genex: improve unit testing for $<TARGET_NAME_IF_EXISTS:...>

Fixes: #19696

Tests/RunCMake/GeneratorExpression/RunCMakeTest.cmake

@@ -35,6 +35,9 @@ run_cmake(TARGET_NAME_IF_EXISTS-no-arg)
 run_cmake(TARGET_NAME_IF_EXISTS-empty-arg)
 run_cmake(TARGET_NAME_IF_EXISTS)
 run_cmake(TARGET_NAME_IF_EXISTS-not-a-target)
+run_cmake(TARGET_NAME_IF_EXISTS-alias-target)
+run_cmake(TARGET_NAME_IF_EXISTS-imported-target)
+run_cmake(TARGET_NAME_IF_EXISTS-imported-global-target)
 run_cmake(REMOVE_DUPLICATES-empty)
 run_cmake(REMOVE_DUPLICATES-1)
 run_cmake(REMOVE_DUPLICATES-2)

Tests/RunCMake/GeneratorExpression/TARGET_NAME_IF_EXISTS-alias-target-check.cmake

@@ -0,0 +1,5 @@
+file(READ "${RunCMake_TEST_BINARY_DIR}/TARGET_NAME_IF_EXISTS-generated-alias.txt" content)
+
+if(NOT content STREQUAL aliasTarget)
+  set(RunCMake_TEST_FAILED "actual content:\n ${content}\nbut expected [[aliasTarget]]")
+endif()

Tests/RunCMake/GeneratorExpression/TARGET_NAME_IF_EXISTS-alias-target.cmake

@@ -0,0 +1,8 @@
+enable_language(CXX)
+
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/dummy_executable.cpp" "int main(int,char**) { return 0; }\n")
+add_executable(executableTarget "${CMAKE_CURRENT_BINARY_DIR}/dummy_executable.cpp")
+add_executable(aliasTarget ALIAS executableTarget)
+
+cmake_policy(SET CMP0070 NEW)
+file(GENERATE OUTPUT TARGET_NAME_IF_EXISTS-generated-alias.txt CONTENT "$<TARGET_NAME_IF_EXISTS:aliasTarget>")

Tests/RunCMake/GeneratorExpression/TARGET_NAME_IF_EXISTS-imported-global-target-check.cmake

@@ -0,0 +1,5 @@
+file(READ "${RunCMake_TEST_BINARY_DIR}/TARGET_NAME_IF_EXISTS-generated-imported-global.txt" content)
+
+if(NOT content STREQUAL importedGlobalTarget)
+  set(RunCMake_TEST_FAILED "actual content:\n ${content}\nbut expected [[importedGlobalTarget]]")
+endif()

Tests/RunCMake/GeneratorExpression/TARGET_NAME_IF_EXISTS-imported-global-target.cmake

@@ -0,0 +1,4 @@
+add_executable(importedGlobalTarget IMPORTED GLOBAL)
+
+cmake_policy(SET CMP0070 NEW)
+file(GENERATE OUTPUT TARGET_NAME_IF_EXISTS-generated-imported-global.txt CONTENT "$<TARGET_NAME_IF_EXISTS:importedGlobalTarget>")

Tests/RunCMake/GeneratorExpression/TARGET_NAME_IF_EXISTS-imported-target-check.cmake

@@ -0,0 +1,5 @@
+file(READ "${RunCMake_TEST_BINARY_DIR}/TARGET_NAME_IF_EXISTS-generated-imported.txt" content)
+
+if(NOT content STREQUAL importedTarget)
+  set(RunCMake_TEST_FAILED "actual content:\n ${content}\nbut expected [[importedTarget]]")
+endif()

Tests/RunCMake/GeneratorExpression/TARGET_NAME_IF_EXISTS-imported-target.cmake

@@ -0,0 +1,4 @@
+add_executable(importedTarget IMPORTED)
+
+cmake_policy(SET CMP0070 NEW)
+file(GENERATE OUTPUT TARGET_NAME_IF_EXISTS-generated-imported.txt CONTENT "$<TARGET_NAME_IF_EXISTS:importedTarget>")