Add support for path completion (#2608)

Co-authored-by: Michael Davis <[email protected]>
Co-authored-by: Pascal Kuthe <[email protected]>

book/src/editor.md

@@ -33,6 +33,7 @@
 | `cursorcolumn` | Highlight all columns with a cursor | `false` |
 | `gutters` | Gutters to display: Available are `diagnostics` and `diff` and `line-numbers` and `spacer`, note that `diagnostics` also includes other features like breakpoints, 1-width padding will be inserted if gutters is non-empty | `["diagnostics", "spacer", "line-numbers", "spacer", "diff"]` |
 | `auto-completion` | Enable automatic pop up of auto-completion | `true` |
+| `path-completion` | Enable filepath completion. Show files and directories if an existing path at the cursor was recognized, either absolute or relative to the current opened document or current working directory (if the buffer is not yet saved). Defaults to true. | `true` |
 | `auto-format` | Enable automatic formatting on save | `true` |
 | `idle-timeout` | Time in milliseconds since last keypress before idle timers trigger. | `250` |
 | `completion-timeout` | Time in milliseconds after typing a word character before completions are shown, set to 5 for instant.  | `250` |

book/src/languages.md

@@ -69,6 +69,7 @@ These configuration keys are available:
 | `formatter`           | The formatter for the language, it will take precedence over the lsp when defined. The formatter must be able to take the original file as input from stdin and write the formatted file to stdout |
 | `soft-wrap` | [editor.softwrap](./configuration.md#editorsoft-wrap-section)
 | `text-width`          |  Maximum line length. Used for the `:reflow` command and soft-wrapping if `soft-wrap.wrap-at-text-width` is set, defaults to `editor.text-width`   |
+| `path-completion`     | Overrides the `editor.path-completion` config key for the language. |
 | `workspace-lsp-roots`     | Directories relative to the workspace root that are treated as LSP roots. Should only be set in `.helix/config.toml`. Overwrites the setting of the same name in `config.toml` if set. |
 | `persistent-diagnostic-sources` | An array of LSP diagnostic sources assumed unchanged when the language server resends the same set of diagnostics. Helix can track the position for these diagnostics internally instead. Useful for diagnostics that are recomputed on save.
 

helix-core/src/completion.rs

@@ -0,0 +1,12 @@
+use std::borrow::Cow;
+
+use crate::Transaction;
+
+#[derive(Debug, PartialEq, Clone)]
+pub struct CompletionItem {
+    pub transaction: Transaction,
+    pub label: Cow<'static, str>,
+    pub kind: Cow<'static, str>,
+    /// Containing Markdown
+    pub documentation: String,
+}

helix-core/src/lib.rs

@@ -3,6 +3,7 @@ pub use encoding_rs as encoding;
 pub mod auto_pairs;
 pub mod chars;
 pub mod comment;
+pub mod completion;
 pub mod config;
 pub mod diagnostic;
 pub mod diff;
@@ -63,6 +64,7 @@ pub use selection::{Range, Selection};
 pub use smallvec::{smallvec, SmallVec};
 pub use syntax::Syntax;
 
+pub use completion::CompletionItem;
 pub use diagnostic::Diagnostic;
 
 pub use line_ending::{LineEnding, NATIVE_LINE_ENDING};

helix-core/src/syntax.rs

@@ -125,6 +125,9 @@ pub struct LanguageConfiguration {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub formatter: Option<FormatterConfiguration>,
 
+    /// If set, overrides `editor.path-completion`.
+    pub path_completion: Option<bool>,
+
     #[serde(default)]
     pub diagnostic_severity: Severity,
 

helix-event/src/cancel.rs

@@ -1,19 +1,287 @@
+use std::borrow::Borrow;
 use std::future::Future;
+use std::sync::atomic::AtomicU64;
+use std::sync::atomic::Ordering::Relaxed;
+use std::sync::Arc;
 
-pub use oneshot::channel as cancelation;
-use tokio::sync::oneshot;
+use tokio::sync::Notify;
 
