clang-tidy: Don't append compiler commands if using -p

When the -p option is given to clang-tidy, it doesn't need the compile
command line to be appended. It can get everything it needs from the
compile_commands.json file in the directory specified with the -p option.
When the compiler being used is not the system default compiler,
clang-tidy has been observed to pick up the wrong headers when the
compiler command line is given, but not if only the -p option is used.
Therefore, don't append the compiler command line if -p is present in
the <LANG>_CLANG_TIDY target property.

Fixes: #24017

3 files changed, 18 insertions, 0 deletions

diff --git a/Tests/RunCMake/ClangTidy/RunCMakeTest.cmake b/Tests/RunCMake/ClangTidy/RunCMakeTest.cmake
index ee41d94..5e3fbc4 100644
--- a/Tests/RunCMake/ClangTidy/RunCMakeTest.cmake
+++ b/Tests/RunCMake/ClangTidy/RunCMakeTest.cmake
@@ -29,3 +29,4 @@ if (NOT RunCMake_GENERATOR STREQUAL "Watcom WMake")
   endif()
 endif()
 run_tidy(C-bad)
+run_tidy(compdb)
diff --git a/Tests/RunCMake/ClangTidy/compdb.cmake b/Tests/RunCMake/ClangTidy/compdb.cmake
new file mode 100644
index 0000000..f83e0ae
--- /dev/null
+++ b/Tests/RunCMake/ClangTidy/compdb.cmake
@@ -0,0 +1,7 @@
+enable_language(C)
+
+# Include a --checks option to confirm that we don't match options that start
+# with --, only a standalone --
+set(CMAKE_C_CLANG_TIDY "${PSEUDO_TIDY}" -p ${CMAKE_BINARY_DIR} --checks=*)
+
+add_executable(main main.c)
diff --git a/Tests/RunCMake/pseudo_tidy.c b/Tests/RunCMake/pseudo_tidy.c
index 2feeb0f..a43133b 100644
--- a/Tests/RunCMake/pseudo_tidy.c
+++ b/Tests/RunCMake/pseudo_tidy.c
@@ -5,6 +5,16 @@ int main(int argc, char* argv[])
 {
   int i;
   for (i = 1; i < argc; ++i) {
+    if (strcmp(argv[i], "-p") == 0) {
+      // Ensure compile commands were not appended after the source file
+      for (++i; i < argc; ++i) {
+        if (strcmp(argv[i], "--") == 0) {
+          fprintf(stderr, "Command line arguments unexpectedly appended\n");
+          return 1;
+        }
+      }
+      return 0;
+    }
     if (strcmp(argv[i], "-bad") == 0) {
       fprintf(stdout, "stdout from bad command line arg '-bad'\n");
       fprintf(stderr, "stderr from bad command line arg '-bad'\n");