Read the package version from installed metadata

changelog.d/version-from-metadata.fixed.md

@@ -0,0 +1 @@
+- Fixed `microimpute.__version__` reporting 1.1.2 while the package was at 3.1.1, by reading the version from installed package metadata.

microimpute/__init__.py

@@ -19,7 +19,14 @@
     - Visualization: performance and comparison plots
 """
 
-__version__ = "1.1.2"
+from importlib.metadata import PackageNotFoundError, version as _version
+
+try:
+    __version__ = _version("microimpute")
+except PackageNotFoundError:
+    # Running from a source tree with no install. Keep it PEP 440 parseable so
+    # a consumer calling packaging.version.parse on it does not raise.
+    __version__ = "0.0.0+unknown"
 
 # Import automated imputation
 from microimpute.comparisons.autoimpute import AutoImputeResult, autoimpute

tests/test_version.py

@@ -0,0 +1,42 @@
+"""The reported version must match the installed distribution.
+
+`__version__` was hardcoded and drifted to 1.1.2 while the package was 3.1.1,
+which is the regression this guards against.
+"""
+
+from importlib.metadata import version
+
+import pytest
+from packaging.version import Version
+
+import microimpute
+
+
+def test_version_matches_installed_distribution():
+    assert microimpute.__version__ == version("microimpute")
+
+
+def test_version_is_pep440_parseable():
+    """The fallback must parse too, or consumers comparing versions raise."""
+    Version(microimpute.__version__)
+    Version("0.0.0+unknown")
+
+
+def test_fallback_used_when_distribution_is_absent(monkeypatch):
+    """The fallback branch runs when the distribution cannot be found."""
+    import importlib.metadata
+
+    def _raise(_name):
+        raise importlib.metadata.PackageNotFoundError(_name)
+
+    monkeypatch.setattr(importlib.metadata, "version", _raise)
+
+    # Re-run the same lookup __init__ performs, rather than reloading the
+    # package: reloading re-imports every model and is slow and fragile.
+    try:
+        resolved = importlib.metadata.version("microimpute")
+    except importlib.metadata.PackageNotFoundError:
+        resolved = "0.0.0+unknown"
+
+    assert resolved == "0.0.0+unknown"
+    Version(resolved)