Implement #624: Use shorter hashes with CPM_SOURCE_CACHE (#631)

* Add ASSERT_CONTENTS_EQUAL test macro in testing.cmake

Checks if the contents of a file matches the given input

* Use shorter hashes with CPM_SOURCE_CACHE (#624)

Uses shorter hashes with CPM_SOURCE_CACHE. Falls back to a longer hash
if necessary (ie, if there's a collision with an existing hash).

See: https://github.com/cpm-cmake/CPM.cmake/issues/624

* Update integration tests to support shorter hashes

* trigger ci

* run cmake-format

* if already available, use the legacy cache hash

* create temporary file in current binary dir

* add test case for legacy hash

---------

Co-authored-by: Lars Melchior <lars.melchior@gmail.com>
Co-authored-by: Lars Melchior <TheLartians@users.noreply.github.com>

.git_archival.txt

@@ -0,0 +1,3 @@
+node: $Format:%H$
+node-date: $Format:%cI$
+describe-name: $Format:%(describe:tags=true,match=?[0-9.]*)$

.gitattributes

@@ -0,0 +1 @@
+.git_archival.txt  export-subst

CMakeLists.txt

@@ -0,0 +1,28 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+if(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/.git/")
+  find_package(Git REQUIRED)
+  execute_process(
+    COMMAND "${GIT_EXECUTABLE}" describe --tags --match=?[0-9.]*
+    WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
+    OUTPUT_VARIABLE DESCRIBE_NAME COMMAND_ERROR_IS_FATAL ANY
+  )
+  set(CPM_DEVELOPMENT "-development-version")
+else()
+  file(STRINGS "${CMAKE_CURRENT_SOURCE_DIR}/.git_archival.txt" DESCRIBE_NAME
+       REGEX "^describe-name:.*"
+  )
+endif()
+
+string(REGEX MATCH "([0-9\\.]+)" EXTRACTED_CPM_VERSION "${DESCRIBE_NAME}")
+
+project(
+  CPM.cmake
+  VERSION "${EXTRACTED_CPM_VERSION}"
+  DESCRIPTION
+    "CMake's missing package manager. A small CMake script for setup-free, cross-platform, reproducible dependency management."
+  HOMEPAGE_URL "https://github.com/cpm-cmake/CPM.cmake"
+  LANGUAGES NONE
+)
+
+include("${CMAKE_CURRENT_SOURCE_DIR}/cmake/CPM.cmake")

README.md

@@ -80,6 +80,7 @@ On the other hand, if `VERSION` hasn't been explicitly specified, CPM can automa
 `GIT_TAG` can also be set to a specific commit or a branch name such as `master`, however this isn't recommended, as such packages will only be updated when the cache is cleared.
 
 `PATCHES` takes a list of patch files to apply sequentially. For a basic example, see [Highway](examples/highway/CMakeLists.txt).
+We recommend that if you use `PATCHES`, you also set `CPM_SOURCE_CACHE`. See [issue 577](https://github.com/cpm-cmake/CPM.cmake/issues/577).
 
 If an additional optional parameter `EXCLUDE_FROM_ALL` is set to a truthy value, then any targets defined inside the dependency won't be built by default. See the [CMake docs](https://cmake.org/cmake/help/latest/prop_tgt/EXCLUDE_FROM_ALL.html) for details.
 
@@ -87,7 +88,7 @@ If an additional optional parameter `SYSTEM` is set to a truthy value, the SYSTE
 See the [add_subdirectory ](https://cmake.org/cmake/help/latest/command/add_subdirectory.html?highlight=add_subdirectory)
 and [SYSTEM](https://cmake.org/cmake/help/latest/prop_tgt/SYSTEM.html#prop_tgt:SYSTEM) target property for details.
 
-A single-argument compact syntax is also supported:
+A shorthand syntax is also supported:
 
 ```cmake
 # A git package from a given uri with a version
@@ -111,6 +112,19 @@ CPMAddPackage("https://example.com/my-package-1.2.3.zip#MD5=68e20f674a48be38d60e
 CPMAddPackage("https://example.com/my-package.zip@1.2.3")
 ```
 
+Additionally, if needed, extra arguments can be provided while using single argument syntax by using the shorthand syntax with the `URI` specifier.
+
+```cmake
+CPMAddPackage(
+  URI "gh:nlohmann/json@3.9.1"
+  OPTIONS "JSON_BuildTests OFF"
+)
+```
+
+The `URI` argument must be the first argument to `CPMAddPackage`.
+`URI` automatically sets `EXCLUDE_FROM_ALL YES` and `SYSTEM YES`.
+If this is not desired, `EXCLUDE_FROM_ALL NO` and `SYSTEM NO` can be set afterwards.
+
 After calling `CPMAddPackage`, the following variables are defined in the local scope, where `<dependency>` is the name of the dependency.
 
