Warn when trying many versions

In pathological cases, it's hard to follow why the resolution is slow. This is an attempt to give the user an indication what is slow (boto3) and how to fix this (add a manual boto3 constraint). This also helps to determine if this is a pathological case or a server that doesn't support range requests.

The values i picked are somewhat arbitrary.

```
$ uv pip install bio_embeddings
  ⠸ pytest==8.0.2
warning: Downloading metadata for more than 50 different versions of boto3. Consider adding a stricter version constraint for this package to speed up resolution.
  warning: Downloading metadata for more than 50 different versions of botocore. Consider adding a stricter version constraint for this package to speed up resolution.
  ⠼ boto3==1.26.85
```

`warn_user!` interacts badly with the `Reporter`, do we have a way to pause-and-restart the restart the reporter when showing our own messages, similar to tqdm or `IndicatifLayer`?

Cargo.lock

@@ -4420,6 +4420,7 @@ dependencies = [
  "uv-git",
  "uv-normalize",
  "uv-traits",
+ "uv-warnings",
  "zip",
 ]
 

crates/uv-distribution/Cargo.toml

@@ -18,7 +18,7 @@ distribution-filename = { path = "../distribution-filename", features = ["serde"
 distribution-types = { path = "../distribution-types" }
 install-wheel-rs = { path = "../install-wheel-rs" }
 pep440_rs = { path = "../pep440-rs" }
-pep508_rs = { path =     "../pep508-rs" }
+pep508_rs = { path = "../pep508-rs" }
 platform-tags = { path = "../platform-tags" }
 uv-cache = { path = "../uv-cache" }
 uv-client = { path = "../uv-client" }
@@ -27,6 +27,7 @@ uv-fs = { path = "../uv-fs", features = ["tokio"] }
 uv-git = { path = "../uv-git", features = ["vendored-openssl"] }
 uv-normalize = { path = "../uv-normalize" }
 uv-traits = { path = "../uv-traits" }
+uv-warnings = { path = "../uv-warnings" }
 pypi-types = { path = "../pypi-types" }
 
 anyhow = { workspace = true }
@@ -36,7 +37,7 @@ nanoid = { workspace = true }
 reqwest = { workspace = true }
 rmp-serde = { workspace = true }
 rustc-hash = { workspace = true }
-serde = { workspace = true , features = ["derive"] }
+serde = { workspace = true, features = ["derive"] }
 tempfile = { workspace = true }
 thiserror = { workspace = true }
 tokio = { workspace = true }

crates/uv-distribution/src/distribution_database.rs

@@ -4,6 +4,8 @@ use std::path::Path;
 use std::sync::Arc;
 
 use futures::{FutureExt, TryStreamExt};
+use rustc_hash::FxHashMap;
+use tokio::sync::Mutex;
 use tokio_util::compat::FuturesAsyncReadCompatExt;
 use tracing::{info_span, instrument, Instrument};
 use url::Url;
@@ -17,13 +19,20 @@ use uv_cache::{Cache, CacheBucket, Timestamp, WheelCache};
 use uv_client::{CacheControl, CachedClientError, Connectivity, RegistryClient};
 use uv_fs::metadata_if_exists;
 use uv_git::GitSource;
+use uv_normalize::PackageName;
 use uv_traits::{BuildContext, NoBinary, NoBuild};
+use uv_warnings::warn_user;
 
 use crate::download::{BuiltWheel, UnzippedWheel};
 use crate::locks::Locks;
 use crate::reporter::Facade;
 use crate::{DiskWheel, Error, LocalWheel, Reporter, SourceDistCachedBuilder};
 
+/// Warn when more than this many versions were requested for a single package.
+const METADATA_REQUEST_WARN_THRESHOLD: usize = 50;
+/// Warn when more than this many source dist build were requested for a single package.
+const BUILD_REQUEST_WARN_THRESHOLD: usize = 5;
+
 /// A cached high-level interface to convert distributions (a requirement resolved to a location)
 /// to a wheel or wheel metadata.
 ///
@@ -41,6 +50,8 @@ pub struct DistributionDatabase<'a, Context: BuildContext + Send + Sync> {
     reporter: Option<Arc<dyn Reporter>>,
     locks: Arc<Locks>,
     client: &'a RegistryClient,
+    metadata_request_counts: Mutex<FxHashMap<PackageName, usize>>,
+    build_request_counts: Mutex<FxHashMap<PackageName, usize>>,
     build_context: &'a Context,
     builder: SourceDistCachedBuilder<'a, Context>,
 }
@@ -57,6 +68,8 @@ impl<'a, Context: BuildContext + Send + Sync> DistributionDatabase<'a, Context>
             reporter: None,
             locks: Arc::new(Locks::default()),
             client,
+            metadata_request_counts: Mutex::new(FxHashMap::default()),
+            build_request_counts: Mutex::new(FxHashMap::default()),
             build_context,
             builder: SourceDistCachedBuilder::new(build_context, client, tags),
         }
@@ -358,6 +371,20 @@ impl<'a, Context: BuildContext + Send + Sync> DistributionDatabase<'a, Context>
     ) -> Result<(Metadata21, Option<Url>), Error> {
         match dist {
             Dist::Built(built_dist) => {
+                let count: usize = *self
+                    .metadata_request_counts
+                    .lock()
+                    .await
+                    .entry(built_dist.name().clone())
+                    .and_modify(|count| *count += 1)
+                    .or_insert(1);
+                if count == METADATA_REQUEST_WARN_THRESHOLD {
+                    warn_user!(
+                        "Downloading metadata for more than {METADATA_REQUEST_WARN_THRESHOLD} different versions of {}. \
+                        Consider adding a stricter version constraint for this package to speed up resolution.",
+                        built_dist.name()
+                    );
+                }
                 Ok((self.client.wheel_metadata(built_dist).boxed().await?, None))
             }
             Dist::Source(source_dist) => {
@@ -371,6 +398,21 @@ impl<'a, Context: BuildContext + Send + Sync> DistributionDatabase<'a, Context>
                     return Err(Error::NoBuild);
                 }
 
+                let count: usize = *self
+                    .build_request_counts
+                    .lock()
+                    .await
+                    .entry(source_dist.name().clone())
+                    .and_modify(|count| *count += 1)
+                    .or_insert(1);
+                if count == BUILD_REQUEST_WARN_THRESHOLD {
+                    warn_user!(
+                        "Building more than {METADATA_REQUEST_WARN_THRESHOLD} source distribution versions of {}. \
+                        Consider adding a stricter version constraint for this package to speed up resolution.",
+                        source_dist.name()
+                    );
+                }
+
                 let lock = self.locks.acquire(dist).await;
                 let _guard = lock.lock().await;