From bb807bd7b07aec488b5f4715973bcd4414c48b10 Mon Sep 17 00:00:00 2001
From: Will Temple <witemple@microsoft.com>
Date: Wed, 7 May 2025 13:25:13 -0700
Subject: [PATCH 1/2] hsjs: Improve handling of property serialization for JSON

---
 .../http-server-js/src/common/serialization/json.ts |  8 +++++---
 packages/http-server-js/src/util/case.ts            | 13 +++++++++++++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/packages/http-server-js/src/common/serialization/json.ts b/packages/http-server-js/src/common/serialization/json.ts
index 9422271d8c9..d3222d62a90 100644
--- a/packages/http-server-js/src/common/serialization/json.ts
+++ b/packages/http-server-js/src/common/serialization/json.ts
@@ -20,7 +20,7 @@ import {
 import { getHeaderFieldOptions, getPathParamOptions, getQueryParamOptions } from "@typespec/http";
 import { JsContext, Module } from "../../ctx.js";
 import { reportDiagnostic } from "../../lib.js";
-import { access, parseCase } from "../../util/case.js";
+import { access, objectLiteralProperty, parseCase } from "../../util/case.js";
 import { differentiateUnion, writeCodeTree } from "../../util/differentiate.js";
 import { UnimplementedError } from "../../util/error.js";
 import { indent } from "../../util/iter.js";
@@ -106,10 +106,12 @@ function propertyRequiresJsonSerialization(
   module: Module,
   property: ModelProperty,
 ): boolean {
+  const encodedName = resolveEncodedName(ctx.program, property, "application/json");
+  const jsPropertyName = keywordSafe(parseCase(property.name).camelCase);
   return !!(
     isHttpMetadata(ctx, property) ||
     getEncode(ctx.program, property) ||
-    resolveEncodedName(ctx.program, property, "application/json") !== property.name ||
+    encodedName !== jsPropertyName ||
     (isJsonSerializable(property.type) &&
       requiresJsonSerialization(ctx, module, property.type, property))
   );
@@ -190,7 +192,7 @@ function* emitToJson(
           expr = transposeExpressionToJson(ctx, property.type, expr, module);
         }
 
-        yield `  ${encodedName}: ${expr},`;
+        yield `  ${objectLiteralProperty(encodedName)}: ${expr},`;
       }
 
       yield `};`;
diff --git a/packages/http-server-js/src/util/case.ts b/packages/http-server-js/src/util/case.ts
index 02f8878ddda..e1eaf8b8505 100644
--- a/packages/http-server-js/src/util/case.ts
+++ b/packages/http-server-js/src/util/case.ts
@@ -1,6 +1,8 @@
 // Copyright (c) Microsoft Corporation
 // Licensed under the MIT license.
 
+import { KEYWORDS } from "./keywords.js";
+
 /**
  * Separators recognized by the case parser.
  */
@@ -30,6 +32,17 @@ export function isUnspeakable(name: string): boolean {
 
 const JS_IDENTIFIER = /^[a-zA-Z_$][a-zA-Z0-9_$]*$/;
 
+/**
+ * Returns the property name to be used in an object literal.
+ */
+export function objectLiteralProperty(name: string): string {
+  if (!JS_IDENTIFIER.test(name) || KEYWORDS.has(name)) {
+    return JSON.stringify(name);
+  } else {
+    return name;
+  }
+}
+
 /**
  * Returns an access expression for a given subject and key.
  *

From 52c2798380b6c45342925b72bf36059d4106e9a7 Mon Sep 17 00:00:00 2001
From: Will Temple <witemple@microsoft.com>
Date: Wed, 7 May 2025 13:40:25 -0700
Subject: [PATCH 2/2] chronus

---
 ...mple-msft-quote-property-name-json-2025-4-7-13-40-10.md | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 .chronus/changes/witemple-msft-quote-property-name-json-2025-4-7-13-40-10.md

diff --git a/.chronus/changes/witemple-msft-quote-property-name-json-2025-4-7-13-40-10.md b/.chronus/changes/witemple-msft-quote-property-name-json-2025-4-7-13-40-10.md
new file mode 100644
index 00000000000..7e99ec61ee0
--- /dev/null
+++ b/.chronus/changes/witemple-msft-quote-property-name-json-2025-4-7-13-40-10.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/http-server-js"
+---
+
+Fixed an issue in which differences between model and JSON serialized property names were not correctly detected and property names for JSON serialization were not correctly quoted as necessary.
\ No newline at end of file