Box cached client callbacks and CachePolicy

Looking through the stack trace of `allowed_transitive_url_dependency` with a 800KB stack, i found those two to be the major offenders. These changes make `allowed_transitive_url_dependency` pass with a 800KB stack.

crates/puffin-client/src/cached_client.rs

@@ -43,14 +43,15 @@ enum CachedResponse<Payload: Serialize> {
     /// There was no prior cached response or the cache was outdated
     ///
     /// The cache policy is `None` if it isn't storable
-    ModifiedOrNew(Response, Option<CachePolicy>),
+    ModifiedOrNew(Response, Option<Box<CachePolicy>>),
 }
 
 /// Serialize the actual payload together with its caching information
 #[derive(Debug, Deserialize, Serialize)]
 pub struct DataWithCachePolicy<Payload: Serialize> {
     pub data: Payload,
-    cache_policy: CachePolicy,
+    // The cache policy is large (448 bytes at time of writing), reduce the stack size
+    cache_policy: Box<CachePolicy>,
 }
 
 /// Custom caching layer over [`reqwest::Client`] using `http-cache-semantics`.
@@ -232,14 +233,14 @@ impl CachedClient {
                             debug!("Found not-modified response for: {url}");
                             CachedResponse::NotModified(DataWithCachePolicy {
                                 data: cached.data,
-                                cache_policy: new_policy,
+                                cache_policy: Box::new(new_policy),
                             })
                         }
                         AfterResponse::Modified(new_policy, _parts) => {
                             debug!("Found modified response for: {url}");
                             CachedResponse::ModifiedOrNew(
                                 res,
-                                new_policy.is_storable().then_some(new_policy),
+                                new_policy.is_storable().then(|| Box::new(new_policy)),
                             )
                         }
                     }
@@ -272,7 +273,7 @@ impl CachedClient {
             CachePolicy::new(&converted_req.into_parts().0, &converted_res.into_parts().0);
         Ok(CachedResponse::ModifiedOrNew(
             res,
-            cache_policy.is_storable().then_some(cache_policy),
+            cache_policy.is_storable().then(|| Box::new(cache_policy)),
         ))
     }
 }

crates/puffin-client/src/flat_index.rs

@@ -2,7 +2,7 @@ use std::collections::btree_map::Entry;
 use std::collections::BTreeMap;
 use std::path::PathBuf;
 
-use futures::StreamExt;
+use futures::{FutureExt, StreamExt};
 use reqwest::Response;
 use rustc_hash::FxHashMap;
 use tracing::{debug, info_span, instrument, warn, Instrument};
@@ -121,6 +121,7 @@ impl<'a> FlatIndexClient<'a> {
                     .collect();
                 Ok(files)
             }
+            .boxed()
             .instrument(info_span!("parse_flat_index_html", url = % url))
         };
         let files = cached_client

crates/puffin-client/src/registry_client.rs

@@ -5,7 +5,7 @@ use std::str::FromStr;
 
 use async_http_range_reader::{AsyncHttpRangeReader, AsyncHttpRangeReaderError};
 use async_zip::tokio::read::seek::ZipFileReader;
-use futures::TryStreamExt;
+use futures::{FutureExt, TryStreamExt};
 use reqwest::{Client, ClientBuilder, Response, StatusCode};
 use reqwest_retry::policies::ExponentialBackoff;
 use reqwest_retry::RetryTransientMiddleware;
@@ -206,6 +206,7 @@ impl RegistryClient {
                     }
                 }
             }
+            .boxed()
             .instrument(info_span!("parse_simple_api", package = %package_name))
         };
         let result = self
@@ -335,6 +336,7 @@ impl RegistryClient {
                 })?;
                 Ok(metadata)
             }
+            .boxed()
             .instrument(info_span!("read_metadata_range_request", wheel = %filename))
         };