Adding support to automatically version from github tag

Reducing redundancy and picking up the version from the project's GitHub tags so they update automatically with each release.

Author: sean-parent

README.md

@@ -11,6 +11,7 @@ Modern CMake template for C++ header-only libraries with comprehensive infrastru
 
 `cpp-library` provides a standardized CMake infrastructure template for header-only C++ libraries. It eliminates boilerplate and provides consistent patterns for:
 
+- **Project Declaration**: Uses existing `project()` declaration with automatic git tag-based versioning
 - **Library Setup**: INTERFACE targets with proper installation and package config
 - **Testing**: Integrated doctest with CTest and compile-fail test support
 - **Documentation**: Doxygen with doxygen-awesome-css theme
@@ -24,7 +25,9 @@ Use CPMAddPackage to fetch cpp-library directly in your CMakeLists.txt:
 
 ```cmake
 cmake_minimum_required(VERSION 3.20)
-project(your-library VERSION 1.0.0 DESCRIPTION "Your library description" LANGUAGES CXX)
+
+# Project declaration - cpp_library_setup will use this name and detect version from git tags
+project(your-library)
 
 set(CPM_SOURCE_CACHE ${CMAKE_SOURCE_DIR}/.cpm-cache CACHE PATH "CPM cache")
 include(cmake/CPM.cmake)
@@ -34,9 +37,7 @@ CPMAddPackage("gh:stlab/[email protected]")
 include(${cpp-library_SOURCE_DIR}/cpp-library.cmake)
 
 cpp_library_setup(
-    NAME your-library
-    VERSION ${PROJECT_VERSION}
-    DESCRIPTION "${PROJECT_DESCRIPTION}"
+    DESCRIPTION "Your library description"
     NAMESPACE your_namespace
     HEADERS ${CMAKE_CURRENT_SOURCE_DIR}/include/your_namespace/your_header.hpp
     # Optional: add SOURCES for non-header-only libraries
@@ -60,11 +61,12 @@ cpp_library_setup(
 ```cmake
 cpp_library_setup(
     # Required parameters
-    NAME project_name              # e.g., "stlab-enum-ops"
-    VERSION version_string         # e.g., "1.0.0" 
     DESCRIPTION description        # e.g., "Type-safe operators for enums"
     NAMESPACE namespace            # e.g., "stlab"
     
+    # Optional parameters
+    VERSION version_string         # e.g., "1.0.0" (auto-detected from git tags if not provided)
+    
     # Header specification (one required)
     HEADERS header_list            # List of header files
     HEADER_DIR directory           # Directory to install recursively
@@ -87,6 +89,8 @@ cpp_library_setup(
 )
 ```
 
+**Note**: The project name is automatically taken from `PROJECT_NAME` (set by the `project()` command). You must call `project(your-library)` before `cpp_library_setup()`.
+
 ## Features
 ### Non-Header-Only Library Support
 
@@ -110,6 +114,7 @@ cpp_library_setup(
 - **Debug** builds for testing, **Release** for default
 - **Build isolation** with separate build directories
 - **Two-mode operation**: Full infrastructure when top-level, lightweight when consumed
+- **Automatic version detection**: Version is automatically extracted from git tags (e.g., `v1.2.3` becomes `1.2.3`)
 
 ### Testing Features
 
@@ -152,6 +157,13 @@ cpp_library_setup(
 - **Version pinning** for reliable builds
 - **Git tag versioning** for reliable updates
 
+### Version Management
+
+- **Automatic git tag detection**: Version is automatically extracted from the latest git tag
+- **Fallback versioning**: Uses `0.0.0` if no git tag is found (with warning)
+- **Manual override**: You can still specify `VERSION` parameter to override automatic detection
+- **Tag format support**: Supports both `v1.2.3` and `1.2.3` tag formats
+
 ## Example Projects
 
 This template is used by:
@@ -163,7 +175,6 @@ This template is used by:
 
 ```cmake
 cmake_minimum_required(VERSION 3.20)
-project(stlab-enum-ops VERSION 1.0.0 DESCRIPTION "Type-safe operators for enums" LANGUAGES CXX)
 
 # Setup cpp-library infrastructure
 set(CPM_SOURCE_CACHE ${CMAKE_SOURCE_DIR}/.cpm-cache CACHE PATH "CPM cache" FORCE)
@@ -179,8 +190,7 @@ include(${cpp-library_SOURCE_DIR}/cpp-library.cmake)
 # Configure library (handles both lightweight and full modes automatically)
 cpp_library_setup(
     NAME stlab-enum-ops
-    VERSION ${PROJECT_VERSION}
-    DESCRIPTION "${PROJECT_DESCRIPTION}"
+    DESCRIPTION "Type-safe operators for enums"
     NAMESPACE stlab
     HEADERS ${CMAKE_CURRENT_SOURCE_DIR}/include/stlab/enum_ops.hpp
     EXAMPLES enum_ops_example enum_ops_example_fail

cmake/cpp-library-setup.cmake

@@ -2,6 +2,28 @@
 #
 # cpp-library-setup.cmake - Core library setup functionality
 
