[tcgc] always have a serverUrl for easier code usage (#538)

.chronus/changes/always_have_endpoint_template-2024-2-27-16-27-38.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-client-generator-core"
+---
+
+When no server url is passed, we still set serverUrl to `{endpoint}` and make one templateArg for `endpoint`. This way, emitters can always look at a combination of serverUrl and templateArguments to get the full picture

packages/typespec-client-generator-core/src/interfaces.ts

@@ -308,7 +308,7 @@ export interface SdkCredentialType extends SdkTypeBase {
 
 export interface SdkEndpointType extends SdkTypeBase {
   kind: "endpoint";
-  serverUrl?: string;
+  serverUrl: string; // if not specified, we will use value "{endpoint}", and templateArguments will have one parameter called "endpoint"
   templateArguments: SdkPathParameter[];
 }
 

packages/typespec-client-generator-core/src/package.ts

@@ -51,6 +51,7 @@ import {
   getClientNamespaceStringHelper,
   getDocHelper,
   getHashForType,
+  getSdkTypeBaseHelper,
   isNullable,
 } from "./internal-utils.js";
 import { createDiagnostic } from "./lib.js";
@@ -378,10 +379,31 @@ function getSdkEndpointParameter(
   if (servers === undefined || servers.length > 1) {
     // if there is no defined server url, or if there are more than one
     // we will return a mandatory endpoint parameter in initialization
+    const name = "endpoint";
     type = {
       kind: "endpoint",
       nullable: false,
-      templateArguments: [],
+      serverUrl: "{endpoint}",
+      templateArguments: [
+        {
+          name,
+          nameInClient: name,
+          description: "Service host",
+          kind: "path",
+          onClient: true,
+          nullable: false,
+          urlEncode: false,
+          optional: false,
+          serializedName: "endpoint",
+          correspondingMethodParams: [],
+          type: {
+            ...getSdkTypeBaseHelper(context, client.service, "string"),
+            encode: "string",
+          },
+          isApiVersionParam: false,
+          apiVersions: getAvailableApiVersions(context, client.service),
+        },
+      ],
     };
   } else {
     // this means we have one server