Fix no-service-found warning to check for service existence and exclude library namespaces (#8974)

The `no-service-found` warning incorrectly checked for empty routes
instead of checking whether a `@service` decorator exists, and warned on
all namespaces including library namespaces.

## Changes

- **Modified `reportIfNoRoutes` logic**: Now checks
`listServices(program).length === 0` instead of `routes.length === 0` to
determine if any service exists
- **Use `getLocationContext` to filter library code**: Uses
`getLocationContext(program, namespace).type === "project"` to only warn
on user project namespaces, automatically excluding library namespaces
based on source file location
- **Skip global namespace**: Added check to skip the global namespace
(with empty name "")

## Example

Before this change, the following would incorrectly warn on both
namespaces:

```typespec
namespace MyApp {
  @get @route("/app") op appOp(): void;
}

namespace TypeSpec.Library {
  @get @route("/lib") op libOp(): void;
}
```

After this change, only `MyApp` receives the warning since
`TypeSpec.Library` is from a library package (determined by source file
location, not namespace naming).

> [!WARNING]
>
>





<details>

<summary>Original prompt</summary>

> 
> ----
> 
> *This section details on the original issue you should resolve*
> 
>
<__filter_complete__></__filter_complete__></details><issue_title>no-service-found
warning should actually check if there is any service not just
operations</issue_title>

><issue_description>https://azure.github.io/typespec-azure/playground/?e=%40azure-tools%2Ftypespec-autorest&amp;c=aW1wb3J0ICJAYXp1cmUtdG9vbHMvdHlwZXNwZWMtxhVjb3JlIjsKCkBzZXJ2aWNlKCN7IHRpdGxlOiAiQcQiIEFJIiB9KQpuYW1lc3BhY2UgxRcuQUkuUHJvamVjdHMgewoKfQo%3D&amp;options=%7B%7D&amp;vs=%7B%7D
> 
> 
> ```tsp
> import "@azure-tools/typespec-azure-core";
> 
> @service
> namespace Test;
> ```
> 
> 
> Additionally it would be good that the error is not flagged on all
namespaces, maybe only on user namespaces</issue_description>
> 
> ## Comments on the Issue (you are @copilot in this section)
> 
><comments>
></comments>
>

- Fixes #8973

<!-- START COPILOT CODING AGENT SUFFIX -->



<details>

<summary>Original prompt</summary>

> 
> ----
> 
> *This section details on the original issue you should resolve*
> 
> <issue_title>no-service-found warning should actually check if there
is any service not just operations</issue_title>
>
<issue_description>https://azure.github.io/typespec-azure/playground/?e=%40azure-tools%2Ftypespec-autorest&c=aW1wb3J0ICJAYXp1cmUtdG9vbHMvdHlwZXNwZWMtxhVjb3JlIjsKCkBzZXJ2aWNlKCN7IHRpdGxlOiAiQcQiIEFJIiB9KQpuYW1lc3BhY2UgxRcuQUkuUHJvamVjdHMgewoKfQo%3D&options=%7B%7D&vs=%7B%7D
> 
> 
> ```tsp
> import "@azure-tools/typespec-azure-core";
> 
> @service
> namespace Test;
> ```
> 
> 
> Additionally it would be good that the error is not flagged on all
namespaces, maybe only on user namespaces</issue_description>
> 
> ## Comments on the Issue (you are @copilot in this section)
> 
> <comments>
> </comments>
> 


</details>

- Fixes #8973

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---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: timotheeguerin <[email protected]>
Co-authored-by: Timothee Guerin <[email protected]>

Author: Copilot

.chronus/changes/copilot-fix-no-service-check-warning-2025-10-11-9-53-25.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/http"
+---
+
+Do not report `no-service-found` if there is a service even if it has no routes

packages/http/src/operations.ts

@@ -2,6 +2,7 @@ import {
   createDiagnosticCollector,
   Diagnostic,
   DiagnosticCollector,
+  getLocationContext,
   getOverloadedOperation,
   getOverloads,
   listOperationsIn,
@@ -107,10 +108,18 @@ export function getHttpService(
 }
 
 export function reportIfNoRoutes(program: Program, routes: HttpOperation[]) {
-  if (routes.length === 0) {
+  const services = listServices(program);
+  // Only warn if there are no services defined anywhere in the program
+  if (services.length === 0) {
     navigateProgram(program, {
       namespace: (namespace) => {
-        if (namespace.operations.size > 0) {
+        // Skip the global namespace (it has an empty name)
+        if (namespace.name === "") {
+          return;
+        }
+        // Only warn on user project namespaces with operations, not library namespaces
+        const locationContext = getLocationContext(program, namespace);
+        if (namespace.operations.size > 0 && locationContext.type === "project") {
           reportDiagnostic(program, {
             code: "no-service-found",
             format: {