+# Function to get version from git tags
+function(_cpp_library_get_git_version OUTPUT_VAR)
+    # Try to get version from git tags
+    execute_process(
+        COMMAND git describe --tags --abbrev=0
+        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+        OUTPUT_VARIABLE GIT_TAG_VERSION
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+        ERROR_QUIET
+    )
+    
+    # If git tag found, use it (remove 'v' prefix if present)
+    if(GIT_TAG_VERSION)
+        string(REGEX REPLACE "^v" "" CLEAN_VERSION "${GIT_TAG_VERSION}")
+        set(${OUTPUT_VAR} "${CLEAN_VERSION}" PARENT_SCOPE)
+    else()
+        # Fallback to 0.0.0 if no git tag found
+        set(${OUTPUT_VAR} "0.0.0" PARENT_SCOPE)
+        message(WARNING "No git tag found, using version 0.0.0. Consider creating a git tag for proper versioning.")
+    endif()
+endfunction()
+
 function(_cpp_library_setup_core)
     set(oneValueArgs
         NAME
@@ -19,6 +41,15 @@ function(_cpp_library_setup_core)
 
     cmake_parse_arguments(ARG "" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
 
+    # Get version from git tags if not provided
+    if(NOT ARG_VERSION)
+        _cpp_library_get_git_version(GIT_VERSION)
+        set(ARG_VERSION "${GIT_VERSION}")
+    endif()
+    
+    # Note: Project declaration is now handled in the main cpp_library_setup function
+    # No need to check ARG_TOP_LEVEL here for project declaration
+    
     # Extract the library name without namespace prefix for target naming
     string(REPLACE "${ARG_NAMESPACE}-" "" CLEAN_NAME "${ARG_NAME}")
 

cpp-library.cmake

@@ -28,7 +28,6 @@ function(cpp_library_setup)
         FORCE_INIT             # Force regeneration of template files
     )
     set(oneValueArgs
-        NAME                    # Project name (e.g., "stlab-enum-ops")
         VERSION                 # Version string (e.g., "1.0.0") 
         DESCRIPTION             # Description string
         NAMESPACE               # Namespace (e.g., "stlab")
@@ -55,12 +54,6 @@ function(cpp_library_setup)
     endif()
 
     # Validate required arguments
-    if(NOT ARG_NAME)
-        message(FATAL_ERROR "cpp_library_setup: NAME is required")
-    endif()
-    if(NOT ARG_VERSION)
-        message(FATAL_ERROR "cpp_library_setup: VERSION is required")
-    endif()
     if(NOT ARG_DESCRIPTION)
         message(FATAL_ERROR "cpp_library_setup: DESCRIPTION is required")
     endif()
@@ -71,6 +64,12 @@ function(cpp_library_setup)
         message(FATAL_ERROR "cpp_library_setup: Either HEADERS or HEADER_DIR is required")
     endif()
 
+    # Use PROJECT_NAME as the library name
+    if(NOT DEFINED PROJECT_NAME)
+        message(FATAL_ERROR "cpp_library_setup: PROJECT_NAME must be defined. Call project() before cpp_library_setup()")
+    endif()
+    set(ARG_NAME "${PROJECT_NAME}")
+    
     # Set defaults
     if(NOT ARG_REQUIRES_CPP_VERSION)
         set(ARG_REQUIRES_CPP_VERSION 17)
@@ -81,6 +80,32 @@ function(cpp_library_setup)
         set(ARG_FORCE_INIT TRUE)
     endif()
 
+    # Get version from git tags if not provided
+    if(NOT ARG_VERSION)
+        _cpp_library_get_git_version(GIT_VERSION)
+        set(ARG_VERSION "${GIT_VERSION}")
+    endif()
+    
+    # Parse version components for manual setting
+    string(REGEX MATCH "^([0-9]+)\\.([0-9]+)\\.([0-9]+)" VERSION_MATCH "${ARG_VERSION}")
+    if(VERSION_MATCH)
+        set(ARG_VERSION_MAJOR ${CMAKE_MATCH_1})
+        set(ARG_VERSION_MINOR ${CMAKE_MATCH_2})
+        set(ARG_VERSION_PATCH ${CMAKE_MATCH_3})
+    else()
+        set(ARG_VERSION_MAJOR 0)
+        set(ARG_VERSION_MINOR 0)
+        set(ARG_VERSION_PATCH 0)
+    endif()
+    
+    # Update project version if it was detected from git
+    if(NOT DEFINED PROJECT_VERSION OR PROJECT_VERSION STREQUAL "")
+        set(PROJECT_VERSION ${ARG_VERSION} PARENT_SCOPE)
+        set(PROJECT_VERSION_MAJOR ${ARG_VERSION_MAJOR} PARENT_SCOPE)
+        set(PROJECT_VERSION_MINOR ${ARG_VERSION_MINOR} PARENT_SCOPE)
+        set(PROJECT_VERSION_PATCH ${ARG_VERSION_PATCH} PARENT_SCOPE)
+    endif()
+    
     # Create the basic library target (always done)
     _cpp_library_setup_core(
         NAME "${ARG_NAME}"