fix: read package version from pyproject.toml if not found in metadata

aleph_alpha_client/version.py

@@ -1,5 +1,48 @@
 import importlib.metadata
 
-__version__ = importlib.metadata.version("aleph-alpha-client")
+import re
+from pathlib import Path
+import logging
+
 
 MIN_API_VERSION = "1.19.0"
+
+
+def pyproject_version() -> str:
+    """Return the package version specified in pyproject.toml.
+
+    Poetry inject the package version from the pyproject.toml file into the package
+    metadata at build time. This means any user of the package has access to the
+    version (it is send as User-Agent header in requests).
+
+    If this repository is cloned and the package is not installed, the version will
+    be not available (it is 0.0.0 per default). To also provide a version in these
+    cases, this function tries to read the version from the pyproject.toml file.
+
+    To not break imports in cases where both, the pyproject.toml file and the package
+    metadata are not available, no error is raised and a default version of 0.0.0
+    will be returned.
+    """
+    NO_VERSION = "0.0.0"
+    pyproject_path = Path(__file__).resolve().parent.parent / "pyproject.toml"
+
+    if not pyproject_path.is_file():
+        logging.error("pyproject.toml file not found.")
+        return NO_VERSION
+
+    version_pattern = re.compile(r'^version\s*=\s*["\']([^"\']+)["\']', re.MULTILINE)
+
+    with pyproject_path.open("r", encoding="utf-8") as file:
+        content = file.read()
+
+    if (match := version_pattern.search(content)):
+        return match.group(1)
+
+    logging.error("Version not found in pyproject.toml")
+    return NO_VERSION
+
+
+__version__ = importlib.metadata.version("aleph-alpha-client")
+
+if __version__ == "0.0.0":
+    __version__ = pyproject_version()