compile commands header to source heuristic lower-cases filenames before inferring file types

This leads to ".C" files being rewritten as ".c" files and being inferred to be "c" files as opposed to "c++" files.

Fixes https://github.com/clangd/clangd/issues/1108

Reviewed By: sammccall

Differential Revision: https://reviews.llvm.org/D124262

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/unittests/Tooling/CompilationDatabaseTest.cpp b/clang/unittests/Tooling/CompilationDatabaseTest.cpp
index adb9de0..8194dd3 100644
--- a/clang/unittests/Tooling/CompilationDatabaseTest.cpp
+++ b/clang/unittests/Tooling/CompilationDatabaseTest.cpp
@@ -836,6 +836,14 @@ TEST_F(InterpolateTest, Case) {
   EXPECT_EQ(getProxy("foo/bar/baz/shout.C"), "FOO/BAR/BAZ/SHOUT.cc");
 }
 
+TEST_F(InterpolateTest, LanguagePreference) {
+  add("foo/bar/baz/exact.C");
+  add("foo/bar/baz/exact.c");
+  add("other/random/path.cpp");
+  // Proxies for ".H" files are ".C" files, and not ".c files".
+  EXPECT_EQ(getProxy("foo/bar/baz/exact.H"), "foo/bar/baz/exact.C");
+}
+
 TEST_F(InterpolateTest, Aliasing) {
   add("foo.cpp", "-faligned-new");