use only one version definition

Author: kreuzberger

sphinx_test_spec/main.py

@@ -1,12 +1,28 @@
 import os
+from importlib.metadata import PackageNotFoundError
+from importlib.metadata import version as package_version
 
 from sphinx.util import logging
 
 from sphinx_test_spec.builder import TestSpecBuilder, build_testspec_json
 from sphinx_test_spec.domain import MESSAGE_CATALOG_NAME, TestSpecDomain
 
 LOG = logging.getLogger(__name__)
-VERSION = 25.1
+PACKAGE_NAME = "sphinx-test-spec"  # bzw. "sphinx-rst-table"
+
+
+def get_extension_version() -> str:
+    """Return the installed package version from package metadata.
+
+    The version is maintained in ``pyproject.toml`` only. When the package is
+    installed, that value is exposed through Python package metadata and used
+    by Sphinx in ``setup()``. The fallback is only for direct source-tree usage
+    without an installed distribution.
+    """
+    try:
+        return package_version(PACKAGE_NAME)
+    except PackageNotFoundError:
+        return "0+unknown"
 
 
 def rst_testspec_jinja(app, docname, source):
@@ -40,4 +56,8 @@ def setup(app):
     LOG.debug(f"using locale dir {locale_dir}")
     app.add_message_catalog(MESSAGE_CATALOG_NAME, locale_dir)
 
-    return {"version": VERSION, "parallel_read_safe": True, "parallel_write_safe": True}
+    return {
+        "version": get_extension_version(),
+        "parallel_read_safe": True,
+        "parallel_write_safe": True,
+    }