Add C# nameing convention linter rules - batch1

.chronus/changes/add-csharp-model-suffix-rules-2026-7-10-9-20-0.md

@@ -0,0 +1,8 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-client-generator-core"
+  - "@azure-tools/typespec-azure-rulesets"
+---
+
+Add `csharp-model-suffix` and `csharp-use-standard-acronyms` linter rules for C# SDK model naming.

packages/typespec-azure-rulesets/src/rulesets/client-sdk.ts

@@ -5,5 +5,7 @@ import type { LinterRuleSet } from "@typespec/compiler";
 export default {
   enable: {
     "@azure-tools/typespec-client-generator-core/csharp-no-url-suffix": true,
+    "@azure-tools/typespec-client-generator-core/csharp-model-suffix": true,
+    "@azure-tools/typespec-client-generator-core/csharp-use-standard-acronyms": true,
   },
 } satisfies LinterRuleSet;

packages/typespec-azure-rulesets/test/validate-rules-defined.test.ts

@@ -51,9 +51,13 @@ describe("expect all rules to be defined", () => {
     });
   });
 
-  it("client-sdk enables csharp-no-url-suffix", () => {
+  it("client-sdk enables C# naming rules", () => {
     const ruleset = $linter.ruleSets?.["client-sdk"];
     ok(ruleset);
     ok(ruleset.enable?.["@azure-tools/typespec-client-generator-core/csharp-no-url-suffix"]);
+    ok(ruleset.enable?.["@azure-tools/typespec-client-generator-core/csharp-model-suffix"]);
+    ok(
+      ruleset.enable?.["@azure-tools/typespec-client-generator-core/csharp-use-standard-acronyms"],
+    );
   });
 });

packages/typespec-client-generator-core/README.md

@@ -118,11 +118,13 @@ Available ruleSets:
 
 ## Rules
 
-| Name                                                                                                                                                                                      | Description                                                                                     |
-| ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
-| [`@azure-tools/typespec-client-generator-core/require-client-suffix`](https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/rules/require-client-suffix)   | Client names should end with 'Client'.                                                          |
-| [`@azure-tools/typespec-client-generator-core/property-name-conflict`](https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/rules/property-name-conflict) | Avoid naming conflicts between a property and a model of the same name.                         |
-| [`@azure-tools/typespec-client-generator-core/csharp-no-url-suffix`](https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/rules/csharp-no-url-suffix)     | Properties ending with 'Url' should use 'Uri' suffix instead to follow .NET naming conventions. |
+| Name                                                                                                                                                                                                  | Description                                                                                     |
+| ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
+| [`@azure-tools/typespec-client-generator-core/require-client-suffix`](https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/rules/require-client-suffix)               | Client names should end with 'Client'.                                                          |
+| [`@azure-tools/typespec-client-generator-core/property-name-conflict`](https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/rules/property-name-conflict)             | Avoid naming conflicts between a property and a model of the same name.                         |
+| [`@azure-tools/typespec-client-generator-core/csharp-no-url-suffix`](https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/rules/csharp-no-url-suffix)                 | Properties ending with 'Url' should use 'Uri' suffix instead to follow .NET naming conventions. |
+| [`@azure-tools/typespec-client-generator-core/csharp-model-suffix`](https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/rules/csharp-model-suffix)                   | Model names should use recommended suffixes for C# SDKs.                                        |
+| [`@azure-tools/typespec-client-generator-core/csharp-use-standard-acronyms`](https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/rules/csharp-use-standard-acronyms) | C# SDK names should use standard acronym casing.                                                |
 
 ## Decorators
 

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

@@ -1,11 +1,24 @@
 import { defineLinter } from "@typespec/compiler";
+import { csharpModelSuffixRule } from "./rules/csharp-model-suffix.js";
 import { csharpNoUrlSuffixRule } from "./rules/csharp-no-url-suffix.js";
+import { csharpUseStandardAcronymsRule } from "./rules/csharp-use-standard-acronyms.js";
 import { propertyNameConflictRule } from "./rules/property-name-conflict.rule.js";
 import { requireClientSuffixRule } from "./rules/require-client-suffix.rule.js";
 
-const rules = [requireClientSuffixRule, propertyNameConflictRule, csharpNoUrlSuffixRule];
+const rules = [
+  requireClientSuffixRule,
+  propertyNameConflictRule,
+  csharpNoUrlSuffixRule,
+  csharpModelSuffixRule,
+  csharpUseStandardAcronymsRule,
+];
 
