From f29f9fa365aae6021c14f9abfa4d76ce898318a7 Mon Sep 17 00:00:00 2001
From: Duncan Ogilvie <mr.exodia.tpodt@gmail.com>
Date: Thu, 26 Nov 2020 23:51:25 +0100
Subject: [PATCH] Implement CMake bootstrapping + integration

---
 cmake/CMakeLists.txt  |  23 +++++++++
 cmake/cmake.toml      |  13 +++++
 cmake/cmkr.cmake      | 112 ++++++++++++++++++++++++++++++++++++++++++
 cmake/src/example.cpp |   6 +++
 src/gen.cpp           |  10 +++-
 5 files changed, 163 insertions(+), 1 deletion(-)
 create mode 100644 cmake/CMakeLists.txt
 create mode 100644 cmake/cmake.toml
 create mode 100644 cmake/cmkr.cmake
 create mode 100644 cmake/src/example.cpp

diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
new file mode 100644
index 0000000..4fb8b85
--- /dev/null
+++ b/cmake/CMakeLists.txt
@@ -0,0 +1,23 @@
+# This file was generated automatically by cmkr.
+
+# Regenerate CMakeLists.txt file when necessary
+include(cmkr.cmake OPTIONAL RESULT_VARIABLE CMKR_INCLUDE_RESULT)
+if(CMKR_INCLUDE_RESULT)
+	cmkr()
+endif()
+
+cmake_minimum_required(VERSION 3.15)
+
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
+set(example_PROJECT_VERSION 0.1.0)
+project(example VERSION ${example_PROJECT_VERSION})
+
+set(EXAMPLE_SOURCES
+	"src/example.cpp"
+	)
+
+add_executable(example  ${EXAMPLE_SOURCES})
+
+
+
diff --git a/cmake/cmake.toml b/cmake/cmake.toml
new file mode 100644
index 0000000..b8089b3
--- /dev/null
+++ b/cmake/cmake.toml
@@ -0,0 +1,13 @@
+# This is a minimal example project used for testing the cmkr bootstrapping process
+
+[cmake]
+minimum = "3.15"
+
+[project]
+name = "example"
+version = "0.1.0"
+
+[[bin]]
+name = "example"
+type = "exe"
+sources = ["src/example.cpp"]
\ No newline at end of file
diff --git a/cmake/cmkr.cmake b/cmake/cmkr.cmake
new file mode 100644
index 0000000..09721fa
--- /dev/null
+++ b/cmake/cmkr.cmake
@@ -0,0 +1,112 @@
+include_guard()
+
+# Disable cmkr if no cmake.toml file is found
+if(NOT EXISTS ${CMAKE_CURRENT_LIST_DIR}/cmake.toml)
+    message(STATUS "[cmkr] Not found: ${CMAKE_CURRENT_LIST_DIR}/cmake.toml")
+    macro(cmkr)
+    endmacro()
+    return()
+endif()
+
+# Add a build-time dependency on the contents of cmake.toml to regenerate the CMakeLists.txt when modified
+configure_file(${CMAKE_CURRENT_LIST_DIR}/cmake.toml ${CMAKE_CURRENT_BINARY_DIR}/cmake.toml COPYONLY)
+
+# Helper macro to execute a process (COMMAND_ERROR_IS_FATAL ANY is 3.19 and higher)
+macro(cmkr_exec)
+    execute_process(COMMAND ${ARGV} RESULT_VARIABLE CMKR_EXEC_RESULT)
+    if(NOT CMKR_EXEC_RESULT EQUAL 0)
+        message(FATAL_ERROR "cmkr_exec(${ARGV}) failed (exit code ${CMKR_EXEC_RESULT})")
+    endif()
+endmacro()
+
+# Windows-specific hack (CMAKE_EXECUTABLE_PREFIX is not set at the moment)
+if(WIN32)
+    set(CMKR_EXECUTABLE_NAME "cmkr.exe")
+else()
+    set(CMKR_EXECUTABLE_NAME "cmkr")
+endif()
+
+# Use cached cmkr if found
+if(DEFINED CACHE{CMKR_EXECUTABLE} AND EXISTS ${CMKR_EXECUTABLE})
+    message(VERBOSE "[cmkr] Found cmkr: '${CMKR_EXECUTABLE}'")
+else()
+    if(DEFINED CACHE{CMKR_EXECUTABLE})
+        message(VERBOSE "[cmkr] '${CMKR_EXECUTABLE}' not found")
+    endif()
+    set(CMKR_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/_cmkr)
+    set(CMKR_EXECUTABLE ${CMAKE_CURRENT_BINARY_DIR}/_cmkr/bin/${CMKR_EXECUTABLE_NAME} CACHE INTERNAL "Full path to cmkr executable")
+    if(NOT EXISTS ${CMKR_EXECUTABLE})
+        message(VERBOSE "[cmkr] Bootstrapping '${CMKR_EXECUTABLE}'")
+        message(STATUS "[cmkr] Fetching cmkr...")
+        if(EXISTS ${CMKR_DIRECTORY})
+            cmkr_exec(${CMAKE_COMMAND} -E rm -rf ${CMKR_DIRECTORY})
+        endif()
+        find_package(Git QUIET REQUIRED)
+        set(CMKR_REPO "https://github.com/mrexodia/cmkr")
+        cmkr_exec(${GIT_EXECUTABLE} clone ${CMKR_REPO} ${CMKR_DIRECTORY})
+        cmkr_exec(${CMAKE_COMMAND} ${CMKR_DIRECTORY} -B${CMKR_DIRECTORY}/build -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=${CMKR_DIRECTORY})
+        cmkr_exec(${CMAKE_COMMAND} --build ${CMKR_DIRECTORY}/build --parallel --config Release)
