[main] optparse: fix wrong "unknown flag" error message

Author: silverweed

main/src/optparse.hxx

@@ -265,10 +265,13 @@ public:
    {
       bool forcePositional = false;
 
+      // Contains one or more flags coming from one of the arguments (e.g. "-abc" may be split
+      // into flags "a", "b", and "c", which will be stored in `argStr`).
       std::vector<std::string_view> argStr;
 
       for (std::size_t i = 0; i < nArgs && fErrors.empty(); ++i) {
          const char *arg = args[i];
+         const char *const argOrig = arg;
 
          if (strcmp(arg, "--") == 0) {
             forcePositional = true;
@@ -322,7 +325,7 @@ public:
                std::string_view argS = argStr[j];
                const auto *exp = GetExpectedFlag(argS);
                if (!exp) {
-                  fErrors.push_back(std::string("Unknown flag: ") + args[j]);
+                  fErrors.push_back(std::string("Unknown flag: ") + argOrig);
                   break;
                }
 

main/test/optparse_test.cxx

@@ -476,3 +476,20 @@ TEST(OptParse, PositionalMixedWithFlags)
    EXPECT_EQ(opts.GetSwitch("noarg"), true);
    EXPECT_EQ(opts.GetArgs(), std::vector<std::string>({"somename", "bar"}));
 }
+
+TEST(OptParse, UnexpectedFlagComplex)
+{
+   ROOT::RCmdLineOpts opts;
+   opts.AddFlag({"-c", "--compress"}, ROOT::RCmdLineOpts::EFlagType::kWithArg);
+   opts.AddFlag({"--recreate"});
+   opts.AddFlag({"--replace"});
+   opts.AddFlag({"-r", "--recursive"});
+   opts.AddFlag({"-h", "--help"});
+   opts.AddFlag({"-v"});
+   opts.AddFlag({"-vv"});
+
+   const char *args[] = {"rootcp", "--recreate", "-r", "test.root", "copy1.root", "-c", "505", "-vvv"};
+   opts.Parse(args, std::size(args));
+
+   EXPECT_EQ(opts.GetErrors(), std::vector<std::string>({"Unknown flag: -vvv"}));
+}