src: add config file support

Author: marco-ippolito

Makefile

@@ -807,6 +807,7 @@ doc: $(NODE_EXE) doc-only ## Build Node.js, and then build the documentation wit
 
 out/doc:
 	mkdir -p $@
+	cp doc/node_config_json_schema.json $@
 
 # If it's a source tarball, doc/api already contains the generated docs.
 # Just copy everything under doc/api over.

doc/api/cli.md

@@ -911,6 +911,77 @@ added: v23.6.0
 
 Enable experimental import support for `.node` addons.
 
+### `--experimental-config-file`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+> Stability: 1.0 - Early development
+
+Use this flag to specify a configuration file that will be loaded and parsed
+before the application starts.
+Node.js will read the configuration file and apply the settings.
+The configuration file should be a JSON file
+with the following structure:
+
+```json
+{
+  "experimental": {
+    "transform_types": true
+  },
+  "import": [
+    "amaro/transform"
+  ],
+  "test": {
+    "only": true
+  }
+}
+```
+
+Each key in the configuration file corresponds to a flag that can be passed
+as a command-line argument. The value of the key is the value that would be
+passed to the flag.
+
+For example, the configuration file above is equivalent to
+the following command-line arguments:
+
+```bash
+node --experimental-transform-types --import amaro/transform
+```
+
+The priority in configuration is as follows:
+
+* NODE\_OPTIONS and command-line options
+* Config file
+* Dotenv NODE\_OPTIONS
+
+If multiple keys are present in the configuration file,
+the last one will override the previous ones.
+Unknown keys will be ignored.
+
+It possible to use the official json schema to validate the configuration file,
+which may vary depending on the Node.js version.
+
+```json
+{
+  "$schema": "https://nodejs.org/dist/REPLACEME/docs/node_config_json_schema.json",
+}
+```
+
+Node.js will not sanitize or perform validation on the user-provided configuration,
+so **NEVER** use untrusted configuration files.
+In the example below `--some-other-flag`
+will not be sanitized and will be passed to the Node.js process.
+
+```json
+{
+  "import": [
+    "amaro/transform --some-other-flag"
+  ],
+}
+```
+
 ### `--experimental-eventsource`
 
 <!-- YAML

doc/node.1

@@ -166,6 +166,9 @@ Interpret the entry point as a URL.
 .It Fl -experimental-addon-modules
 Enable experimental addon module support.
 .
+.It Fl -experimental-config-file
+Enable support for experimental config file
+.
 .It Fl -experimental-import-meta-resolve
 Enable experimental ES modules support for import.meta.resolve().
 .

doc/node_config_json_schema.json

@@ -0,0 +1,33 @@
+{
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "type": "object",
+    "properties": {
+        "experimental": {
+            "type": "object",
+            "properties": {
+                "transform_types": {
+                    "type": "boolean"
+                }
+            },
+            "required": [],
+            "additionalProperties": false
+        },
+        "import": {
+            "type": "array",
+            "items": {
+                "type": "string"
+            }
+        },
+        "test": {
+            "type": "object",
+            "properties": {
+                "only": {
+                    "type": "boolean"
+                }
+            },
+            "required": [],
+            "additionalProperties": false
+        }
+    },
+    "additionalProperties": false
+}

lib/internal/process/pre_execution.js

@@ -116,6 +116,8 @@ function prepareExecution(options) {
   initializeSourceMapsHandlers();
   initializeDeprecations();
 
+  setupConfigFile();
+
   require('internal/dns/utils').initializeDns();
 
   if (isMainThread) {
@@ -312,6 +314,12 @@ function setupSQLite() {
   BuiltinModule.allowRequireByUsers('sqlite');
 }
 
+function setupConfigFile() {
+  if (getOptionValue('--experimental-config-file')) {
+    emitExperimentalWarning('--experimental-config-file');
+  }
+}
+
 function setupQuic() {
   if (!getOptionValue('--experimental-quic')) {
     return;

node.gyp

@@ -130,6 +130,7 @@
       'src/node_process_events.cc',
       'src/node_process_methods.cc',
       'src/node_process_object.cc',
+      'src/node_rc.cc',
       'src/node_realm.cc',
       'src/node_report.cc',
       'src/node_report_module.cc',
@@ -262,6 +263,7 @@
       'src/node_platform.h',
       'src/node_process.h',
       'src/node_process-inl.h',
+      'src/node_rc.h',
       'src/node_realm.h',
       'src/node_realm-inl.h',
       'src/node_report.h',

src/node.cc

@@ -21,6 +21,7 @@
 
 #include "node.h"
 #include "node_dotenv.h"
+#include "node_rc.h"
 #include "node_task_runner.h"
 
 // ========== local headers ==========
@@ -150,6 +151,9 @@ namespace per_process {
 // Instance is used to store environment variables including NODE_OPTIONS.
 node::Dotenv dotenv_file = Dotenv();
 
+// node_rc.h
+node::ConfigReader config_reader = ConfigReader();
+
 // node_revert.h
 // Bit flag used to track security reverts.
 unsigned int reverted_cve = 0;
@@ -884,6 +888,23 @@ static ExitCode InitializeNodeWithArgsInternal(
     per_process::dotenv_file.AssignNodeOptionsIfAvailable(&node_options);
   }
 
+  auto result = per_process::config_reader.GetDataFromArgs(*argv);
+  if (result.has_value()) {
+    switch (per_process::config_reader.ParseConfig(result.value())) {
+      case ConfigReader::ParseResult::Valid:
+        break;
+      case ConfigReader::ParseResult::InvalidContent:
+        errors->push_back(result.value() + ": invalid format");
+        break;
+      case ConfigReader::ParseResult::FileError:
+        errors->push_back(result.value() + ": not found");
+        break;
+      default:
+        UNREACHABLE();
+    }
+    per_process::config_reader.AssignNodeOptions(&node_options);
+  }
+
 #if !defined(NODE_WITHOUT_NODE_OPTIONS)
   if (!(flags & ProcessInitializationFlags::kDisableNodeOptionsEnv)) {
     // NODE_OPTIONS environment variable is preferred over the file one.

src/node_options.cc

@@ -671,6 +671,9 @@ 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",
+            "set config file from supplied file",
+            &EnvironmentOptions::experimental_config_file);
   AddOption("--test",
             "launch test runner on startup",
             &EnvironmentOptions::test_runner);

src/node_options.h

@@ -256,6 +256,7 @@ class EnvironmentOptions : public Options {
 
   bool report_exclude_env = false;
   bool report_exclude_network = false;
+  std::string experimental_config_file;
 
   inline DebugOptions* get_debug_options() { return &debug_options_; }
   inline const DebugOptions& debug_options() const { return debug_options_; }