Add option for local package override (#123)

* add option for local package override

* print info on the source directory

README.md

@@ -137,6 +137,12 @@ CPM can be configured to use `find_package` to search for locally installed depe
 If the option `CPM_LOCAL_PACKAGES_ONLY` is set, CPM will emit an error if the dependency is not found locally.
 These options can also be set as environmental variables.
 
+## Local package override
+
+Library developers are often in the situation where they work on a locally checked out dependency at the same time as on a consumer.
+It is possible to override the consumer's dependency version with the local one by supplying the CMake option `CPM_<dependency name>_SOURCE`.
+For example, to use the local version of `Dep` at the absolute path `/path/to/dep`, the consumer can be build with `cmake -H. -Bbuild -DCPM_Dep_SOURCE=/path/to/dep`.
+
 ## Snippets
 
 These examples demonstrate how to include some well-known projects with CPM.

cmake/CPM.cmake

@@ -28,7 +28,7 @@
 
 cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
 
-set(CURRENT_CPM_VERSION 0.25.1)
+set(CURRENT_CPM_VERSION 0.26)
 
 if(CPM_DIRECTORY)
   if(NOT CPM_DIRECTORY STREQUAL CMAKE_CURRENT_LIST_DIR)
@@ -243,12 +243,23 @@ function(CPMAddPackage)
     return()
   endif()
 
+  # Check for manual overrides
+  if (NOT "${CPM_${CPM_ARGS_NAME}_SOURCE}" STREQUAL "")
+    set(PACKAGE_SOURCE ${CPM_${CPM_ARGS_NAME}_SOURCE})
+    set(CPM_${CPM_ARGS_NAME}_SOURCE "")
+    CPMAddPackage(
+      NAME ${CPM_ARGS_NAME}
+      SOURCE_DIR ${PACKAGE_SOURCE}
+    )
+    cpm_export_variables(${CPM_ARGS_NAME})
+    return()
+  endif()
+
   # Check for available declaration
-  if (DEFINED "CPM_DECLARATION_${CPM_ARGS_NAME}" AND NOT "${CPM_DECLARATION_${CPM_ARGS_NAME}}" STREQUAL "")
+  if (NOT "${CPM_DECLARATION_${CPM_ARGS_NAME}}" STREQUAL "")
     set(declaration ${CPM_DECLARATION_${CPM_ARGS_NAME}})
     set(CPM_DECLARATION_${CPM_ARGS_NAME} "")
     CPMAddPackage(${declaration})
-    set(CPM_DECLARATION_${CPM_ARGS_NAME} "${declaration}")
     cpm_export_variables(${CPM_ARGS_NAME})
     # checking again to ensure version and option compatibility
     CPMCheckIfPackageAlreadyAdded(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" "${CPM_ARGS_OPTIONS}")
@@ -279,6 +290,8 @@ function(CPMAddPackage)
 
   if (DEFINED CPM_ARGS_GIT_TAG)
     set(PACKAGE_INFO "${CPM_ARGS_GIT_TAG}")
+  elseif(DEFINED CPM_ARGS_SOURCE_DIR)
+    set(PACKAGE_INFO "${CPM_ARGS_SOURCE_DIR}")
   else()
     set(PACKAGE_INFO "${CPM_ARGS_VERSION}")
   endif()

test/unit/package-lock.cmake

@@ -45,4 +45,5 @@ ASSERT_NOT_EXISTS(${CMAKE_CURRENT_LIST_DIR}/test_project/package-lock.cmake)
 updatePackageLock()
 ASSERT_EXISTS(${CMAKE_CURRENT_LIST_DIR}/test_project/package-lock.cmake)
 configureWithDeclare(NO)
+execute_process(COMMAND ${CMAKE_COMMAND} -E rm -f ${CMAKE_CURRENT_LIST_DIR}/test_project/package-lock.cmake)
 

test/unit/package-override.cmake

@@ -0,0 +1,20 @@
+
+include(CMakePackageConfigHelpers)
+include(${CPM_PATH}/testing.cmake)
+
+set(TEST_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR}/project-override)
+
+execute_process(COMMAND ${CMAKE_COMMAND} -E rm -rf ${TEST_BUILD_DIR})
+
+configure_package_config_file(
+  "${CMAKE_CURRENT_LIST_DIR}/test_project/OverrideCMakeLists.txt.in"
+  "${CMAKE_CURRENT_LIST_DIR}/test_project/CMakeLists.txt"
+  INSTALL_DESTINATION ${CMAKE_CURRENT_BINARY_DIR}/junk
+)
+
+execute_process(
+  COMMAND ${CMAKE_COMMAND} -H${CMAKE_CURRENT_LIST_DIR}/test_project -B${TEST_BUILD_DIR} -DCPM_Dependency_SOURCE=${CMAKE_CURRENT_LIST_DIR}/test_project/dependency
+  RESULT_VARIABLE ret
+)
+
+ASSERT_EQUAL(${ret} "0")

test/unit/test_project/OverrideCMakeLists.txt.in

@@ -0,0 +1,19 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+project(CPMTest)
+
+# ---- Options ----
+
+option(ENABLE_TEST_COVERAGE "Enable test coverage" OFF)
+
+# ---- Dependencies ----
+
+include(@CPM_PATH@/CPM.cmake)
+
+CPMAddPackage(
+  NAME Dependency
+)
+
+# ---- Call dependency method to validate correct addition of directory ----
+
+dependency_function()