Support negated flags in SearchNullaryOption with last-wins semantics.

`blaze --nomaster_bazelrc --master_bazelrc` now uses the master bazelrc.

RELNOTES: None
PiperOrigin-RevId: 183083839

3 files changed, 21 insertions, 20 deletions

diff --git a/src/main/cpp/blaze_util.cc b/src/main/cpp/blaze_util.cc
index 3b5d5dd322..f0a6f21e6d 100644
--- a/src/main/cpp/blaze_util.cc
+++ b/src/main/cpp/blaze_util.cc
@@ -103,25 +103,23 @@ const char* SearchUnaryOption(const vector<string>& args,
   return GetUnaryOption(args[i].c_str(), NULL, key);
 }
 
-static bool SearchNullaryOption(const vector<string>& args,
-                                const char *key,
-                                const bool include_positional_params) {
+bool SearchNullaryOption(const vector<string>& args,
+                         const string& flag_name,
+                         const bool default_value) {
+  const string positive_flag = "--" + flag_name;
+  const string negative_flag = "--no" + flag_name;
+  bool result = default_value;
   for (vector<string>::size_type i = 0; i < args.size(); i++) {
     if (args[i] == "--") {
-      if (!include_positional_params) {
-        return false;
-      }
-      continue;
+      break;
     }
-    if (GetNullaryOption(args[i].c_str(), key)) {
-      return true;
+    if (GetNullaryOption(args[i].c_str(), positive_flag.c_str())) {
+      result = true;
+    } else if (GetNullaryOption(args[i].c_str(), negative_flag.c_str())) {
+      result = false;
     }
   }
-  return false;
-}
-
-bool SearchNullaryOption(const vector<string>& args, const char *key) {
-  return SearchNullaryOption(args, key, false);
+  return result;
 }
 
 bool VerboseLogging() { return !GetEnv("VERBOSE_BLAZE_CLIENT").empty(); }
diff --git a/src/main/cpp/blaze_util.h b/src/main/cpp/blaze_util.h
index 0fc1a22b23..fa056b5ff0 100644
--- a/src/main/cpp/blaze_util.h
+++ b/src/main/cpp/blaze_util.h
@@ -57,11 +57,14 @@ bool GetNullaryOption(const char *arg, const char *key);
 const char* SearchUnaryOption(const std::vector<std::string>& args,
                               const char* key);
 
-// Searches for 'key' in 'args' using GetNullaryOption.
-// Arguments found after '--' are omitted from the search.
-// Returns true iff key is a flag in args.
+// Searches for '--flag_name' and '--noflag_name' in 'args' using
+// GetNullaryOption. Arguments found after '--' are omitted from the search.
+// Returns true if '--flag_name' is a flag in args and '--noflag_name' does not
+// appear after its last occurrence. If neither '--flag_name' nor
+// '--noflag_name' appear, returns 'default_value'. Otherwise, returns false.
 bool SearchNullaryOption(const std::vector<std::string>& args,
-                         const char* key);
+                         const std::string& flag_name,
+                         const bool default_value);
 
 // Enable messages mostly of interest to developers.
 bool VerboseLogging();
diff --git a/src/main/cpp/option_processor.cc b/src/main/cpp/option_processor.cc
index 07ea0665c6..4a6e57980b 100644
--- a/src/main/cpp/option_processor.cc
+++ b/src/main/cpp/option_processor.cc
@@ -327,8 +327,8 @@ blaze_exit_code::ExitCode OptionProcessor::ParseOptions(
   }
 
   bool use_master_blazerc = true;
-  if (SearchNullaryOption(cmd_line_->startup_args, "--nomaster_blazerc") ||
-      SearchNullaryOption(cmd_line_->startup_args, "--nomaster_bazelrc")) {
+  if (!SearchNullaryOption(cmd_line_->startup_args, "master_blazerc", true) ||
+      !SearchNullaryOption(cmd_line_->startup_args, "master_bazelrc", true)) {
     use_master_blazerc = false;
   }