Add option for local package override (#123)

* add option for local package override

* print info on the source directory

README.md

@@ -73,7 +73,7 @@ CPMAddPackage(
 target_link_libraries(tests Catch2)
 ```
 
-See the [examples directory](https://github.com/TheLartians/CPM/tree/master/examples) for complete examples with source code or the [wiki](https://github.com/TheLartians/CPM/wiki/More-Snippets) for example snippets.
+See the [examples directory](https://github.com/TheLartians/CPM.cmake/tree/master/examples) for complete examples with source code or the [wiki](https://github.com/TheLartians/CPM.cmake/wiki/More-Snippets) for example snippets.
 
 ## Adding CPM
 
@@ -84,7 +84,7 @@ mkdir -p cmake
 wget -O cmake/CPM.cmake https://github.com/TheLartians/CPM.cmake/releases/latest/download/CPM.cmake
 ```
 
-You can also use CMake to download CPM for you. See the [wiki](https://github.com/TheLartians/CPM/wiki/Adding-CPM) for more details.
+You can also use CMake to download CPM for you. See the [wiki](https://github.com/TheLartians/CPM.cmake/wiki/Downloading-CPM.cmake-in-CMake) for more details.
 
 ## Updating CPM
 
@@ -95,7 +95,7 @@ Dependencies using CPM will automatically use the updated script of the outermos
 
 - **Small and reusable projects** CPM takes care of all project dependencies, allowing developers to focus on creating small, well-tested libraries.
 - **Cross-Platform** CPM adds projects directly at the configure stage and is compatible with all CMake toolchains and generators.
-- **Reproducable builds** By versioning dependencies via git commits or tags it is ensured that a project will always be buildable.
+- **Reproducible builds** By versioning dependencies via git commits or tags it is ensured that a project will always be buildable.
 - **Recursive dependencies** Ensures that no dependency is added twice and all are added in the minimum required version.
 - **Plug-and-play** No need to install anything. Just add the script to your project and you're good to go.
 - **No packaging required** Simply add all external sources as a dependency.
@@ -103,9 +103,9 @@ Dependencies using CPM will automatically use the updated script of the outermos
 
 ## Limitations
 
-- **No pre-built binaries** For every new build directory, all dependencies are initially downloaded and built from scratch. To avoid extra downloads it is recommend to set the [`CPM_SOURCE_CACHE`](#CPM_SOURCE_CACHE) environmental variable. Using a caching compiler such as [ccahe](https://github.com/TheLartians/Ccache.cmake) can drastically reduce build time.
-- **Dependent on good CMakeLists** Many libraries do not have CMakeLists that work well for subprojects. Luckily this is slowly changing, however, until then, some manual configuration may be required (see the snippets [below](#snippets) for examples). For best practices on preparing projects for CPM, see the [wiki](https://github.com/TheLartians/CPM/wiki/Preparing-projects-for-CPM). 
-- **First version used** In diamond-shaped dependency graphs (e.g. `A` depends on `C`@1.1 and `B`, which itself depends on `C`@1.2 the first added dependency will be used (in this case `C`@1.1). In this case, B requires a newer version of `C` than `A`, so CPM will emit a warning. This can be resolved by adding a new version of the dependency in the outermost project.
+- **No pre-built binaries** For every new build directory, all dependencies are initially downloaded and built from scratch. To avoid extra downloads it is recommend to set the [`CPM_SOURCE_CACHE`](#CPM_SOURCE_CACHE) environmental variable. Using a caching compiler such as [ccache](https://github.com/TheLartians/Ccache.cmake) can drastically reduce build time.
+- **Dependent on good CMakeLists** Many libraries do not have CMakeLists that work well for subprojects. Luckily this is slowly changing, however, until then, some manual configuration may be required (see the snippets [below](#snippets) for examples). For best practices on preparing projects for CPM, see the [wiki](https://github.com/TheLartians/CPM.cmake/wiki/Preparing-projects-for-CPM.cmake). 
+- **First version used** In diamond-shaped dependency graphs (e.g. `A` depends on `C`@1.1 and `B`, which itself depends on `C`@1.2 the first added dependency will be used (in this case `C`@1.1). In this case, B requires a newer version of `C` than `A`, so CPM will emit a warning. This can be easily resolved by adding a new version of the dependency in the outermost project, or by introducing a [package lock file](https://github.com/TheLartians/CPM.cmake/wiki/Package-lock).
 
