Use assumed ABI3 version for shared objects without ".abi3."

Allow auditing arbitrary shared objects, not necessarily containing
".abi3." in their name, if --assume-minimum-abi3 option is specified:
suppose that all shared objects use this ABI3 version then.

This makes the tool more convenient to use for non-wheel-packaged
extensions.

Also specify the default, 3.2, ABI version in a single place only and
use "None" instead of the default value elsewhere.

abi3audit/_audit.py

@@ -89,7 +89,7 @@ def __rich_console__(self, console: Console, options: ConsoleOptions) -> RenderR
             yield f"[green]:thumbs_up: {self.so}"
 
 
-def audit(so: SharedObject, assume_minimum_abi3: PyVersion = PyVersion(3, 2)) -> AuditResult:
+def audit(so: SharedObject, assume_minimum_abi3: PyVersion = None) -> AuditResult:
     # We might fail to retrieve a minimum abi3 baseline if our context
     # (the shared object or its containing wheel) isn't actually tagged
     # as abi3 compatible.

abi3audit/_cli.py

@@ -220,18 +220,19 @@ def main() -> None:
     parser.add_argument(
         "--assume-minimum-abi3",
         action=_PyVersionAction,
-        default=PyVersion(3, 2),
         help="assumed abi3 version (3.x, with x>=2) if it cannot be detected",
     )
     args = parser.parse_args()
 
     if args.debug:
         logging.root.setLevel("DEBUG")
 
+    assume_minimum_abi3 = args.assume_minimum_abi3
+
     specs = []
     for spec in args.specs:
         try:
-            specs.extend(make_specs(spec))
+            specs.extend(make_specs(spec, assume_minimum_abi3))
         except InvalidSpec as e:
             console.log(f"[red]:thumbs_down: processing error: {e}")
             sys.exit(1)
@@ -253,7 +254,7 @@ def main() -> None:
                 status.update(f"{spec}: auditing {so}")
 
                 try:
-                    result = audit(so, assume_minimum_abi3=args.assume_minimum_abi3)
+                    result = audit(so, assume_minimum_abi3)
                     all_passed = all_passed and bool(result)
                 except AuditError as exc:
                     # TODO(ww): Refine exceptions and error states here.

abi3audit/_extract.py

@@ -13,6 +13,7 @@
 from typing import Union
 from zipfile import ZipFile
 
+from abi3info.models import PyVersion
 from packaging import utils
 from packaging.tags import Tag
 
@@ -89,7 +90,7 @@ def _extractor(self) -> Extractor:
 Spec = Union[WheelSpec, SharedObjectSpec, PyPISpec]
 
 
-def make_specs(val: str) -> list[Spec]:
+def make_specs(val: str, assume_minimum_abi3: PyVersion = None) -> list[Spec]:
     """
     Constructs a (minimally) valid list of `Spec` instances from the given input.
     """
@@ -101,10 +102,13 @@ def make_specs(val: str) -> list[Spec]:
         return [WheelSpec(val)]
     elif any(val.endswith(suf) for suf in _SHARED_OBJECT_SUFFIXES):
         # NOTE: We allow untagged shared objects when they're indirectly
-        # audited (e.g. via an abi3 wheel), but not directly (since
-        # without a tag here we don't know if it's abi3 at all).
-        if ".abi3." not in val:
-            raise InvalidSpec(f"'{val}' must contain '.abi3.' to be recognized as a shared object")
+        # audited (e.g. via an abi3 wheel), but when auditing them directly we
+        # only allow them if we have a minimum abi3 version to check against.
+        if assume_minimum_abi3 is None and ".abi3." not in val:
+            raise InvalidSpec(
+                f"'{val}' must contain '.abi3.' to be recognized as a shared "
+                + "object or assumed minimum ABI3 version must be specified"
+            )
         return [SharedObjectSpec(val)]
     elif re.match(_DISTRIBUTION_NAME_RE, val, re.IGNORECASE):
         return [PyPISpec(val)]

abi3audit/_object.py

@@ -32,7 +32,7 @@ def __init__(self, extractor: extract.SharedObjectExtractor):
         self._extractor = extractor
         self.path = self._extractor.path
 
-    def abi3_version(self, assume_lowest: PyVersion = PyVersion(3, 2)) -> PyVersion | None:
+    def abi3_version(self, assume_lowest: PyVersion) -> PyVersion | None:
         # If we're dealing with a shared object that was extracted from a wheel,
         # we try and suss out the abi3 version from the wheel's own tags.
         if self._extractor.parent is not None:
@@ -50,14 +50,18 @@ def abi3_version(self, assume_lowest: PyVersion = PyVersion(3, 2)) -> PyVersion
         # filename. This doesn't tell us anything about the specific abi3 version, so
         # we assume the lowest.
         if ".abi3" in self._extractor.path.suffixes:
+            if assume_lowest is None:
+                assume_lowest = PyVersion(3, 2)
+
             logger.debug(
                 "no wheel to infer abi3 version from; assuming (%s)",
                 assume_lowest,
             )
             return assume_lowest
 
-        # With no wheel tags and no filename tag, we have nothing to go on.
-        return None
+        # With no wheel tags and no filename tag, fall back on the assumed ABI
+        # version (which is possibly None).
+        return assume_lowest
 
     def __str__(self) -> str:
         parents = []