Fixes to allowing missing file / folders for cached artifacts during build, correcting an issue described here: rust-lang#57958

Author: x46085

src/librustc_incremental/persist/fs.rs

@@ -927,7 +927,10 @@ fn all_except_most_recent(
 fn safe_remove_dir_all(p: &Path) -> io::Result<()> {
     if p.exists() {
         let canonicalized = p.canonicalize()?;
-        std_fs::remove_dir_all(canonicalized)
+        match std_fs::remove_dir_all(canonicalized) {
+            Err(ref err) if err.kind() == io::ErrorKind::NotFound => Ok(()),
+            result => result,
+        }
     } else {
         Ok(())
     }

src/librustc_incremental/persist/load.rs

@@ -39,8 +39,7 @@ impl LoadResult<(PreviousDepGraph, WorkProductMap)> {
             }
             LoadResult::DataOutOfDate => {
                 if let Err(err) = delete_all_session_dir_contents(sess) {
-                    sess.err(&format!(
-                        "Failed to delete invalidated or incompatible \
+                    sess.warn(&format!("Failed to delete invalidated or incompatible \
                                       incremental compilation session directory contents `{}`: {}.",
                         dep_graph_path(sess).display(),
                         err

src/librustc_incremental/persist/save.rs

@@ -119,6 +119,22 @@ where
         }
     }
 
+    let folder_path = path_buf.parent().unwrap();
+
+    if !folder_path.exists() {
+        match fs::create_dir_all(&folder_path) {
+            Ok(()) => {
+                debug!("save: created new dep-graph folder");
+            }
+            Err(err) => {
+                sess.warn(&format!("failed to create missing directory for dep-graph `{}`: {}",
+                                   path_buf.display(),
+                                   err));
+                return;
+            }
+        }
+    }
+
     // generate the data in a memory buffer
     let mut encoder = Encoder::new(Vec::new());
     file_format::write_file_header(&mut encoder);