-const csharpRules = [propertyNameConflictRule, csharpNoUrlSuffixRule];
+const csharpRules = [
+  propertyNameConflictRule,
+  csharpNoUrlSuffixRule,
+  csharpModelSuffixRule,
+  csharpUseStandardAcronymsRule,
+];
 
 export const $linter = defineLinter({
   rules,

packages/typespec-client-generator-core/src/rules/codefix-helpers.ts

@@ -1,15 +1,9 @@
-import type {
-  CodeFix,
-  InsertTextCodeFixEdit,
-  Model,
-  ModelProperty,
-  Program,
-} from "@typespec/compiler";
+import type { CodeFix, InsertTextCodeFixEdit, Program, Type } from "@typespec/compiler";
 import {
   createSourceFile,
   defineCodeFix,
-  getNamespaceFullName,
   getSourceLocation,
+  getTypeName,
   resolvePath,
 } from "@typespec/compiler";
 import type { TypeSpecScriptNode } from "@typespec/compiler/ast";
@@ -18,53 +12,32 @@ import { SyntaxKind } from "@typespec/compiler/ast";
 /**
  * Get the namespace name for a target type.
  */
-function getTargetNamespace(target: Model | ModelProperty): string {
-  if (target.kind === "ModelProperty") {
-    const model = target.model;
-    if (model?.namespace) {
-      return getNamespaceFullName(model.namespace);
-    }
-    return "";
-  }
-  if (target.namespace) {
-    return getNamespaceFullName(target.namespace);
-  }
-  return "";
+function getTargetNamespace(target: Type): string {
+  const shortRef = buildShortRef(target);
+  const fqn = buildFqn(target);
+  return fqn.endsWith(`.${shortRef}`) ? fqn.slice(0, -shortRef.length - 1) : "";
 }
 
 /**
  * Build a short reference for a type target (e.g., "Model.property").
  * Used for same-file augment decorators where the namespace is already in scope.
  */
-function buildShortRef(target: Model | ModelProperty): string {
-  if (target.kind === "ModelProperty") {
-    const model = target.model;
-    return model ? `${model.name}.${target.name}` : target.name;
+function buildShortRef(target: Type): string {
+  if (target.kind === "UnionVariant" && typeof target.name === "string") {
+    return `${getTypeName(target.union, { nameOnly: true, printable: true })}.${target.name}`;
   }
-  return target.name;
+  return getTypeName(target, { nameOnly: true, printable: true });
 }
 
 /**
  * Build the fully qualified name for a type target (e.g., "Azure.Service.Model.property").
  * Used for cross-file augment decorators where the namespace may not be in scope.
  */
-function buildFqn(target: Model | ModelProperty): string {
-  if (target.kind === "ModelProperty") {
-    const model = target.model;
-    if (model && model.namespace) {
-      const nsName = getNamespaceFullName(model.namespace);
-      return nsName ? `${nsName}.${model.name}.${target.name}` : `${model.name}.${target.name}`;
-    } else if (model) {
-      return `${model.name}.${target.name}`;
-    }
-    return target.name;
-  }
-  // Model
-  if (target.namespace) {
-    const nsName = getNamespaceFullName(target.namespace);
-    return nsName ? `${nsName}.${target.name}` : target.name;
+function buildFqn(target: Type): string {
+  if (target.kind === "UnionVariant" && typeof target.name === "string") {
+    return `${getTypeName(target.union, { printable: true })}.${target.name}`;
   }
-  return target.name;
+  return getTypeName(target, { printable: true });
 }
 
 function getLineEnd(text: string, start: number): number {
@@ -119,7 +92,7 @@ function findUsingInsertPos(
  * @param args The decorator arguments as literal strings.
  */
 export function createAugmentDecoratorCodeFix(
-  target: Model | ModelProperty,
+  target: Type,
   decoratorName: string,
   args?: string[],
 ): CodeFix {
@@ -159,7 +132,7 @@ export function createAugmentDecoratorCodeFix(
  * @param args The decorator arguments as literal strings.
  */
 export function createClientTspAugmentDecoratorCodeFix(
-  target: Model | ModelProperty,
+  target: Type,
   decoratorName: string,
   program: Program,
   args?: string[],

packages/typespec-client-generator-core/src/rules/csharp-model-suffix.md

@@ -0,0 +1,48 @@
+C# SDK model names should use these recommended suffixes:
+
+- Use `Config` instead of `Options`, except for client options.
+- Use `Content` instead of `Request`.
+- Use `Result` instead of `Response`.
+
+The rule checks the C#-resolved model name and respects `@clientName` overrides.
+
+#### ❌ Incorrect
+
+```tsp
+model SearchOptions {
+  filter: string;
+}
+
+model CreateWidgetRequest {
+  name: string;
+}
+
+model CreateWidgetResponse {
+  id: string;
+}
+```
+
+#### ✅ Correct
+
+```tsp
+model SearchConfig {
+  filter: string;
+}
+
+model CreateWidgetContent {
+  name: string;
+}
+
+model CreateWidgetResult {
+  id: string;
+}
+```
+
+Or using `@@clientName` in `client.tsp` to override just the C# name:
+
+```tsp
+// client.tsp
+@@clientName(SearchOptions, "SearchConfig", "csharp");
+@@clientName(CreateWidgetRequest, "CreateWidgetContent", "csharp");
+@@clientName(CreateWidgetResponse, "CreateWidgetResult", "csharp");
+```

