Add DEPENDENCY_ADDED property (#50)

* add DEPENDENCY_ADDED property

* update examples

* Update README.md

* Update README.md

* Update CPM.cmake

* Update README.md

README.md

@@ -2,7 +2,8 @@
 
 # CPM
 
-CPM is a simple dependency manager written in CMake built on top of CMake's built-in [FetchContent](https://cmake.org/cmake/help/latest/module/FetchContent.html) module.
+CPM is a CMake script that adds dependency management capabilities to CMake. 
+It's built as an extension of CMake's [FetchContent](https://cmake.org/cmake/help/latest/module/FetchContent.html) module that adds version control and simpler usage.
 
 ## Supported projects
 
@@ -10,24 +11,29 @@ Any project that you can add via `add_subdirectory` should already work with CPM
 
 ## Usage
 
-After `CPM.cmake` has been added to your project, you can call `CPMAddPackage` for every dependency of the project with the following named parameters.
+After `CPM.cmake` has been added to your project, the function `CPMAddPackage` can be used to fetch and configure all dependencies.
+Afterwards all targets defined in the dependencies can be used.
+`CPMAddPackage` takes the following named arguments.
 
 ```cmake
 CPMAddPackage(
-  NAME          # The dependency name (usually chosen to match the target name)
+  NAME          # The name of the dependency (should be chosen to match the main target's name)
   VERSION       # The minimum version of the dependency (optional, defaults to 0)
   OPTIONS       # Configuration options passed to the dependency (optional)
   DOWNLOAD_ONLY # If set, the project is downloaded, but not configured (optional)
-  [...]         # Source options, see below
+  [...]         # Origin paramters forwarded to FetchContent_Declare, see below
 )
 ```
 
-The command downloads the project defined by the source options if a newer version hasn't been included before.
-The source is usually a git repository, but svn and direct urls are als supported.
-See the [FetchContent](https://cmake.org/cmake/help/latest/module/FetchContent.html) documentation for all available options.
-If a `GIT_TAG` hasn't been explicitly specified it defaults to `v$VERSION` which is a common convention for github projects.
+The origin is usually specified by a `GIT_REPOSITORY`, but [svn revisions and direct URLs are also supported](https://cmake.org/cmake/help/latest/module/FetchContent.html#declaring-content-details).
+If `GIT_TAG` hasn't been explicitly specified it defaults to `v(VERSION)`, a common convention for github projects.
+`GIT_TAG` can also be set to a branch name such as `master` to download the most recent version.
 
-After calling `CPMAddPackage`, the variables `(DEPENDENCY)_SOURCE_DIR` and `(DEPENDENCY)_BINARY_DIR` are set, where `(DEPENDENCY)` is the name of the dependency.
+Besides downloading and to configuring the dependency, 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.
+- `(DEPENDENCY)_BINARY_DIR` is the path to the build directory of the dependency.
+- `(DEPENDENCY)_ADDED` is set to `YES` if the dependency has not been added before, otherwise it is set to `NO`.
 
 ## Full Example
 
@@ -70,9 +76,9 @@ To update CPM to the newest version, simply update the script in the project's c
 
 ## Snipplets
 
-These are some small snipplets demonstrating how to include some projects used with CPM.
+These examples demonstrate how to include some well-known projects with CPM.
 
-### Catch2
+### [Catch2](https://github.com/catchorg/Catch2.git)
 
 Has a CMakeLists.txt that supports `add_subdirectory`.
 
@@ -84,7 +90,9 @@ CPMAddPackage(
 )
 ```
 
-### google/benchmark
+See [here](https://github.com/TheLartians/CPM/blob/master/examples/doctest/CMakeLists.txt) for doctest example.
+
+### [google/benchmark](https://github.com/google/benchmark.git)
 
 Has a CMakeLists.txt that supports `add_subdirectory`, but needs some configuring to work without external dependencies.
 
@@ -94,33 +102,53 @@ CPMAddPackage(
   GIT_REPOSITORY https://github.com/google/benchmark.git
   VERSION 1.4.1
   OPTIONS
-   "BENCHMARK_ENABLE_TESTING Off"
+    "BENCHMARK_ENABLE_TESTING Off"
 )
 
 # needed to compile with C++17
 set_target_properties(benchmark PROPERTIES CXX_STANDARD 17)
 ```
 
-### Lua
+### [nlohmann/json](https://github.com/nlohmann/json)
 
