Export diagnostic-collecting API for downstream emitter composition

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

@@ -3,6 +3,7 @@
 
 import { createSdkContext, SdkContext } from "@azure-tools/typespec-client-generator-core";
 import {
+  Diagnostic,
   EmitContext,
   getDirectoryPath,
   joinPaths,
@@ -48,17 +49,35 @@ function findProjectRoot(path: string): string | undefined {
 }
 
 /**
- * The entry point for the emitter. This function is called by the typespec compiler.
+ * Creates a code model by executing the full emission logic.
+ * This function can be called by downstream emitters to generate a code model and collect diagnostics.
+ * 
+ * @example
+ * ```typescript
+ * import { createCodeModel } from "@typespec/http-client-csharp";
+ * 
+ * export async function $onEmit(context: EmitContext<MyEmitterOptions>) {
+ *   const [, diagnostics] = await createCodeModel(context);
+ *   // Process diagnostics as needed
+ *   context.program.reportDiagnostics(diagnostics);
+ * }
+ * ```
+ * 
  * @param context - The emit context
+ * @returns A tuple containing void and any diagnostics that were generated during the emission
  * @beta
  */
-export async function $onEmit(context: EmitContext<CSharpEmitterOptions>) {
+export async function createCodeModel(
+  context: EmitContext<CSharpEmitterOptions>,
+): Promise<[void, readonly Diagnostic[]]> {
   const program: Program = context.program;
   const options = resolveOptions(context);
   const outputFolder = context.emitterOutputDir;
 
   /* set the log level. */
-  const logger = new Logger(program, options.logLevel ?? LoggerLevel.INFO);
+  const logger = new Logger(program, options.logLevel ?? LoggerLevel.INFO, true);
+
+  const diagnostics: Diagnostic[] = [];
 
   if (!program.compilerOptions.noEmit && !program.hasError()) {
     // Write out the dotnet model to the output path
@@ -70,22 +89,25 @@ export async function $onEmit(context: EmitContext<CSharpEmitterOptions>) {
       ),
       logger,
     );
-    program.reportDiagnostics(sdkContext.diagnostics);
+    diagnostics.push(...sdkContext.diagnostics);
 
-    let root = createModel(sdkContext);
+    const [root, modelDiagnostics] = createModel(sdkContext);
+    diagnostics.push(...modelDiagnostics);
 
     if (root) {
-      root = options["update-code-model"](root, sdkContext);
+      const updatedRoot = options["update-code-model"](root, sdkContext);
+      diagnostics.push(...logger.getDiagnostics());
+
       const generatedFolder = resolvePath(outputFolder, "src", "Generated");
 
       if (!fs.existsSync(generatedFolder)) {
         fs.mkdirSync(generatedFolder, { recursive: true });
       }
 
       // emit tspCodeModel.json
-      await writeCodeModel(sdkContext, root, outputFolder);
+      await writeCodeModel(sdkContext, updatedRoot, outputFolder);
 
-      const namespace = root.name;
+      const namespace = updatedRoot.name;
       const configurations: Configuration = createConfiguration(options, namespace, sdkContext);
 
       //emit configuration.json
@@ -133,6 +155,18 @@ export async function $onEmit(context: EmitContext<CSharpEmitterOptions>) {
       }
     }
   }
+
+  return [undefined as void, diagnostics];
+}
+
+/**
+ * The entry point for the emitter. This function is called by the typespec compiler.
+ * @param context - The emit context
+ * @beta
+ */
+export async function $onEmit(context: EmitContext<CSharpEmitterOptions>) {
+  const [, diagnostics] = await createCodeModel(context);
+  context.program.reportDiagnostics(diagnostics);
 }
 
 export function createConfiguration(

packages/http-client-csharp/emitter/src/lib/client-model-builder.ts

@@ -7,6 +7,7 @@ import {
   SdkHttpOperation,
   UsageFlags,
 } from "@azure-tools/typespec-client-generator-core";
+import { Diagnostic } from "@typespec/compiler";
 import { CSharpEmitterContext } from "../sdk-context.js";
 import { CodeModel } from "../type/code-model.js";
 import { InputEnumType, InputLiteralType, InputModelType } from "../type/input-type.js";
@@ -22,11 +23,24 @@ import {
 