-pub type CancelTx = oneshot::Sender<()>;
-pub type CancelRx = oneshot::Receiver<()>;
-
-pub async fn cancelable_future<T>(future: impl Future<Output = T>, cancel: CancelRx) -> Option<T> {
+pub async fn cancelable_future<T>(
+    future: impl Future<Output = T>,
+    cancel: impl Borrow<TaskHandle>,
+) -> Option<T> {
     tokio::select! {
         biased;
-        _ = cancel => {
+        _ = cancel.borrow().canceled() => {
             None
         }
         res = future => {
             Some(res)
         }
     }
 }
+
+#[derive(Default, Debug)]
+struct Shared {
+    state: AtomicU64,
+    // `Notify` has some features that we don't really need here because it
+    // supports waking single tasks (`notify_one`) and does its own (more
+    // complicated) state tracking, we could reimplement the waiter linked list
+    // with modest effort and reduce memory consumption by one word/8 bytes and
+    // reduce code complexity/number of atomic operations.
+    //
+    // I don't think that's worth the complexity (unsafe code).
+    //
+    // if we only cared about async code then we could also only use a notify
+    // (without the generation count), this would be equivalent (or maybe more
+    // correct if we want to allow cloning the TX) but it would be extremly slow
+    // to frequently check for cancelation from sync code
+    notify: Notify,
+}
+
+impl Shared {
+    fn generation(&self) -> u32 {
+        self.state.load(Relaxed) as u32
+    }
+
+    fn num_running(&self) -> u32 {
+        (self.state.load(Relaxed) >> 32) as u32
+    }
+
+    /// Increments the generation count and sets `num_running`
+    /// to the provided value, this operation is not with
+    /// regard to the generation counter (doesn't use `fetch_add`)
+    /// so the calling code must ensure it cannot execute concurrently
+    /// to maintain correctness (but not safety)
+    fn inc_generation(&self, num_running: u32) -> (u32, u32) {
+        let state = self.state.load(Relaxed);
+        let generation = state as u32;
+        let prev_running = (state >> 32) as u32;
+        // no need to create a new generation if the refcount is zero (fastpath)
+        if prev_running == 0 && num_running == 0 {
+            return (generation, 0);
+        }
+        let new_generation = generation.saturating_add(1);
+        self.state.store(
+            new_generation as u64 | ((num_running as u64) << 32),
+            Relaxed,
+        );
+        self.notify.notify_waiters();
+        (new_generation, prev_running)
+    }
+
+    fn inc_running(&self, generation: u32) {
+        let mut state = self.state.load(Relaxed);
+        loop {
+            let current_generation = state as u32;
+            if current_generation != generation {
+                break;
+            }
+            let off = 1 << 32;
+            let res = self.state.compare_exchange_weak(
+                state,
+                state.saturating_add(off),
+                Relaxed,
+                Relaxed,
+            );
+            match res {
+                Ok(_) => break,
+                Err(new_state) => state = new_state,
+            }
+        }
+    }
+
+    fn dec_running(&self, generation: u32) {
+        let mut state = self.state.load(Relaxed);
+        loop {
+            let current_generation = state as u32;
+            if current_generation != generation {
+                break;
+            }
+            let num_running = (state >> 32) as u32;
+            // running can't be zero here, that would mean we miscounted somewhere
+            assert_ne!(num_running, 0);
+            let off = 1 << 32;
+            let res = self
+                .state
+                .compare_exchange_weak(state, state - off, Relaxed, Relaxed);
+            match res {
+                Ok(_) => break,
+                Err(new_state) => state = new_state,
+            }
+        }
+    }
+}
+
+// This intentionally doesn't implement `Clone` and requires a mutable reference
+// for cancelation to avoid races (in inc_generation).
+
+/// A task controller allows managing a single subtask enabling the controller
+/// to cancel the subtask and to check whether it is still running.
+///
+/// For efficiency reasons the controller can be reused/restarted,
+/// in that case the previous task is automatically canceled.
+///
+/// If the controller is dropped, the subtasks are automatically canceled.
+#[derive(Default, Debug)]
+pub struct TaskController {
+    shared: Arc<Shared>,
+}
+
+impl TaskController {
+    pub fn new() -> Self {
+        TaskController::default()
+    }
+    /// Cancels the active task (handle).
+    ///
+    /// Returns whether any tasks were still running before the cancelation.
+    pub fn cancel(&mut self) -> bool {
+        self.shared.inc_generation(0).1 != 0
+    }
+
+    /// Checks whether there are any task handles
+    /// that haven't been dropped (or canceled) yet.
+    pub fn is_running(&self) -> bool {