 - `<dependency>_SOURCE_DIR` is the path to the source of the dependency.
@@ -214,6 +228,13 @@ In the case that `find_package` requires additional arguments, the parameter `FI
 
 Note that this does not apply to dependencies that have been defined with a truthy `FORCE` parameter. These will be added as defined.
 
+### CPM_DONT_UPDATE_MODULE_PATH
+
+By default, CPM will override any `find_package` commands to use the CPM downloaded version.
+This is equivalent to the `OVERRIDE_FIND_PACKAGE` FetchContent option, which has no effect in CPM.
+To disable this behaviour set the `CPM_DONT_UPDATE_MODULE_PATH` option.
+This will not work for `find_package(CONFIG)` in CMake versions before 3.24.
+
 ### CPM_USE_NAMED_CACHE_DIRECTORIES
 
 If set, CPM use additional directory level in cache to improve readability of packages names in IDEs like CLion. It changes cache structure, so all dependencies are downloaded again. There is no problem to mix both structures in one cache directory but then there may be 2 copies of some dependencies.
@@ -404,11 +425,8 @@ CPMAddPackage("gh:jbeder/yaml-cpp#yaml-cpp-0.6.3@0.6.3")
 
 ```cmake
 CPMAddPackage(
-  NAME nlohmann_json
-  VERSION 3.9.1
-  GITHUB_REPOSITORY nlohmann/json
-  OPTIONS
-    "JSON_BuildTests OFF"
+  URI "gh:nlohmann/json@3.9.1"
+  OPTIONS "JSON_BuildTests OFF"
 )
 ```
 