 /**
  * Creates the code model from the SDK context.
+ * This function follows TypeSpec best practices by returning diagnostics alongside the result.
+ * 
+ * @example
+ * ```typescript
+ * import { createModel } from "@typespec/http-client-csharp";
+ * import { Logger } from "@typespec/http-client-csharp/lib/logger";
+ * 
+ * const logger = new Logger(program, LoggerLevel.INFO, true); // Enable diagnostic collection
+ * const sdkContext = createCSharpEmitterContext(context, logger);
+ * const [codeModel, diagnostics] = createModel(sdkContext);
+ * // Process the code model and handle diagnostics
+ * ```
+ * 
  * @param sdkContext - The SDK context
- * @returns The code model
+ * @returns A tuple containing the code model and any diagnostics that were generated
  * @beta
  */
-export function createModel(sdkContext: CSharpEmitterContext): CodeModel {
+export function createModel(sdkContext: CSharpEmitterContext): [CodeModel, readonly Diagnostic[]] {
   const sdkPackage = sdkContext.sdkPackage;
 
   // TO-DO: Consider exposing the namespace hierarchy in the code model https://github.com/microsoft/typespec/issues/8332
@@ -60,7 +74,7 @@ export function createModel(sdkContext: CSharpEmitterContext): CodeModel {
     auth: processServiceAuthentication(sdkContext, sdkPackage),
   };
 
-  return clientModel;
+  return [clientModel, sdkContext.logger.getDiagnostics()];
 }
 
 /**

packages/http-client-csharp/emitter/src/lib/logger.ts

@@ -1,8 +1,9 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License. See License.txt in the project root for license information.
 
-import { DiagnosticReport, NoTarget, Program, Tracer } from "@typespec/compiler";
+import { Diagnostic, DiagnosticReport, NoTarget, Program, Tracer } from "@typespec/compiler";
 import {
+  createDiagnostic,
   DiagnosticMessagesMap,
   getTracer,
   reportDiagnostic as libReportDiagnostic,
@@ -17,11 +18,22 @@ export class Logger {
   private tracer: Tracer;
   private level: LoggerLevel;
   private program: Program;
+  private collectedDiagnostics: Diagnostic[] | undefined;
 
-  public constructor(program: Program, level: LoggerLevel) {
+  public constructor(program: Program, level: LoggerLevel, collectDiagnostics: boolean = false) {
     this.tracer = getTracer(program);
     this.level = level;
     this.program = program;
+    this.collectedDiagnostics = collectDiagnostics ? [] : undefined;
+  }
+
+  /**
+   * Get collected diagnostics. Only available if the logger was created with collectDiagnostics=true.
+   * @returns The collected diagnostics.
+   * @beta
+   */
+  public getDiagnostics(): readonly Diagnostic[] {
+    return this.collectedDiagnostics ?? [];
   }
 
   trace(level: LoggerLevel, message: string): void {
@@ -63,7 +75,13 @@ export class Logger {
   reportDiagnostic<C extends keyof DiagnosticMessagesMap, M extends keyof DiagnosticMessagesMap[C]>(
     diag: DiagnosticReport<DiagnosticMessagesMap, C, M>,
   ): void {
-    libReportDiagnostic(this.program, diag);
+    if (this.collectedDiagnostics) {
+      // In collecting mode, store the diagnostic instead of reporting it
+      this.collectedDiagnostics.push(createDiagnostic(diag));
+    } else {
+      // In normal mode, report the diagnostic directly
+      libReportDiagnostic(this.program, diag);
+    }
   }
 
