target_sources: Interpret relative paths as relative to the calling directory

Previously the command considered non-absolute source file paths relative to
the associated target on the LHS. This causes problems in incremental builds
where files are added from subdirectories and forces users to workaround by
manually converting to absolute paths. Change this to enable more intuitive
usage by projects.

Fixes #17981

8 files changed, 135 insertions, 0 deletions

diff --git a/Tests/CMakeCommands/target_sources/CMakeLists.txt b/Tests/CMakeCommands/target_sources/CMakeLists.txt
new file mode 100644
index 0000000..ab14855
--- /dev/null
+++ b/Tests/CMakeCommands/target_sources/CMakeLists.txt
@@ -0,0 +1,36 @@
+
+cmake_minimum_required(VERSION 3.12)
+cmake_policy(SET CMP0076 NEW)
+
+project(target_sources)
+
+add_library(target_sources_lib)
+target_compile_definitions(target_sources_lib PRIVATE "-DIS_LIB")
+add_subdirectory(subdir)
+
+set(subdir_fullpath "${CMAKE_CURRENT_LIST_DIR}/subdir")
+
+get_property(target_sources_lib_property TARGET target_sources_lib PROPERTY SOURCES)
+if (NOT "$<1:${subdir_fullpath}/subdir_empty_1.cpp>" IN_LIST target_sources_lib_property)
+  message(SEND_ERROR "target_sources_lib: Generator expression to absolute sub directory file not found")
+endif()
+if (NOT "$<1:${subdir_fullpath}/../empty_1.cpp>" IN_LIST target_sources_lib_property)
+  message(SEND_ERROR "target_sources_lib: Generator expression to absolute main directory file not found")
+endif()
+if (NOT "${subdir_fullpath}/subdir_empty_2.cpp" IN_LIST target_sources_lib_property)
+  message(SEND_ERROR "target_sources_lib: Relative sub directory file not converted to absolute")
+endif()
+if (NOT "$<1:empty_2.cpp>" IN_LIST target_sources_lib_property)
+  message(SEND_ERROR "target_sources_lib: Generator expression to relative main directory file not found")
+endif()
+if (NOT "${subdir_fullpath}/../empty_3.cpp" IN_LIST target_sources_lib_property)
+  message(SEND_ERROR "target_sources_lib: Relative main directory file not converted to absolute")
+endif()
+
+add_executable(target_sources main.cpp)
+target_link_libraries(target_sources target_sources_lib)
+
+get_property(target_sources_property TARGET target_sources PROPERTY SOURCES)
+if (NOT "main.cpp" IN_LIST target_sources_property)
+  message(SEND_ERROR "target_sources: Relative main directory file converted to absolute")
+endif()
diff --git a/Tests/CMakeCommands/target_sources/empty_1.cpp b/Tests/CMakeCommands/target_sources/empty_1.cpp
new file mode 100644
index 0000000..01e5b07
--- /dev/null
+++ b/Tests/CMakeCommands/target_sources/empty_1.cpp
@@ -0,0 +1,21 @@
+#ifdef IS_LIB
+
+#  ifdef _WIN32
+__declspec(dllexport)
+#  endif
+  int internal_empty_1()
+{
+  return 0;
+}
+
+#else
+
+#  ifdef _WIN32
+__declspec(dllexport)
+#  endif
+  int empty_1()
+{
+  return 0;
+}
+
+#endif
diff --git a/Tests/CMakeCommands/target_sources/empty_2.cpp b/Tests/CMakeCommands/target_sources/empty_2.cpp
new file mode 100644
index 0000000..48ae8bb
--- /dev/null
+++ b/Tests/CMakeCommands/target_sources/empty_2.cpp
@@ -0,0 +1,7 @@
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+  int empty_2()
+{
+  return 0;
+}
diff --git a/Tests/CMakeCommands/target_sources/empty_3.cpp b/Tests/CMakeCommands/target_sources/empty_3.cpp
new file mode 100644
index 0000000..bd3a6d1
--- /dev/null
+++ b/Tests/CMakeCommands/target_sources/empty_3.cpp
@@ -0,0 +1,7 @@
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+  int empty_3()
+{
+  return 0;
+}
diff --git a/Tests/CMakeCommands/target_sources/main.cpp b/Tests/CMakeCommands/target_sources/main.cpp
new file mode 100644
index 0000000..622771c
--- /dev/null
+++ b/Tests/CMakeCommands/target_sources/main.cpp
@@ -0,0 +1,16 @@
+#include <iostream>
+
+int empty_1();
+int subdir_empty_1();
+int subdir_empty_2();
+
+int main()
+{
+  int e1 = empty_1();
+  int se1 = subdir_empty_1();
+  int se2 = subdir_empty_2();
+
+  std::cout << e1 << " " << se1 << " " << se2 << std::endl;
+
+  return 0;
+}
diff --git a/Tests/CMakeCommands/target_sources/subdir/CMakeLists.txt b/Tests/CMakeCommands/target_sources/subdir/CMakeLists.txt
new file mode 100644
index 0000000..f749f1d
--- /dev/null
+++ b/Tests/CMakeCommands/target_sources/subdir/CMakeLists.txt
@@ -0,0 +1,6 @@
+
+target_sources(target_sources_lib PUBLIC $<1:${CMAKE_CURRENT_LIST_DIR}/subdir_empty_1.cpp>
+                                         $<1:${CMAKE_CURRENT_LIST_DIR}/../empty_1.cpp>
+                                         subdir_empty_2.cpp
+                                  PRIVATE $<1:empty_2.cpp>
+                                          ../empty_3.cpp)
diff --git a/Tests/CMakeCommands/target_sources/subdir/subdir_empty_1.cpp b/Tests/CMakeCommands/target_sources/subdir/subdir_empty_1.cpp
new file mode 100644
index 0000000..3c61321
--- /dev/null
+++ b/Tests/CMakeCommands/target_sources/subdir/subdir_empty_1.cpp
@@ -0,0 +1,21 @@
+#ifdef IS_LIB
+
+#  ifdef _WIN32
+__declspec(dllexport)
+#  endif
+  int internal_subdir_empty_1()
+{
+  return 0;
+}
+
+#else
+
+#  ifdef _WIN32
+__declspec(dllexport)
+#  endif
+  int subdir_empty_1()
+{
+  return 0;
+}
+
+#endif
diff --git a/Tests/CMakeCommands/target_sources/subdir/subdir_empty_2.cpp b/Tests/CMakeCommands/target_sources/subdir/subdir_empty_2.cpp
new file mode 100644
index 0000000..47fa736
--- /dev/null
+++ b/Tests/CMakeCommands/target_sources/subdir/subdir_empty_2.cpp
@@ -0,0 +1,21 @@
+#ifdef IS_LIB
+
+#  ifdef _WIN32
+__declspec(dllexport)
+#  endif
+  int internal_subdir_empty_2()
+{
+  return 0;
+}
+
+#else
+
+#  ifdef _WIN32
+__declspec(dllexport)
+#  endif
+  int subdir_empty_2()
+{
+  return 0;
+}
+
+#endif