Fix support for source subdirectories (#238)

* add support for source subdirectories

* style fixes

* remove debug log

* grammar fix in comment

cmake/CPM.cmake

@@ -388,6 +388,7 @@ function(CPMAddPackage)
       NO_CACHE
       GIT_SHALLOW
       EXCLUDE_FROM_ALL
+      SOURCE_SUBDIR
   )
 
   set(multiValueArgs URL OPTIONS)
@@ -549,11 +550,11 @@ function(CPMAddPackage)
       set(${CPM_ARGS_NAME}_BINARY_DIR ${CMAKE_BINARY_DIR}/_deps/${lower_case_name}-build)
       set(${CPM_ARGS_NAME}_ADDED YES)
       set(${CPM_ARGS_NAME}_SOURCE_DIR ${download_directory})
-      if(NOT CPM_ARGS_DOWNLOAD_ONLY AND EXISTS ${download_directory}/CMakeLists.txt)
-        cpm_add_subdirectory(
-          ${download_directory} ${${CPM_ARGS_NAME}_BINARY_DIR} "${CPM_ARGS_EXCLUDE_FROM_ALL}"
-        )
-      endif()
+      cpm_add_subdirectory(
+        "${CPM_ARGS_NAME}" "${DOWNLOAD_ONLY}"
+        "${${CPM_ARGS_NAME}_SOURCE_DIR}/${CPM_ARGS_SOURCE_SUBDIR}" "${${CPM_ARGS_NAME}_BINARY_DIR}"
+        "${CPM_ARGS_EXCLUDE_FROM_ALL}"
+      )
       set(CPM_SKIP_FETCH TRUE)
       set(PACKAGE_INFO "${PACKAGE_INFO} at ${download_directory}")
     else()
@@ -592,7 +593,12 @@ function(CPMAddPackage)
     cpm_declare_fetch(
       "${CPM_ARGS_NAME}" "${CPM_ARGS_VERSION}" "${PACKAGE_INFO}" "${CPM_ARGS_UNPARSED_ARGUMENTS}"
     )
-    cpm_fetch_package("${CPM_ARGS_NAME}" "${DOWNLOAD_ONLY}" "${CPM_ARGS_EXCLUDE_FROM_ALL}")
+    cpm_fetch_package("${CPM_ARGS_NAME}")
+    cpm_add_subdirectory(
+      "${CPM_ARGS_NAME}" "${DOWNLOAD_ONLY}"
+      "${${CPM_ARGS_NAME}_SOURCE_DIR}/${CPM_ARGS_SOURCE_SUBDIR}" "${${CPM_ARGS_NAME}_BINARY_DIR}"
+      "${CPM_ARGS_EXCLUDE_FROM_ALL}"
+    )
     cpm_get_fetch_properties("${CPM_ARGS_NAME}")
   endif()
 
@@ -715,36 +721,44 @@ function(cpm_get_fetch_properties PACKAGE)
   )
 endfunction()
 
-function(cpm_add_subdirectory SOURCE_DIR BINARY_DIR EXCLUDE)
-  if(EXCLUDE)
-    set(addSubdirectoryExtraArgs EXCLUDE_FROM_ALL)
-  else()
-    set(addSubdirectoryExtraArgs "")
+# adds a package as a subdirectory if viable, according to provided options
+function(cpm_add_subdirectory PACKAGE DOWNLOAD_ONLY SOURCE_DIR BINARY_DIR EXCLUDE)
+  if(NOT DOWNLOAD_ONLY AND EXISTS ${SOURCE_DIR}/CMakeLists.txt)
+    if(EXCLUDE)
+      set(addSubdirectoryExtraArgs EXCLUDE_FROM_ALL)
+    else()
+      set(addSubdirectoryExtraArgs "")
+    endif()
+    set(CPM_OLD_INDENT "${CPM_INDENT}")
+    set(CPM_INDENT "${CPM_INDENT} ${PACKAGE}:")
+    add_subdirectory(${SOURCE_DIR} ${BINARY_DIR} ${addSubdirectoryExtraArgs})
+    set(CPM_INDENT "${CPM_OLD_INDENT}")
   endif()
-  add_subdirectory(${SOURCE_DIR} ${BINARY_DIR} ${addSubdirectoryExtraArgs})
 endfunction()
 
-# downloads a previously declared package via FetchContent
-function(cpm_fetch_package PACKAGE DOWNLOAD_ONLY EXCLUDE)
+# downloads a previously declared package via FetchContent and exports the variables
+# `${PACKAGE}_SOURCE_DIR` and `${PACKAGE}_BINARY_DIR` to the parent scope
+function(cpm_fetch_package PACKAGE)
   if(${CPM_DRY_RUN})
     message(STATUS "${CPM_INDENT} package ${PACKAGE} not fetched (dry run)")
     return()
   endif()
 
   FetchContent_GetProperties(${PACKAGE})
-  string(TOLOWER "${PACKAGE}" lower_case_name)
 
   if(NOT ${lower_case_name}_POPULATED)
     FetchContent_Populate(${PACKAGE})
-    if(NOT DOWNLOAD_ONLY AND EXISTS ${${lower_case_name}_SOURCE_DIR}/CMakeLists.txt)
-      set(CPM_OLD_INDENT "${CPM_INDENT}")
-      set(CPM_INDENT "${CPM_INDENT} ${PACKAGE}:")
-      cpm_add_subdirectory(
-        ${${lower_case_name}_SOURCE_DIR} ${${lower_case_name}_BINARY_DIR} "${EXCLUDE}"
-      )
-      set(CPM_INDENT "${CPM_OLD_INDENT}")
-    endif()
   endif()
+
+  string(TOLOWER "${PACKAGE}" lower_case_name)
+  set(${PACKAGE}_SOURCE_DIR
+      ${${lower_case_name}_SOURCE_DIR}
+      PARENT_SCOPE
+  )
+  set(${PACKAGE}_BINARY_DIR
+      ${${lower_case_name}_BINARY_DIR}
+      PARENT_SCOPE
+  )
 endfunction()
 
 # splits a package option

test/unit/local_dependency/SubdirCMakeLists.txt.in

@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+project(CPMTest)
+
+# ---- Dependencies ----
+
+include(@CPM_PATH@/CPM.cmake)
+
+CPMAddPackage(
+  NAME Dependency
+  SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/dependency
+  SOURCE_SUBDIR inner
+)
+
+# ---- Call inner dependency method to validate correct addition of subdirectory ----
+
+inner_dependency_function()

test/unit/local_dependency/dependency/inner/CMakeLists.txt

@@ -0,0 +1,3 @@
+function(inner_dependency_function)
+  message("called inner method")
+endfunction()

test/unit/subdir.cmake

@@ -0,0 +1,17 @@
+include(CMakePackageConfigHelpers)
+include(${CPM_PATH}/testing.cmake)
+
+set(TEST_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR}/source_dir)
+
+configure_package_config_file(
+  "${CMAKE_CURRENT_LIST_DIR}/local_dependency/SubdirCMakeLists.txt.in"
+  "${CMAKE_CURRENT_LIST_DIR}/local_dependency/CMakeLists.txt"
+  INSTALL_DESTINATION ${CMAKE_CURRENT_BINARY_DIR}/junk
+)
+
+execute_process(
+  COMMAND ${CMAKE_COMMAND} "-H${CMAKE_CURRENT_LIST_DIR}/local_dependency" "-B${TEST_BUILD_DIR}"
+  RESULT_VARIABLE ret
+)
+
+assert_equal(${ret} "0")