+        self.shared.num_running() != 0
+    }
+
+    /// Starts a new task and cancels the previous task (handles).
+    pub fn restart(&mut self) -> TaskHandle {
+        TaskHandle {
+            generation: self.shared.inc_generation(1).0,
+            shared: self.shared.clone(),
+        }
+    }
+}
+
+impl Drop for TaskController {
+    fn drop(&mut self) {
+        self.cancel();
+    }
+}
+
+/// A handle that is used to link a task with a task controller.
+///
+/// It can be used to cancel async futures very efficiently but can also be checked for
+/// cancelation very quickly (single atomic read) in blocking code.
+/// The handle can be cheaply cloned (reference counted).
+///
+/// The TaskController can check whether a task is "running" by inspecting the
+/// refcount of the (current) tasks handles. Therefore, if that information
+/// is important, ensure that the handle is not dropped until the task fully
+/// completes.
+pub struct TaskHandle {
+    shared: Arc<Shared>,
+    generation: u32,
+}
+
+impl Clone for TaskHandle {
+    fn clone(&self) -> Self {
+        self.shared.inc_running(self.generation);
+        TaskHandle {
+            shared: self.shared.clone(),
+            generation: self.generation,
+        }
+    }
+}
+
+impl Drop for TaskHandle {
+    fn drop(&mut self) {
+        self.shared.dec_running(self.generation);
+    }
+}
+
+impl TaskHandle {
+    /// Waits until [`TaskController::cancel`] is called for the corresponding
+    /// [`TaskController`]. Immediately returns if `cancel` was already called since
+    pub async fn canceled(&self) {
+        let notified = self.shared.notify.notified();
+        if !self.is_canceled() {
+            notified.await
+        }
+    }
+
+    pub fn is_canceled(&self) -> bool {
+        self.generation != self.shared.generation()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::future::poll_fn;
+
+    use futures_executor::block_on;
+    use tokio::task::yield_now;
+
+    use crate::{cancelable_future, TaskController};
+
+    #[test]
+    fn immediate_cancel() {
+        let mut controller = TaskController::new();
+        let handle = controller.restart();
+        controller.cancel();
+        assert!(handle.is_canceled());
+        controller.restart();
+        assert!(handle.is_canceled());
+
+        let res = block_on(cancelable_future(
+            poll_fn(|_cx| std::task::Poll::Ready(())),
+            handle,
+        ));
+        assert!(res.is_none());
+    }
+
+    #[test]
+    fn running_count() {
+        let mut controller = TaskController::new();
+        let handle = controller.restart();
+        assert!(controller.is_running());
+        assert!(!handle.is_canceled());
+        drop(handle);
+        assert!(!controller.is_running());
+        assert!(!controller.cancel());
+        let handle = controller.restart();
+        assert!(!handle.is_canceled());
+        assert!(controller.is_running());
+        let handle2 = handle.clone();
+        assert!(!handle.is_canceled());
+        assert!(controller.is_running());
+        drop(handle2);
+        assert!(!handle.is_canceled());
+        assert!(controller.is_running());
+        assert!(controller.cancel());
+        assert!(handle.is_canceled());
+        assert!(!controller.is_running());
+    }
+
+    #[test]
+    fn no_cancel() {
+        let mut controller = TaskController::new();
+        let handle = controller.restart();
+        assert!(!handle.is_canceled());
+
+        let res = block_on(cancelable_future(
+            poll_fn(|_cx| std::task::Poll::Ready(())),
+            handle,
+        ));
+        assert!(res.is_some());
+    }
+
+    #[test]
+    fn delayed_cancel() {
+        let mut controller = TaskController::new();
+        let handle = controller.restart();
+
+        let mut hit = false;
+        let res = block_on(cancelable_future(
+            async {
+                controller.cancel();
+                hit = true;
+                yield_now().await;
+            },
+            handle,
+        ));
+        assert!(res.is_none());
+        assert!(hit);
+    }
+}

helix-event/src/lib.rs

@@ -32,7 +32,7 @@
 //! to helix-view in the future if we manage to detach the compositor from its rendering backend.
 
 use anyhow::Result;
-pub use cancel::{cancelable_future, cancelation, CancelRx, CancelTx};
+pub use cancel::{cancelable_future, TaskController, TaskHandle};
 pub use debounce::{send_blocking, AsyncHook};
 pub use redraw::{
     lock_frame, redraw_requested, request_redraw, start_frame, RenderLockGuard, RequestRedrawOnDrop,

helix-stdx/Cargo.toml

@@ -18,6 +18,8 @@ ropey = { version = "1.6.1", default-features = false }
 which = "7.0"
 regex-cursor = "0.1.4"
 bitflags = "2.6"
+once_cell = "1.19"
+regex-automata = "0.4.8"
 
 [target.'cfg(windows)'.dependencies]
 windows-sys = { version = "0.59", features = ["Win32_Foundation", "Win32_Security", "Win32_Security_Authorization", "Win32_Storage_FileSystem", "Win32_System_Threading"] }