From 0db1bf4df7cfff67a28c813a130945ee95356a18 Mon Sep 17 00:00:00 2001
From: Charlie Marsh <charlie.r.marsh@gmail.com>
Date: Fri, 7 Jun 2024 15:05:14 -0700
Subject: [PATCH] Avoid pre-fetching for unbounded minimum versions (#4149)

## Summary

I think we should be able to model PubGrub such that this isn't
necessary (at least for the case described in the issue), but for now,
let's just avoid attempting to build very old distributions in
prefetching.

Closes https://github.com/astral-sh/uv/issues/4136.
---
 crates/uv-resolver/src/resolver/batch_prefetch.rs |  3 ++-
 crates/uv-resolver/src/resolver/mod.rs            | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/crates/uv-resolver/src/resolver/batch_prefetch.rs b/crates/uv-resolver/src/resolver/batch_prefetch.rs
index 0368caba7..dce938e3e 100644
--- a/crates/uv-resolver/src/resolver/batch_prefetch.rs
+++ b/crates/uv-resolver/src/resolver/batch_prefetch.rs
@@ -132,7 +132,8 @@ impl BatchPrefetcher {
             let CandidateDist::Compatible(dist) = candidate.dist() else {
                 continue;
             };
-            // Avoid building a lot of source distributions.
+
+            // Avoid prefetching source distributions, which could be expensive.
             if !dist.prefetchable() {
                 continue;
             }
diff --git a/crates/uv-resolver/src/resolver/mod.rs b/crates/uv-resolver/src/resolver/mod.rs
index ece717239..80bd0d4f3 100644
--- a/crates/uv-resolver/src/resolver/mod.rs
+++ b/crates/uv-resolver/src/resolver/mod.rs
@@ -3,6 +3,7 @@
 use std::borrow::Cow;
 use std::collections::BTreeMap;
 use std::fmt::{Display, Formatter};
+use std::ops::Bound;
 use std::sync::Arc;
 use std::thread;
 
@@ -1402,6 +1403,20 @@ impl<InstalledPackages: InstalledPackagesProvider> ResolverState<InstalledPackag
                     return Ok(None);
                 };
 
+                // Avoid prefetching source distributions with unbounded lower-bound ranges. This
+                // often leads to failed attempts to build legacy versions of packages that are
+                // incompatible with modern build tools.
+                if !dist.prefetchable() {
+                    if !self.selector.use_highest_version(&package_name) {
+                        if let Some((lower, _)) = range.iter().next() {
+                            if lower == &Bound::Unbounded {
+                                debug!("Skipping prefetch for unbounded minimum-version range: {package_name} ({range})");
+                                return Ok(None);
+                            }
+                        }
+                    }
+                }
+
                 // Emit a request to fetch the metadata for this version.
                 if self.index.distributions().register(candidate.version_id()) {
                     let dist = dist.for_resolution().to_owned();