2 files changed, 86 insertions, 6 deletions

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index c74dfb39..5498a437 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -4773,6 +4773,8 @@ fn shell(cx: &mut compositor::Context, cmd: &str, behavior: &ShellBehavior) {
     let mut ranges = SmallVec::with_capacity(selection.len());
     let text = doc.text().slice(..);
 
+    let mut offset = 0isize;
+
     for range in selection.ranges() {
         let fragment = range.slice(text);
         let (output, success) = match shell_impl(shell, cmd, pipe.then(|| fragment.into())) {
@@ -4788,13 +4790,23 @@ fn shell(cx: &mut compositor::Context, cmd: &str, behavior: &ShellBehavior) {
             return;
         }
 
-        let (from, to) = match behavior {
-            ShellBehavior::Replace => (range.from(), range.to()),
-            ShellBehavior::Insert => (range.from(), range.from()),
-            ShellBehavior::Append => (range.to(), range.to()),
-            _ => (range.from(), range.from()),
+        let output_len = output.chars().count();
+
+        let (from, to, deleted_len) = match behavior {
+            ShellBehavior::Replace => (range.from(), range.to(), range.len()),
+            ShellBehavior::Insert => (range.from(), range.from(), 0),
+            ShellBehavior::Append => (range.to(), range.to(), 0),
+            _ => (range.from(), range.from(), 0),
         };
-        ranges.push(Range::new(to, to + output.chars().count()));
+
+        // These `usize`s cannot underflow because selection ranges cannot overlap.
+        // Once the MSRV is 1.66.0 (mixed_integer_ops is stabilized), we can use checked
+        // arithmetic to assert this.
+        let anchor = (to as isize + offset - deleted_len as isize) as usize;
+        let new_range = Range::new(anchor, anchor + output_len).with_direction(range.direction());
+        ranges.push(new_range);
+        offset = offset + output_len as isize - deleted_len as isize;
+
         changes.push((from, to, Some(output)));
     }
 
diff --git a/helix-term/tests/test/commands.rs b/helix-term/tests/test/commands.rs
index e78e6c9f..114bf222 100644
--- a/helix-term/tests/test/commands.rs
+++ b/helix-term/tests/test/commands.rs
@@ -215,3 +215,71 @@ async fn test_multi_selection_paste() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+#[tokio::test(flavor = "multi_thread")]
+async fn test_multi_selection_shell_commands() -> anyhow::Result<()> {
+    // pipe
+    test((
+        platform_line(indoc! {"\
+            #[|lorem]#
+            #(|ipsum)#
+            #(|dolor)#
+            "})
+        .as_str(),
+        "|echo foo<ret>",
+        platform_line(indoc! {"\
+            #[|foo
+            ]#
+            #(|foo
+            )#
+            #(|foo
+            )#
+            "})
+        .as_str(),
+    ))
+    .await?;
+
+    // insert-output
+    test((
+        platform_line(indoc! {"\
+            #[|lorem]#
+            #(|ipsum)#
+            #(|dolor)#
+            "})
+        .as_str(),
+        "!echo foo<ret>",
+        platform_line(indoc! {"\
+            #[|foo
+            ]#lorem
+            #(|foo
+            )#ipsum
+            #(|foo
+            )#dolor
+            "})
+        .as_str(),
+    ))
+    .await?;
+
+    // append-output
+    test((
+        platform_line(indoc! {"\
+            #[|lorem]#
+            #(|ipsum)#
+            #(|dolor)#
+            "})
+        .as_str(),
+        "<A-!>echo foo<ret>",
+        platform_line(indoc! {"\
+            lorem#[|foo
+            ]#
+            ipsum#(|foo
+            )#
+            dolor#(|foo
+            )#
+            "})
+        .as_str(),
+    ))
+    .await?;
+
+    Ok(())
+}