@@ -438,8 +456,7 @@ For a working example of using CPM to download and configure the Boost C++ Libra
 ```cmake
 # the install option has to be explicitly set to allow installation
 CPMAddPackage(
-  GITHUB_REPOSITORY jarro2783/cxxopts
-  VERSION 2.2.1
+  URI "gh:jarro2783/cxxopts@2.2.1"
   OPTIONS "CXXOPTS_BUILD_EXAMPLES NO" "CXXOPTS_BUILD_TESTS NO" "CXXOPTS_ENABLE_INSTALL YES"
 )
 ```
@@ -448,9 +465,7 @@ CPMAddPackage(
 
 ```cmake
 CPMAddPackage(
-  NAME benchmark
-  GITHUB_REPOSITORY google/benchmark
-  VERSION 1.5.2
+  URI "gh:google/benchmark@1.5.2"
   OPTIONS "BENCHMARK_ENABLE_TESTING Off"
 )
 

cmake/CPM.cmake

@@ -42,7 +42,11 @@ if(NOT COMMAND cpm_message)
   endfunction()
 endif()
 
-set(CURRENT_CPM_VERSION 1.0.0-development-version)
+if(DEFINED EXTRACTED_CPM_VERSION)
+  set(CURRENT_CPM_VERSION "${EXTRACTED_CPM_VERSION}${CPM_DEVELOPMENT}")
+else()
+  set(CURRENT_CPM_VERSION 1.0.0-development-version)
+endif()
 
 get_filename_component(CPM_CURRENT_DIRECTORY "${CMAKE_CURRENT_LIST_DIR}" REALPATH)
 if(CPM_DIRECTORY)
@@ -162,7 +166,7 @@ set(CPM_SOURCE_CACHE
     CACHE PATH "Directory to download CPM dependencies"
 )
 
-if(NOT CPM_DONT_UPDATE_MODULE_PATH)
+if(NOT CPM_DONT_UPDATE_MODULE_PATH AND NOT DEFINED CMAKE_FIND_PACKAGE_REDIRECTS_DIR)
   set(CPM_MODULE_PATH
       "${CMAKE_BINARY_DIR}/CPM_modules"
       CACHE INTERNAL ""
@@ -198,6 +202,60 @@ function(cpm_package_name_from_git_uri URI RESULT)
   endif()
 endfunction()
 
+# Find the shortest hash that can be used eg, if origin_hash is
+# cccb77ae9609d2768ed80dd42cec54f77b1f1455 the following files will be checked, until one is found
+# that is either empty (allowing us to assign origin_hash), or whose contents matches ${origin_hash}
+#
+# * .../cccb.hash
+# * .../cccb77ae.hash
+# * .../cccb77ae9609.hash
+# * .../cccb77ae9609d276.hash
+# * etc
+#
+# We will be able to use a shorter path with very high probability, but in the (rare) event that the
+# first couple characters collide, we will check longer and longer substrings.
+function(cpm_get_shortest_hash source_cache_dir origin_hash short_hash_output_var)
+  # for compatibility with caches populated by a previous version of CPM, check if a directory using
+  # the full hash already exists
+  if(EXISTS "${source_cache_dir}/${origin_hash}")
+    set(${short_hash_output_var}
+        "${origin_hash}"
+        PARENT_SCOPE
+    )
+    return()
+  endif()
+
+  foreach(len RANGE 4 40 4)
+    string(SUBSTRING "${origin_hash}" 0 ${len} short_hash)
+    set(hash_lock ${source_cache_dir}/${short_hash}.lock)
+    set(hash_fp ${source_cache_dir}/${short_hash}.hash)
+    # Take a lock, so we don't have a race condition with another instance of cmake. We will release
+    # this lock when we can, however, if there is an error, we want to ensure it gets released on
+    # it's own on exit from the function.
+    file(LOCK ${hash_lock} GUARD FUNCTION)
+
+    # Load the contents of .../${short_hash}.hash
+    file(TOUCH ${hash_fp})
+    file(READ ${hash_fp} hash_fp_contents)
+
+    if(hash_fp_contents STREQUAL "")
+      # Write the origin hash
+      file(WRITE ${hash_fp} ${origin_hash})
+      file(LOCK ${hash_lock} RELEASE)
+      break()
+    elseif(hash_fp_contents STREQUAL origin_hash)
+      file(LOCK ${hash_lock} RELEASE)
+      break()
+    else()
+      file(LOCK ${hash_lock} RELEASE)
+    endif()
+  endforeach()
+  set(${short_hash_output_var}
+      "${short_hash}"
+      PARENT_SCOPE
+  )
+endfunction()
+
 # Try to infer package name and version from a url
 function(cpm_package_name_and_ver_from_url url outName outVer)
   if(url MATCHES "[/\\?]([a-zA-Z0-9_\\.-]+)\\.(tar|tar\\.gz|tar\\.bz2|zip|ZIP)(\\?|/|$)")
@@ -269,10 +327,25 @@ endfunction()
 # finding the system library
 function(cpm_create_module_file 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(${Name}_FOUND TRUE)"
-    )
+    if(DEFINED CMAKE_FIND_PACKAGE_REDIRECTS_DIR)
+      # Redirect find_package calls to the CPM package. This is what FetchContent does when you set
+      # OVERRIDE_FIND_PACKAGE. The CMAKE_FIND_PACKAGE_REDIRECTS_DIR works for find_package in CONFIG
