fix(generate-lockfile): hold lock before querying index

src/cargo/ops/cargo_generate_lockfile.rs

@@ -166,12 +166,17 @@ pub fn update_lockfile(ws: &Workspace<'_>, opts: &UpdateOptions<'_>) -> CargoRes
     Ok(())
 }
 
+/// Prints lockfile change statuses.
+///
+/// This would acquire the package-cache lock, as it may update the index to
+/// show users latest available versions.
 pub fn print_lockfile_changes(
     gctx: &GlobalContext,
     previous_resolve: Option<&Resolve>,
     resolve: &Resolve,
     registry: &mut PackageRegistry<'_>,
 ) -> CargoResult<()> {
+    let _lock = gctx.acquire_package_cache_lock(CacheLockMode::DownloadExclusive)?;
     if let Some(previous_resolve) = previous_resolve {
         print_lockfile_sync(gctx, previous_resolve, resolve, registry)
     } else {

src/cargo/ops/resolve.rs

@@ -256,11 +256,6 @@ fn resolve_with_registry<'gctx>(
         false
     };
     if print {
-        // We only want one Cargo at a time resolving a crate graph since this can
-        // involve a lot of frobbing of the global caches.
-        let _lock = ws
-            .gctx()
-            .acquire_package_cache_lock(CacheLockMode::DownloadExclusive)?;
         ops::print_lockfile_changes(ws.gctx(), prev.as_ref(), &resolve, registry)?;
     }
     Ok(resolve)

tests/testsuite/generate_lockfile.rs

@@ -266,11 +266,9 @@ fn generate_lockfile_holds_lock_and_offline() {
         .run();
 
     p.cargo("generate-lockfile --offline")
-        .with_status(101)
         .with_stderr_contains(
             "\
-[..]thread 'main' panicked[..]
+[LOCKING] 2 packages
-[..]package cache lock is not currently held[..]
 ",
         )
         .run();