check if package added before find_package (#115)

* call FetchContent_GetProperties before checking populated

* fix old CPM.cmake links

* update description

* bump version

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
 
@@ -103,8 +103,8 @@ 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). 
+- **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 resolved by adding a new version of the dependency in the outermost project.
 
 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).
@@ -140,7 +140,7 @@ These options can also be set as environmental variables.
 ## 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 +270,4 @@ 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
 # ----------- 
@@ -28,7 +28,7 @@
 
 cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
 
-set(CURRENT_CPM_VERSION 0.21)
+set(CURRENT_CPM_VERSION 0.23)
 
 if(CPM_DIRECTORY)
   if(NOT ${CPM_DIRECTORY} MATCHES ${CMAKE_CURRENT_LIST_DIR})
@@ -90,8 +90,8 @@ function(cpm_find_package NAME VERSION)
   string(REPLACE " " ";" EXTRA_ARGS "${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)
@@ -116,13 +116,28 @@ function(CPMFindPackage)
   )
 
   cmake_parse_arguments(CPM_ARGS "" "${oneValueArgs}" "" ${ARGN})
-  
+
+  if (NOT DEFINED CPM_ARGS_VERSION)
+    if (DEFINED CPM_ARGS_GIT_TAG) 
+      cpm_get_version_from_git_tag("${CPM_ARGS_GIT_TAG}" CPM_ARGS_VERSION)
+    endif()
+    if (NOT DEFINED CPM_ARGS_VERSION) 
+      set(CPM_ARGS_VERSION 0)
+    endif()
+  endif()
+
   if (CPM_DOWNLOAD_ALL)
     CPMAddPackage(${ARGN})
     cpm_export_variables()
     return()
   endif()
 
+  CPMCheckIfPackageAlreadyAdded(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" "${CPM_ARGS_OPTIONS}")
+  if (CPM_PACKAGE_ALREADY_ADDED)
+    cpm_export_variables()
+    return()
+  endif()
+
   cpm_find_package(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" ${CPM_ARGS_FIND_PACKAGE_ARGUMENTS})
 
   if(NOT CPM_PACKAGE_FOUND)
@@ -132,6 +147,33 @@ function(CPMFindPackage)
 
 endfunction()
 
+# 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}).")
+    endif()
+    if (CPM_ARGS_OPTIONS)
+      foreach(OPTION ${CPM_ARGS_OPTIONS})
+        cpm_parse_option(${OPTION})
+        if(NOT "${${OPTION_KEY}}" STREQUAL ${OPTION_VALUE})
+          message(WARNING "${CPM_INDENT} ignoring package option for ${CPM_ARGS_NAME}: ${OPTION_KEY} = ${OPTION_VALUE} (${${OPTION_KEY}})")
+        endif()
+      endforeach()
+    endif()
+    cpm_fetch_package(${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)
+    SET(CPM_PACKAGE_ALREADY_ADDED YES PARENT_SCOPE)
+    cpm_export_variables()
+  else()
+    SET(CPM_PACKAGE_ALREADY_ADDED NO PARENT_SCOPE)
+  endif()
+endfunction()
+
 # Download and add a package from source
 function(CPMAddPackage)
 
@@ -153,18 +195,6 @@ function(CPMAddPackage)
 
   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} ${CPM_ARGS_VERSION})")
-    endif()
-  endif()
-
   if (NOT DEFINED CPM_ARGS_VERSION)
     if (DEFINED CPM_ARGS_GIT_TAG) 
       cpm_get_version_from_git_tag("${CPM_ARGS_GIT_TAG}" CPM_ARGS_VERSION)
@@ -194,28 +224,24 @@ function(CPMAddPackage)
     list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS GIT_REPOSITORY "https://gitlab.com/${CPM_ARGS_GITLAB_REPOSITORY}.git")
   endif()
 
-  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}).")
-    endif()
-    if (CPM_ARGS_OPTIONS)
-      foreach(OPTION ${CPM_ARGS_OPTIONS})
-        cpm_parse_option(${OPTION})
-        if(NOT "${${OPTION_KEY}}" STREQUAL ${OPTION_VALUE})
-          message(WARNING "${CPM_INDENT} ignoring package option for ${CPM_ARGS_NAME}: ${OPTION_KEY} = ${OPTION_VALUE} (${${OPTION_KEY}})")
-        endif()
-      endforeach()
-    endif()
-    cpm_fetch_package(${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(${CPM_ARGS_NAME}_ADDED NO)
+  CPMCheckIfPackageAlreadyAdded(${CPM_ARGS_NAME} "${CPM_ARGS_VERSION}" "${CPM_ARGS_OPTIONS}")
+  if (CPM_PACKAGE_ALREADY_ADDED)
     cpm_export_variables()
     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)
+      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)
@@ -320,7 +346,8 @@ function (cpm_fetch_package PACKAGE DOWNLOAD_ONLY)
   set(CPM_OLD_INDENT "${CPM_INDENT}")
   set(CPM_INDENT "${CPM_INDENT} ${PACKAGE}:")
   if(${DOWNLOAD_ONLY})
-    if(NOT "${PACKAGE}_POPULATED")
+    FetchContent_GetProperties(${PACKAGE})
+    if(NOT ${PACKAGE}_POPULATED)
       FetchContent_Populate(${PACKAGE})
     endif()
   else()