FPHSA: Improve error message when VERSION_VAR is empty or has been unset()

Previously, when `VERSION_VAR` is set but empty, FPHSA emitted a
confusing error message, saying that the package was found but of an
unsuitable version "".  Fix the error message to state that the package
was not found.

Fixes: #23807

5 files changed, 19 insertions, 3 deletions

diff --git a/Modules/FindPackageHandleStandardArgs.cmake b/Modules/FindPackageHandleStandardArgs.cmake
index fbcf7cd88b..6de7dbf129 100644
--- a/Modules/FindPackageHandleStandardArgs.cmake
+++ b/Modules/FindPackageHandleStandardArgs.cmake
@@ -535,9 +535,10 @@ function(FIND_PACKAGE_HANDLE_STANDARD_ARGS _NAME _FIRST_ARG)
   set(VERSION_MSG "")
   set(VERSION_OK TRUE)
 
-  # check with DEFINED here as the requested or found version may be "0"
+  # check that the version variable is not empty to avoid emitting a misleading
+  # message (i.e. `Found unsuitable version ""`)
   if (DEFINED ${_NAME}_FIND_VERSION)
-    if(DEFINED ${FPHSA_VERSION_VAR})
+    if(NOT "${${FPHSA_VERSION_VAR}}" STREQUAL "")
       set(_FOUND_VERSION ${${FPHSA_VERSION_VAR}})
       if (FPHSA_HANDLE_VERSION_RANGE)
         set (FPCV_HANDLE_VERSION_RANGE HANDLE_VERSION_RANGE)
@@ -547,6 +548,7 @@ function(FIND_PACKAGE_HANDLE_STANDARD_ARGS _NAME _FIRST_ARG)
       find_package_check_version ("${_FOUND_VERSION}" VERSION_OK RESULT_MESSAGE_VARIABLE VERSION_MSG
         ${FPCV_HANDLE_VERSION_RANGE})
     else()
+      set(VERSION_OK FALSE)
       # if the package was not found, but a version was given, add that to the output:
       if(${_NAME}_FIND_VERSION_EXACT)
         set(VERSION_MSG "(Required is exact version \"${${_NAME}_FIND_VERSION}\")")
diff --git a/Tests/RunCMake/FPHSA/RunCMakeTest.cmake b/Tests/RunCMake/FPHSA/RunCMakeTest.cmake
index 28b8570d0d..e389e6b981 100644
--- a/Tests/RunCMake/FPHSA/RunCMakeTest.cmake
+++ b/Tests/RunCMake/FPHSA/RunCMakeTest.cmake
@@ -38,9 +38,12 @@ run_cmake(exact_1.2.3.5)
 unset(RunCMake_DEFAULT_stderr)
 
 # check if searching for a version 0 works
-list(APPEND RunCMake_TEST_OPTIONS "-DCMAKE_MODULE_PATH=${CMAKE_CURRENT_LIST_DIR}" "-DPseudo_VERSION=0")
+set(RunCMake_TEST_OPTIONS "-DCMAKE_MODULE_PATH=${CMAKE_CURRENT_LIST_DIR}" "-DPseudo_VERSION=0")
 run_cmake(exact_0_matching)
 
+set(RunCMake_TEST_OPTIONS "-DCMAKE_MODULE_PATH=${CMAKE_CURRENT_LIST_DIR}" "-DPseudo_VERSION=")
+run_cmake(empty_version)
+
 # check custom error message
 set(RunCMake_TEST_OPTIONS "-DCMAKE_MODULE_PATH=${CMAKE_CURRENT_LIST_DIR}" "-DCustomMessage_VERSION=1.2.3.4")
 run_cmake(custom_message_1)
diff --git a/Tests/RunCMake/FPHSA/empty_version-result.txt b/Tests/RunCMake/FPHSA/empty_version-result.txt
new file mode 100644
index 0000000000..d00491fd7e
--- /dev/null
+++ b/Tests/RunCMake/FPHSA/empty_version-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/FPHSA/empty_version-stderr.txt b/Tests/RunCMake/FPHSA/empty_version-stderr.txt
new file mode 100644
index 0000000000..3b60c7aac4
--- /dev/null
+++ b/Tests/RunCMake/FPHSA/empty_version-stderr.txt
@@ -0,0 +1,9 @@
+^CMake Error at [^
+]*/Modules/FindPackageHandleStandardArgs.cmake:[0-9]+ \(message\):
+  Could NOT find Pseudo: \(Required is at least version "1"\) \(found TRUE\)
+Call Stack \(most recent call first\):
+  [^
+]*/Modules/FindPackageHandleStandardArgs.cmake:[0-9]+ \(_FPHSA_FAILURE_MESSAGE\)
+  FindPseudo.cmake:[0-9]+ \(find_package_handle_standard_args\)
+  empty_version.cmake:[0-9]+ \(find_package\)
+  CMakeLists.txt:[0-9]+ \(include\)$
diff --git a/Tests/RunCMake/FPHSA/empty_version.cmake b/Tests/RunCMake/FPHSA/empty_version.cmake
new file mode 100644
index 0000000000..7b7ff34f9a
--- /dev/null
+++ b/Tests/RunCMake/FPHSA/empty_version.cmake
@@ -0,0 +1 @@
+find_package(Pseudo 1 REQUIRED)