From 2356e3ad167b705aebc9e052fc5ce1a8a29ae3d8 Mon Sep 17 00:00:00 2001
From: Marco Ippolito <marcoippolito54@gmail.com>
Date: Sat, 31 Jan 2026 15:50:29 +0100
Subject: [PATCH] src: allow empty --experimental-config-file

---
 doc/api/cli.md                                | 11 ++++++--
 doc/api/test.md                               |  2 +-
 doc/node.1                                    |  9 ++++--
 lib/internal/process/pre_execution.js         |  3 +-
 src/node_config_file.cc                       | 13 +++++++--
 src/node_options.cc                           | 14 ++++++----
 test/parallel/test-cli-node-options-docs.js   |  1 +
 test/parallel/test-config-file.js             | 28 +++++++++++++++++++
 test/parallel/test-runner-flag-propagation.js |  2 --
 9 files changed, 66 insertions(+), 17 deletions(-)

diff --git a/doc/api/cli.md b/doc/api/cli.md
index 065439a777e5dc..a0526760676220 100644
--- a/doc/api/cli.md
+++ b/doc/api/cli.md
@@ -1014,7 +1014,7 @@ added:
 
 Enable experimental import support for `.node` addons.
 
-### `--experimental-config-file=config`
+### `--experimental-config-file=path`, `--experimental-config-file`
 
 <!-- YAML
 added:
@@ -1025,6 +1025,10 @@ added:
 > Stability: 1.0 - Early development
 
 If present, Node.js will look for a configuration file at the specified path.
+If the path is not specified, Node.js will look for a `node.config.json` file
+in the current working directory.
+The alias `--experimental-default-config-file` is equivalent to
+`--experimental-config-file` without an argument.
 Node.js will read the configuration file and apply the settings. The
 configuration file should be a JSON file with the following structure. `vX.Y.Z`
 in the `$schema` must be replaced with the version of Node.js you are using.
@@ -1131,9 +1135,10 @@ added:
 
 > Stability: 1.0 - Early development
 
-If the `--experimental-default-config-file` flag is present, Node.js will look for a
+This flag is an alias for `--experimental-config-file` without an argument.
+If present, Node.js will look for a
 `node.config.json` file in the current working directory and load it as a
-as configuration file.
+configuration file.
 
 ### `--experimental-eventsource`
 
diff --git a/doc/api/test.md b/doc/api/test.md
index 6daa84d3b32f09..9ccc3e5400a716 100644
--- a/doc/api/test.md
+++ b/doc/api/test.md
@@ -4131,7 +4131,7 @@ Can be used to abort test subtasks when the test has been aborted.
 [`suite()`]: #suitename-options-fn
 [`test()`]: #testname-options-fn
 [code coverage]: #collecting-code-coverage
-[configuration files]: cli.md#--experimental-config-fileconfig
+[configuration files]: cli.md#--experimental-config-filepath---experimental-config-file
 [describe options]: #describename-options-fn
 [it options]: #testname-options-fn
 [running tests from the command line]: #running-tests-from-the-command-line
diff --git a/doc/node.1 b/doc/node.1
index 6d16ef84c45df0..90b21fc1e7bc63 100644
--- a/doc/node.1
+++ b/doc/node.1
@@ -602,8 +602,10 @@ It is possible to run code containing inline types unless the
 .It Fl -experimental-addon-modules
 Enable experimental import support for \fB.node\fR addons.
 .
-.It Fl -experimental-config-file Ns = Ns Ar config
+.It Fl -experimental-config-file= Ns Ar config , Fl -experimental-config-file , Fl -experimental-default-config-file
 If present, Node.js will look for a configuration file at the specified path.
+If the path is not specified, Node.js will look for a \fBnode.config.json\fR file
+in the current working directory.
 Node.js will read the configuration file and apply the settings. The
 configuration file should be a JSON file with the following structure. \fBvX.Y.Z\fR
 in the \fB$schema\fR must be replaced with the version of Node.js you are using.
@@ -689,9 +691,10 @@ Node.js will not sanitize or perform validation on the user-provided configurati
 so \fBNEVER\fR use untrusted configuration files.
 .
 .It Fl -experimental-default-config-file
-If the \fB--experimental-default-config-file\fR flag is present, Node.js will look for a
+This flag is an alias for \fB--experimental-config-file\fR without an argument.
+If present, Node.js will look for a
 \fBnode.config.json\fR file in the current working directory and load it as a
-as configuration file.
+configuration file.
 .
 .It Fl -experimental-eventsource
 Enable exposition of EventSource Web API on the global scope.
diff --git a/lib/internal/process/pre_execution.js b/lib/internal/process/pre_execution.js
index 0902536708bf1d..091bc18bbc3530 100644
--- a/lib/internal/process/pre_execution.js
+++ b/lib/internal/process/pre_execution.js
@@ -382,7 +382,8 @@ function setupSQLite() {
 
