fix(resolver): raise ResolverException on cutoff, validate age, reduce log noise

- Raise ResolverException instead of ValueError when all candidates are
  older than max-release-age cutoff, consistent with resolver error handling.
- Validate that max_release_age is positive in set_max_release_age().
- Move "found N candidate(s)" log inside the max_age_cutoff block so it
  only fires when filtering is active.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Rohan Devasthale <rdevasth@redhat.com>

Author: rd4398

src/fromager/context.py

@@ -122,6 +122,8 @@ def max_release_age(self) -> datetime.timedelta | None:
 
     def set_max_release_age(self, days: int) -> None:
         """Set the maximum release age in days."""
+        if days < 1:
+            raise ValueError(f"max_release_age must be positive, got {days}")
         self._max_release_age = datetime.timedelta(days=days)
 
     def enable_parallel_builds(self) -> None:

src/fromager/resolver.py

@@ -237,9 +237,15 @@ def find_all_matching_from_provider(
         provider: The provider to query for candidates.
         req: The requirement to match.
         max_age_cutoff: If set, reject candidates published before this time.
+            Raises ``ResolverException`` if all candidates are older than
+            the cutoff.
 
     Returns list of (url, version) tuples sorted by version (highest first).
 
+    Raises:
+        ResolverException: If ``max_age_cutoff`` is set and every candidate
+            is older than the cutoff.
+
     IMPORTANT: This bypasses resolvelib's full resolver to collect all matching
     candidates. This is safe ONLY because BaseProvider.get_dependencies() returns
     an empty list (no transitive dependencies to resolve). The empty incompatibilities
@@ -272,38 +278,35 @@ def find_all_matching_from_provider(
 
     # Materialize candidates so we can iterate more than once if filtering
     candidates_list = list(candidates)
-    logger.info(
-        "%s: found %d candidate(s) matching %s",
-        req.name,
-        len(candidates_list),
-        req,
-    )
 
     if max_age_cutoff is not None:
+        logger.info(
+            "%s: found %d candidate(s) matching %s",
+            req.name,
+            len(candidates_list),
+            req,
+        )
         max_age_days = (datetime.datetime.now(datetime.UTC) - max_age_cutoff).days
         filtered = [
             c
             for c in candidates_list
             if c.upload_time is None or c.upload_time >= max_age_cutoff
         ]
-        if filtered:
+        dropped = len(candidates_list) - len(filtered)
+        if dropped:
             logger.info(
                 "%s: have %d candidate(s) of %s published within %d days",
                 req.name,
                 len(filtered),
                 req,
                 max_age_days,
             )
-            candidates_list = filtered
-        else:
-            logger.warning(
-                "%s: all %d candidate(s) of %s are older than %d days, "
-                "keeping all to avoid empty resolution",
-                req.name,
-                len(candidates_list),
-                req,
-                max_age_days,
+        if not filtered:
+            raise resolvelib.resolvers.ResolverException(
+                f"all {len(candidates_list)} candidate(s) for {req} were "
+                f"published before the max-release-age cutoff"
             )
+        candidates_list = filtered
 
     # Convert candidates to list of (url, version) tuples
     # Candidates are sorted by version (highest first) by BaseProvider.find_matches()

tests/test_cooldown.py

@@ -759,10 +759,8 @@ def test_max_release_age_disabled_returns_all() -> None:
     assert "1.2.2" in versions
 
 
-def test_max_release_age_all_too_old_keeps_all(
-    caplog: pytest.LogCaptureFixture,
-) -> None:
-    """When all versions are older than cutoff, keep all to avoid empty resolution."""
+def test_max_release_age_all_too_old_raises() -> None:
+    """When all versions are older than cutoff, raise ResolverException."""
     max_age_cutoff = _BOOTSTRAP_TIME + datetime.timedelta(days=1)
     with requests_mock.Mocker() as r:
         r.get(
@@ -771,15 +769,14 @@ def test_max_release_age_all_too_old_keeps_all(
             headers={"Content-Type": _PYPI_SIMPLE_JSON_CONTENT_TYPE},
         )
         provider = resolver.PyPIProvider(include_sdists=True)
-        with caplog.at_level(logging.WARNING, logger="fromager.resolver"):
-            results = resolver.find_all_matching_from_provider(
+        with pytest.raises(
+            resolvelib.resolvers.ResolverException,
+            match=r"all 3 candidate.*max-release-age cutoff",
+        ):
+            resolver.find_all_matching_from_provider(
                 provider, Requirement("test-pkg"), max_age_cutoff=max_age_cutoff
             )
 
-    versions = [str(v) for _, v in results]
-    assert len(versions) == 3
-    assert "keeping all to avoid empty resolution" in caplog.text
-
 
 def test_max_release_age_candidates_without_upload_time_pass_through() -> None:
     """Candidates without upload_time are not filtered out by max-release-age."""