Do not create public alias for omitted top-level deps

Summary:
Previously, a workspace member fixup containing `omit_deps` would cause the dependency to be omitted as a dependency of the workspace member, and would **usually** also skip generating Rust library targets and `alias` for that dependency, effectively omitting it from the dependency graph.

Except in the case that some other transitive dependency path to that dependency existed, in which case Rust library targets would be produced (correct behavior) and as an unintended side effect a publi `alias` target would also be produced.

This diff fixes the unintended effect by making workspace member `omit_deps` cause `alias` targets to be omitted for that dependency. You will only get `alias` targets for things that are actually a dependency of some workspace member after taking into account `omit_deps` fixups, whether or not the thing is part of the transitive dependency graph somewhere.

Reviewed By: capickett

Differential Revision: D116041689

fbshipit-source-id: 9212d429b077a587255a5c35b857ca7f916082bb

Author: David Tolnay

src/index.rs

@@ -180,30 +180,22 @@ impl<'meta> Index<'meta> {
 
         // Compute public set, with pkgid mapped to rename if it has one. Public set is
         // anything in top_levels, or first-order dependencies of any workspace member.
-        index.public_targets = index
-            .workspace_members
-            .iter()
-            .flat_map(|member| &index.pkgid_to_node[&member.id].deps)
-            .flat_map(|node_dep| {
-                let pkg = &index.pkgid_to_pkg[&node_dep.pkg];
-                node_dep.dep_kinds.iter().map(|dep_kind| {
-                    let name = node_dep
-                        .name
-                        .as_deref()
-                        .or(dep_kind.extern_name.as_deref())
-                        .unwrap();
-                    let target_req = dep_kind.target_req();
-                    let opt_rename = dep_renamed.get(name).cloned();
-                    ((pkg.id, target_req), opt_rename)
-                })
-            })
-            .chain(top_levels.iter().flat_map(|&pkgid| {
-                [
-                    ((pkgid, TargetReq::Lib), None),
-                    ((pkgid, TargetReq::EveryBin), None),
-                ]
-            }))
-            .collect::<BTreeMap<_, _>>();
+        let mut public_targets = BTreeMap::new();
+        for platform_name in config.platform.keys() {
+            for member in &index.workspace_members {
+                for target in &member.targets {
+                    for dep in index.resolved_deps_for_target(member, target, platform_name) {
+                        let rename = dep_renamed.get(dep.rename).copied();
+                        public_targets.insert((dep.package.id, dep.dep_kind.target_req()), rename);
+                    }
+                }
+            }
+        }
+        if let Some(top_level) = top_levels {
+            public_targets.insert((top_level, TargetReq::Lib), None);
+            public_targets.insert((top_level, TargetReq::EveryBin), None);
+        }
+        index.public_targets = public_targets;
 
         for (&(id, _), &rename) in &index.public_targets {
             index.public_packages.insert(id, rename);