fix(bootstrap): don't call get_resolver_provider hook in cache lookups

src/fromager/bootstrapper.py

@@ -1100,13 +1100,17 @@ def _download_wheel_from_cache(
             f"checking if wheel was already uploaded to {self.cache_wheel_server_url}"
         )
         try:
-            wheel_url, _ = resolver.resolve(
-                ctx=self.ctx,
-                req=Requirement(f"{req.name}=={resolved_version}"),
+            # Use PyPIProvider directly for cache lookups, bypassing resolver
+            # hooks. Cache servers are always simple PyPI index servers.
+            pinned_req = Requirement(f"{req.name}=={resolved_version}")
+            provider = resolver.PyPIProvider(
                 sdist_server_url=self.cache_wheel_server_url,
                 include_sdists=False,
                 include_wheels=True,
+                constraints=self.ctx.constraints,
             )
+            results = resolver.find_all_matching_from_provider(provider, pinned_req)
+            wheel_url, _ = results[0]
             wheelfile_name = pathlib.Path(urlparse(wheel_url).path)
             pbi = self.ctx.package_build_info(req)
             expected_build_tag = pbi.build_tag(resolved_version)

tests/test_bootstrapper.py

@@ -370,3 +370,41 @@ def mock_bootstrap_impl(
                     success_key_10 = f"{canonicalize_name('testpkg')}==1.0"
                     assert success_key_20 in tmp_context.dependency_graph.nodes
                     assert success_key_10 in tmp_context.dependency_graph.nodes
+
+
+@patch("fromager.resolver.find_all_matching_from_provider")
+@patch("fromager.resolver.PyPIProvider")
+def test_download_wheel_from_cache_bypasses_hooks(
+    mock_pypi_provider: Mock,
+    mock_find_all: Mock,
+    tmp_context: WorkContext,
+) -> None:
+    """Verify _download_wheel_from_cache uses PyPIProvider directly, not hooks."""
+    bt = bootstrapper.Bootstrapper(tmp_context)
+    bt.cache_wheel_server_url = "https://cache.example.com/simple/"
+
+    mock_provider = Mock()
+    mock_pypi_provider.return_value = mock_provider
+    # Raise so the except clause returns (None, None) before hitting
+    # network calls later in the function.
+    mock_find_all.side_effect = RuntimeError("no match")
+
+    with patch("fromager.overrides.find_and_invoke") as mock_override:
+        result = bt._download_wheel_from_cache(
+            req=Requirement("test-pkg"),
+            resolved_version=Version("1.0.0"),
+        )
+
+    assert result == (None, None)
+
+    # Hook system must NOT be called for cache lookups
+    mock_override.assert_not_called()
+
+    # PyPIProvider must be instantiated directly
+    mock_pypi_provider.assert_called_once_with(
+        sdist_server_url="https://cache.example.com/simple/",
+        include_sdists=False,
+        include_wheels=True,
+        constraints=tmp_context.constraints,
+    )
+    mock_find_all.assert_called_once_with(mock_provider, Requirement("test-pkg==1.0.0"))