win: use file path as ID when the filesystem doesn't support IDs

src/bin/edit/documents.rs

@@ -32,7 +32,7 @@ impl Document {
             tb.write_file(&mut file)?;
         }
 
-        if let Ok(id) = sys::file_id(&file) {
+        if let Ok(id) = sys::file_id(None, path) {
             self.file_id = Some(id);
         }
 
@@ -52,7 +52,7 @@ impl Document {
             tb.read_file(&mut file, encoding)?;
         }
 
-        if let Ok(id) = sys::file_id(&file) {
+        if let Ok(id) = sys::file_id(None, path) {
             self.file_id = Some(id);
         }
 
@@ -156,13 +156,10 @@ impl DocumentManager {
             Err(err) => return Err(err),
         };
 
-        let file_id = match &file {
-            Some(file) => Some(sys::file_id(file)?),
-            None => None,
-        };
+        let file_id = Some(sys::file_id(file.as_ref(), &path)?);
 
         // Check if the file is already open.
-        if file_id.is_some() && self.update_active(|doc| doc.file_id == file_id) {
+        if self.update_active(|doc| doc.file_id == file_id) {
             let doc = self.active_mut().unwrap();
             if let Some(goto) = goto {
                 doc.buffer.borrow_mut().cursor_move_to_logical(goto);

src/bin/edit/draw_filepicker.rs

@@ -116,7 +116,7 @@ pub fn draw_file_picker(ctx: &mut Context, state: &mut State) {
                 && let Some(path) = doit.as_deref()
                 && let Some(doc) = state.documents.active()
                 && let Some(file_id) = &doc.file_id
-                && sys::file_id_at(path).is_ok_and(|id| &id == file_id)
+                && sys::file_id(None, path).is_ok_and(|id| &id == file_id)
             {
                 state.file_picker_overwrite_warning = doit.take();
             }

src/sys/mod.rs

@@ -3,11 +3,6 @@
 
 //! Platform abstractions.
 
-use std::fs::File;
-use std::path::Path;
-
-use crate::apperr;
-
 #[cfg(unix)]
 mod unix;
 #[cfg(windows)]
@@ -20,9 +15,3 @@ pub use std::fs::canonicalize;
 pub use unix::*;
 #[cfg(windows)]
 pub use windows::*;
-
-pub fn file_id_at(path: &Path) -> apperr::Result<FileId> {
-    let file = File::open(path)?;
-    let file_id = file_id(&file)?;
-    Ok(file_id)
-}

src/sys/unix.rs

@@ -10,6 +10,7 @@ use std::ffi::{CStr, c_int, c_void};
 use std::fs::{self, File};
 use std::mem::{self, ManuallyDrop, MaybeUninit};
 use std::os::fd::{AsRawFd as _, FromRawFd as _};
+use std::path::Path;
 use std::ptr::{self, NonNull, null_mut};
 use std::{thread, time};
 
@@ -350,8 +351,13 @@ pub struct FileId {
     st_ino: libc::ino_t,
 }
 
-/// Returns a unique identifier for the given file.
-pub fn file_id(file: &File) -> apperr::Result<FileId> {
+/// Returns a unique identifier for the given file by handle or path.
+pub fn file_id(file: Option<&File>, path: &Path) -> apperr::Result<FileId> {
+    let file = match file {
+        Some(f) => f,
+        None => &File::open(path)?,
+    };
+
     unsafe {
         let mut stat = MaybeUninit::<libc::stat>::uninit();
         check_int_return(libc::fstat(file.as_raw_fd(), stat.as_mut_ptr()))?;

src/sys/windows.rs

@@ -398,24 +398,40 @@ pub fn open_stdin_if_redirected() -> Option<File> {
 }
 
 /// A unique identifier for a file.
-#[derive(Clone)]
-#[repr(transparent)]
-pub struct FileId(FileSystem::FILE_ID_INFO);
+pub enum FileId {
+    Id(FileSystem::FILE_ID_INFO),
+    Path(PathBuf),
+}
 
 impl PartialEq for FileId {
     fn eq(&self, other: &Self) -> bool {
-        // Lowers to an efficient word-wise comparison.
-        const SIZE: usize = std::mem::size_of::<FileSystem::FILE_ID_INFO>();
-        let a: &[u8; SIZE] = unsafe { mem::transmute(&self.0) };
-        let b: &[u8; SIZE] = unsafe { mem::transmute(&other.0) };
-        a == b
+        match (self, other) {
+            (FileId::Id(left), FileId::Id(right)) => {
+                // Lowers to an efficient word-wise comparison.
+                const SIZE: usize = std::mem::size_of::<FileSystem::FILE_ID_INFO>();
+                let a: &[u8; SIZE] = unsafe { mem::transmute(left) };
+                let b: &[u8; SIZE] = unsafe { mem::transmute(right) };
+                a == b
+            }
+            (FileId::Path(left), FileId::Path(right)) => left == right,
+            _ => false,
+        }
     }
 }
 
 impl Eq for FileId {}
 
-/// Returns a unique identifier for the given file.
-pub fn file_id(file: &File) -> apperr::Result<FileId> {
+/// Returns a unique identifier for the given file by handle or path.
+pub fn file_id(file: Option<&File>, path: &Path) -> apperr::Result<FileId> {
+    let file = match file {
+        Some(f) => f,
+        None => &File::open(path)?,
+    };
+
+    file_id_from_handle(file).or_else(|_| Ok(FileId::Path(std::fs::canonicalize(path)?)))
+}
+
+fn file_id_from_handle(file: &File) -> apperr::Result<FileId> {
     unsafe {
         let mut info = MaybeUninit::<FileSystem::FILE_ID_INFO>::uninit();
         check_bool_return(FileSystem::GetFileInformationByHandleEx(
@@ -424,7 +440,7 @@ pub fn file_id(file: &File) -> apperr::Result<FileId> {
             info.as_mut_ptr() as *mut _,
             mem::size_of::<FileSystem::FILE_ID_INFO>() as u32,
         ))?;
-        Ok(FileId(info.assume_init()))
+        Ok(FileId::Id(info.assume_init()))
     }
 }