packages/typespec-client-generator-core/src/rules/csharp-model-suffix.ts

@@ -0,0 +1,88 @@
+import { Model, createRule, fileRef, getNamespaceFullName, paramMessage } from "@typespec/compiler";
+import { createTCGCContext } from "../context.js";
+import { getLibraryName } from "../public-utils.js";
+import { createClientTspAugmentDecoratorCodeFix } from "./codefix-helpers.js";
+
+interface SuffixConvention {
+  messageId: "options" | "request" | "response";
+  badSuffix: string;
+  replacementSuffix: string;
+  shouldSkip?: (model: Model, csharpName: string) => boolean;
+}
+
+const suffixConventions: readonly SuffixConvention[] = [
+  {
+    messageId: "options",
+    badSuffix: "Options",
+    replacementSuffix: "Config",
+    shouldSkip: (_model, csharpName) => csharpName.endsWith("ClientOptions"),
+  },
+  {
+    messageId: "request",
+    badSuffix: "Request",
+    replacementSuffix: "Content",
+  },
+  {
+    messageId: "response",
+    badSuffix: "Response",
+    replacementSuffix: "Result",
+    shouldSkip: isStandardAzureCoreErrorResponse,
+  },
+];
+
+function getSuggestedName(name: string, convention: SuffixConvention) {
+  return name.slice(0, -convention.badSuffix.length) + convention.replacementSuffix;
+}
+
+export const csharpModelSuffixRule = createRule({
+  name: "csharp-model-suffix",
+  docs: fileRef.fromPackageRoot("src/rules/csharp-model-suffix.md"),
+  description: "Model names should use recommended suffixes for C# SDKs.",
+  severity: "warning",
+  url: "https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/rules/csharp-model-suffix",
+  messages: {
+    options: paramMessage`Model '${"modelName"}' ends with 'Options'. Use 'Config' suffix instead (e.g. '${"suggestion"}'). Use @clientName("${"suggestion"}", "csharp") to rename it for C#.`,
+    request: paramMessage`Model '${"modelName"}' ends with 'Request'. Use 'Content' suffix instead (e.g. '${"suggestion"}'). Use @clientName("${"suggestion"}", "csharp") to rename it for C#.`,
+    response: paramMessage`Model '${"modelName"}' ends with 'Response'. Use 'Result' suffix instead (e.g. '${"suggestion"}'). Use @clientName("${"suggestion"}", "csharp") to rename it for C#.`,
+  },
+  create(context) {
+    const tcgcContext = createTCGCContext(
+      context.program,
+      "@azure-tools/typespec-client-generator-core",
+      { mutateNamespace: false },
+    );
+
+    return {
+      model: (model: Model) => {
+        if (model.node === undefined) return;
+
+        const csharpName = getLibraryName(tcgcContext, model, "csharp");
+        const convention = suffixConventions.find(
+          (x) => csharpName.endsWith(x.badSuffix) && !x.shouldSkip?.(model, csharpName),
+        );
+        if (convention === undefined) return;
+
+        const suggestion = getSuggestedName(csharpName, convention);
+        context.reportDiagnostic({
+          messageId: convention.messageId,
+          format: { modelName: csharpName, suggestion },
+          target: model,
+          codefixes: [
+            createClientTspAugmentDecoratorCodeFix(model, "clientName", context.program, [
+              `"${suggestion}"`,
+              `"csharp"`,
+            ]),
+          ],
+        });
+      },
+    };
+  },
+});
+
+function isStandardAzureCoreErrorResponse(model: Model, csharpName: string) {
+  if (csharpName !== "ErrorResponse") return false;
+  const namespace = model.namespace ? getNamespaceFullName(model.namespace) : "";
+  return (
+    namespace === "Azure.Core.Foundations" || namespace === "Azure.ResourceManager.CommonTypes"
+  );
+}

packages/typespec-client-generator-core/src/rules/csharp-use-standard-acronyms.md

@@ -0,0 +1,34 @@
+C# SDK names should use standard acronym casing. This initial rule covers `IP`, `DB`, and `OS`.
+
+The rule checks the C#-resolved name and respects `@clientName` overrides.
+
+#### ❌ Incorrect
+
+```tsp
+model IpAddress {
+  value: string;
+}
+
+model CosmosDb {
+  id: string;
+}
+```
+
+#### ✅ Correct
+
+```tsp
+model IPAddress {
+  value: string;
+}
+
+model CosmosDB {
+  id: string;
+}
+```
+
+Or using `@@clientName` in `client.tsp` to override just the C# name:
+
+```tsp
+// client.tsp
+@@clientName(IpAddress, "IPAddress", "csharp");
+```