mv: manages the 'seen' file list before moving

Should help with tests/mv/childproof.sh

src/uu/mv/src/mv.rs

@@ -10,6 +10,7 @@ mod error;
 use clap::builder::ValueParser;
 use clap::{crate_version, error::ErrorKind, Arg, ArgAction, ArgMatches, Command};
 use indicatif::{MultiProgress, ProgressBar, ProgressStyle};
+use std::collections::HashSet;
 use std::env;
 use std::ffi::OsString;
 use std::fs;
@@ -434,6 +435,9 @@ pub fn mv(files: &[OsString], opts: &Options) -> UResult<()> {
 
 #[allow(clippy::cognitive_complexity)]
 fn move_files_into_dir(files: &[PathBuf], target_dir: &Path, opts: &Options) -> UResult<()> {
+    // remember the moved destinations for further usage
+    let mut moved_destinations: HashSet<PathBuf> = HashSet::with_capacity(files.len());
+
     if !target_dir.is_dir() {
         return Err(MvError::NotADirectory(target_dir.quote().to_string()).into());
     }
@@ -471,6 +475,18 @@ fn move_files_into_dir(files: &[PathBuf], target_dir: &Path, opts: &Options) ->
             }
         };
 
+        if moved_destinations.contains(&targetpath) && opts.backup != BackupMode::NumberedBackup {
+            // If the target file was already created in this mv call, do not overwrite
+            return Err(USimpleError::new(
+                1,
+                format!(
+                    "will not overwrite just-created '{}' with '{}'",
+                    targetpath.display(),
+                    sourcepath.display()
+                ),
+            ));
+        }
+
         // Check if we have mv dir1 dir2 dir2
         // And generate an error if this is the case
         if let Ok(canonicalized_source) = sourcepath.canonicalize() {
@@ -513,6 +529,7 @@ fn move_files_into_dir(files: &[PathBuf], target_dir: &Path, opts: &Options) ->
         if let Some(ref pb) = count_progress {
             pb.inc(1);
         }
+        moved_destinations.insert(targetpath.clone());
     }
     Ok(())
 }

tests/by-util/test_mv.rs

@@ -1469,6 +1469,32 @@ fn test_mv_file_into_dir_where_both_are_files() {
         .stderr_contains("mv: failed to access 'b/': Not a directory");
 }
 
+#[test]
+fn test_mv_seen_file() {
+    let ts = TestScenario::new(util_name!());
+    let at = &ts.fixtures;
+
+    at.mkdir("a");
+    at.mkdir("b");
+    at.mkdir("c");
+    at.write("a/f", "a");
+    at.write("b/f", "b");
+
+    ts.ucmd()
+        .arg("a/f")
+        .arg("b/f")
+        .arg("c")
+        .fails()
+        .stderr_contains("will not overwrite just-created 'c/f' with 'b/f'");
+
+    // a/f has been moved into c/f
+    assert!(at.plus("c").join("f").exists());
+    // b/f still exists
+    assert!(at.plus("b").join("f").exists());
+    // a/f no longer exists
+    assert!(!at.plus("a").join("f").exists());
+}
+
 #[test]
 fn test_mv_dir_into_file_where_both_are_files() {
     let scene = TestScenario::new(util_name!());