Add more helpful error message when metadata is malformed, xref #558 #626

Author: timkpaine

src/build/_util.py

@@ -53,6 +53,12 @@ def check_dependency(
         # dependency is not installed in the environment.
         yield (*ancestral_req_strings, normalised_req_string)
     else:
+        if dist.version is None:
+            # Malformed dist-info or some other form of metadata corruption
+            # req.specifier.contains will raise TypeError, so let's do the same
+            # with a more helpful error message
+            msg = f'Package {req.name} has malformed metadata and no version information could be found'
+            raise TypeError(msg)
         if req.specifier and not req.specifier.contains(dist.version, prereleases=True):
             # the installed version is incompatible.
             yield (*ancestral_req_strings, normalised_req_string)

tests/test_projectbuilder.py

@@ -43,6 +43,8 @@ def from_name(cls, name):
             return CircularMockDistribution()
         elif name == 'nested_circular_dep':
             return NestedCircularMockDistribution()
+        elif name == 'malformed_dep':
+            return MalformedMockDistribution()
         raise _importlib.metadata.PackageNotFoundError
 
 
@@ -127,6 +129,11 @@ def read_text(self, filename):
                 """
             ).strip()
 
+class MalformedMockDistribution(MockDistribution):
+    def read_text(self, filename):
+        if filename == 'METADATA':
+            return ""
+
 
 @pytest.mark.parametrize(
     ('requirement_string', 'expected'),
@@ -165,6 +172,13 @@ def test_check_dependency(monkeypatch, requirement_string, expected):
     monkeypatch.setattr(_importlib.metadata, 'Distribution', MockDistribution)
     assert next(build.check_dependency(requirement_string), None) == expected
 
+def test_check_dependency_bad_metadata(monkeypatch):
+    monkeypatch.setattr(_importlib.metadata, 'Distribution', MockDistribution)
+    with pytest.raises(TypeError) as excinfo:
+        with pytest.warns(DeprecationWarning):
+            next(build.check_dependency("malformed_dep==1.0.0"), None)
+    assert "Package malformed_dep has malformed metadata and no version information could be found" in str(excinfo)
+
 
 def test_bad_project(package_test_no_project):
     # Passing a nonexistent project directory