   warn(message: string): void {

packages/http-client-csharp/emitter/test/Unit/auth.test.ts

@@ -30,7 +30,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
     const diagnostics = context.program.diagnostics;
 
     const noAuthDiagnostics = diagnostics.filter(
@@ -72,7 +72,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
     const diagnostics = context.program.diagnostics;
 
     const noAuthDiagnostics = diagnostics.filter(
@@ -114,7 +114,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
     const diagnostics = context.program.diagnostics;
 
     const noAuthDiagnostics = diagnostics.filter(
@@ -154,7 +154,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
     const diagnostics = context.program.diagnostics;
 
     const noAuthDiagnostic = diagnostics.find(
@@ -182,7 +182,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
     const diagnostics = context.program.diagnostics;
 
     const noAuthDiagnostics = diagnostics.filter(
@@ -216,7 +216,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
     const diagnostics = context.program.diagnostics;
 
     const noAuthDiagnostics = diagnostics.filter(
@@ -249,7 +249,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
     const diagnostics = context.program.diagnostics;
 
     // Should have no auth-related diagnostics
@@ -290,7 +290,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     ok(root.auth?.oAuth2);
     strictEqual(root.auth.oAuth2.flows.length, 1);
@@ -322,7 +322,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     ok(root.auth?.oAuth2);
     strictEqual(root.auth.oAuth2.flows.length, 1);
@@ -352,7 +352,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     ok(root.auth?.oAuth2);
     strictEqual(root.auth.oAuth2.flows.length, 1);
@@ -389,7 +389,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     ok(root.auth?.oAuth2);
     strictEqual(root.auth.oAuth2.flows.length, 2);
@@ -426,7 +426,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     ok(root.auth?.oAuth2);
     strictEqual(root.auth.oAuth2.flows.length, 1);
@@ -454,7 +454,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     ok(root.auth?.oAuth2);
     strictEqual(root.auth.oAuth2.flows.length, 1);
@@ -482,7 +482,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     // Should have both OAuth2 and API key auth
     ok(root.auth?.oAuth2);
@@ -513,7 +513,7 @@ describe("Test auth", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     ok(root.auth?.oAuth2);
     strictEqual(root.auth.oAuth2.flows.length, 1);

packages/http-client-csharp/emitter/test/Unit/client-converter.test.ts

@@ -28,7 +28,7 @@ describe("isMultiServiceClient", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     const client = root.clients[0];
     ok(client, "Client should exist");
@@ -81,7 +81,7 @@ describe("isMultiServiceClient", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
     strictEqual(root.name, "Service.MultiService", "Root namespace should be Service.MultiService");
 
     const client = root.clients[0];
@@ -147,7 +147,7 @@ describe("isMultiServiceClient", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
     strictEqual(root.name, "Service.MultiService", "Root namespace should be Service.MultiService");
 
     const client = root.clients[0];
@@ -219,7 +219,7 @@ describe("isMultiServiceClient", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
     strictEqual(root.name, "Service.MultiService", "Root namespace should be Service.MultiService");
 
     const clients = root.clients;

packages/http-client-csharp/emitter/test/Unit/client-initialization.test.ts

@@ -34,7 +34,7 @@ describe("ClientInitialization", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     const client = root.clients[0];
     ok(client, "Client should exist");
@@ -59,7 +59,7 @@ describe("ClientInitialization", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     const client = root.clients[0];
     // initializedBy field should exist on the client (may be undefined or have a value)
@@ -84,7 +84,7 @@ describe("ClientInitialization", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     const client = root.clients[0];
     ok(client.parameters, "Client should have parameters");
@@ -113,7 +113,7 @@ describe("ClientInitialization", () => {
     );
     const context = createEmitterContext(program);
     const sdkContext = await createCSharpSdkContext(context);
-    const root = createModel(sdkContext);
+    const [root] = createModel(sdkContext);
 
     const client = root.clients[0];
     ok("initializedBy" in client, "Parent client should have initializedBy field");