 For projects with more complex needs and where an extra setup step doesn't matter, it may be worth to check out an external C++ package manager such as [vcpkg](https://github.com/microsoft/vcpkg), [conan](https://conan.io) or [hunter](https://github.com/ruslo/hunter).
 Dependencies added with `CPMFindPackage` should work with external package managers.
@@ -137,10 +137,16 @@ 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.
-See the [wiki](https://github.com/TheLartians/CPM/wiki/More-Snippets) for more snippets.
+See the [wiki](https://github.com/TheLartians/CPM.cmake/wiki/More-Snippets) for more snippets.
 
 ### [Catch2](https://github.com/catchorg/Catch2)
 
@@ -270,4 +276,4 @@ For a full example on using CPM to download and configure lua with sol2 see [her
 
 ### Full Examples
 
-See the [examples directory](https://github.com/TheLartians/CPM/tree/master/examples) for full examples with source code and check out the [wiki](https://github.com/TheLartians/CPM/wiki/More-Snippets) for many more example snippets.
+See the [examples directory](https://github.com/TheLartians/CPM.cmake/tree/master/examples) for full examples with source code and check out the [wiki](https://github.com/TheLartians/CPM.cmake/wiki/More-Snippets) for many more example snippets.

cmake/CPM.cmake

@@ -1,6 +1,6 @@
-# TheLartians/CPM - A simple Git dependency manager
-# =================================================
-# See https://github.com/TheLartians/CPM for usage and update instructions.
+# CPM.cmake - CMake's missing package manager
+# ===========================================
+# See https://github.com/TheLartians/CPM.cmake for usage and update instructions.
 #
 # MIT License
 # ----------- 
@@ -28,11 +28,11 @@
 
 cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
 
-set(CURRENT_CPM_VERSION 0.20)
+set(CURRENT_CPM_VERSION 0.26)
 
 if(CPM_DIRECTORY)
-  if(NOT ${CPM_DIRECTORY} MATCHES ${CMAKE_CURRENT_LIST_DIR})
-    if (${CPM_VERSION} VERSION_LESS ${CURRENT_CPM_VERSION})
+  if(NOT CPM_DIRECTORY STREQUAL CMAKE_CURRENT_LIST_DIR)
+    if (CPM_VERSION VERSION_LESS CURRENT_CPM_VERSION)
       message(AUTHOR_WARNING "${CPM_INDENT} \
 A dependency is using a more recent CPM version (${CURRENT_CPM_VERSION}) than the current project (${CPM_VERSION}). \
 It is recommended to upgrade CPM to the most recent version. \
@@ -41,14 +41,25 @@ See https://github.com/TheLartians/CPM.cmake for more information."
     endif()
     return()
   endif()
+
+  get_property(CPM_INITIALIZED GLOBAL "" PROPERTY CPM_INITIALIZED SET)   
+  if (CPM_INITIALIZED)
+    return()
+  endif()
 endif()
 
+set_property(GLOBAL PROPERTY CPM_INITIALIZED true) 
+
 option(CPM_USE_LOCAL_PACKAGES "Always try to use `find_package` to get dependencies" $ENV{CPM_USE_LOCAL_PACKAGES})
 option(CPM_LOCAL_PACKAGES_ONLY "Only use `find_package` to get dependencies" $ENV{CPM_LOCAL_PACKAGES_ONLY})
 option(CPM_DOWNLOAD_ALL "Always download dependencies from source" $ENV{CPM_DOWNLOAD_ALL})
+option(CPM_DONT_UPDATE_MODULE_PATH "Don't update the module path to allow using find_package" $ENV{CPM_DONT_UPDATE_MODULE_PATH})
+option(CPM_DONT_CREATE_PACKAGE_LOCK "Don't create a package lock file in the binary path" $ENV{CPM_DONT_CREATE_PACKAGE_LOCK})
+option(CPM_INCLUDE_ALL_IN_PACKAGE_LOCK "Add all packages added through CPM.cmake to the package lock" $ENV{CPM_INCLUDE_ALL_IN_PACKAGE_LOCK})
 
 set(CPM_VERSION ${CURRENT_CPM_VERSION} CACHE INTERNAL "")
 set(CPM_DIRECTORY ${CMAKE_CURRENT_LIST_DIR} CACHE INTERNAL "")
+set(CPM_FILE ${CMAKE_CURRENT_LIST_FILE} CACHE INTERNAL "")
 set(CPM_PACKAGES "" CACHE INTERNAL "")
 set(CPM_DRY_RUN OFF CACHE INTERNAL "Don't download or configure dependencies (for testing)")
 
