Fix enum member names: use enum type name as prefix instead of _ for leading-digit identifiers

packages/typespec-test/test/ai/generated/typespec-ts/review/ai-client.api.md

@@ -784,7 +784,7 @@ export type InternalConnectionPropertiesUnion = InternalConnectionPropertiesApiK
 
 // @public
 export enum KnownVersions {
-    _20240701Preview = "2024-07-01-preview"
+    Versions20240701Preview = "2024-07-01-preview"
 }
 
 // @public

packages/typespec-test/test/ai/generated/typespec-ts/src/models/models.ts

@@ -747,5 +747,5 @@ export function evaluationScheduleArrayDeserializer(result: Array<EvaluationSche
 /** Azure AI API versions */
 export enum KnownVersions {
   /** Azure AI API version 2024-07-01-preview. */
-  _20240701Preview = "2024-07-01-preview",
+  Versions20240701Preview = "2024-07-01-preview",
 }

packages/typespec-test/test/batch_modular/generated/typespec-ts/review/batch.api.md

@@ -1413,7 +1413,7 @@ export interface JobStatistics {
 
 // @public
 export enum KnownVersions {
-    _20230501170 = "2023-05-01.17.0"
+    Versions20230501170 = "2023-05-01.17.0"
 }
 
 // @public

packages/typespec-test/test/batch_modular/generated/typespec-ts/src/models/models.ts

@@ -5715,7 +5715,7 @@ export function nodeVMExtensionArrayDeserializer(result: Array<NodeVMExtension>)
 /** The Azure Batch service version. */
 export enum KnownVersions {
   /** API Version 2023-05-01.17.0 */
-  _20230501170 = "2023-05-01.17.0",
+  Versions20230501170 = "2023-05-01.17.0",
 }
 
 export type GetNodeFileResponse = {

packages/typespec-test/test/overloads_modular/generated/typespec-ts/review/overload_modular.api.md

@@ -26,7 +26,7 @@ export interface FooOperationsOperations {
 
 // @public
 export enum KnownVersions {
-    _20220830 = "2022-08-30"
+    Versions20220830 = "2022-08-30"
 }
 
 // @public (undocumented)

packages/typespec-test/test/overloads_modular/generated/typespec-ts/src/models/models.ts

@@ -10,5 +10,5 @@
 /** The Contoso Widget Manager service version. */
 export enum KnownVersions {
   /** Version 2022-08-31 */
-  _20220830 = "2022-08-30",
+  Versions20220830 = "2022-08-30",
 }

packages/typespec-test/test/widget_dpg/generated/typespec-ts/review/widget_dpg.api.md

@@ -47,7 +47,7 @@ export type ContinuablePage<TElement, TPage = TElement[]> = TPage & {
 
 // @public
 export enum KnownVersions {
-    _100 = "1.0.0"
+    Versions100 = "1.0.0"
 }
 
 // @public

packages/typespec-test/test/widget_dpg/generated/typespec-ts/src/models/models.ts

@@ -116,5 +116,5 @@ export function nonReferencedModelDeserializer(item: any): NonReferencedModel {
 /** The Contoso Widget Manager service version. */
 export enum KnownVersions {
   /** Version 2022-08-31 */
-  _100 = "1.0.0",
+  Versions100 = "1.0.0",
 }

packages/typespec-ts/src/lib.ts

@@ -573,7 +573,7 @@ const libDef = {
     "prefix-adding-in-enum-member": {
       severity: "warning",
       messages: {
-        default: paramMessage`Enum member name ${"memberName"} is normalized to ${"normalizedName"} with "_" prefix.`
+        default: paramMessage`Enum member name ${"memberName"} is not a valid TypeScript identifier. It has been renamed to ${"normalizedName"} using the enum type name ${"enumTypeName"} as prefix.`
       }
     },
     "default-value-object": {

packages/typespec-ts/src/modular/emitModels.ts

@@ -602,7 +602,12 @@ export function buildEnumTypes(
     name: `Known${normalizeModelName(context, type)}`,
     isExported: true,
     members: type.values.map((value) =>
-      emitEnumMember(context, value, reportMemberNameDiagnostic)
+      emitEnumMember(
+        context,
+        value,
+        normalizeName(type.name, NameType.Interface, true),
+        reportMemberNameDiagnostic
+      )
     )
   };
 
