From 9278a681864bef1b9f32309f0a49c454de36b49a Mon Sep 17 00:00:00 2001
From: Nik Revenco <154856872+NikitaRevenco@users.noreply.github.com>
Date: Wed, 19 Mar 2025 15:08:58 +0000
Subject: [PATCH] fix: account for inserted and deleted lines

_
---
 helix-term/src/handlers/blame.rs | 48 ++++++++++++++++++++++++++++++--
 helix-view/src/handlers.rs       |  4 +++
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/helix-term/src/handlers/blame.rs b/helix-term/src/handlers/blame.rs
index c4f80d0b..640e3a72 100644
--- a/helix-term/src/handlers/blame.rs
+++ b/helix-term/src/handlers/blame.rs
@@ -9,6 +9,7 @@ use crate::{events::PostCommand, job};
 #[derive(Default)]
 pub struct BlameHandler {
     worker: Option<JoinHandle<anyhow::Result<String>>>,
+    cursor_line: u32,
 }
 
 impl helix_event::AsyncHook for BlameHandler {
@@ -31,11 +32,32 @@ impl helix_event::AsyncHook for BlameHandler {
             file,
             cursor_line,
             diff_providers,
+            removed_lines_count,
+            added_lines_count,
         } = event;
 
+        self.cursor_line = cursor_line;
+
+        // convert 0-based line numbers into 1-based line numbers
+        let cursor_line = cursor_line + 1;
+
+        // the line for which we compute the blame
+        // Because gix_blame doesn't care about stuff that is not commited, we have to "normalize" the
+        // line number to account for uncommited code.
+        //
+        // You'll notice that blame_line can be 0 when, for instance we have:
+        // - removed 0 lines
+        // - added 10 lines
+        // - cursor_line is 8
+        //
+        // So when our cursor is on the 10th added line or earlier, blame_line will be 0. This means
+        // the blame will be incorrect. But that's fine, because when the cursor_line is on some hunk,
+        // we can show to the user nothing at all
+        let blame_line = cursor_line.saturating_sub(added_lines_count) + removed_lines_count;
+
         let worker = tokio::spawn(async move {
             diff_providers
-                .blame_line(&file, cursor_line)
+                .blame_line(&file, blame_line)
                 .map(|s| s.to_string())
         });
         self.worker = Some(worker);
@@ -43,6 +65,7 @@ impl helix_event::AsyncHook for BlameHandler {
     }
 
     fn finish_debounce(&mut self) {
+        let cursor_line = self.cursor_line;
         if let Some(worker) = &self.worker {
             if worker.is_finished() {
                 let worker = self.worker.take().unwrap();
@@ -52,7 +75,14 @@ impl helix_event::AsyncHook for BlameHandler {
                     };
                     job::dispatch(move |editor, _| {
                         let doc = doc_mut!(editor);
-                        doc.blame = Some(outcome);
+                        // if we're on a line that hasn't been commited yet, just show nothing at all
+                        // in order to reduce visual noise.
+                        // Because the git hunks already imply this information
+                        let blame_text = doc
+                            .diff_handle()
+                            .is_some_and(|diff| diff.load().hunk_at(cursor_line, false).is_none())
+                            .then_some(outcome);
+                        doc.blame = blame_text;
                     })
                     .await;
                 });
@@ -82,11 +112,25 @@ pub(super) fn register_hooks(handlers: &Handlers) {
             return Ok(());
         };
 
+        let hunks = doc.diff_handle().unwrap().load();
+
+        let mut removed_lines_count: u32 = 0;
+        let mut added_lines_count: u32 = 0;
+        for hunk in hunks.hunks_intersecting_line_ranges(std::iter::once((0, cursor_line as usize)))
+        {
+            let lines_inserted = hunk.after.end - hunk.after.start;
+            let lines_removed = hunk.before.end - hunk.before.start;
+            added_lines_count += lines_inserted;
+            removed_lines_count += lines_removed;
+        }
+
         send_blocking(
             &tx,
             BlameEvent::PostCommand {
                 file,
                 cursor_line,
+                removed_lines_count,
+                added_lines_count,
                 // ok to clone because diff_providers is very small
                 diff_providers: event.cx.editor.diff_providers.clone(),
             },
diff --git a/helix-view/src/handlers.rs b/helix-view/src/handlers.rs
index 6090bf84..d596d94a 100644
--- a/helix-view/src/handlers.rs
+++ b/helix-view/src/handlers.rs
@@ -24,6 +24,10 @@ pub enum BlameEvent {
     PostCommand {
         file: PathBuf,
         cursor_line: u32,
+        /// How many lines were removed before cursor_line
+        removed_lines_count: u32,
+        /// How many lines were added before cursor_line
+        added_lines_count: u32,
         diff_providers: DiffProviderRegistry,
     },
 }