@@ -60,6 +71,20 @@ endif()
 
 set(CPM_SOURCE_CACHE ${CPM_SOURCE_CACHE_DEFAULT} CACHE PATH "Directory to downlaod CPM dependencies")
 
+if (NOT CPM_DONT_UPDATE_MODULE_PATH)
+  set(CPM_MODULE_PATH "${CMAKE_BINARY_DIR}/CPM_modules" CACHE INTERNAL "")
+  # remove old modules
+  FILE(REMOVE_RECURSE ${CPM_MODULE_PATH})
+  file(MAKE_DIRECTORY ${CPM_MODULE_PATH})
+  # locally added CPM modules should override global packages
+  set(CMAKE_MODULE_PATH "${CPM_MODULE_PATH};${CMAKE_MODULE_PATH}")
+endif()
+
+if (NOT CPM_DONT_CREATE_PACKAGE_LOCK)
+  set(CPM_PACKAGE_LOCK_FILE "${CMAKE_BINARY_DIR}/cpm-package-lock.cmake" CACHE INTERNAL "")
+  file(WRITE ${CPM_PACKAGE_LOCK_FILE} "# CPM Package Lock\n# This file should be committed to version control\n\n")
+endif()
+
 include(FetchContent)
 include(CMakeParseArguments)
 
@@ -72,14 +97,23 @@ function(cpm_find_package NAME VERSION)
   string(REPLACE " " ";" EXTRA_ARGS "${ARGN}")
   find_package(${NAME} ${VERSION} ${EXTRA_ARGS} QUIET)
   if(${CPM_ARGS_NAME}_FOUND)
-    message(STATUS "${CPM_INDENT} using local package ${CPM_ARGS_NAME}@${${CPM_ARGS_NAME}_VERSION}")
-    CPMRegisterPackage(${CPM_ARGS_NAME} "${${CPM_ARGS_NAME}_VERSION}")
+    message(STATUS "${CPM_INDENT} using local package ${CPM_ARGS_NAME}@${VERSION}")
+    CPMRegisterPackage(${CPM_ARGS_NAME} "${VERSION}")
     set(CPM_PACKAGE_FOUND YES PARENT_SCOPE)
   else()
     set(CPM_PACKAGE_FOUND NO PARENT_SCOPE)
   endif()
 endfunction()
 
+# Create a custom FindXXX.cmake module for a CPM package
+# This prevents `find_package(NAME)` from finding the system library
+function(CPMCreateModuleFile Name)
+  if (NOT CPM_DONT_UPDATE_MODULE_PATH)
+    # erase any previous modules
+    FILE(WRITE ${CPM_MODULE_PATH}/Find${Name}.cmake "include(${CPM_FILE})\n${ARGN}\nset(${Name}_FOUND TRUE)")
+  endif()
+endfunction()
+
 # Find a package locally or fallback to CPMAddPackage
 function(CPMFindPackage)
   set(oneValueArgs
@@ -89,54 +123,6 @@ function(CPMFindPackage)
   )
 
   cmake_parse_arguments(CPM_ARGS "" "${oneValueArgs}" "" ${ARGN})
-  
-  if (CPM_DOWNLOAD_ALL)
-    CPMAddPackage(${ARGN})
-    cpm_export_variables()
-    return()
-  endif()
-
-  cpm_find_package(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" ${CPM_ARGS_FIND_PACKAGE_ARGUMENTS})
-
-  if(NOT CPM_PACKAGE_FOUND)
-    CPMAddPackage(${ARGN})
-    cpm_export_variables()
-  endif()
-
-endfunction()
-
-# Download and add a package from source
-function(CPMAddPackage)
-
-  set(oneValueArgs
-    NAME
-    VERSION
-    GIT_TAG
-    DOWNLOAD_ONLY
-    GITHUB_REPOSITORY
-    GITLAB_REPOSITORY
-    SOURCE_DIR
-    DOWNLOAD_COMMAND
-    FIND_PACKAGE_ARGUMENTS
-  )
-
-  set(multiValueArgs
-    OPTIONS
-  )
-
-  cmake_parse_arguments(CPM_ARGS "" "${oneValueArgs}" "${multiValueArgs}" "${ARGN}")
-
-  if(CPM_USE_LOCAL_PACKAGES OR CPM_LOCAL_PACKAGES_ONLY)
-    cpm_find_package(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" ${CPM_ARGS_FIND_PACKAGE_ARGUMENTS})
-
-    if(CPM_PACKAGE_FOUND)
-      return()
-    endif()
-
-    if(CPM_LOCAL_PACKAGES_ONLY) 
-      message(SEND_ERROR "CPM: ${CPM_ARGS_NAME} not found via find_package(${CPM_ARGS_NAME} ${CPM_ARGS_VERSION})")
-    endif()
-  endif()
 
   if (NOT DEFINED CPM_ARGS_VERSION)
     if (DEFINED CPM_ARGS_GIT_TAG) 
@@ -147,27 +133,30 @@ function(CPMAddPackage)
     endif()
   endif()
 