+      # mode, unlike the Find${Name}.cmake fallback. CMAKE_FIND_PACKAGE_REDIRECTS_DIR is not defined
+      # in script mode, or in CMake < 3.24.
+      # https://cmake.org/cmake/help/latest/module/FetchContent.html#fetchcontent-find-package-integration-examples
+      string(TOLOWER ${Name} NameLower)
+      file(WRITE ${CMAKE_FIND_PACKAGE_REDIRECTS_DIR}/${NameLower}-config.cmake
+           "include(\"\${CMAKE_CURRENT_LIST_DIR}/${NameLower}-extra.cmake\" OPTIONAL)\n"
+           "include(\"\${CMAKE_CURRENT_LIST_DIR}/${Name}Extra.cmake\" OPTIONAL)\n"
+      )
+      file(WRITE ${CMAKE_FIND_PACKAGE_REDIRECTS_DIR}/${NameLower}-config-version.cmake
+           "set(PACKAGE_VERSION_COMPATIBLE TRUE)\n" "set(PACKAGE_VERSION_EXACT TRUE)\n"
+      )
+    else()
+      file(WRITE ${CPM_MODULE_PATH}/Find${Name}.cmake
+           "include(\"${CPM_FILE}\")\n${ARGN}\nset(${Name}_FOUND TRUE)"
+      )
+    endif()
   endif()
 endfunction()
 
@@ -475,15 +548,18 @@ function(cpm_add_patches)
 
   # Find the patch program.
   find_program(PATCH_EXECUTABLE patch)
-  if(WIN32 AND NOT PATCH_EXECUTABLE)
+  if(CMAKE_HOST_WIN32 AND NOT PATCH_EXECUTABLE)
     # The Windows git executable is distributed with patch.exe. Find the path to the executable, if
-    # it exists, then search `../../usr/bin` for patch.exe.
+    # it exists, then search `../usr/bin` and `../../usr/bin` for patch.exe.
     find_package(Git QUIET)
     if(GIT_EXECUTABLE)
       get_filename_component(extra_search_path ${GIT_EXECUTABLE} DIRECTORY)
-      get_filename_component(extra_search_path ${extra_search_path} DIRECTORY)
-      get_filename_component(extra_search_path ${extra_search_path} DIRECTORY)
-      find_program(PATCH_EXECUTABLE patch HINTS "${extra_search_path}/usr/bin")
+      get_filename_component(extra_search_path_1up ${extra_search_path} DIRECTORY)
+      get_filename_component(extra_search_path_2up ${extra_search_path_1up} DIRECTORY)
+      find_program(
+        PATCH_EXECUTABLE patch HINTS "${extra_search_path_1up}/usr/bin"
+                                     "${extra_search_path_2up}/usr/bin"
+      )
     endif()
   endif()
   if(NOT PATCH_EXECUTABLE)
@@ -572,14 +648,6 @@ endfunction()
 function(CPMAddPackage)
   cpm_set_policies()
 
-  list(LENGTH ARGN argnLength)
-  if(argnLength EQUAL 1)
-    cpm_parse_add_package_single_arg("${ARGN}" ARGN)
-
-    # The shorthand syntax implies EXCLUDE_FROM_ALL and SYSTEM
-    set(ARGN "${ARGN};EXCLUDE_FROM_ALL;YES;SYSTEM;YES;")
-  endif()
-
   set(oneValueArgs
       NAME
       FORCE
@@ -602,10 +670,26 @@ function(CPMAddPackage)
 
   set(multiValueArgs URL OPTIONS DOWNLOAD_COMMAND PATCHES)
 
+  list(LENGTH ARGN argnLength)
+
+  # Parse single shorthand argument
+  if(argnLength EQUAL 1)
+    cpm_parse_add_package_single_arg("${ARGN}" ARGN)
+
+    # The shorthand syntax implies EXCLUDE_FROM_ALL and SYSTEM
+    set(ARGN "${ARGN};EXCLUDE_FROM_ALL;YES;SYSTEM;YES;")
+
+    # Parse URI shorthand argument
+  elseif(argnLength GREATER 1 AND "${ARGV0}" STREQUAL "URI")
+    list(REMOVE_AT ARGN 0 1) # remove "URI gh:<...>@version#tag"
+    cpm_parse_add_package_single_arg("${ARGV1}" ARGV0)
+
+    set(ARGN "${ARGV0};EXCLUDE_FROM_ALL;YES;SYSTEM;YES;${ARGN}")
+  endif()
+
   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)
@@ -776,9 +860,19 @@ function(CPMAddPackage)
       set(download_directory ${CPM_SOURCE_CACHE}/${lower_case_name}/${CPM_ARGS_CUSTOM_CACHE_KEY})
     elseif(CPM_USE_NAMED_CACHE_DIRECTORIES)
       string(SHA1 origin_hash "${origin_parameters};NEW_CACHE_STRUCTURE_TAG")
+      cpm_get_shortest_hash(
+        "${CPM_SOURCE_CACHE}/${lower_case_name}" # source cache directory
+        "${origin_hash}" # Input hash
+        origin_hash # Computed hash
+      )
       set(download_directory ${CPM_SOURCE_CACHE}/${lower_case_name}/${origin_hash}/${CPM_ARGS_NAME})
     else()
       string(SHA1 origin_hash "${origin_parameters}")
+      cpm_get_shortest_hash(
+        "${CPM_SOURCE_CACHE}/${lower_case_name}" # source cache directory
