Add a helper function for applying transactions

It is easy to forget to call `Document::apply` and/or `View::apply` in
the correct order. This commit introduces a helper function which
closes over both calls.

2 files changed, 19 insertions, 5 deletions

diff --git a/helix-view/src/document.rs b/helix-view/src/document.rs
index 631c540b..93708339 100644
--- a/helix-view/src/document.rs
+++ b/helix-view/src/document.rs
@@ -24,7 +24,7 @@ use helix_core::{
     DEFAULT_LINE_ENDING,
 };
 
-use crate::{DocumentId, Editor, View, ViewId};
+use crate::{apply_transaction, DocumentId, Editor, View, ViewId};
 
 /// 8kB of buffer space for encoding and decoding `Rope`s.
 const BUF_SIZE: usize = 8192;
@@ -617,8 +617,7 @@ impl Document {
         // This is not considered a modification of the contents of the file regardless
         // of the encoding.
         let transaction = helix_core::diff::compare_ropes(self.text(), &rope);
-        self.apply(&transaction, view.id);
-        view.apply(&transaction, self);
+        apply_transaction(&transaction, self, view);
         self.append_changes_to_history(view.id);
         self.reset_modified();
 
@@ -811,6 +810,9 @@ impl Document {
     }
 
     /// Apply a [`Transaction`] to the [`Document`] to change its text.
+    /// Instead of calling this function directly, use [crate::apply_transaction]
+    /// to ensure that the transaction is applied to the appropriate [`View`] as
+    /// well.
     pub fn apply(&mut self, transaction: &Transaction, view_id: ViewId) -> bool {
         // store the state just before any changes are made. This allows us to undo to the
         // state just before a transaction was applied.
@@ -865,8 +867,7 @@ impl Document {
 
     pub fn restore(&mut self, view: &mut View) {
         if let Some(revert) = self.savepoint.take() {
-            self.apply(&revert, view.id);
-            view.apply(&revert, self);
+            apply_transaction(&revert, self, view);
         }
     }
 
diff --git a/helix-view/src/lib.rs b/helix-view/src/lib.rs
index 0145677d..276be441 100644
--- a/helix-view/src/lib.rs
+++ b/helix-view/src/lib.rs
@@ -64,6 +64,19 @@ pub fn align_view(doc: &Document, view: &mut View, align: Align) {
     view.offset.row = line.saturating_sub(relative);
 }
 
+/// Applies a [`helix_core::Transaction`] to the given [`Document`]
+/// and [`View`].
+pub fn apply_transaction(
+    transaction: &helix_core::Transaction,
+    doc: &mut Document,
+    view: &mut View,
+) -> bool {
+    // This is a short function but it's easy to call `Document::apply`
+    // without calling `View::apply` or in the wrong order. The transaction
+    // must be applied to the document before the view.
+    doc.apply(transaction, view.id) && view.apply(transaction, doc)
+}
+
 pub use document::Document;
 pub use editor::Editor;
 pub use theme::Theme;