Support multiple --bazelrc on command line

src/main/cpp/blaze_util.cc

@@ -74,6 +74,39 @@ bool GetNullaryOption(const char *arg, const char *key) {
   return true;
 }
 
+std::vector<const char*> SearchNaryOption(const vector<string>& args,
+                              const char *key) {
+  vector<const char *> values;
+  if (args.empty()) {
+    return values;
+  }
+
+  bool found_dupe = false;  // true if 'key' was found twice
+  vector<string>::size_type i = 0;
+
+  for (; i < args.size(); ++i) {
+    if (args[i] == "--") {
+      // If the current argument is "--", all following args are target names.
+      // If 'key' was not found, 'value' is nullptr and we can return that.
+      // If 'key' was found exactly once, then 'value' has the value and again
+      // we can return that.
+      // If 'key' was found more than once then we could not have reached this
+      // line, because we would have broken out of the loop when 'key' was found
+      // the second time.
+      return values;
+    }
+    const char* result = GetUnaryOption(args[i].c_str(),
+                                        args[i + 1].c_str(),
+                                        key);
+    if (result != NULL) {
+      // 'key' was found and 'result' has its value.
+      values.push_back(result);
+    }
+  }
+
+  return values;
+}
+
 const char* SearchUnaryOption(const vector<string>& args,
                               const char *key, bool warn_if_dupe) {
   if (args.empty()) {

src/main/cpp/blaze_util.h

@@ -53,6 +53,9 @@ bool GetNullaryOption(const char *arg, const char *key);
 const char* SearchUnaryOption(const std::vector<std::string>& args,
                               const char* key, bool warn_if_dupe);
 
+std::vector<const char*> SearchNaryOption(const std::vector<std::string>& args,
+                              const char* key);
+
 // 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

src/main/cpp/option_processor.cc

@@ -24,6 +24,7 @@
 #include <set>
 #include <sstream>
 #include <utility>
+#include <iostream>
 
 #include "src/main/cpp/blaze_util.h"
 #include "src/main/cpp/blaze_util_platform.h"
@@ -41,6 +42,8 @@ extern char **environ;
 
 namespace blaze {
 
+using std::cout;
+using std::endl;
 using std::map;
 using std::set;
 using std::string;
@@ -201,11 +204,14 @@ std::set<std::string> GetOldRcPaths(
         internal::FindRcAlongsideBinary(cwd, path_to_binary);
     candidate_bazelrc_paths = {workspace_rc, binary_rc, system_bazelrc_path};
   }
-  string user_bazelrc_path = internal::FindLegacyUserBazelrc(
-      SearchUnaryOption(startup_args, "--bazelrc", /* warn_if_dupe */ true),
-      workspace);
-  if (!user_bazelrc_path.empty()) {
-    candidate_bazelrc_paths.push_back(user_bazelrc_path);
+  vector<const char *> cmd_line_rc_files = SearchNaryOption(startup_args, "--bazelrc");
+  for (int i=0; i<cmd_line_rc_files.size(); i++) {
+    string user_bazelrc_path = internal::FindLegacyUserBazelrc(
+        cmd_line_rc_files[i],
+        workspace);
+    if (!user_bazelrc_path.empty()) {
+      candidate_bazelrc_paths.push_back(user_bazelrc_path);
+    }
   }
   // DedupeBlazercPaths returns paths whose canonical path could be computed,
   // therefore these paths must exist.
@@ -370,20 +376,18 @@ blaze_exit_code::ExitCode OptionProcessor::GetRcFiles(
 
   // Get the command-line provided rc, passed as --bazelrc or nothing if the
   // flag is absent.
-  const char* cmd_line_rc_file =
-      SearchUnaryOption(cmd_line->startup_args, "--bazelrc",
-                        /* warn_if_dupe */ true);
-  if (cmd_line_rc_file != nullptr) {
-    string absolute_cmd_line_rc = blaze::AbsolutePathFromFlag(cmd_line_rc_file);
-    // Unlike the previous 3 paths, where we ignore it if the file does not
-    // exist or is unreadable, since this path is explicitly passed, this is an
-    // error. Check this condition here.
-    if (!blaze_util::CanReadFile(absolute_cmd_line_rc)) {
-      BAZEL_LOG(ERROR) << "Error: Unable to read .bazelrc file '"
-                       << absolute_cmd_line_rc << "'.";
-      return blaze_exit_code::BAD_ARGV;
-    }
-    rc_files.push_back(absolute_cmd_line_rc);
+  vector<const char *> cmd_line_rc_files = SearchNaryOption(cmd_line->startup_args, "--bazelrc");
+  for (int i=0; i< cmd_line_rc_files.size(); i++) {
+        string absolute_cmd_line_rc = blaze::AbsolutePathFromFlag(cmd_line_rc_files[i]);
+        // Unlike the previous 3 paths, where we ignore it if the file does not
+        // exist or is unreadable, since this path is explicitly passed, this is an
+        // error. Check this condition here.
+        if (!blaze_util::CanReadFile(absolute_cmd_line_rc)) {
+          BAZEL_LOG(ERROR) << "Error: Unable to read .bazelrc file '"
+                           << absolute_cmd_line_rc << "'.";
+          return blaze_exit_code::BAD_ARGV;
+        }
+        rc_files.push_back(absolute_cmd_line_rc);
   }
 
   // Log which files we're looking for before removing duplicates and