[python] fix casing enum

.chronus/changes/python-fixCasingEnum-2026-3-9-16-6-39.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/http-client-python"
+---
+
+Fix casing for enums with mix of numbers and letters

packages/http-client-python/emitter/src/utils.ts

@@ -45,7 +45,7 @@ function deconstruct(
 
   return `${identifier}`
     .replace(/([a-z]+)([A-Z])/g, "$1 $2") // Add a space in between camelCase words(e.g. fooBar => foo Bar)
-    .replace(/(\d+)/g, " $1 ") // Adds a space after numbers(e.g. foo123 => foo123 bar)
+    .replace(/(\d{2,})/g, " $1 ") // Adds a space around multi-digit numbers (e.g. foo123 => foo 123), but not single digits to preserve acronyms like A2A
     .replace(/\b([A-Z]+)([A-Z])s([^a-z])(.*)/g, "$1$2« $3$4") // Add a space after a plural upper cased word(e.g. MBsFoo => MBs Foo)
     .replace(/\b([A-Z]+)([A-Z])([a-z]+)/g, "$1 $2$3") // Add a space between an upper case word(2 char+) and the last capital case.(e.g. SQLConnection -> SQL Connection)
     .replace(/«/g, "s")
@@ -102,9 +102,7 @@ function filterEmptyStrings(arr: string[]): string[] {
 export function camelToSnakeCase(name: string): string {
   if (!name) return name;
   const words = filterEmptyStrings(normalize(name, false, 6));
-  const result = words.join("_").toLowerCase();
-  const result_final = result.replace(/([^\d])_(\d+)/g, "$1$2");
-  return result_final;
+  return words.join("_").toLowerCase();
 }
 
 export function getImplementation(

packages/http-client-python/emitter/test/utils.test.ts

@@ -9,11 +9,16 @@ describe("typespec-python: utils", () => {
       StandardSSDLRS: "standard_ssdlrs",
       QRCode: "qr_code",
       MicroQRCode: "micro_qr_code",
-      detection_01: "detection01",
-      "v1.1-preview.1": "v1_1_preview1",
+      detection_01: "detection_01",
+      "v1.1-preview.1": "v1_1_preview_1",
       pointInTimeUTC: "point_in_time_utc",
       diskSizeGB: "disk_size_gb",
       lastModifiedTS: "last_modified_ts",
+      // Fix for GitHub issue #10312: preserve underscores before numbers (dates)
+      WebSearchPreview_2025_03_11: "web_search_preview_2025_03_11",
+      Default_2024_11_15: "default_2024_11_15",
+      // Fix for GitHub issue #10312: don't insert underscores around single digits in acronyms
+      A2a: "a2a",
     };
     for (const [input, expected] of Object.entries(cases)) {
       strictEqual(camelToSnakeCase(input), expected);