cmake: Use generator expression to determine libnvim-test path

Prior to CMake 2.8.12, generator expressions could only be used in
custom commands so the path to libnvim-test in test/config/paths.lua was
set by inspecting the target's LOCATION property.  Post 2.8.12, the
file(GENERATE) command exists to handle this, but it can't interpolate
normal CMake variables.

In order to bridge the gap while < 2.8.12 is supported, use
configure_file() to create paths.lua.gen with the
$<TARGET_FILE:nvim-test> generator expression and then generate the
final paths.lua file.

Closes #7077

1 files changed, 21 insertions, 14 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 74ff32a23d..14eb4c952b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -507,17 +507,6 @@ if(BUSTED_PRG)
   get_property(TEST_INCLUDE_DIRS DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
     PROPERTY INCLUDE_DIRECTORIES)
 
-  # Set policy CMP0026 to OLD so we avoid CMake warnings on newer
-  # versions of cmake.
-  if(POLICY CMP0026)
-    cmake_policy(SET CMP0026 OLD)
-  endif()
-  if(CMAKE_GENERATOR MATCHES "Visual Studio")
-    set(TEST_LIBNVIM_PATH ${CMAKE_BINARY_DIR}/lib/nvim-test.dll)
-  else()
-    get_target_property(TEST_LIBNVIM_PATH nvim-test LOCATION)
-  endif()
-
   # When running tests from 'ninja' we need to use the
   # console pool: to do so we need to use the USES_TERMINAL
   # option, but this is only available in CMake 3.2
@@ -526,9 +515,27 @@ if(BUSTED_PRG)
     list(APPEND TEST_TARGET_ARGS "USES_TERMINAL")
   endif()
 
-  configure_file(
-    test/config/paths.lua.in
-    ${CMAKE_BINARY_DIR}/test/config/paths.lua)
+  if(${CMAKE_VERSION} VERSION_LESS 2.8.12)
+    if(CMAKE_GENERATOR MATCHES "Visual Studio")
+      set(TEST_LIBNVIM_PATH ${CMAKE_BINARY_DIR}/lib/nvim-test.dll)
+    else()
+      get_target_property(TEST_LIBNVIM_PATH nvim-test LOCATION)
+    endif()
+    configure_file(
+      ${CMAKE_SOURCE_DIR}/test/config/paths.lua.in
+      ${CMAKE_BINARY_DIR}/test/config/paths.lua)
+  else()
+    # To avoid duplicating paths.lua.in while we still support CMake < 2.8.12,
+    # use configure_file() to add the generator expression and then generate
+    # the final file
+    set(TEST_LIBNVIM_PATH $<TARGET_FILE:nvim-test>)
+    configure_file(
+      ${CMAKE_SOURCE_DIR}/test/config/paths.lua.in
+      ${CMAKE_BINARY_DIR}/test/config/paths.lua.gen)
+    file(GENERATE
+      OUTPUT ${CMAKE_BINARY_DIR}/test/config/paths.lua
+      INPUT ${CMAKE_BINARY_DIR}/test/config/paths.lua.gen)
+  endif()
 
   set(UNITTEST_PREREQS nvim-test unittest-headers)
   set(FUNCTIONALTEST_PREREQS nvim printargs-test shell-test)