@@ -653,24 +658,31 @@ function getExtensibleEnumDescription(
 function emitEnumMember(
   context: SdkContext,
   member: SdkEnumValueType,
+  enumTypeName?: string,
   reportMemberNameDiagnostic = false // if reportMemberNameDiagnostic is true, it will report diagnostic for enum member name
 ): EnumMemberStructure {
-  const normalizedMemberName = context.rlcOptions?.ignoreEnumMemberNameNormalize
+  let normalizedMemberName = context.rlcOptions?.ignoreEnumMemberNameNormalize
     ? fixLeadingNumber(member.name, NameType.EnumMemberName) // need to fix the leading number also for enum member
     : normalizeName(member.name, NameType.EnumMemberName, true);
+  // If the member name starts with _ due to a leading digit (not because the original has _),
+  // replace the _ prefix with the enum type name for a more descriptive identifier
   if (
-    reportMemberNameDiagnostic &&
     normalizedMemberName.toLowerCase().startsWith("_") &&
-    !member.name.toLowerCase().startsWith("_")
+    !member.name.toLowerCase().startsWith("_") &&
+    enumTypeName
   ) {
-    reportDiagnostic(context.program, {
-      code: "prefix-adding-in-enum-member",
-      format: {
-        memberName: member.name,
-        normalizedName: normalizedMemberName
-      },
-      target: NoTarget
-    });
+    normalizedMemberName = enumTypeName + normalizedMemberName.slice(1);
+    if (reportMemberNameDiagnostic) {
+      reportDiagnostic(context.program, {
+        code: "prefix-adding-in-enum-member",
+        format: {
+          memberName: member.name,
+          normalizedName: normalizedMemberName,
+          enumTypeName
+        },
+        target: NoTarget
+      });
+    }
   }
   const memberStructure: EnumMemberStructure = {
     kind: StructureKind.EnumMember,

packages/typespec-ts/test/modularUnit/enumUnion.spec.ts

@@ -3,24 +3,29 @@ import { emitModularModelsFromTypeSpec } from "../util/emitUtil.js";
 import { assert } from "chai";
 
 describe("model type", () => {
-  describe("number | numeric literal | nullable", () => {
-    it("number enum and not ignore warnings", async () => {
+  describe("enum member name with leading digits", () => {
+    it("should rename numeric enum member using enum type name prefix and report a warning", async () => {
       try {
         await emitModularModelsFromTypeSpec(
           `
+            union ExtensibleNum {
+              One: 1,
+              \`2\`: 2,
+            }
             model Test {
-              color: 1 | 2;
+              num: ExtensibleNum;
             }
             op read(@body body: Test): void;
             `,
           {
-            mustEmptyDiagnostic: true
+            mustEmptyDiagnostic: true,
+            "experimental-extensible-enums": true
           }
         );
       } catch (e: any) {
         assert.strictEqual(
           e[0].message,
-          'Enum member name 1 is normalized to _1 with "_" prefix.'
+          "Enum member name 2 is not a valid TypeScript identifier. It has been renamed to ExtensibleNum2 using the enum type name ExtensibleNum as prefix."
         );
       }
     });

packages/typespec-ts/test/modularUnit/scenarios/models/deserialization/extends.md

@@ -693,8 +693,8 @@ export enum KnownVersions {
   /** 2024-07-01-preview */
   PreviewVersion = "2024-07-01-preview",
   /** 2024-07-01 */
-  _20240701 = "2024-07-01",
+  Versions20240701 = "2024-07-01",
   /** 2024-08-01-preview */
-  _20240801Preview = "2024-08-01-preview",
+  Versions20240801Preview = "2024-08-01-preview",
 }
 ```

packages/typespec-ts/test/modularUnit/scenarios/models/serialization/enumKeyNorm.md

@@ -131,13 +131,13 @@ export enum KnownExtensibleString {
   /** _10Pascal */
   _10Pascal = "_10Pascal",
   /** 090 */
-  _090 = "090",
+  ExtensibleString090 = "090",
   /** 10 */
-  _10 = "10",
+  ExtensibleString10 = "10",
   /** 20 */
-  _20 = "20",
+  ExtensibleString20 = "20",
   /** 1.0 */
-  _10 = "1.0",
+  ExtensibleString10 = "1.0",
   /** -2.0 */
   "Item-1.0" = "-2.0",
 }
@@ -150,11 +150,11 @@ export enum KnownExtensibleNumber {
   /** 1 */
   One = 1,
   /** 2 */
-  _2 = 2,
+  ExtensibleNumber2 = 2,
   /** -2.1 */
-  _21 = -2.1,
+  ExtensibleNumber21 = -2.1,
   /** 3 */
-  _3 = 3,
+  ExtensibleNumber3 = 3,
 }
 
 /** Type of ExtensibleNumber */
@@ -167,6 +167,6 @@ export enum KnownVersions {
   /** 2024-07-01 */
   StableVersion = "2024-07-01",
   /** 2024-08-01-preview */
-  _20240801Preview = "2024-08-01-preview",
+  Versions20240801Preview = "2024-08-01-preview",
 }
 ```