Use importlib.metadata for guess_version instead of importing the module (#171)

Co-authored-by: Bernát Gábor <bgabor8@bloomberg.net>

CHANGES.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 2.3.1
+
+- Use `importlib.metadata` to guess version of package before fallback to `pkg.__version__`.
+
 ## 2.3.0
 
 - Move to a package layout

pyproject.toml

@@ -23,7 +23,7 @@ optional-dependencies.test = [
   "pytest>=7.1.3",
   "pytest-cov>=3",
   "pytest-mock>=3.8.2",
-  "virtualenv<21,>=20.16.4",
+  "virtualenv<21,>=20.16.5",
 ]
 optional-dependencies.graphviz = [
   "graphviz>=0.20.1",

src/pipdeptree/__init__.py

@@ -41,6 +41,17 @@ def guess_version(pkg_key, default="?"):
     :returns: version
     :rtype: string
     """
+    try:
+        if sys.version_info >= (3, 8):  # pragma: >=3.8 cover
+            import importlib.metadata as importlib_metadata
+        else:  # pragma: <3.8 cover
+            import importlib_metadata
+        return importlib_metadata.version(pkg_key)
+    except ImportError:
+        pass
+    # Avoid AssertionError with setuptools, see https://github.com/tox-dev/pipdeptree/issues/162
+    if pkg_key in {"setuptools"}:
+        return default
     try:
         m = import_module(pkg_key)
     except ImportError:

tests/guess_version_setuptools.py

@@ -0,0 +1,16 @@
+import sys
+
+import pipdeptree
+
+if sys.version_info >= (3, 8):
+    import importlib.metadata as importlib_metadata
+else:
+    import importlib_metadata
+
+
+def raise_import_error(name):
+    raise ImportError(name)
+
+
+importlib_metadata.version = raise_import_error
+print(pipdeptree.guess_version("setuptools"), end="")

tests/test_pipdeptree.py

@@ -1,7 +1,9 @@
 import platform
+import subprocess
 import sys
 from contextlib import contextmanager
 from itertools import chain
+from pathlib import Path
 from tempfile import NamedTemporaryFile
 
 try:
@@ -488,3 +490,9 @@ def test_custom_interpreter(tmp_path, monkeypatch, capfd, args_joined):
     assert context.value.code == 1
     assert not out
     assert err == "graphviz functionality is not supported when querying" " non-host python\n"
+
+
+def test_guess_version_setuptools():
+    script = Path(__file__).parent / "guess_version_setuptools.py"
+    output = subprocess.check_output([sys.executable, script], text=True)
+    assert output == "?"