src: allow to negate boolean CLI flags

This change allows all boolean flags to be negated using the `--no-`
prefix.
Flags that are `true` by default (for example `--deprecation`) are
still documented as negations.
With this change, it becomes possible to easily flip the default
value of a boolean flag and to override the value of a flag passed
in the NODE_OPTIONS environment variable.
`process.allowedNodeEnvironmentFlags` contains both the negated and
non-negated versions of boolean flags.

Co-authored-by: Anna Henningsen <anna@addaleax.net>

PR-URL: https://github.com/nodejs/node/pull/39023
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 31 insertions, 5 deletions

diff --git a/src/node_options-inl.h b/src/node_options-inl.h
index 4e1a12296bc..7facb22afc3 100644
--- a/src/node_options-inl.h
+++ b/src/node_options-inl.h
@@ -23,12 +23,14 @@ template <typename Options>
 void OptionsParser<Options>::AddOption(const char* name,
                                        const char* help_text,
                                        bool Options::* field,
-                                       OptionEnvvarSettings env_setting) {
+                                       OptionEnvvarSettings env_setting,
+                                       bool default_is_true) {
   options_.emplace(name,
                    OptionInfo{kBoolean,
                               std::make_shared<SimpleOptionField<bool>>(field),
                               env_setting,
-                              help_text});
+                              help_text,
+                              default_is_true});
 }
 
 template <typename Options>
@@ -186,7 +188,8 @@ auto OptionsParser<Options>::Convert(
   return OptionInfo{original.type,
                     Convert(original.field, get_child),
                     original.env_setting,
-                    original.help_text};
+                    original.help_text,
+                    original.default_is_true};
 }
 
 template <typename Options>
@@ -225,6 +228,10 @@ inline std::string RequiresArgumentErr(const std::string& arg) {
   return arg + " requires an argument";
 }
 
+inline std::string NegationImpliesBooleanError(const std::string& arg) {
+  return arg + " is an invalid negation because it is not a boolean option";
+}
+
 // We store some of the basic information around a single Parse call inside
 // this struct, to separate storage of command line arguments and their
 // handling. In particular, this makes it easier to introduce 'synthetic'
@@ -325,6 +332,13 @@ void OptionsParser<Options>::Parse(
         name[i] = '-';
     }
 
+    // Convert --no-foo to --foo and keep in mind that we're negating.
+    bool is_negation = false;
+    if (name.find("--no-") == 0) {
+      name.erase(2, 3);  // remove no-
+      is_negation = true;
+    }
+
     {
       auto it = aliases_.end();
       // Expand aliases:
@@ -367,7 +381,12 @@ void OptionsParser<Options>::Parse(
     }
 
     {
-      auto implications = implications_.equal_range(name);
+      std::string implied_name = name;
+      if (is_negation) {
+        // Implications for negated options are defined with "--no-".
+        implied_name.insert(2, "no-");
+      }
+      auto implications = implications_.equal_range(implied_name);
       for (auto it = implications.first; it != implications.second; ++it) {
         if (it->second.type == kV8Option) {
           v8_args->push_back(it->second.name);
@@ -384,6 +403,13 @@ void OptionsParser<Options>::Parse(
     }
 
     const OptionInfo& info = it->second;
+
+    // Some V8 options can be negated and they are validated by V8 later.
+    if (is_negation && info.type != kBoolean && info.type != kV8Option) {
+      errors->push_back(NegationImpliesBooleanError(arg));
+      break;
+    }
+
     std::string value;
     if (info.type != kBoolean && info.type != kNoOp && info.type != kV8Option) {
       if (equals_index != std::string::npos) {
@@ -412,7 +438,7 @@ void OptionsParser<Options>::Parse(
 
     switch (info.type) {
       case kBoolean:
-        *Lookup<bool>(info.field, options) = true;
+        *Lookup<bool>(info.field, options) = !is_negation;
         break;
       case kInteger:
         *Lookup<int64_t>(info.field, options) = std::atoll(value.c_str());