-Has no CMakeLists.txt, so a target must be created manually.
+Header-only library with a huge git repositoy.
+Instead of downloading the whole repositoy, we fetch the zip included with the release and create our own target.
+
+```cmake
+CPMAddPackage(
+  NAME nlohmann_json
+  VERSION 3.6.1  
+  URL https://github.com/nlohmann/json/releases/download/v3.6.1/include.zip
+  URL_HASH SHA256=69cc88207ce91347ea530b227ff0776db82dcb8de6704e1a3d74f4841bc651cf
+)
+
+if (nlohmann_json_ADDED)
+  add_library(nlohmann_json INTERFACE)
+  target_include_directories(nlohmann_json INTERFACE ${nlohmann_json_SOURCE_DIR})
+endif()
+```
+
+### [Lua](https://www.lua.org)
+
+Library without CMakeLists.txt, target must be created manually.
 
 ```cmake
 CPMAddPackage(
   NAME lua
   GIT_REPOSITORY https://github.com/lua/lua.git
   VERSION 5-3-4
-  GIT_SHALLOW YES
   DOWNLOAD_ONLY YES
 )
 
-FILE(GLOB lua_sources ${lua_SOURCE_DIR}/*.c)
-add_library(lua STATIC ${lua_sources})
+if (lua_ADDED)
+  FILE(GLOB lua_sources ${lua_SOURCE_DIR}/*.c)
+  add_library(lua STATIC ${lua_sources})
 
-target_include_directories(lua
-  PUBLIC
-    $<BUILD_INTERFACE:${lua_SOURCE_DIR}>
-)
+  target_include_directories(lua
+    PUBLIC
+      $<BUILD_INTERFACE:${lua_SOURCE_DIR}>
+  )
+endif()
 ```
 
 ## Local packages
@@ -130,12 +158,13 @@ If `CPM_LOCAL_PACKAGES_ONLY` is set, CPM will error when dependency is not found
 
 ## Advantages
 
-- **Small repos** CPM takes care of project dependencies, allowing you to focus on creating small, well-tested frameworks.
+- **Small and reusable projects** CPM takes care of project dependencies, allowing developers to focus on creating small, well-tested frameworks.
 - **Cross-Plattform** CPM adds projects via `add_subdirectory`, which is compatible with all cmake toolchains and generators.
 - **Reproducable builds** By using versioning via git tags it is ensured that a project will always be in the same state everywhere.
+- **Recursive dependencies** Ensures that no dependency is added twice and is added in the minimum required version.
 - **No installation required** No need to install anything. Just add the script to your project and you're good to go.
 - **No Setup required** There is a good chance your existing projects already work as CPM dependencies.
-- **Simple source distribution** CPM makes including projects with source files easy, reducing the need for monolithic header files.
+- **Simple source distribution** CPM makes including projects with source files and dependencies easy, reducing the need for monolithic header files.
 
 ## Limitations
 
@@ -143,4 +172,4 @@ If `CPM_LOCAL_PACKAGES_ONLY` is set, CPM will error when dependency is not found
 - **No auto-update** To update a dependency, version must be adapted manually and there is no way for CPM to figure out the most recent version.
 - **No pre-built binaries** Unless they are installed or included in the linked repository. 
 
-For projects with more complex needs and an extra setup step doesn't matter, it is worth to check out fully featured C++ package managers such as [conan](https://conan.io) or [hunter](https://github.com/ruslo/hunter) instead.
+For projects with more complex needs and where an extra setup step doesn't matter, it is worth to check out fully featured C++ package managers such as [conan](https://conan.io) or [hunter](https://github.com/ruslo/hunter).

cmake/CPM.cmake

@@ -28,7 +28,7 @@
 
 cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
 
-set(CURRENT_CPM_VERSION 0.9) 
+set(CURRENT_CPM_VERSION 0.10) 
 
 if(CPM_DIRECTORY)
   if(NOT ${CPM_DIRECTORY} MATCHES ${CMAKE_CURRENT_LIST_DIR})
@@ -139,6 +139,7 @@ function(CPMAddPackage)
     CPMGetProperties(${CPM_ARGS_NAME})
     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 NO PARENT_SCOPE)  
     return()
   endif()
 
@@ -156,6 +157,7 @@ function(CPMAddPackage)
   CPMGetProperties(${CPM_ARGS_NAME})
   SET(${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 YES PARENT_SCOPE)  
 endfunction()
 
 function (CPM_DECLARE_PACKAGE PACKAGE VERSION GIT_TAG)

examples/benchmark/CMakeLists.txt

@@ -18,8 +18,10 @@ CPMAddPackage(
     "BENCHMARK_ENABLE_TESTING Off"
 )
 
-# patch google benchmark target
-set_target_properties(benchmark PROPERTIES CXX_STANDARD 17)
+if (benchmark_ADDED)
+  # patch google benchmark target
+  set_target_properties(benchmark PROPERTIES CXX_STANDARD 17)
+endif()
 
 # ---- Executable ----
 

examples/doctest/CMakeLists.txt

@@ -19,7 +19,6 @@ CPMAddPackage(
   GIT_REPOSITORY https://github.com/onqtam/doctest.git
   VERSION 2.3.2
   GIT_TAG 2.3.2
-  GIT_SHALLOW True
 )
 