-  if (NOT DEFINED CPM_ARGS_GIT_TAG)
-    set(CPM_ARGS_GIT_TAG v${CPM_ARGS_VERSION})
+  if (CPM_DOWNLOAD_ALL)
+    CPMAddPackage(${ARGN})
+    cpm_export_variables(${CPM_ARGS_NAME})
+    return()
   endif()
 
-  list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS GIT_TAG ${CPM_ARGS_GIT_TAG})
-
-  if(CPM_ARGS_DOWNLOAD_ONLY)
-    set(DOWNLOAD_ONLY ${CPM_ARGS_DOWNLOAD_ONLY})
-  else()
-    set(DOWNLOAD_ONLY NO)
+  CPMCheckIfPackageAlreadyAdded(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" "${CPM_ARGS_OPTIONS}")
+  if (CPM_PACKAGE_ALREADY_ADDED)
+    cpm_export_variables(${CPM_ARGS_NAME})
+    return()
   endif()
 
-  if (CPM_ARGS_GITHUB_REPOSITORY)
-    list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS GIT_REPOSITORY "https://github.com/${CPM_ARGS_GITHUB_REPOSITORY}.git")
+  cpm_find_package(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" ${CPM_ARGS_FIND_PACKAGE_ARGUMENTS})
+
+  if(NOT CPM_PACKAGE_FOUND)
+    CPMAddPackage(${ARGN})
+    cpm_export_variables(${CPM_ARGS_NAME})
   endif()
 
-  if (CPM_ARGS_GITLAB_REPOSITORY)
-    list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS GIT_REPOSITORY "https://gitlab.com/${CPM_ARGS_GITLAB_REPOSITORY}.git")
-  endif()
+endfunction()
 