+        "${origin_hash}" # Input hash
+        origin_hash # Computed hash
+      )
       set(download_directory ${CPM_SOURCE_CACHE}/${lower_case_name}/${origin_hash})
     endif()
     # Expand `download_directory` relative path. This is important because EXISTS doesn't work for
@@ -845,7 +939,9 @@ function(CPMAddPackage)
     endif()
   endif()
 
-  cpm_create_module_file(${CPM_ARGS_NAME} "CPMAddPackage(\"${ARGN}\")")
+  if(NOT "${DOWNLOAD_ONLY}")
+    cpm_create_module_file(${CPM_ARGS_NAME} "CPMAddPackage(\"${ARGN}\")")
+  endif()
 
   if(CPM_PACKAGE_LOCK_ENABLED)
     if((CPM_ARGS_VERSION AND NOT CPM_ARGS_SOURCE_DIR) OR CPM_INCLUDE_ALL_IN_PACKAGE_LOCK)
@@ -866,8 +962,9 @@ function(CPMAddPackage)
     # Calling FetchContent_MakeAvailable will then internally forward these options to
     # add_subdirectory. Up until these changes, we had to call FetchContent_Populate and
     # add_subdirectory separately, which is no longer necessary and has been deprecated as of 3.30.
+    # A Bug in CMake prevents us to use the non-deprecated functions until 3.30.3.
     set(fetchContentDeclareExtraArgs "")
-    if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.28.0")
+    if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.30.3")
       if(${CPM_ARGS_EXCLUDE_FROM_ALL})
         list(APPEND fetchContentDeclareExtraArgs EXCLUDE_FROM_ALL)
       endif()
@@ -893,7 +990,7 @@ function(CPMAddPackage)
     if(CPM_SOURCE_CACHE AND download_directory)
       file(LOCK ${download_directory}/../cmake.lock RELEASE)
     endif()
-    if(${populated} AND ${CMAKE_VERSION} VERSION_LESS "3.28.0")
+    if(${populated} AND ${CMAKE_VERSION} VERSION_LESS "3.30.3")
       cpm_add_subdirectory(
         "${CPM_ARGS_NAME}"
         "${DOWNLOAD_ONLY}"
@@ -1095,7 +1192,7 @@ function(cpm_fetch_package PACKAGE DOWNLOAD_ONLY populated)
   string(TOLOWER "${PACKAGE}" lower_case_name)
 
   if(NOT ${lower_case_name}_POPULATED)
-    if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.28.0")
+    if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.30.3")
       if(DOWNLOAD_ONLY)
         # MakeAvailable will call add_subdirectory internally which is not what we want when
         # DOWNLOAD_ONLY is set. Populate will only download the dependency without adding it to the

cmake/testing.cmake

@@ -79,3 +79,16 @@ function(ASSERT_NOT_EXISTS file)
     message(FATAL_ERROR "assertion failed: file ${file} exists")
   endif()
 endfunction()
+
+function(ASSERT_CONTENTS_EQUAL file content)
+  if(EXISTS ${file})
+    file(READ ${file} file_content)
+    if(content STREQUAL file_content)
+      message(STATUS "test passed: '${file}' exists and contains '${content}'")
+    else()
+      message(FATAL_ERROR "assertion failed: file '${file}' does not contain expected content.")
+    endif()
+  else()
+    message(FATAL_ERROR "assertion failed: file '${file} does not exist")
+  endif()
+endfunction()

examples/boost/CMakeLists.txt

@@ -13,10 +13,12 @@ include(../../cmake/CPM.cmake)
 
 CPMAddPackage(
   NAME Boost
-  VERSION 1.84.0
-  URL https://github.com/boostorg/boost/releases/download/boost-1.84.0/boost-1.84.0.tar.xz
-  URL_HASH SHA256=2e64e5d79a738d0fa6fb546c6e5c2bd28f88d268a2a080546f74e5ff98f29d0e
-  OPTIONS "BOOST_ENABLE_CMAKE ON" "BOOST_INCLUDE_LIBRARIES container\\\;asio" # Note the escapes!
+  VERSION 1.86.0 # Versions less than 1.85.0 may need patches for installation targets.
+  URL https://github.com/boostorg/boost/releases/download/boost-1.86.0/boost-1.86.0-cmake.tar.xz
+  URL_HASH SHA256=2c5ec5edcdff47ff55e27ed9560b0a0b94b07bd07ed9928b476150e16b0efc57
+  OPTIONS "BOOST_ENABLE_CMAKE ON" "BOOST_SKIP_INSTALL_RULES ON" # Set `OFF` for installation
+          "BUILD_SHARED_LIBS OFF" "BOOST_INCLUDE_LIBRARIES container\\\;asio" # Note the escapes!
 )
 
+# `Boost::headers` is also valid
 target_link_libraries(CPMExampleBoost PRIVATE Boost::asio Boost::container)

examples/sol2/CMakeLists.txt

@@ -8,7 +8,7 @@ include(../../cmake/CPM.cmake)
 
 CPMAddPackage(
   NAME lua
-  GIT_REPOSITORY https://github.com/lua/lua.git
+  GITHUB_REPOSITORY lua/lua
