cmake module: Better warnings and error messages in some cases.

1 files changed, 2 insertions, 0 deletions

diff --git a/mesonbuild/cmake/generator.py b/mesonbuild/cmake/generator.py
index b68778d88..f274bce61 100644
--- a/mesonbuild/cmake/generator.py
+++ b/mesonbuild/cmake/generator.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 from .. import mesonlib
+from .. import mlog
 from .common import cmake_is_debug
 import typing as T
 
@@ -66,6 +67,7 @@ def parse_generator_expressions(
 
     def target_file(arg: str) -> str:
         if arg not in trace.targets:
+            mlog.warning(f"Somewhere in your CMakeLists.txt you have '$<TARGET_FILE:{arg}>'. In cmake, this evaluates to the path to '{arg}'. If '{arg}' does not exist, cmake errors out. We think that '{arg}' does not exist, so we do not know its path and just return an empty string.")
             return ''
         tgt = trace.targets[arg]