-  if (${CPM_ARGS_NAME} IN_LIST CPM_PACKAGES)
+# checks if a package has been added before
+function(CPMCheckIfPackageAlreadyAdded CPM_ARGS_NAME CPM_ARGS_VERSION CPM_ARGS_OPTIONS)
+  if ("${CPM_ARGS_NAME}" IN_LIST CPM_PACKAGES)
     CPMGetPackageVersion(${CPM_ARGS_NAME} CPM_PACKAGE_VERSION)
     if(${CPM_PACKAGE_VERSION} VERSION_LESS ${CPM_ARGS_VERSION})
       message(WARNING "${CPM_INDENT} requires a newer version of ${CPM_ARGS_NAME} (${CPM_ARGS_VERSION}) than currently included (${CPM_PACKAGE_VERSION}).")
@@ -180,15 +169,116 @@ function(CPMAddPackage)
         endif()
       endforeach()
     endif()
-    cpm_fetch_package(${CPM_ARGS_NAME} ${DOWNLOAD_ONLY})
     cpm_get_fetch_properties(${CPM_ARGS_NAME})
-    SET(${CPM_ARGS_NAME}_SOURCE_DIR "${${CPM_ARGS_NAME}_SOURCE_DIR}")
-    SET(${CPM_ARGS_NAME}_BINARY_DIR "${${CPM_ARGS_NAME}_BINARY_DIR}")  
     SET(${CPM_ARGS_NAME}_ADDED NO)
-    cpm_export_variables()
+    SET(CPM_PACKAGE_ALREADY_ADDED YES PARENT_SCOPE)
+    cpm_export_variables(${CPM_ARGS_NAME})
+  else()
+    SET(CPM_PACKAGE_ALREADY_ADDED NO PARENT_SCOPE)
+  endif()
+endfunction()
+
+# Download and add a package from source
+function(CPMAddPackage)
+
+  set(oneValueArgs
+    NAME
+    VERSION
+    GIT_TAG
+    DOWNLOAD_ONLY
+    GITHUB_REPOSITORY
+    GITLAB_REPOSITORY
+    GIT_REPOSITORY
+    SOURCE_DIR
+    DOWNLOAD_COMMAND
+    FIND_PACKAGE_ARGUMENTS
+  )
+
+  set(multiValueArgs
+    OPTIONS
+  )
+
+  cmake_parse_arguments(CPM_ARGS "" "${oneValueArgs}" "${multiValueArgs}" "${ARGN}")
+
+  # Set default values for arguments
+
+  if (NOT DEFINED CPM_ARGS_VERSION)
+    if (DEFINED CPM_ARGS_GIT_TAG) 
+      cpm_get_version_from_git_tag("${CPM_ARGS_GIT_TAG}" CPM_ARGS_VERSION)
+    endif()
+    if (NOT DEFINED CPM_ARGS_VERSION) 
+      set(CPM_ARGS_VERSION 0)
+    endif()
+  endif()
+
+  if(CPM_ARGS_DOWNLOAD_ONLY)
+    set(DOWNLOAD_ONLY ${CPM_ARGS_DOWNLOAD_ONLY})
+  else()
+    set(DOWNLOAD_ONLY NO)
+  endif()
+
+  if (CPM_ARGS_GITHUB_REPOSITORY)
+    set(CPM_ARGS_GIT_REPOSITORY "https://github.com/${CPM_ARGS_GITHUB_REPOSITORY}.git")
+  endif()
+
+  if (CPM_ARGS_GITLAB_REPOSITORY)
+    list(CPM_ARGS_GIT_REPOSITORY "https://gitlab.com/${CPM_ARGS_GITLAB_REPOSITORY}.git")
+  endif()
+
+  if (DEFINED CPM_ARGS_GIT_REPOSITORY)
+    list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS GIT_REPOSITORY ${CPM_ARGS_GIT_REPOSITORY})
+    if (NOT DEFINED CPM_ARGS_GIT_TAG)
+      set(CPM_ARGS_GIT_TAG v${CPM_ARGS_VERSION})
+    endif()
+  endif()
+
+  if (CPM_ARGS_GIT_TAG)
+    list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS GIT_TAG ${CPM_ARGS_GIT_TAG})
+  endif()
+
+  # Check if package has been added before
+  CPMCheckIfPackageAlreadyAdded(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" "${CPM_ARGS_OPTIONS}")
+  if (CPM_PACKAGE_ALREADY_ADDED)
+    cpm_export_variables(${CPM_ARGS_NAME})
     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 (NOT "${CPM_DECLARATION_${CPM_ARGS_NAME}}" STREQUAL "")
+    set(declaration ${CPM_DECLARATION_${CPM_ARGS_NAME}})
+    set(CPM_DECLARATION_${CPM_ARGS_NAME} "")
+    CPMAddPackage(${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}")
+    return()
+  endif()
+
+  if(CPM_USE_LOCAL_PACKAGES OR CPM_LOCAL_PACKAGES_ONLY)
+    cpm_find_package(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" ${CPM_ARGS_FIND_PACKAGE_ARGUMENTS})
+
+    if(CPM_PACKAGE_FOUND)
+      cpm_export_variables(${CPM_ARGS_NAME})
+      return()
+    endif()
+
+    if(CPM_LOCAL_PACKAGES_ONLY) 
+      message(SEND_ERROR "CPM: ${CPM_ARGS_NAME} not found via find_package(${CPM_ARGS_NAME} ${CPM_ARGS_VERSION})")
+    endif()
+  endif()
+
   CPMRegisterPackage(${CPM_ARGS_NAME} ${CPM_ARGS_VERSION})
 
   if (CPM_ARGS_OPTIONS)
@@ -198,28 +288,28 @@ function(CPMAddPackage)
     endforeach()
   endif()
 
-  set(FETCH_CONTENT_DECLARE_EXTRA_OPTS "")
-
   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()
 
   if (DEFINED CPM_ARGS_DOWNLOAD_COMMAND)
-    set(FETCH_CONTENT_DECLARE_EXTRA_OPTS DOWNLOAD_COMMAND ${CPM_ARGS_DOWNLOAD_COMMAND})
+    list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS DOWNLOAD_COMMAND ${CPM_ARGS_DOWNLOAD_COMMAND})
   elseif(DEFINED CPM_ARGS_SOURCE_DIR)
-    set(FETCH_CONTENT_DECLARE_EXTRA_OPTS SOURCE_DIR ${CPM_ARGS_SOURCE_DIR})
+    list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS SOURCE_DIR ${CPM_ARGS_SOURCE_DIR})
   elseif (CPM_SOURCE_CACHE)
     string(TOLOWER ${CPM_ARGS_NAME} lower_case_name)
     set(origin_parameters ${CPM_ARGS_UNPARSED_ARGUMENTS})
     list(SORT origin_parameters)
     string(SHA1 origin_hash "${origin_parameters}")
     set(download_directory ${CPM_SOURCE_CACHE}/${lower_case_name}/${origin_hash})
-    list(APPEND FETCH_CONTENT_DECLARE_EXTRA_OPTS SOURCE_DIR ${download_directory})
+    list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS SOURCE_DIR ${download_directory})
     if (EXISTS ${download_directory})
       # disable the download command to allow offline builds
-      list(APPEND FETCH_CONTENT_DECLARE_EXTRA_OPTS DOWNLOAD_COMMAND "${CMAKE_COMMAND}")
+      list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS DOWNLOAD_COMMAND "${CMAKE_COMMAND}")
       set(PACKAGE_INFO "${download_directory}")
     else()
       # remove timestamps so CMake will re-download the dependency
@@ -228,22 +318,81 @@ function(CPMAddPackage)
     endif()
   endif()
 