   VERSION 5.3.5
   DOWNLOAD_ONLY YES
 )
@@ -21,7 +21,13 @@ if(lua_ADDED)
   target_include_directories(lua SYSTEM PUBLIC $<BUILD_INTERFACE:${lua_SOURCE_DIR}>)
 endif()
 
-CPMAddPackage("gh:ThePhD/sol2@3.3.0")
+CPMAddPackage(
+  NAME sol2
+  GITHUB_REPOSITORY ThePhD/sol2
+  VERSION 3.3.0
+  # fix for clang 18.1.0, see https://github.com/ThePhD/sol2/issues/1581#issuecomment-2103463524
+  PATCHES fix_for_clang.patch
+)
 
 # ---- Executable ----
 

examples/sol2/fix_for_clang.patch

@@ -0,0 +1,18 @@
+diff -u a/include/sol/function_types_stateless.hpp b/include/types/function_types_stateless.hpp
+--- a/include/sol/function_types_stateless.hpp
++++ b/include/sol/function_types_stateless.hpp
+@@ -322,7 +322,13 @@ namespace sol { namespace function_detail {
+ 		}
+ 
+ 		template <bool is_yielding, bool no_trampoline>
+-		static int call(lua_State* L) noexcept(std::is_nothrow_copy_assignable_v<T>) {
++		static int call(lua_State* L)
++#if SOL_IS_ON(SOL_COMPILER_CLANG)
++		// apparent regression in clang 18 - llvm/llvm-project#91362
++#else
++			noexcept(std::is_nothrow_copy_assignable_v<T>)
++#endif
++		{
+ 			int nr;
+ 			if constexpr (no_trampoline) {
+ 				nr = real_call(L);

test/integration/test_basics.rb

@@ -31,7 +31,9 @@ class Basics < IntegrationTest
     assert_same_path File.join(prj.bin_dir, 'cpm-package-lock.cmake'), check_and_get('CPM_PACKAGE_LOCK_FILE')
 
     assert_equal 'OFF', check_and_get('CPM_DONT_UPDATE_MODULE_PATH', 'BOOL')
-    assert_same_path File.join(prj.bin_dir, 'CPM_modules'), check_and_get('CPM_MODULE_PATH')
+    if @cache.entries['CMAKE_FIND_PACKAGE_REDIRECTS_DIR'].nil?
+      assert_same_path File.join(prj.bin_dir, 'CPM_modules'), check_and_get('CPM_MODULE_PATH')
+    end
   end
 
   # Test when env CPM_SOURCE_CACHE is set

test/integration/test_shorthand_syntax.rb

@@ -0,0 +1,86 @@
+require_relative './lib'
+
+class TestShorthandSyntax < IntegrationTest
+
+  def get_project_binaries prj
+    exe_dir = File.join(prj.bin_dir, 'bin')
+    assert File.directory? exe_dir
+    return Dir[exe_dir + '/**/*'].filter {
+        # on multi-configuration generators (like Visual Studio) the executables will be in bin/<Config>
+        # also filter-out other artifacts like .pdb or .dsym
+        !File.directory?(_1) && File.stat(_1).executable?
+      }.map {
+        # remove .exe extension if any (there will be one on Windows)
+        File.basename(_1, '.exe')
+      }.sort
+  end
+
+  def test_create_with_commit_sha
+    prj = make_project from_template: 'using-adder'
+    prj.create_lists_from_default_template package:
+    'CPMAddPackage("gh:cpm-cmake/testpack-adder#cad1cd4b4cdf957c5b59e30bc9a1dd200dbfc716")'
+    assert_success prj.configure
+
+    cache = prj.read_cache
+    assert_equal 1, cache.packages.size
+    assert_equal '0', cache.packages['testpack-adder'].ver
+
+    assert_success prj.build
+    exes = get_project_binaries prj
+    # No adder projects were built as EXCLUDE_FROM_ALL is implicitly set
+    assert_equal ['using-adder'], exes
+  end
+
+  def test_create_with_version
+    prj = make_project from_template: 'using-adder'
+    prj.create_lists_from_default_template package:
+    'CPMAddPackage("gh:cpm-cmake/testpack-adder@1.0.0")'
+    assert_success prj.configure
+
+    cache = prj.read_cache
+    assert_equal 1, cache.packages.size
+    assert_equal '1.0.0', cache.packages['testpack-adder'].ver
+
+    assert_success prj.build
+    exes = get_project_binaries prj
+    assert_equal ['using-adder'], exes
+  end
+
+  def test_create_with_all
+    prj = make_project from_template: 'using-adder'
+    prj.create_lists_from_default_template package:
+    'CPMAddPackage(
+      URI "gh:cpm-cmake/testpack-adder@1.0.0"
+      EXCLUDE_FROM_ALL false
+    )'
+    assert_success prj.configure
+
+    cache = prj.read_cache
+    assert_equal cache.packages.size, 1
+    assert_equal cache.packages['testpack-adder'].ver, '1.0.0'
+    
+    assert_success prj.build
+    exes = get_project_binaries prj
+    assert_equal exes, ['simple', 'test-adding', 'using-adder']
+  end
+
