Remove unnecessary second download phase

Author: Jon Gjengset

src/cargo/core/package.rs

@@ -434,6 +434,10 @@ impl<'cfg> PackageSet<'cfg> {
         self.packages.keys().cloned()
     }
 
+    pub fn packages<'a>(&'a self) -> impl Iterator<Item = &'a Package> + 'a {
+        self.packages.values().filter_map(|p| p.borrow())
+    }
+
     pub fn enable_download<'a>(&'a self) -> CargoResult<Downloads<'a, 'cfg>> {
         assert!(!self.downloading.replace(true));
         let timeout = ops::HttpTimeout::new(self.config)?;

src/cargo/ops/cargo_output_metadata.rs

@@ -126,6 +126,9 @@ fn build_resolve_graph(
     } else {
         crate::core::resolver::features::ForceAllTargets::No
     };
+
+    // Note that even with --filter-platform we end up downloading host dependencies as well,
+    // as that is the behavior of download_accessible.
     let ws_resolve = ops::resolve_ws_with_opts(
         ws,
         &target_data,
@@ -136,23 +139,9 @@ fn build_resolve_graph(
         force_all,
     )?;
 
-    // Download all Packages. This is needed to serialize the information for every package.
-    // Note that even with --filter-platform we end up downloading host dependencies as well,
-    // as that is the behavior of download_accessible.
     let package_map: BTreeMap<PackageId, Package> = ws_resolve
         .pkg_set
-        .download_accessible(
-            &ws_resolve.targeted_resolve,
-            &ws.members_with_features(&specs, &requested_features)?
-                .into_iter()
-                .map(|(p, _)| p.package_id())
-                .collect::<Vec<_>>(),
-            HasDevUnits::Yes,
-            &requested_kinds,
-            &target_data,
-            force_all,
-        )?
-        .into_iter()
+        .packages()
         // This is a little lazy, but serde doesn't handle Rc fields very well.
         .map(|pkg| (pkg.package_id(), Package::clone(pkg)))
         .collect();

src/cargo/ops/tree/mod.rs

@@ -167,23 +167,9 @@ pub fn build_and_print(ws: &Workspace<'_>, opts: &TreeOptions) -> CargoResult<()
         force_all,
     )?;
 
-    // Download all Packages. Some display formats need to display package metadata.
-    // This may trigger some unnecessary downloads, but trying to figure out a
-    // minimal set would be difficult.
     let package_map: HashMap<PackageId, &Package> = ws_resolve
         .pkg_set
-        .download_accessible(
-            &ws_resolve.targeted_resolve,
-            &ws.members_with_features(&specs, &requested_features)?
-                .into_iter()
-                .map(|(p, _)| p.package_id())
-                .collect::<Vec<_>>(),
-            has_dev,
-            &requested_kinds,
-            &target_data,
-            force_all,
-        )?
-        .into_iter()
+        .packages()
         .map(|pkg| (pkg.package_id(), pkg))
         .collect();