-  cpm_declare_fetch(${CPM_ARGS_NAME} ${CPM_ARGS_VERSION} ${PACKAGE_INFO} "${CPM_ARGS_UNPARSED_ARGUMENTS}" ${FETCH_CONTENT_DECLARE_EXTRA_OPTS})
+  CPMCreateModuleFile(${CPM_ARGS_NAME} "CPMAddPackage(${ARGN})")
+
+  if (CPM_PACKAGE_LOCK_ENABLED)
+    if ((CPM_ARGS_VERSION AND NOT CPM_ARGS_SOURCE_DIR) OR CPM_INCLUDE_ALL_IN_PACKAGE_LOCK)
+      cpm_add_to_package_lock(${CPM_ARGS_NAME} "${ARGN}")
+    elseif(CPM_ARGS_SOURCE_DIR)
+      cpm_add_comment_to_package_lock(${CPM_ARGS_NAME} "local directory")
+    else()
+      cpm_add_comment_to_package_lock(${CPM_ARGS_NAME} "${ARGN}")
+    endif()
+  endif()
+
+  cpm_declare_fetch(${CPM_ARGS_NAME} ${CPM_ARGS_VERSION} ${PACKAGE_INFO} ${CPM_ARGS_UNPARSED_ARGUMENTS})
   cpm_fetch_package(${CPM_ARGS_NAME} ${DOWNLOAD_ONLY})
   cpm_get_fetch_properties(${CPM_ARGS_NAME})
+
   SET(${CPM_ARGS_NAME}_ADDED YES)
-  cpm_export_variables()
+  cpm_export_variables(${CPM_ARGS_NAME})
 endfunction()
 
+# Fetch a previously declared package
+macro(CPMGetPackage Name)
+  if (DEFINED "CPM_DECLARATION_${Name}")
+    CPMAddPackage(
+      NAME ${Name}
+    )
+  else()
+    message(SEND_ERROR "Cannot retrieve package ${Name}: no declaration available")
+  endif()
+endmacro()
+
 # export variables available to the caller to the parent scope
 # expects ${CPM_ARGS_NAME} to be set
-macro(cpm_export_variables)
-  SET(${CPM_ARGS_NAME}_SOURCE_DIR "${${CPM_ARGS_NAME}_SOURCE_DIR}" PARENT_SCOPE)
-  SET(${CPM_ARGS_NAME}_BINARY_DIR "${${CPM_ARGS_NAME}_BINARY_DIR}" PARENT_SCOPE)
-  SET(${CPM_ARGS_NAME}_ADDED "${${CPM_ARGS_NAME}_ADDED}" PARENT_SCOPE)
+macro(cpm_export_variables name)
+  SET(${name}_SOURCE_DIR "${${name}_SOURCE_DIR}" PARENT_SCOPE)
+  SET(${name}_BINARY_DIR "${${name}_BINARY_DIR}" PARENT_SCOPE)
+  SET(${name}_ADDED "${${name}_ADDED}" PARENT_SCOPE)
 endmacro()
 
