Fix epoch handling in version comparisons

- If epoch is not specified in new version, it's inherited from
  current packages.
- Epoch is used only for some of the provides.

Fixes: #5

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: frenzymadness

fedora_revdep_check.py

@@ -228,6 +228,16 @@ def simulate_version_change(self, srpm_name: str, new_version: str) -> Dict:
                 'binary_packages': []
             }
 
+        # If new_version doesn't include an epoch, inherit it from current packages
+        if ':' not in new_version:
+            # Get epoch from first package (all packages from same SRPM should have same epoch)
+            current_epoch = binary_packages[0].get_epoch()
+            if current_epoch and current_epoch != '0':
+                new_version = f"{current_epoch}:{new_version}"
+                if self.verbose:
+                    print(f"No epoch specified in new version, using epoch {current_epoch} from current package")
+                    print(f"Testing with version: {new_version}\n")
+
         if self.verbose:
             print(f"Found {len(binary_packages)} binary package(s) from {srpm_name}:")
             for pkg in binary_packages:
@@ -406,7 +416,19 @@ def _check_requirement_conflict(
         # Check if new version satisfies all constraints
         if constraints:
             for constraint in constraints:
-                if not self._version_satisfies(new_version, constraint['op'], constraint['version']):
+                # Determine which new version to use based on whether the provide uses epochs
+                # Check if any current provide has an epoch in its version
+                provide_uses_epoch = False
+                for pkg, prov_str, prov_version in prov_info_list:
+                    current_ver = prov_version if prov_version else pkg.get_version()
+                    if ':' in current_ver:
+                        provide_uses_epoch = True
+                        break
+
+                # Use appropriate version: with or without epoch depending on provide format
+                version_to_check = new_version if provide_uses_epoch else new_version.split(':', 1)[-1]
+
+                if not self._version_satisfies(version_to_check, constraint['op'], constraint['version']):
                     # New version fails - now check if current version also fails
                     # to determine if this is a new problem or already broken
                     current_version_also_fails = False

tests/conftest.py

@@ -33,6 +33,8 @@
     create_multi_binary_scenario,
     create_same_srpm_dependency_scenario,
     create_already_broken_scenario,
+    create_epoch_package_scenario,
+    create_epoch_with_dist_provides_scenario,
 )
 from fedora_revdep_check import FedoraRevDepChecker  # noqa: E402
 
@@ -120,6 +122,18 @@ def already_broken_base():
     return create_already_broken_scenario()
 
 
+@pytest.fixture
+def epoch_package_base():
+    """Provide a mock DNF base with packages that have epochs."""
+    return create_epoch_package_scenario()
+
+
+@pytest.fixture
+def epoch_with_dist_provides_base():
+    """Provide a mock DNF base with packages that have both RPM and dist provides."""
+    return create_epoch_with_dist_provides_scenario()
+
+
 @pytest.fixture
 def checker_instance(mock_dnf_base):
     """

tests/fixtures/mock_packages.py

@@ -613,3 +613,97 @@ def create_already_broken_scenario():
     ]
 
     return MockBase(packages=packages)
+
+
+def create_epoch_package_scenario():
+    """
+    Create a scenario with packages that have epochs.
+
+    Scenario:
+    - sphinx 1:8.0.0 currently installed (epoch 1)
+    - reverse-dep requires sphinx >= 1:8.0.0
+    - Upgrading to 9.0.0 without specifying epoch should inherit epoch 1
+    - So 1:9.0.0 should satisfy the requirement (not 0:9.0.0 which would fail)
+    """
+    packages = [
+        # Sphinx package with epoch 1
+        MockPackage(
+            name='python3-sphinx',
+            version='8.0.0',
+            release='1.fc40',
+            arch='noarch',
+            source_name='sphinx',
+            epoch='1',
+            provides=[
+                'python3-sphinx',
+                'python3-sphinx = 1:8.0.0-1.fc40',
+                'python3dist(sphinx) = 8.0.0',
+            ]
+        ),
+        # Reverse dependency requiring >= 1:8.0.0
+        MockPackage(
+            name='python3-docs',
+            version='1.0.0',
+            release='1.fc40',
+            arch='noarch',
+            source_name='python-docs',
+            requires=[
+                'python3-sphinx >= 1:8.0.0',
+            ]
+        ),
+    ]
+
+    return MockBase(packages=packages)
+
+
+def create_epoch_with_dist_provides_scenario():
+    """
+    Create a scenario with packages that have both RPM and dist provides.
+
+    Scenario:
+    - sphinx 1:8.0.0 currently installed (epoch 1)
+    - Provides both python3-sphinx (with epoch) and python3dist(sphinx) (without epoch)
+    - reverse-dep-rpm requires python3-sphinx >= 1:8.0.0 (RPM provide with epoch)
+    - reverse-dep-dist requires python3dist(sphinx) < 10~~ (dist provide without epoch)
+    - Upgrading to 9.1.0 should satisfy both (use epoch for RPM, not for dist)
+    """
+    packages = [
+        # Sphinx package with epoch 1
+        MockPackage(
+            name='python3-sphinx',
+            version='8.0.0',
+            release='1.fc40',
+            arch='noarch',
+            source_name='sphinx',
+            epoch='1',
+            provides=[
+                'python3-sphinx',
+                'python3-sphinx = 1:8.0.0-1.fc40',
+                'python3dist(sphinx) = 8.0.0',
+            ]
+        ),
+        # Reverse dependency requiring RPM package with epoch
+        MockPackage(
+            name='python3-docs',
+            version='1.0.0',
+            release='1.fc40',
+            arch='noarch',
+            source_name='python-docs',
+            requires=[
+                'python3-sphinx >= 1:8.0.0',
+            ]
+        ),
+        # Reverse dependency requiring dist provide without epoch
+        MockPackage(
+            name='python3-myst-parser',
+            version='5.0.0',
+            release='1.fc40',
+            arch='noarch',
+            source_name='python-myst-parser',
+            requires=[
+                'python3dist(sphinx) < 10~~',
+            ]
+        ),
+    ]
+
+    return MockBase(packages=packages)