 # ---- Create binary ----

examples/json/CMakeLists.txt

@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+# ---- Dependencies ----
+
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME nlohmann_json
+  VERSION 3.6.1  
+  # not using the repo as it takes forever to clone
+  URL https://github.com/nlohmann/json/releases/download/v3.6.1/include.zip
+  URL_HASH SHA256=69cc88207ce91347ea530b227ff0776db82dcb8de6704e1a3d74f4841bc651cf
+)
+
+if(nlohmann_json_ADDED)
+  add_library(nlohmann_json INTERFACE)
+  target_include_directories(nlohmann_json INTERFACE ${nlohmann_json_SOURCE_DIR})
+endif()
+
+# ---- Executable ----
+
+add_executable(CPMJSONExample "main.cpp")
+set_target_properties(CPMJSONExample PROPERTIES CXX_STANDARD 17)        
+target_link_libraries(CPMJSONExample nlohmann_json)

examples/json/main.cpp

@@ -0,0 +1,25 @@
+#include <nlohmann/json.hpp>
+#include <iostream>
+#include <iomanip>
+
+int main(){
+  
+  nlohmann::json json = {
+    {"pi", 3.141},
+    {"happy", true},
+    {"name", "Niels"},
+    {"nothing", nullptr},
+    {"answer", {
+      {"everything", 42}
+    }},
+    {"list", {1, 0, 2}},
+    {"object", {
+      {"currency", "USD"},
+      {"value", 42.99}
+    }}
+  };
+
+  std::cout << "declared JSON object: " << std::setw(2) << json << std::endl;
+
+  return 0;
+}

examples/simple_match/CMakeLists.txt

@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+# ---- Dependencies ----
+
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME simple_match
+  GIT_REPOSITORY https://github.com/jbandela/simple_match.git
+  GIT_TAG a3ab17f3d98db302de68ad85ed399a42ae41889e
+  DOWNLOAD_ONLY True
+)
+
+if(simple_match_ADDED)
+  add_library(simple_match INTERFACE IMPORTED)
+  target_include_directories(simple_match INTERFACE "${simple_match_SOURCE_DIR}/include")
+endif()
+
+# ---- Executable ----
+
+add_executable(CPMSimpleMatchExample "main.cpp")
+set_target_properties(CPMSimpleMatchExample PROPERTIES CXX_STANDARD 17)        
+target_link_libraries(CPMSimpleMatchExample simple_match)
+

examples/simple_match/main.cpp

@@ -0,0 +1,34 @@
+#include <simple_match/simple_match.hpp>
+
+#include <iostream>
+
+int main(int argc, char ** argv){
+  using namespace simple_match;
+  using namespace simple_match::placeholders;
+
+  std::string input;
+  std::cout << "please enter a number or 'quit' to exit" << std::endl;
+
+  while (true) {
+    std::cout << "> ";
+    std::getline(std::cin, input);
+    if (input == "quit") { break; }
+    int x;
+    try {
+      x = std::stoi(input);
+    } catch(std::invalid_argument &) {
+      std::cout << "invalid input" << std::endl;
+      continue;
+    }
+    
+    match(x,
+      1, []() {std::cout << "The answer is one\n"; },
+      2, []() {std::cout << "The answer is two\n"; },
+      _x < 10, [](auto&& a) {std::cout << "The answer " << a << " is less than 10\n"; },
+      10 < _x < 20,	[](auto&& a) {std::cout << "The answer " << a  << " is between 10 and 20 exclusive\n"; },
+      _, []() {std::cout << "Did not match\n"; }
+    );
+  }
+
+  return 0;
+}

examples/yaml/CMakeLists.txt

@@ -0,0 +1,25 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+# ---- Dependencies ----
+
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME yaml-cpp
+  GIT_REPOSITORY https://github.com/jbeder/yaml-cpp.git
+  # 0.6.2 uses depricated CMake syntax
+  VERSION 0.6.3                                  
+  # 0.6.3 is not released yet, so use the most recent commit
+  GIT_TAG 012269756149ae99745b6dafefd415843d7420bb 
+  OPTIONS
+    "YAML_CPP_BUILD_TESTS Off"
+    "YAML_CPP_BUILD_CONTRIB Off"
+    "YAML_CPP_BUILD_TOOLS Off"
+)
+
+# ---- Executable ----
+
+add_executable(CPMYamlExample "main.cpp")
+set_target_properties(CPMYamlExample PROPERTIES CXX_STANDARD 17)        
+target_link_libraries(CPMYamlExample yaml-cpp)
+

examples/yaml/main.cpp

@@ -0,0 +1,14 @@
+#include <yaml-cpp/yaml.h>
+#include <iostream>
+
+int main(int argc, char ** argv){
+  if (argc != 2) {
+    std::cout << "usage: " << argv[0] << " <path to yaml file>" << std::endl;
+    return 1;
+  }
+
+  YAML::Node config = YAML::LoadFile(argv[1]);
+  std::cout << "Parsed YAML:\n" << config << std::endl;
+
+  return 0;
+}

examples/yaml/monsters.yaml

@@ -0,0 +1,21 @@
+- name: Ogre
+  position: [0, 5, 0]
+  powers:
+    - name: Club
+      damage: 10
+    - name: Fist
+      damage: 8
+- name: Dragon
+  position: [1, 0, 10]
+  powers:
+    - name: Fire Breath
+      damage: 25
+    - name: Claws
+      damage: 15
+- name: Wizard
+  position: [5, -3, 0]
+  powers:
+    - name: Acid Rain
+      damage: 50
+    - name: Staff
+      damage: 3