-# declares that a package has been added to CPM
+# declares a package, so that any call to CPMAddPackage for the 
+# package name will use these arguments instead 
+macro(CPMDeclarePackage Name)
+  if (NOT DEFINED "CPM_DECLARATION_${Name}")
+    set("CPM_DECLARATION_${Name}" "${ARGN}")
+  endif()
+endmacro()
+
+function(cpm_add_to_package_lock Name)
+  if (NOT CPM_DONT_CREATE_PACKAGE_LOCK)
+    file(APPEND ${CPM_PACKAGE_LOCK_FILE} "# ${Name}\nCPMDeclarePackage(${Name} \"${ARGN}\")\n")
+  endif()
+endfunction()
+
+function(cpm_add_comment_to_package_lock Name)
+  if (NOT CPM_DONT_CREATE_PACKAGE_LOCK)
+    file(APPEND ${CPM_PACKAGE_LOCK_FILE} "# ${Name} (unversioned)\n# CPMDeclarePackage(${Name} \"${ARGN}\")\n")
+  endif()
+endfunction()
+
+# includes the package lock file if it exists and creates a target
+# `cpm-write-package-lock` to update it
+macro(CPMUsePackageLock file)
+  if (NOT CPM_DONT_CREATE_PACKAGE_LOCK)
+    get_filename_component(CPM_ABSOLUTE_PACKAGE_LOCK_PATH ${file} ABSOLUTE)
+    if(EXISTS ${CPM_ABSOLUTE_PACKAGE_LOCK_PATH})
+      include(${CPM_ABSOLUTE_PACKAGE_LOCK_PATH})
+    endif()
+    if (NOT TARGET cpm-update-package-lock)
+      add_custom_target(cpm-update-package-lock COMMAND ${CMAKE_COMMAND} -E copy ${CPM_PACKAGE_LOCK_FILE} ${CPM_ABSOLUTE_PACKAGE_LOCK_PATH})
+    endif()
+    set(CPM_PACKAGE_LOCK_ENABLED true)
+  endif()
+endmacro()
+
+# registers a package that has been added to CPM
 function(CPMRegisterPackage PACKAGE VERSION)
   list(APPEND CPM_PACKAGES ${PACKAGE})
   set(CPM_PACKAGES ${CPM_PACKAGES} CACHE INTERNAL "")
@@ -264,8 +413,7 @@ function (cpm_declare_fetch PACKAGE VERSION INFO)
     return()
   endif()
 
-  FetchContent_Declare(
-    ${PACKAGE}
+  FetchContent_Declare(${PACKAGE}
     ${ARGN}
   )
 endfunction()
@@ -283,22 +431,22 @@ endfunction()
 
 # downloads a previously declared package via FetchContent
 function (cpm_fetch_package PACKAGE DOWNLOAD_ONLY)  
-
   if (${CPM_DRY_RUN}) 
     message(STATUS "${CPM_INDENT} package ${PACKAGE} not fetched (dry run)")
     return()
   endif()
 
-  set(CPM_OLD_INDENT "${CPM_INDENT}")
-  set(CPM_INDENT "${CPM_INDENT} ${PACKAGE}:")
-  if(${DOWNLOAD_ONLY})
-    if(NOT "${PACKAGE}_POPULATED")
+  if(DOWNLOAD_ONLY)
+    FetchContent_GetProperties(${PACKAGE})
+    if(NOT ${PACKAGE}_POPULATED)
       FetchContent_Populate(${PACKAGE})
     endif()
   else()
+    set(CPM_OLD_INDENT "${CPM_INDENT}")
+    set(CPM_INDENT "${CPM_INDENT} ${PACKAGE}:")
     FetchContent_MakeAvailable(${PACKAGE})
+    set(CPM_INDENT "${CPM_OLD_INDENT}")
   endif()
-  set(CPM_INDENT "${CPM_OLD_INDENT}")
 endfunction()
 
 # splits a package option

cmake/testing.cmake

@@ -20,3 +20,15 @@ endfunction()
 function(ASSERTION_FAILED)
   message(FATAL_ERROR "assertion failed: ${ARGN}")
 endfunction()
+
+function(ASSERT_EXISTS file)
+  if (NOT EXISTS ${file}) 
+    message(FATAL_ERROR "assertion failed: file ${file} does not exist")
+  endif()
+endfunction()
+
+function(ASSERT_NOT_EXISTS file)
+  if (EXISTS ${file}) 
+    message(FATAL_ERROR "assertion failed: file ${file} exists")
+  endif()
+endfunction()

test/unit/modules.cmake

@@ -0,0 +1,30 @@
+
+include(CMakePackageConfigHelpers)
+include(${CPM_PATH}/testing.cmake)
+
+set(TEST_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR}/modules)
+
+function(initProjectWithDependency TEST_DEPENDENCY_NAME)
+  configure_package_config_file(
+    "${CMAKE_CURRENT_LIST_DIR}/test_project/ModuleCMakeLists.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${TEST_BUILD_DIR}"
+    RESULT_VARIABLE ret
+  )
+
+  ASSERT_EQUAL(${ret} "0")
+endfunction()
+
+initProjectWithDependency(A)
+ASSERT_EXISTS(${TEST_BUILD_DIR}/CPM_modules)
+ASSERT_EXISTS(${TEST_BUILD_DIR}/CPM_modules/FindA.cmake)
+ASSERT_NOT_EXISTS(${TEST_BUILD_DIR}/CPM_modules/FindB.cmake)
+
+initProjectWithDependency(B)
+ASSERT_NOT_EXISTS(${TEST_BUILD_DIR}/CPM_modules/FindA.cmake)
+ASSERT_EXISTS(${TEST_BUILD_DIR}/CPM_modules/FindB.cmake)

