store multiple snapshots on the document at once

Fixing autocomplete required moving the document savepoint before the
asynchronous completion request. However, this in turn causes new bugs:

If the completion popup is open, the savepoint is restored when the
popup closes (or another entry is selected). However, at that point
a new completion request might already have been created which
would have replaced the new savepoint (therefore leading to incorrectly
applied complies).

This commit fixes that bug by allowing in arbitrary number of
savepoints to be tracked on the document. The savepoints are reference
counted and therefore remain valid as long as any reference to them
remains. Weak reference are stored on the document and any reference
that can not be upgraded anymore (hence no strong reference remain)
are automatically discarded.

3 files changed, 16 insertions, 9 deletions

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index bc0e8ebe..01673c89 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -4181,7 +4181,7 @@ pub fn completion(cx: &mut Context) {
     iter.reverse();
     let offset = iter.take_while(|ch| chars::char_is_word(*ch)).count();
     let start_offset = cursor.saturating_sub(offset);
-    doc.savepoint(&view);
+    let savepoint = doc.savepoint(view);
 
     cx.callback(
         future,
@@ -4209,6 +4209,7 @@ pub fn completion(cx: &mut Context) {
             let ui = compositor.find::<ui::EditorView>().unwrap();
             ui.set_completion(
                 editor,
+                savepoint,
                 items,
                 offset_encoding,
                 start_offset,
diff --git a/helix-term/src/ui/completion.rs b/helix-term/src/ui/completion.rs
index 179a8cf8..ef88938f 100644
--- a/helix-term/src/ui/completion.rs
+++ b/helix-term/src/ui/completion.rs
@@ -1,12 +1,13 @@
 use crate::compositor::{Component, Context, Event, EventResult};
 use helix_view::{
+    document::SavePoint,
     editor::CompleteAction,
     theme::{Modifier, Style},
     ViewId,
 };
 use tui::{buffer::Buffer as Surface, text::Span};
 
-use std::borrow::Cow;
+use std::{borrow::Cow, sync::Arc};
 
 use helix_core::{Change, Transaction};
 use helix_view::{graphics::Rect, Document, Editor};
@@ -101,6 +102,7 @@ impl Completion {
 
     pub fn new(
         editor: &Editor,
+        savepoint: Arc<SavePoint>,
         mut items: Vec<CompletionItem>,
         offset_encoding: helix_lsp::OffsetEncoding,
         start_offset: usize,
@@ -213,11 +215,10 @@ impl Completion {
             let (view, doc) = current!(editor);
 
             // if more text was entered, remove it
-            doc.restore(view);
+            doc.restore(view, &savepoint);
 
             match event {
                 PromptEvent::Abort => {
-                    doc.restore(view);
                     editor.last_completion = None;
                 }
                 PromptEvent::Update => {
@@ -235,7 +236,6 @@ impl Completion {
                     );
 
                     // initialize a savepoint
-                    doc.savepoint(&view);
                     doc.apply(&transaction, view.id);
 
                     editor.last_completion = Some(CompleteAction {
diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index 62f04cc9..c81ae635 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -940,17 +940,25 @@ impl EditorView {
         }
     }
 
+    #[allow(clippy::too_many_arguments)]
     pub fn set_completion(
         &mut self,
         editor: &mut Editor,
+        savepoint: Arc<SavePoint>,
         items: Vec<helix_lsp::lsp::CompletionItem>,
         offset_encoding: helix_lsp::OffsetEncoding,
         start_offset: usize,
         trigger_offset: usize,
         size: Rect,
     ) {
-        let mut completion =
-            Completion::new(editor, items, offset_encoding, start_offset, trigger_offset);
+        let mut completion = Completion::new(
+            editor,
+            savepoint,
+            items,
+            offset_encoding,
+            start_offset,
+            trigger_offset,
+        );
 
         if completion.is_empty() {
             // skip if we got no completion results
@@ -969,8 +977,6 @@ impl EditorView {
         self.completion = None;
 
         // Clear any savepoints
-        let doc = doc_mut!(editor);
-        doc.savepoint = None;
         editor.clear_idle_timer(); // don't retrigger
     }