+        cmkr_exec(${CMAKE_COMMAND} --install ${CMKR_DIRECTORY}/build --config Release --prefix ${CMKR_DIRECTORY} --component cmkr)
+        if(NOT EXISTS ${CMKR_EXECUTABLE})
+            message(FATAL_ERROR "[cmkr] Failed to bootstrap '${CMKR_EXECUTABLE}'")
+        endif()
+        cmkr_exec(${CMKR_EXECUTABLE} version OUTPUT_VARIABLE CMKR_VERSION)
+        string(STRIP ${CMKR_VERSION} CMKR_VERSION)
+        message(STATUS "[cmkr] Bootstrapped ${CMKR_EXECUTABLE}")
+    else()
+        message(VERBOSE "[cmkr] Found cmkr: '${CMKR_EXECUTABLE}'")
+    endif()
+endif()
+execute_process(COMMAND ${CMKR_EXECUTABLE} version
+    OUTPUT_VARIABLE CMKR_VERSION
+    RESULT_VARIABLE CMKR_EXEC_RESULT
+)
+if(NOT CMKR_EXEC_RESULT EQUAL 0)
+    unset(CMKR_EXECUTABLE CACHE)
+    message(FATAL_ERROR "[cmkr] Failed to get version, try clearing the cache and rebuilding")
+endif()
+string(STRIP ${CMKR_VERSION} CMKR_VERSION)
+message(STATUS "[cmkr] Using ${CMKR_VERSION}")
+
+# This is the macro that contains black magic
+macro(cmkr)
+    # When this macro is called from the generated file, fake some internal CMake variables
+    get_source_file_property(CMKR_CURRENT_LIST_FILE ${CMAKE_CURRENT_LIST_FILE} CMKR_CURRENT_LIST_FILE)
+    if(CMKR_CURRENT_LIST_FILE)
+        set(CMAKE_CURRENT_LIST_FILE ${CMKR_CURRENT_LIST_FILE})
+        get_filename_component(CMAKE_CURRENT_LIST_DIR ${CMAKE_CURRENT_LIST_FILE} DIRECTORY)
+    endif()
+
+    # File-based include guard (include_guard is not documented to work)
+    get_source_file_property(CMKR_INCLUDE_GUARD ${CMAKE_CURRENT_LIST_FILE} CMKR_INCLUDE_GUARD)
+    if(NOT CMKR_INCLUDE_GUARD)
+        set_source_files_properties(${CMAKE_CURRENT_LIST_FILE} PROPERTIES CMKR_INCLUDE_GUARD TRUE)
+
+        # Generate CMakeLists.txt
+        cmkr_exec(${CMKR_EXECUTABLE} gen -y
+            WORKING_DIRECTORY ${CMAKE_CURRENT_LIST_DIR}
+            OUTPUT_VARIABLE CMKR_GEN_OUTPUT
+        )
+        string(STRIP ${CMKR_GEN_OUTPUT} CMKR_GEN_OUTPUT)
+        message(STATUS "[cmkr] ${CMKR_GEN_OUTPUT}")
+
+        # Copy the now-generated CMakeLists.txt to CMakerLists.txt
+        # This is done because you cannot include() a file you are currently in
+        set(CMKR_TEMP_FILE ${CMAKE_CURRENT_LIST_DIR}/CMakerLists.txt)
+        configure_file(CMakeLists.txt ${CMKR_TEMP_FILE} COPYONLY)
+        
+        # Add the macro required for the hack at the start of the cmkr macro
+        set_source_files_properties(${CMKR_TEMP_FILE} PROPERTIES
+            CMKR_CURRENT_LIST_FILE ${CMAKE_CURRENT_LIST_FILE}
+        )
+        
+        # 'Execute' the newly-generated CMakeLists.txt
+        include(${CMKR_TEMP_FILE})
+        
+        # Delete the generated file
+        file(REMOVE ${CMKR_TEMP_FILE})
+        
+        # Do not execute the rest of the original CMakeLists.txt
+        return()
+    endif()
+endmacro()
\ No newline at end of file
diff --git a/cmake/src/example.cpp b/cmake/src/example.cpp
new file mode 100644
index 0000000..50a67c2
--- /dev/null
+++ b/cmake/src/example.cpp
@@ -0,0 +1,6 @@
+#include <cstdio>
+
+int main()
+{
+    puts("Hello from cmkr!");
+}
\ No newline at end of file
diff --git a/src/gen.cpp b/src/gen.cpp
index ff406a3..065e4b3 100644
--- a/src/gen.cpp
+++ b/src/gen.cpp
@@ -109,7 +109,15 @@ int generate_cmake(const char *path) {
     if (fs::exists(fs::path(path) / "cmake.toml")) {
         cmake::CMake cmake(path, false);
         std::stringstream ss;
-        ss << "# This file was generated automatically by cmkr.\n\n";
+        ss << "# This file was generated automatically by cmkr.\n";
+        ss << "\n";
+        
+        ss << "# Regenerate CMakeLists.txt file when necessary\n";
+        ss << "include(cmkr.cmake OPTIONAL RESULT_VARIABLE CMKR_INCLUDE_RESULT)\n";
+        ss << "if(CMKR_INCLUDE_RESULT)\n";
+        ss << "\tcmkr()\n";
+        ss << "endif()\n";
+        ss << "\n";
 
         if (!cmake.cmake_version.empty()) {
             ss << "cmake_minimum_required(VERSION " << cmake.cmake_version << ")\n\n";