test/unit/package-lock.cmake

@@ -0,0 +1,49 @@
+
+include(CMakePackageConfigHelpers)
+include(${CPM_PATH}/testing.cmake)
+
+set(TEST_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR}/package-lock)
+
+function(configureWithDeclare DECLARE_DEPENDENCY)
+  execute_process(COMMAND ${CMAKE_COMMAND} -E rm -rf ${TEST_BUILD_DIR})
+
+  if (DECLARE_DEPENDENCY)
+    set(PREPARE_CODE "CPMDeclarePackage(Dependency
+      NAME Dependency 
+      SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/test_project/dependency
+    )")
+  else()
+    set(PREPARE_CODE "")
+  endif()
+
+  configure_package_config_file(
+    "${CMAKE_CURRENT_LIST_DIR}/test_project/PackageLockCMakeLists.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${TEST_BUILD_DIR} -DCPM_INCLUDE_ALL_IN_PACKAGE_LOCK=1
+    RESULT_VARIABLE ret
+  )
+
+  ASSERT_EQUAL(${ret} "0")
+endfunction()
+
+function(updatePackageLock)
+  execute_process(
+    COMMAND ${CMAKE_COMMAND} --build ${TEST_BUILD_DIR} --target cpm-update-package-lock
+    RESULT_VARIABLE ret
+  )
+
+  ASSERT_EQUAL(${ret} "0")
+endfunction()
+
+execute_process(COMMAND ${CMAKE_COMMAND} -E rm -f ${CMAKE_CURRENT_LIST_DIR}/test_project/package-lock.cmake)
+configureWithDeclare(YES)
+ASSERT_NOT_EXISTS(${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/source_dir.cmake

@@ -4,15 +4,17 @@ include(${CPM_PATH}/testing.cmake)
 
 set(TEST_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR}/source_dir)
 
+set(TEST_DEPENDENCY_NAME Dependency)
+
 configure_package_config_file(
-  "${CMAKE_CURRENT_LIST_DIR}/source_dir/CMakeLists.txt.in"
-  "${CMAKE_CURRENT_LIST_DIR}/source_dir/CMakeLists.txt"
+  "${CMAKE_CURRENT_LIST_DIR}/test_project/ModuleCMakeLists.txt.in"
+  "${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}/source_dir" "-B${TEST_BUILD_DIR}"
+  ${CMAKE_COMMAND} "-H${CMAKE_CURRENT_LIST_DIR}/test_project" "-B${TEST_BUILD_DIR}"
   RESULT_VARIABLE ret
 )
 

test/unit/source_dir/.gitignore

@@ -1 +0,0 @@
-/CMakeLists.txt

test/unit/test_project/.gitignore

@@ -0,0 +1,2 @@
+/CMakeLists.txt
+/package-lock.cmake

test/unit/test_project/ModuleCMakeLists.txt.in

@@ -0,0 +1,26 @@
+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 @TEST_DEPENDENCY_NAME@
+  SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/dependency
+)
+
+# ---- check if generated modules override find_package ----
+
+if (@test_check_find_package@)
+  find_package(@TEST_DEPENDENCY_NAME@ REQUIRED)
+endif()
+
+# ---- Call dependency method to validate correct addition of directory ----
+
+dependency_function()

test/unit/test_project/OverrideCMakeLists.txt.in

@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
 
-project(CPMExampleCatch2)
+project(CPMTest)
 
 # ---- Options ----
 
@@ -12,7 +12,6 @@ include(@CPM_PATH@/CPM.cmake)
 
 CPMAddPackage(
   NAME Dependency
-  SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/dependency
 )
 
 # ---- Call dependency method to validate correct addition of directory ----

test/unit/test_project/PackageLockCMakeLists.txt.in

@@ -0,0 +1,20 @@
+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)
+CPMUsePackageLock(package-lock.cmake)
+
+@PREPARE_CODE@
+
+CPMGetPackage(Dependency)
+
+# ---- Call dependency method to validate correct addition of directory ----
+
+dependency_function()