Add spector test for alternate-type with emitter fixes for external types (#861)

Co-authored-by: Anton Kolesnyk <antkmsft@users.noreply.github.com>

Author: Copilot

packages/typespec-rust/.scripts/tspcompile.js

@@ -156,6 +156,9 @@ function should_generate(name) {
   return true
 }
 
+// When https://github.com/Azure/typespec-azure/pull/3950 is merged, and we use the newer version of @azure-tools/azure-http-specs,
+// we can remove alternate_types from below, add it to azureHttpSpecsGroup above, and remove the checked-in tsp files
+// from packages\typespec-rust\test\spector\azure\client-generator-core\alternate-type\.
 const alternate_types = pkgRoot + 'test/tsp/AlternateTypes';
 generate('alternate_types', alternate_types, 'test/other/alternate_types');
 
@@ -192,6 +195,9 @@ generate('pub_crate', pub_crate, 'test/other/pub_crate');
 const client_option = pkgRoot + 'test/tsp/ClientOption';
 generate('client_option', client_option, 'test/other/client_option');
 
+const spector_alternatetype = pkgRoot + 'test/spector/azure/client-generator-core/alternate-type/client.tsp';
+generate('spector_alternatetype', spector_alternatetype, 'test/spector/azure/client-generator-core/alternate-type');
+
 loopSpec(httpSpecsGroup, httpSpecs)
 loopSpec(azureHttpSpecsGroup, azureHttpSpecs)
 

packages/typespec-rust/src/emitter.ts

@@ -25,7 +25,7 @@ export async function $onEmit(context: EmitContext<RustEmitterOptions>) {
   let failed = false;
   try {
     const adapter = await Adapter.create(context);
-    const crate = adapter.tcgcToCrate();
+    const crate = adapter.tcgcToCrate(context);
 
     await mkdir(`${context.emitterOutputDir}/src`, { recursive: true });
 

packages/typespec-rust/src/tcgcadapter/adapter.ts

@@ -14,6 +14,7 @@ import * as utils from '../utils/utils.js';
 import * as tcgc from '@azure-tools/typespec-client-generator-core';
 import * as rust from '../codemodel/index.js';
 import {FinalStateValue} from "@azure-tools/typespec-azure-core";
+import {EmitContext, NoTarget} from "@typespec/compiler";
 
 /** ErrorCode defines the types of adapter errors */
 export type ErrorCode =
@@ -114,8 +115,8 @@ export class Adapter {
   }
 
   /** performs all the steps to convert tcgc to a crate */
-  tcgcToCrate(): rust.Crate {
-    this.adaptTypes();
+  tcgcToCrate(context: EmitContext<RustEmitterOptions>): rust.Crate {
+    this.adaptTypes(context);
     this.adaptClients();
 
     // marker models don't require serde so exclude them from the check
@@ -146,10 +147,17 @@ export class Adapter {
   }
 
   /** converts all tcgc types to their Rust type equivalent */
-  private adaptTypes(): void {
+  private adaptTypes(context: EmitContext<RustEmitterOptions>): void {
     for (const sdkUnion of this.ctx.sdkPackage.unions.filter(u => u.kind === 'union')) {
       if (!sdkUnion.discriminatedOptions) {
-        throw new AdapterError('UnsupportedTsp', 'non-discriminated unions are not supported', sdkUnion.__raw?.node);
+        // When https://github.com/microsoft/typespec/issues/9749 is fixed, we can return to throwing an exception here.
+        context.program.reportDiagnostic({
+          code: 'UnsupportedTsp',
+          severity: 'warning',
+          message: `Non-discriminated unions ('${sdkUnion.name}') are not supported. No type will be generated.`,
+          target: NoTarget,
+        })
+        continue;
       }
       const rustUnion = this.getDiscriminatedUnion(sdkUnion);
       this.crate.unions.push(rustUnion);