fix(cpp): Actually use the VERSION file (cucumber#376)

* fix(cpp): Actually use the VERSION file

Similar to what cucumber#328 added to the C library, actually use the `VERSION`
file to set the project version for the C++ library, and use the
resulting project version to set the shared library version and ABi
version (CMake `SOVERSION`).

Fixes cucumber#375.

* Changelog entry for PR cucumber#376

Author: musicinmybrain

CHANGELOG.md

@@ -8,6 +8,9 @@ This document is formatted according to the principles of [Keep A CHANGELOG](htt
 
 ## [Unreleased]
 
+### Fixed
+- [cpp] Actually use the VERSION file ([#376](https://github.com/cucumber/gherkin/pull/376))
+
 ## [32.1.1] - 2025-04-11
 ### Fixed
 - [Java] Avoid unnecessary unboxing to Character

cpp/CMakeLists.txt

@@ -1,12 +1,21 @@
-###
-#
-# Project
-# name and version
-#
-###
-cmake_minimum_required(VERSION 3.12 FATAL_ERROR)
+set(VERSION 30.0.4)
 
-project(cucumber_gherkin VERSION 30.0.4 LANGUAGES C CXX)
+if(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/VERSION")
+    file(STRINGS "VERSION" LINES)
+    list(GET LINES 0 VERSION)
+endif()
+
+# Crude Semver parsing
+if("${VERSION}" MATCHES "^([^\\.]+)\\.([^\\.]+)\\.([^\\.]+)$")
+    set(VER_MAJOR ${CMAKE_MATCH_1})
+    set(VER_MINOR ${CMAKE_MATCH_2})
+    set(VER_PATCH ${CMAKE_MATCH_3})
+else()
+    message(FATAL_ERROR "unable to parse version: ${VERSION}")
+endif()
+
+cmake_minimum_required(VERSION 3.12 FATAL_ERROR)
+project(cucumber_gherkin VERSION ${VERSION} LANGUAGES C CXX)
 
 ###
 #

cpp/src/lib/gherkin/CMakeLists.txt

@@ -35,8 +35,8 @@ set_target_properties(
     cucumber_gherkin_lib
     PROPERTIES
         CXX_STANDARD 20
-        VERSION 30.0.4
-        SOVERSION 30
+        VERSION ${VERSION}
+        SOVERSION ${VER_MAJOR}
         EXPORT_NAME gherkin
         OUTPUT_NAME cucumber_gherkin
 )