refactor: eliminate duplicated wheel server retry loop

BootstrapRequirementResolver._resolve() and wheels.resolve_prebuilt_wheel()
both implemented the "try each wheel server until one succeeds" pattern with
different error handling:
- Bootstrap path caught narrow exceptions (ResolverException | NoSuchProjectError)
  and raised ValueError with no exception details
- Wheel path caught broad Exception and raised ExceptionGroup with collected errors

This inconsistency meant:
- Different exception types were swallowed in different code paths
- Bootstrap path lost exception details (no ExceptionGroup)
- Callers couldn't distinguish failure types

Solution:
- Created resolve_all_prebuilt_wheels() that returns all matching versions
- Made resolve_prebuilt_wheel() call it and return first result
- Made bootstrap resolver use resolve_all_prebuilt_wheels()
- Now both code paths use consistent ExceptionGroup-based error handling

Benefits:
- Single source of truth for wheel server retry logic
- Consistent exception handling across all resolution paths
- Better error reporting with ExceptionGroup containing details from all servers
- Reduces code duplication by ~20 lines

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: Rohan Devasthale <rdevasth@redhat.com>

Author: rd4398

src/fromager/bootstrap_requirement_resolver.py

@@ -9,8 +9,6 @@
 import logging
 import typing
 
-import pypi_simple.errors
-import resolvelib.resolvers
 from packaging.requirements import Requirement
 from packaging.version import Version
 
@@ -155,27 +153,12 @@ def _resolve(
             wheel_server_urls = wheels.get_wheel_server_urls(
                 self.ctx, req, cache_wheel_server_url=resolver.PYPI_SERVER_URL
             )
-
-            # Try each wheel server until one succeeds
-            for url in wheel_server_urls:
-                try:
-                    provider = wheels.get_prebuilt_wheel_provider(
-                        ctx=self.ctx, req=req, wheel_server_url=url, req_type=req_type
-                    )
-                    results = resolver.find_all_matching_from_provider(provider, req)
-                    # find_all_matching_from_provider never returns empty list - raises instead
-                    return results
-                except (
-                    resolvelib.resolvers.ResolverException,
-                    pypi_simple.errors.NoSuchProjectError,
-                ) as e:
-                    # Only catch expected "not found" exceptions - try next server
-                    # Let auth failures, network errors, and plugin bugs propagate
-                    logger.debug(f"{req.name}: no matching wheel on {url}: {e}")
-                    continue
-            # If we get here, no wheel server succeeded
-            raise ValueError(
-                f"Could not find a prebuilt wheel for {req} on {' or '.join(wheel_server_urls)}"
+            # Use shared retry loop logic from wheels module
+            return wheels.resolve_all_prebuilt_wheels(
+                ctx=self.ctx,
+                req=req,
+                wheel_server_urls=wheel_server_urls,
+                req_type=req_type,
             )
         else:
             # Resolve source (sdist)

src/fromager/wheels.py

@@ -485,18 +485,19 @@ def get_prebuilt_wheel_provider(
     )
 
 
-@metrics.timeit(description="resolve wheel")
-def resolve_prebuilt_wheel(
+def resolve_all_prebuilt_wheels(
     *,
     ctx: context.WorkContext,
     req: Requirement,
     wheel_server_urls: list[str],
     req_type: requirements_file.RequirementType | None = None,
-) -> tuple[str, Version]:
-    """Return (URL, version) for the best matching wheel version.
+) -> list[tuple[str, Version]]:
+    """Return all matching wheel versions from the first successful server.
 
-    Tries wheel servers in order and returns result from the first that succeeds.
-    Returns the highest matching version.
+    Tries wheel servers in order and returns all matching versions from the
+    first server that has any matches. Results are sorted by version (highest first).
+
+    Raises ExceptionGroup if no server has matching wheels.
     """
     excs: list[Exception] = []
     for url in wheel_server_urls:
@@ -509,13 +510,32 @@ def resolve_prebuilt_wheel(
             # Get all matching candidates from provider
             results = resolver.find_all_matching_from_provider(provider, req)
             # find_all_matching_from_provider never returns empty list - raises instead
-            # Return highest version (first in sorted list)
-            wheel_url, version = results[0]
-            return str(wheel_url), version
+            return results
         except Exception as e:
             excs.append(e)
 
     raise ExceptionGroup(
         f"Could not find a prebuilt wheel for {req} on {' or '.join(wheel_server_urls)}",
         excs,
     )
+
+
+@metrics.timeit(description="resolve wheel")
+def resolve_prebuilt_wheel(
+    *,
+    ctx: context.WorkContext,
+    req: Requirement,
+    wheel_server_urls: list[str],
+    req_type: requirements_file.RequirementType | None = None,
+) -> tuple[str, Version]:
+    """Return (URL, version) for the best matching wheel version.
+
+    Tries wheel servers in order and returns result from the first that succeeds.
+    Returns the highest matching version.
+    """
+    results = resolve_all_prebuilt_wheels(
+        ctx=ctx, req=req, wheel_server_urls=wheel_server_urls, req_type=req_type
+    )
+    # Return highest version (first in sorted list)
+    wheel_url, version = results[0]
+    return str(wheel_url), version