
+
+it("targets the service namespace when no SDK clients are found", async () => {
+  const [, diagnostics] = await EmitterTester.compileAndDiagnose(
+    t.code`
+    #suppress "@typespec/http-client-python/no-sdk-clients" "This service intentionally has no client."
+    @service namespace ${t.namespace("Service")} {}
+  `,
+    {
+      compilerOptions: {
+        options: {
+          "@typespec/http-client-python": {
+            "emit-yaml-only": true,
+          },
+        },
+      },
+    },
+  );
+
+  expectDiagnostics(diagnostics, []);
+});
+
+it("generates models when no service exists", async () => {
+  const outputDir = await mkdtemp(join(tmpdir(), "typespec-python-models-"));
+  try {
+    const [, diagnostics] = await EmitterTester.compileAndDiagnose(
+      `
+        import "@azure-tools/typespec-client-generator-core";
+        using Azure.ClientGenerator.Core;
+
+        #suppress "@typespec/http-client-python/no-sdk-clients" "This model-only package intentionally has no client."
+        @access(Access.public)
+        @usage(Usage.input | Usage.output)
+        @clientNamespace("Models")
+        model Widget {}
+      `,
+      {
+        compilerOptions: {
+          options: {
+            "@typespec/http-client-python": {
+              "emitter-output-dir": outputDir,
+            },
+          },
+        },
+      },
+    );
+
+    expectDiagnostics(diagnostics, []);
+    const model = await readFile(
+      join(outputDir, "models", "models", "_models.py"),
+      "utf-8",
+    );
+    expect(model).toContain("class Widget");
+  } finally {
+    await rm(outputDir, { recursive: true, force: true });
+  }
+}, 30_000);

packages/http-client-python/emitter/test/test-host.ts

@@ -0,0 +1,22 @@
+import { resolvePath } from "@typespec/compiler";
+import { createTester, mockFile } from "@typespec/compiler/testing";
+import { $onEmit } from "../src/emitter.js";
+
+const PythonTester = createTester(resolvePath(import.meta.dirname, "../.."), {
+  libraries: ["@azure-tools/typespec-client-generator-core"],
+});
+
+export const Tester = PythonTester;
+export const EmitterTester = PythonTester.files({
+  "node_modules/@typespec/http-client-python/package.json": JSON.stringify({
+    name: "@typespec/http-client-python",
+    version: "0.0.0",
+    exports: { ".": "./index.js" },
+  }),
+  "node_modules/@typespec/http-client-python/index.js": mockFile.js({
+    $onEmit,
+  }),
+}).emit("@typespec/http-client-python", {
+  "generate-packaging-files": false,
+  "use-pyodide": true,
+});