 function initializeConfigFileSupport() {
   if (getOptionValue('--experimental-default-config-file') ||
-      getOptionValue('--experimental-config-file')) {
+      getOptionValue('--experimental-config-file') ||
+      getOptionValue('--experimental-config-file=')) {
     emitExperimentalWarning('--experimental-config-file');
   }
 }
diff --git a/src/node_config_file.cc b/src/node_config_file.cc
index 4205a3cee7e52a..7f1ee739677a76 100644
--- a/src/node_config_file.cc
+++ b/src/node_config_file.cc
@@ -17,13 +17,22 @@ std::optional<std::string_view> ConfigReader::GetDataFromArgs(
   for (auto it = args.begin(); it != args.end(); ++it) {
     if (*it == flag_path) {
       // Case: "--experimental-config-file foo"
-      if (auto next = std::next(it); next != args.end()) {
+      if (auto next = std::next(it);
+          next != args.end() && !next->starts_with("-")) {
         return *next;
       }
+      // Case: "--experimental-config-file" without argument, use default
+      has_default_config_file = true;
     } else if (it->starts_with(flag_path)) {
       // Case: "--experimental-config-file=foo"
       if (it->size() > flag_path.size() && (*it)[flag_path.size()] == '=') {
-        return std::string_view(*it).substr(flag_path.size() + 1);
+        std::string_view value =
+            std::string_view(*it).substr(flag_path.size() + 1);
+        if (value.empty()) {
+          has_default_config_file = true;
+        } else {
+          return value;
+        }
       }
     } else if (*it == default_file || it->starts_with(default_file)) {
       has_default_config_file = true;
diff --git a/src/node_options.cc b/src/node_options.cc
index 22fe0f61da8c69..9860f9ba633ef9 100644
--- a/src/node_options.cc
+++ b/src/node_options.cc
@@ -868,12 +868,16 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
             "set environment variables from supplied file",
             &EnvironmentOptions::optional_env_file);
   Implies("--env-file-if-exists", "[has_env_file_string]");
-  AddOption("--experimental-config-file",
+  AddOption("--experimental-config-file=",
             "set config file from supplied file",
-            &EnvironmentOptions::experimental_config_file_path);
-  AddOption("--experimental-default-config-file",
-            "set config file from default config file",
-            &EnvironmentOptions::experimental_default_config_file);
+            &EnvironmentOptions::experimental_config_file_path,
+            kDisallowedInEnvvar);
+  AddOption("--experimental-config-file",
+            "set default config file",
+            &EnvironmentOptions::experimental_default_config_file,
+            kDisallowedInEnvvar);
+  AddAlias("--experimental-config-file <arg>", "--experimental-config-file=");
+  AddAlias("--experimental-default-config-file", "--experimental-config-file");
   AddOption("--test",
             "launch test runner on startup",
             &EnvironmentOptions::test_runner,
diff --git a/test/parallel/test-cli-node-options-docs.js b/test/parallel/test-cli-node-options-docs.js
index 80caa29d4263ef..534c99c04de964 100644
--- a/test/parallel/test-cli-node-options-docs.js
+++ b/test/parallel/test-cli-node-options-docs.js
@@ -122,5 +122,6 @@ for (const [, envVar, config] of nodeOptionsCC.matchAll(addOptionRE)) {
 
 // add alias handling
 manPagesOptions.delete('-trace-events-enabled');
+manPagesOptions.delete('-experimental-default-config-file');
 
 assert.strictEqual(manPagesOptions.size, 0, `Man page options not documented: ${[...manPagesOptions]}`);
diff --git a/test/parallel/test-config-file.js b/test/parallel/test-config-file.js
index c18cc0d45683b6..ffdf004b4adec4 100644
--- a/test/parallel/test-config-file.js
+++ b/test/parallel/test-config-file.js
@@ -371,6 +371,34 @@ test('should use node.config.json as default', onlyIfNodeOptionsSupport, async (
   assert.strictEqual(result.code, 0);
 });
 
+test('should use node.config.json when --experimental-config-file has no argument',
+     onlyIfNodeOptionsSupport, async () => {
+       const result = await spawnPromisified(process.execPath, [
+         '--no-warnings',
+         '--experimental-config-file',
+         '-p', 'http.maxHeaderSize',
+       ], {
+         cwd: fixtures.path('rc/default'),
+       });
+       assert.strictEqual(result.stderr, '');
+       assert.strictEqual(result.stdout, '10\n');
+       assert.strictEqual(result.code, 0);
+     });
+
+test('should use node.config.json when --experimental-config-file= has empty argument',
+     onlyIfNodeOptionsSupport, async () => {
+       const result = await spawnPromisified(process.execPath, [
+         '--no-warnings',
+         '--experimental-config-file=',
+         '-p', 'http.maxHeaderSize',
+       ], {
+         cwd: fixtures.path('rc/default'),
+       });
+       assert.strictEqual(result.stderr, '');
+       assert.strictEqual(result.stdout, '10\n');
+       assert.strictEqual(result.code, 0);
+     });
+
 test('should override node.config.json when specificied', onlyIfNodeOptionsSupport, async () => {
   const result = await spawnPromisified(process.execPath, [
     '--no-warnings',
diff --git a/test/parallel/test-runner-flag-propagation.js b/test/parallel/test-runner-flag-propagation.js
index f4e9849cce77d0..a48d6b6bfe9938 100644
--- a/test/parallel/test-runner-flag-propagation.js
+++ b/test/parallel/test-runner-flag-propagation.js
@@ -15,8 +15,6 @@ const runner = path.join(fixtureDir, 'runner.mjs');
 describe('test runner flag propagation', () => {
   describe('via command line', () => {
     const flagPropagationTests = [
-      ['--experimental-config-file', 'node.config.json', ''],
-      ['--experimental-default-config-file', '', false],
       ['--env-file', '.env', '.env'],
       ['--env-file-if-exists', '.env', '.env'],
       ['--test-concurrency', '2', '2'],