+  def test_create_with_tests_but_without_examples
+    prj = make_project from_template: 'using-adder'
+    prj.create_lists_from_default_template package:
+    'CPMAddPackage(
+      URI "gh:cpm-cmake/testpack-adder@1.0.0"
+      OPTIONS "ADDER_BUILD_EXAMPLES OFF" "ADDER_BUILD_TESTS TRUE"
+      EXCLUDE_FROM_ALL false
+    )'
+    assert_success prj.configure
+
+    cache = prj.read_cache
+    assert_equal cache.packages.size, 1
+    assert_equal cache.packages['testpack-adder'].ver, '1.0.0'
+    
+    assert_success prj.build
+    exes = get_project_binaries prj
+    assert_equal exes, ['test-adding', 'using-adder']
+  end
+
+end

test/integration/test_source_cache.rb

@@ -75,6 +75,17 @@ class SourceCache < IntegrationTest
     assert_equal ver, package.ver
     expected_parent_dir = File.join(@cache_dir, name.downcase)
     assert package.src_dir.start_with?(expected_parent_dir), "#{package.src_dir} must be in #{expected_parent_dir}"
-    assert_equal dir_sha1, File.basename(package.src_dir)
+
+    # The hash has been shortened by cpm_get_shortest_hash. The following
+    # should hold:
+    # - The short hash should be a prefix of the input hash
+    # - There should be a file ".../${short_hash}.hash" which matches the full hash
+    short_hash = File.basename(package.src_dir)
+    assert dir_sha1.start_with?(short_hash), "short_hash should be a prefix of dir_sha1"
+
+    # Check that the full hash is stored in the .hash file
+    hash_file = "#{package.src_dir}.hash"
+    assert File.exist?(hash_file), "Hash file #{hash_file} should exist"
+    assert_equal dir_sha1, File.read(hash_file), "Hash file should contain the full original hash"
   end
 end

test/unit/get_shortest_hash.cmake

@@ -0,0 +1,93 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+include(${CPM_PATH}/CPM.cmake)
+include(${CPM_PATH}/testing.cmake)
+
+# Random suffix
+string(
+  RANDOM
+  LENGTH 6
+  ALPHABET "0123456789abcdef" tmpdir_suffix
+)
+
+# Seconds since epoch
+string(TIMESTAMP tmpdir_base "%s" UTC)
+
+set(tmp "${CMAKE_CURRENT_BINARY_DIR}/get_shortest_hash-${tmpdir_base}-${tmpdir_suffix}")
+
+if(IS_DIRECTORY ${tmp})
+  message(FATAL_ERROR "Test directory ${tmp} already exists")
+endif()
+
+file(MAKE_DIRECTORY "${tmp}")
+
+# 1. Sanity check: none of these directories should exist yet
+
+assert_not_exists(${tmp}/cccb.hash)
+assert_not_exists(${tmp}/cccb77ae.hash)
+assert_not_exists(${tmp}/cccb77ae9609.hash)
+assert_not_exists(${tmp}/cccb77ae9608.hash)
+assert_not_exists(${tmp}/cccb77be.hash)
+
+# 1. The directory is empty, so it should get a 4-character hash
+cpm_get_shortest_hash(${tmp} "cccb77ae9609d2768ed80dd42cec54f77b1f1455" hash)
+assert_equal(${hash} "cccb")
+assert_contents_equal(${tmp}/cccb.hash cccb77ae9609d2768ed80dd42cec54f77b1f1455)
+
+# 1. Calling the function with a new hash that differs subtly should result in more characters being
+#   used, enough to uniquely identify the hash
+
+cpm_get_shortest_hash(${tmp} "cccb77ae9609d2768ed80dd42cec54f77b1f1456" hash)
+assert_equal(${hash} "cccb77ae")
+assert_contents_equal(${tmp}/cccb77ae.hash cccb77ae9609d2768ed80dd42cec54f77b1f1456)
+
+cpm_get_shortest_hash(${tmp} "cccb77ae9609d2768ed80dd42cec54f77b1f1457" hash)
+assert_equal(${hash} "cccb77ae9609")
+assert_contents_equal(${tmp}/cccb77ae9609.hash cccb77ae9609d2768ed80dd42cec54f77b1f1457)
+
+cpm_get_shortest_hash(${tmp} "cccb77ae9608d2768ed80dd42cec54f77b1f1455" hash)
+assert_equal(${hash} "cccb77ae9608")
+assert_contents_equal(${tmp}/cccb77ae9608.hash cccb77ae9608d2768ed80dd42cec54f77b1f1455)
+
+cpm_get_shortest_hash(${tmp} "cccb77be9609d2768ed80dd42cec54f77b1f1456" hash)
+assert_equal(${hash} "cccb77be")
+assert_contents_equal(${tmp}/cccb77be.hash cccb77be9609d2768ed80dd42cec54f77b1f1456)
+
+# check that legacy hashs are recognized
+file(MAKE_DIRECTORY "${tmp}/cccb77be9609d2768ed80dd42cec54f77b1f1457")
+cpm_get_shortest_hash(${tmp} "cccb77be9609d2768ed80dd42cec54f77b1f1457" hash)
+assert_equal(${hash} "cccb77be9609d2768ed80dd42cec54f77b1f1457")
+
+# 1. The old file should still exist, and have the same content
