1 files changed, 24 insertions, 1 deletions
diff --git a/helix-view/src/document.rs b/helix-view/src/document.rs
index 798b5400..d308d013 100644
--- a/helix-view/src/document.rs
+++ b/helix-view/src/document.rs
@@ -19,6 +19,7 @@ use std::future::Future;
 use std::path::{Path, PathBuf};
 use std::str::FromStr;
 use std::sync::Arc;
+use std::time::SystemTime;
 
 use helix_core::{
     encoding,
@@ -135,6 +136,10 @@ pub struct Document {
 
     pub savepoint: Option<Transaction>,
 
+    // Last time we wrote to the file. This will carry the time the file was last opened if there
+    // were no saves.
+    last_saved_time: SystemTime,
+
     last_saved_revision: usize,
     version: i32, // should be usize?
     pub(crate) modified_since_accessed: bool,
@@ -160,6 +165,7 @@ impl fmt::Debug for Document {
             .field("changes", &self.changes)
             .field("old_state", &self.old_state)
             // .field("history", &self.history)
+            .field("last_saved_time", &self.last_saved_time)
             .field("last_saved_revision", &self.last_saved_revision)
             .field("version", &self.version)
             .field("modified_since_accessed", &self.modified_since_accessed)
@@ -382,6 +388,7 @@ impl Document {
             version: 0,
             history: Cell::new(History::default()),
             savepoint: None,
+            last_saved_time: SystemTime::now(),
             last_saved_revision: 0,
             modified_since_accessed: false,
             language_server: None,
@@ -577,9 +584,11 @@ impl Document {
 
         let encoding = self.encoding;
 
+        let last_saved_time = self.last_saved_time;
+
         // We encode the file according to the `Document`'s encoding.
         let future = async move {
-            use tokio::fs::File;
+            use tokio::{fs, fs::File};
             if let Some(parent) = path.parent() {
                 // TODO: display a prompt asking the user if the directories should be created
                 if !parent.exists() {
@@ -591,6 +600,17 @@ impl Document {
                 }
             }
 
+            // Protect against overwriting changes made externally
+            if !force {
+                if let Ok(metadata) = fs::metadata(&path).await {
+                    if let Ok(mtime) = metadata.modified() {
+                        if last_saved_time < mtime {
+                            bail!("file modified by an external process, use :w! to overwrite");
+                        }
+                    }
+                }
+            }
+
             let mut file = File::create(&path).await?;
             to_writer(&mut file, encoding, &text).await?;
 
@@ -668,6 +688,8 @@ impl Document {
         self.append_changes_to_history(view);
         self.reset_modified();
 
+        self.last_saved_time = SystemTime::now();
+
         self.detect_indent_and_line_ending();
 
         match provider_registry.get_diff_base(&path) {
@@ -1016,6 +1038,7 @@ impl Document {
             rev
         );
         self.last_saved_revision = rev;
+        self.last_saved_time = SystemTime::now();
     }
 
     /// Get the document's latest saved revision.