tests/integration/test_simulation.py

@@ -187,3 +187,40 @@ def test_simulate_version_change_already_broken_package(self, already_broken_bas
         for conflict in new_pkg_conflicts:
             assert conflict['already_broken'] is False
             assert 'python3dist(library) < 5.0' in conflict['failed_constraint']
+
+    def test_simulate_version_change_inherits_epoch(self, epoch_package_base):
+        """Test that new version without epoch inherits epoch from current package."""
+        checker = FedoraRevDepChecker(verbose=False, base=epoch_package_base)
+
+        # Current package is 1:8.0.0, upgrading to 9.0.0 (without epoch)
+        # should be interpreted as 1:9.0.0, not 0:9.0.0
+        # reverse-dep requires >= 1:8.0.0, so 1:9.0.0 should satisfy it
+        results = checker.simulate_version_change('sphinx', '9.0.0')
+
+        assert 'error' not in results
+        # The new_version should be transformed to include epoch
+        assert results['new_version'] == '1:9.0.0'
+
+        # Should have no conflicts (1:9.0.0 >= 1:8.0.0)
+        assert len(results['conflicts']) == 0
+
+    def test_simulate_version_change_epoch_only_for_rpm_provides(self, epoch_with_dist_provides_base):
+        """Test that epoch is only used for RPM provides, not for dist provides."""
+        checker = FedoraRevDepChecker(verbose=False, base=epoch_with_dist_provides_base)
+
+        # Current package is 1:8.0.0 with both RPM and dist provides
+        # Upgrading to 9.1.0 should:
+        # - Use 1:9.1.0 for RPM package provides (with epoch)
+        # - Use 9.1.0 for dist provides (without epoch)
+        # reverse-dep-rpm requires python3-sphinx >= 1:8.0.0 (should be satisfied)
+        # reverse-dep-dist requires python3dist(sphinx) < 10~~ (should be satisfied)
+        results = checker.simulate_version_change('sphinx', '9.1.0')
+
+        assert 'error' not in results
+        assert results['new_version'] == '1:9.1.0'
+
+        # Should have no conflicts
+        # Both requirements should be satisfied:
+        # - 1:9.1.0 >= 1:8.0.0 (True)
+        # - 9.1.0 < 10~~ (True)
+        assert len(results['conflicts']) == 0

tests/unit/test_version_operations.py

@@ -137,6 +137,18 @@ def test_version_satisfies_invalid_operator(self, checker):
         assert result is False
 
 
+    @pytest.mark.parametrize("version,op,required,expected", [
+        # Test that new version without epoch is correctly compared
+        # to requirements with epoch (after epoch is inherited)
+        ("1:9.1.0", ">=", "1:8.2.0", True),  # Should satisfy after inheriting epoch 1
+        ("1:9.1.0", ">=", "8.2.0", True),    # Epoch 1 > epoch 0
+    ])
+    def test_version_satisfies_inherited_epoch(self, checker, version, op, required, expected):
+        """Test version comparison when epoch is inherited from current package."""
+        result = checker._version_satisfies(version, op, required)
+        assert result == expected, f"{version} {op} {required} should be {expected}"
+
+
     @pytest.mark.parametrize("version,op,required,expected", [
         # Double tilde (very pre-release)
         ("4.7.0~~alpha", "<", "4.7.0~beta", True),