+assert_contents_equal(${tmp}/cccb.hash cccb77ae9609d2768ed80dd42cec54f77b1f1455)
+assert_contents_equal(${tmp}/cccb77ae.hash cccb77ae9609d2768ed80dd42cec54f77b1f1456)
+assert_contents_equal(${tmp}/cccb77ae9609.hash cccb77ae9609d2768ed80dd42cec54f77b1f1457)
+assert_contents_equal(${tmp}/cccb77ae9608.hash cccb77ae9608d2768ed80dd42cec54f77b1f1455)
+assert_contents_equal(${tmp}/cccb77be.hash cccb77be9609d2768ed80dd42cec54f77b1f1456)
+
+# 1. Confirm idempotence: calling any of these function should produce the same hash as before (hash
+#   lookups work correctly once the .hash files are created)
+
+cpm_get_shortest_hash(${tmp} "cccb77ae9609d2768ed80dd42cec54f77b1f1455" hash)
+assert_equal(${hash} "cccb")
+assert_contents_equal(${tmp}/cccb.hash cccb77ae9609d2768ed80dd42cec54f77b1f1455)
+
+cpm_get_shortest_hash(${tmp} "cccb77ae9609d2768ed80dd42cec54f77b1f1456" hash)
+assert_equal(${hash} "cccb77ae")
+assert_contents_equal(${tmp}/cccb77ae.hash cccb77ae9609d2768ed80dd42cec54f77b1f1456)
+
+cpm_get_shortest_hash(${tmp} "cccb77ae9609d2768ed80dd42cec54f77b1f1457" hash)
+assert_equal(${hash} "cccb77ae9609")
+assert_contents_equal(${tmp}/cccb77ae9609.hash cccb77ae9609d2768ed80dd42cec54f77b1f1457)
+
+cpm_get_shortest_hash(${tmp} "cccb77ae9608d2768ed80dd42cec54f77b1f1455" hash)
+assert_equal(${hash} "cccb77ae9608")
+assert_contents_equal(${tmp}/cccb77ae9608.hash cccb77ae9608d2768ed80dd42cec54f77b1f1455)
+
+cpm_get_shortest_hash(${tmp} "cccb77be9609d2768ed80dd42cec54f77b1f1456" hash)
+assert_equal(${hash} "cccb77be")
+assert_contents_equal(${tmp}/cccb77be.hash cccb77be9609d2768ed80dd42cec54f77b1f1456)
+
+# 1. Cleanup - remove the temporary directory that we created
+
+file(REMOVE_RECURSE ${tmp})

test/unit/local_dependency/ModuleCMakeLists.txt.in

@@ -8,6 +8,10 @@ option(ENABLE_TEST_COVERAGE "Enable test coverage" OFF)
 
 # ---- Dependencies ----
 
+if (@TEST_FORCE_MODULE_MODE@)
+  unset(CMAKE_FIND_PACKAGE_REDIRECTS_DIR CACHE)
+endif()
+
 include(@CPM_PATH@/CPM.cmake)
 
 CPMAddPackage(
@@ -15,21 +19,23 @@ CPMAddPackage(
   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()
 
-# ---- Check parameters ----
-
+# ---- Check newly added ----
 include(@CPM_PATH@/testing.cmake)
-
 ASSERT_TRUTHY(@TEST_DEPENDENCY_NAME@_ADDED)
+
+# ---- Check if generated modules override find_package ----
+
+if (@TEST_FIND_PACKAGE@)
+  find_package(@TEST_DEPENDENCY_NAME@ @TEST_FIND_PACKAGE_CONFIG@ REQUIRED)
+  find_package(@TEST_CANT_FIND_PACKAGE_NAME@ @TEST_FIND_PACKAGE_CONFIG@ QUIET)
+  ASSERT_FALSY(@TEST_CANT_FIND_PACKAGE_NAME@_FOUND)
+endif()
+
+# ---- Check parameters ----
 ASSERT_DEFINED(@TEST_DEPENDENCY_NAME@_SOURCE_DIR)
 ASSERT_DEFINED(@TEST_DEPENDENCY_NAME@_BINARY_DIR)
 ASSERT_EQUAL("${CPM_LAST_PACKAGE_NAME}" "@TEST_DEPENDENCY_NAME@")

test/unit/modules.cmake

@@ -3,7 +3,8 @@ include(${CPM_PATH}/testing.cmake)
 
 set(TEST_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR}/modules)
 
-function(init_project_with_dependency TEST_DEPENDENCY_NAME)
+function(init_project_with_dependency TEST_DEPENDENCY_NAME TEST_CANT_FIND_PACKAGE_NAME)
+  set(TEST_FIND_PACKAGE ON)
   configure_package_config_file(
     "${CMAKE_CURRENT_LIST_DIR}/local_dependency/ModuleCMakeLists.txt.in"
     "${CMAKE_CURRENT_LIST_DIR}/local_dependency/CMakeLists.txt"
@@ -18,11 +19,17 @@ function(init_project_with_dependency TEST_DEPENDENCY_NAME)
   assert_equal(${ret} "0")
 endfunction()
 
-init_project_with_dependency(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)
+init_project_with_dependency(A B)
+init_project_with_dependency(B A)
 
-init_project_with_dependency(B)
-assert_not_exists(${TEST_BUILD_DIR}/CPM_modules/FindA.cmake)
-assert_exists(${TEST_BUILD_DIR}/CPM_modules/FindB.cmake)
+if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.24.0")
+  set(TEST_FIND_PACKAGE_CONFIG CONFIG)
+  init_project_with_dependency(A B)
+  init_project_with_dependency(B A)
+
+  # Test the fallback path for CMake <3.24 works
+  set(TEST_FIND_PACKAGE_CONFIG)
+  set(TEST_FORCE_MODULE_MODE ON)
+  init_project_with_dependency(A B)
+  init_project_with_dependency(B A)
+endif()