2 files changed, 39 insertions, 0 deletions

diff --git a/helix-view/src/document.rs b/helix-view/src/document.rs
index af7e3a7e..7602c9c7 100644
--- a/helix-view/src/document.rs
+++ b/helix-view/src/document.rs
@@ -185,6 +185,8 @@ pub struct Document {
 
     // when document was used for most-recent-used buffer picker
     pub focused_at: std::time::Instant,
+
+    pub readonly: bool,
 }
 
 /// Inlay hints for a single `(Document, View)` combo.
@@ -673,6 +675,7 @@ impl Document {
             config,
             version_control_head: None,
             focused_at: std::time::Instant::now(),
+            readonly: false,
         }
     }
 
@@ -955,6 +958,33 @@ impl Document {
         }
     }
 
+    #[cfg(unix)]
+    // Detect if the file is readonly and change the readonly field if necessary (unix only)
+    pub fn detect_readonly(&mut self) {
+        use rustix::fs::{access, Access};
+        // Allows setting the flag for files the user cannot modify, like root files
+        self.readonly = match &self.path {
+            None => false,
+            Some(p) => access(p, Access::WRITE_OK).is_err(),
+        };
+    }
+
+    #[cfg(not(unix))]
+    // Detect if the file is readonly and change the readonly field if necessary (non-unix os)
+    pub fn detect_readonly(&mut self) {
+        // TODO Use the Windows' function `CreateFileW` to check if a file is readonly
+        // Discussion: https://github.com/helix-editor/helix/pull/7740#issuecomment-1656806459
+        // Vim implementation: https://github.com/vim/vim/blob/4c0089d696b8d1d5dc40568f25ea5738fa5bbffb/src/os_win32.c#L7665
+        // Windows binding: https://microsoft.github.io/windows-docs-rs/doc/windows/Win32/Storage/FileSystem/fn.CreateFileW.html
+        self.readonly = match &self.path {
+            None => false,
+            Some(p) => match std::fs::metadata(p) {
+                Err(_) => false,
+                Ok(metadata) => metadata.permissions().readonly(),
+            },
+        };
+    }
+
     /// Reload the document from its path.
     pub fn reload(
         &mut self,
@@ -969,6 +999,9 @@ impl Document {
             .ok_or_else(|| anyhow!("can't find file to reload from {:?}", self.display_name()))?
             .to_owned();
 
+        // Once we have a valid path we check if its readonly status has changed
+        self.detect_readonly();
+
         let mut file = std::fs::File::open(&path)?;
         let (rope, ..) = from_reader(&mut file, Some(encoding))?;
 
@@ -1018,6 +1051,8 @@ impl Document {
         // and error out when document is saved
         self.path = path;
 
+        self.detect_readonly();
+
         Ok(())
     }
 
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index 2152ff9b..113102b6 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -421,6 +421,7 @@ impl Default for StatusLineConfig {
                 E::Mode,
                 E::Spinner,
                 E::FileName,
+                E::ReadOnlyIndicator,
                 E::FileModificationIndicator,
             ],
             center: vec![],
@@ -473,6 +474,9 @@ pub enum StatusLineElement {
     // The file modification indicator
     FileModificationIndicator,
 
+    /// An indicator that shows `"[readonly]"` when a file cannot be written
+    ReadOnlyIndicator,
+
     /// The file encoding
     FileEncoding,