cmake: Error out on unknown arguments starting with `-`.

Fixes: #21521

Source/cmake.cxx

@@ -846,6 +846,8 @@ void cmake::SetArgs(const std::vector<std::string>& args)
   bool haveToolset = false;
   bool havePlatform = false;
   bool haveBArg = false;
+  bool scriptMode = false;
+  std::string possibleUnknownArg;
 #if !defined(CMAKE_BOOTSTRAP)
   std::string profilingFormat;
   std::string profilingOutput;
@@ -898,7 +900,11 @@ void cmake::SetArgs(const std::vector<std::string>& args)
     CommandArgument{ "-B", "No build directory specified for -B",
                      CommandArgument::Values::One, BuildArgLambda },
     CommandArgument{ "-P", "-P must be followed by a file name.",
-                     CommandArgument::Values::One, IgnoreAndTrueLambda },
+                     CommandArgument::Values::One,
+                     [&](std::string const&, cmake*) -> bool {
+                       scriptMode = true;
+                       return true;
+                     } },
     CommandArgument{ "-D", "-D must be followed with VAR=VALUE.",
                      CommandArgument::Values::One, IgnoreAndTrueLambda },
     CommandArgument{ "-C", "-C must be followed by a file name.",
@@ -1145,14 +1151,28 @@ void cmake::SetArgs(const std::vector<std::string>& args)
         break;
       }
     }
+
+    // We have an issue where arguments to a "-P" script mode
+    // can be provided before the "-P" argument. This means
+    // that we need to lazily check this argument after checking
+    // all args.
+    // Additionally it can't be the source/binary tree location
     if (!parsedCorrectly) {
       cmSystemTools::Error("Run 'cmake --help' for all supported options.");
       exit(1);
+    } else if (!matched && cmHasLiteralPrefix(arg, "-")) {
+      possibleUnknownArg = arg;
     } else if (!matched) {
       this->SetDirectoriesFromFile(arg);
     }
   }
 
+  if (!possibleUnknownArg.empty() && !scriptMode) {
+    cmSystemTools::Error(cmStrCat("Unknown argument ", possibleUnknownArg));
+    cmSystemTools::Error("Run 'cmake --help' for all supported options.");
+    exit(1);
+  }
+
   // Empty instance, platform and toolset if only a generator is specified
   if (this->GlobalGenerator) {
     this->GeneratorInstance = "";

Tests/RunCMake/CommandLine/InvalidArg1-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/CommandLine/InvalidArg1-stderr.txt

@@ -0,0 +1,2 @@
+^CMake Error: Unknown argument -invalid
+CMake Error: Run 'cmake --help' for all supported options.$

Tests/RunCMake/CommandLine/InvalidArg2-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/CommandLine/InvalidArg2-stderr.txt

@@ -0,0 +1,2 @@
+^CMake Error: Unknown argument --invalid
+CMake Error: Run 'cmake --help' for all supported options.$

Tests/RunCMake/CommandLine/RunCMakeTest.cmake

@@ -3,6 +3,8 @@ cmake_minimum_required(VERSION 3.1)
 include(RunCMake)
 
 run_cmake_command(NoArgs ${CMAKE_COMMAND})
+run_cmake_command(InvalidArg1 ${CMAKE_COMMAND} -invalid)
+run_cmake_command(InvalidArg2 ${CMAKE_COMMAND} --invalid)
 run_cmake_command(Wizard ${CMAKE_COMMAND} -i)
 run_cmake_command(C-no-arg ${CMAKE_COMMAND} -B DummyBuildDir -C)
 run_cmake_command(C-no-file ${CMAKE_COMMAND} -B DummyBuildDir -C nosuchcachefile.txt)