Explicitly invalidate the global parse hash in SpecParser construct…

…or (#409)

Explicitly invalidate the global parse hash in `SpecParser` constructor

Python can reuse id of objects after they are garbage-collected, however the global parse hash contains an id of SpecParser instance in order to force parsing on context switches, and when a different instance has the same id, it has no way to detect that.
Explicitly invalidate the global parse hash when a SpecParser instance is created to prevent this issue.
Fixes packit/packit-service#2461.

Reviewed-by: Laura Barcziová

specfile/spec_parser.py

@@ -57,6 +57,10 @@ def __init__(
         self.force_parse = force_parse
         self.spec = None
         self.tainted = False
+        # explicitly invalidate the global parse hash, this `SpecParser` instance could have
+        # been assigned the same id as a previously deleted one and parsing could be
+        # improperly skipped
+        SpecParser._last_parse_hash = None
 
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, SpecParser):
@@ -71,9 +75,12 @@ def __eq__(self, other: object) -> bool:
     def __repr__(self) -> str:
         return f"SpecParser({self.sourcedir!r}, {self.macros!r}, {self.force_parse!r})"
 
+    def id(self) -> int:
+        return id(self)
+
     def __deepcopy__(self, memo: Dict[int, Any]) -> "SpecParser":
         result = self.__class__.__new__(self.__class__)
-        memo[id(self)] = result
+        memo[self.id()] = result
         for k, v in self.__dict__.items():
             if k in ["spec", "tainted"]:
                 continue
@@ -359,7 +366,7 @@ def parse(
         """
         # calculate hash of all input parameters
         payload = (
-            id(self),
+            self.id(),
             self.sourcedir,
             self.macros,
             self.force_parse,

tests/integration/test_specfile.py

@@ -580,6 +580,16 @@ def test_parse_if_necessary(spec_macros):
     flexmock(SpecParser).should_call("_do_parse").once()
     assert spec1.expanded_name == "test"
     assert spec1.expanded_version == "28.1.2~rc2"
+    flexmock(SpecParser).should_receive("id").and_return(12345)
+    flexmock(SpecParser).should_call("_do_parse").once()
+    spec = Specfile(spec_macros)
+    flexmock(SpecParser).should_call("_do_parse").never()
+    assert spec.expanded_name == "test"
+    spec = None
+    flexmock(SpecParser).should_call("_do_parse").once()
+    spec = Specfile(spec_macros)
+    flexmock(SpecParser).should_call("_do_parse").never()
+    assert spec.expanded_name == "test"
 
 
 @pytest.mark.skipif(