[rush] malformed package.json by explicitly setting jsonSyntax to strict

common/changes/@microsoft/rush/kenrick-fix-rush-add_2024-06-27-02-39.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@microsoft/rush",
+      "comment": "Fix an issue where running `rush add` in a project can generate a `package.json` file that uses JSON5 syntax. Package managers expect strict JSON.",
+      "type": "none"
+    }
+  ],
+  "packageName": "@microsoft/rush"
+}

common/changes/@rushstack/node-core-library/kenrick-fix-rush-add_2024-06-27-02-39.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/node-core-library",
+      "comment": "Add support for the `jsonSyntax` option to the `JsonFile.save`, `JsonFile.saveAsync`, and `JsonFile.stringify` functions.",
+      "type": "minor"
+    }
+  ],
+  "packageName": "@rushstack/node-core-library"
+}

common/reviews/api/node-core-library.api.md

@@ -416,7 +416,7 @@ export interface IJsonFileSaveOptions extends IJsonFileStringifyOptions {
 }
 
 // @public
-export interface IJsonFileStringifyOptions {
+export interface IJsonFileStringifyOptions extends IJsonFileParseOptions {
     headerComment?: string;
     ignoreUndefinedValues?: boolean;
     newlineConversion?: NewlineKind;

libraries/node-core-library/src/JsonFile.ts

@@ -128,7 +128,7 @@ export interface IJsonFileLoadAndValidateOptions extends IJsonFileParseOptions,
  *
  * @public
  */
-export interface IJsonFileStringifyOptions {
+export interface IJsonFileStringifyOptions extends IJsonFileParseOptions {
   /**
    * If provided, the specified newline type will be used instead of the default `\r\n`.
    */
@@ -345,17 +345,30 @@ export class JsonFile {
       JsonFile.validateNoUndefinedMembers(newJsonObject);
     }
 
+    let explicitMode: 'json5' | 'json' | 'cjson' | undefined = undefined;
+    switch (options.jsonSyntax) {
+      case JsonSyntax.Strict:
+        explicitMode = 'json';
+        break;
+      case JsonSyntax.JsonWithComments:
+        explicitMode = 'cjson';
+        break;
+      case JsonSyntax.Json5:
+        explicitMode = 'json5';
+        break;
+    }
+
     let stringified: string;
 
     if (previousJson !== '') {
       // NOTE: We don't use mode=json here because comments aren't allowed by strict JSON
       stringified = jju.update(previousJson, newJsonObject, {
-        mode: JsonSyntax.Json5,
+        mode: explicitMode ?? JsonSyntax.Json5,
         indent: 2
       });
     } else if (options.prettyFormatting) {
       stringified = jju.stringify(newJsonObject, {
-        mode: 'json',
+        mode: explicitMode ?? 'json',
         indent: 2
       });
 

libraries/rush-lib/src/api/PackageJsonEditor.ts

@@ -2,7 +2,7 @@
 // See LICENSE in the project root for license information.
 
 import * as semver from 'semver';
-import { InternalError, type IPackageJson, JsonFile, Sort } from '@rushstack/node-core-library';
+import { InternalError, type IPackageJson, JsonFile, Sort, JsonSyntax } from '@rushstack/node-core-library';
 import { cloneDeep } from '../utilities/objectUtilities';
 
 /**
@@ -308,7 +308,10 @@ export class PackageJsonEditor {
     if (this._modified) {
       this._modified = false;
       this._sourceData = this._normalize(this._sourceData);
-      JsonFile.save(this._sourceData, this.filePath, { updateExistingFile: true });
+      JsonFile.save(this._sourceData, this.filePath, {
+        updateExistingFile: true,
+        jsonSyntax: JsonSyntax.Strict
+      });
       return true;
     }
     return false;