From 89236554cffc1a2b637ca3109b853f6cdcb09f5c Mon Sep 17 00:00:00 2001
From: Marco Ippolito <marcoippolito54@gmail.com>
Date: Mon, 27 Apr 2026 18:00:27 +0200
Subject: [PATCH] src: make node.config.json throw at unknown fields

Signed-off-by: Marco Ippolito <marcoippolito54@gmail.com>
---
 src/node_config_file.cc           |  9 +++++++--
 test/fixtures/rc/schema.json      |  6 ++++++
 test/parallel/test-config-file.js | 16 ++++++++++++++--
 3 files changed, 27 insertions(+), 4 deletions(-)
 create mode 100644 test/fixtures/rc/schema.json

diff --git a/src/node_config_file.cc b/src/node_config_file.cc
index 925d71fecc52a3..b2c87970b6ebc1 100644
--- a/src/node_config_file.cc
+++ b/src/node_config_file.cc
@@ -8,6 +8,7 @@ constexpr std::string_view kConfigFileFlag = "--experimental-config-file";
 constexpr std::string_view kDefaultConfigFileFlag =
     "--experimental-default-config-file";
 constexpr std::string_view kDefaultConfigFileName = "node.config.json";
+constexpr std::string_view kSchemaField = "$schema";
 
 inline bool HasEqualsPrefix(std::string_view arg, std::string_view flag) {
   return arg.size() > flag.size() && arg.starts_with(flag) &&
@@ -290,10 +291,14 @@ ParseResult ConfigReader::ParseConfig(const std::string_view& config_path) {
       return ParseResult::InvalidContent;
     }
 
+    if (namespace_name == kSchemaField) {
+      continue;
+    }
+
     // Check if this field is a valid namespace
     if (!valid_namespaces.contains(namespace_name)) {
-      // If not, skip it
-      continue;
+      FPrintF(stderr, "Unknown namespace %s\n", namespace_name);
+      return ParseResult::InvalidContent;
     }
 
     // List of implicit namespace flags
diff --git a/test/fixtures/rc/schema.json b/test/fixtures/rc/schema.json
new file mode 100644
index 00000000000000..2ed2a6711ce6ec
--- /dev/null
+++ b/test/fixtures/rc/schema.json
@@ -0,0 +1,6 @@
+{
+  "$schema": "https://nodejs.org/dist/vX.Y.Z/docs/node-config-schema.json",
+  "nodeOptions": {
+    "max-http-header-size": 10
+  }
+}
diff --git a/test/parallel/test-config-file.js b/test/parallel/test-config-file.js
index 334884d9ed893a..dc70242855de65 100644
--- a/test/parallel/test-config-file.js
+++ b/test/parallel/test-config-file.js
@@ -517,14 +517,26 @@ describe('namespace-scoped options', () => {
     assert.strictEqual(result.code, 9);
   });
 
-  it('should not throw an error when a namespace is not recognised', async () => {
+  it('should throw an error when a namespace is not recognised', async () => {
     const result = await spawnPromisified(process.execPath, [
       '--no-warnings',
       `--experimental-config-file=${fixtures.path('rc/unknown-namespace.json')}`,
       '-p', '"Hello, World!"',
     ]);
+    assert.match(result.stderr, /Unknown namespace an-invalid-namespace/);
+    assert.match(result.stderr, /unknown-namespace\.json: invalid content/);
+    assert.strictEqual(result.stdout, '');
+    assert.strictEqual(result.code, 9);
+  });
+
+  it('should allow the $schema field', async () => {
+    const result = await spawnPromisified(process.execPath, [
+      '--no-warnings',
+      `--experimental-config-file=${fixtures.path('rc/schema.json')}`,
+      '-p', 'http.maxHeaderSize',
+    ]);
     assert.strictEqual(result.stderr, '');
-    assert.strictEqual(result.stdout, 'Hello, World!\n');
+    assert.strictEqual(result.stdout, '10\n');
     assert.strictEqual(result.code, 0);
   });