fix(vendor): dont remove non-cached source

cargo-vendor has a workaround that to mitigate #5956,
it removes all cached sources in order to trigger a re-unpack.
It was meant for dealing with registry sources only, but accidentally
applied to directory source kind.

While directory source kind was invented for vendoring,
and vendoring from one vendored directory to the other seems unusual,
Cargo IMO should not delete any real sources.

It does not mean that registry sources are okay to delete,
In long term, we should explore a way that unpacks `.crate` files
directly, without any removal. See
#12509 (comment)

Author: weihanglo

src/bin/cargo/commands/vendor.rs

@@ -60,7 +60,8 @@ pub fn exec(gctx: &mut GlobalContext, args: &ArgMatches) -> CliResult {
     // to respect any of the `source` configuration in Cargo itself. That's
     // intended for other consumers of Cargo, but we want to go straight to the
     // source, e.g. crates.io, to fetch crates.
-    if !args.flag("respect-source-config") {
+    let respect_source_config = args.flag("respect-source-config");
+    if !respect_source_config {
         gctx.values_mut()?.remove("source");
     }
 
@@ -80,6 +81,7 @@ pub fn exec(gctx: &mut GlobalContext, args: &ArgMatches) -> CliResult {
                 .unwrap_or_default()
                 .cloned()
                 .collect(),
+            respect_source_config,
         },
     )?;
     Ok(())

src/cargo/ops/vendor.rs

@@ -1,8 +1,10 @@
 use crate::core::shell::Verbosity;
+use crate::core::SourceId;
 use crate::core::{GitReference, Package, Workspace};
 use crate::ops;
 use crate::sources::path::PathSource;
 use crate::sources::PathEntry;
+use crate::sources::SourceConfigMap;
 use crate::sources::CRATES_IO_REGISTRY;
 use crate::util::cache_lock::CacheLockMode;
 use crate::util::{try_canonicalize, CargoResult, GlobalContext};
@@ -21,6 +23,7 @@ pub struct VendorOptions<'a> {
     pub versioned_dirs: bool,
     pub destination: &'a Path,
     pub extra: Vec<PathBuf>,
+    pub respect_source_config: bool,
 }
 
 pub fn vendor(ws: &Workspace<'_>, opts: &VendorOptions<'_>) -> CargoResult<()> {
@@ -76,6 +79,32 @@ enum VendorSource {
     },
 }
 
+/// Cache for mapping replaced sources to replacements.
+struct SourceReplacementCache<'gctx> {
+    map: SourceConfigMap<'gctx>,
+    cache: HashMap<SourceId, SourceId>,
+}
+
+impl SourceReplacementCache<'_> {
+    fn new(gctx: &GlobalContext) -> CargoResult<SourceReplacementCache<'_>> {
+        Ok(SourceReplacementCache {
+            map: SourceConfigMap::new(gctx)?,
+            cache: Default::default(),
+        })
+    }
+
+    fn get(&mut self, id: SourceId) -> CargoResult<SourceId> {
+        use std::collections::hash_map::Entry;
+        match self.cache.entry(id) {
+            Entry::Occupied(e) => Ok(e.get().clone()),
+            Entry::Vacant(e) => {
+                let replaced = self.map.load(id, &HashSet::new())?.replaced_source_id();
+                Ok(e.insert(replaced).clone())
+            }
+        }
+    }
+}
+
 fn sync(
     gctx: &GlobalContext,
     workspaces: &[&Workspace<'_>],
@@ -101,6 +130,8 @@ fn sync(
         }
     }
 
+    let mut source_replacement_cache = SourceReplacementCache::new(gctx)?;
+
     // First up attempt to work around rust-lang/cargo#5956. Apparently build
     // artifacts sprout up in Cargo's global cache for whatever reason, although
     // it's unsure what tool is causing these issues at this time. For now we
@@ -121,20 +152,31 @@ fn sync(
             .context("failed to download packages")?;
 
         for pkg in resolve.iter() {
+            let sid = if opts.respect_source_config {
+                source_replacement_cache.get(pkg.source_id())?
+            } else {
+                pkg.source_id()
+            };
+
             // Don't delete actual source code!
-            if pkg.source_id().is_path() {
-                if let Ok(path) = pkg.source_id().url().to_file_path() {
+            if sid.is_path() {
+                if let Ok(path) = sid.url().to_file_path() {
                     if let Ok(path) = try_canonicalize(path) {
                         to_remove.remove(&path);
                     }
                 }
                 continue;
             }
-            if pkg.source_id().is_git() {
+            if sid.is_git() {
                 continue;
             }
-            if let Ok(pkg) = packages.get_one(pkg) {
-                drop(fs::remove_dir_all(pkg.root()));
+
+            // Only delete sources that are safe to delete, i.e. they are caches.
+            if sid.is_registry() {
+                if let Ok(pkg) = packages.get_one(pkg) {
+                    drop(fs::remove_dir_all(pkg.root()));
+                }
+                continue;
             }
         }
     }

tests/testsuite/vendor.rs

@@ -1965,17 +1965,18 @@ fn dont_delete_non_registry_sources_with_respect_source_config() {
 
     add_crates_io_vendor_config(&p);
     p.cargo("vendor --respect-source-config new-vendor-dir")
-        .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] failed to sync
+   Vendoring log v0.3.5 ([ROOT]/foo/vendor/log) to new-vendor-dir/log
+To use vendored sources, add this to your .cargo/config.toml for this project:
 
-Caused by:
-  failed to load pkg lockfile
 
-Caused by:
-  no matching package named `log` found
-  location searched: directory source `[ROOT]/foo/vendor` (which is replacing registry `crates-io`)
-  required by package `foo v0.1.0 ([ROOT]/foo)`
+"#]])
+        .with_stdout_data(str![[r#"
+[source.crates-io]
+replace-with = "vendored-sources"
+
+[source.vendored-sources]
+directory = "new-vendor-dir"
 
 "#]])
         .run();