From 9d73a0d1128f8237eef2d4bf475496d4db081df2 Mon Sep 17 00:00:00 2001
From: Mike Trinkala <trink@acm.org>
Date: Thu, 9 Feb 2023 06:28:33 -0800
Subject: [PATCH] Fix the infinite loop when copying the cursor to the top of
 the file (#5888)

Example:
```
test
testitem
```

Select line 2 with x, then type Alt-C; Helix will go into an infinite
loop. The saturating_sub keeps the head_row and anchor_row pinned at 0,
and a selection is never made since the first line is too short.
---
 helix-term/src/commands.rs        |  4 ++
 helix-term/tests/test/commands.rs | 64 +++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index e6cbed2ce..d7d87b5a1 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -1617,6 +1617,10 @@ fn copy_selection_on_line(cx: &mut Context, direction: Direction) {
                 sels += 1;
             }
 
+            if anchor_row == 0 && head_row == 0 {
+                break;
+            }
+
             i += 1;
         }
     }
diff --git a/helix-term/tests/test/commands.rs b/helix-term/tests/test/commands.rs
index 2ca9e3957..e8d16bfaf 100644
--- a/helix-term/tests/test/commands.rs
+++ b/helix-term/tests/test/commands.rs
@@ -132,6 +132,70 @@ async fn test_selection_duplication() -> anyhow::Result<()> {
         .as_str(),
     ))
     .await?;
+
+    // Copy the selection to previous line, skipping the first line in the file
+    test((
+        platform_line(indoc! {"\
+            test
+            #[testitem|]#
+            "})
+        .as_str(),
+        "<A-C>",
+        platform_line(indoc! {"\
+            test
+            #[testitem|]#
+            "})
+        .as_str(),
+    ))
+    .await?;
+
+    // Copy the selection to previous line, including the first line in the file
+    test((
+        platform_line(indoc! {"\
+            test
+            #[test|]#
+            "})
+        .as_str(),
+        "<A-C>",
+        platform_line(indoc! {"\
+            #[test|]#
+            #(test|)#
+            "})
+        .as_str(),
+    ))
+    .await?;
+
+    // Copy the selection to next line, skipping the last line in the file
+    test((
+        platform_line(indoc! {"\
+            #[testitem|]#
+            test
+            "})
+        .as_str(),
+        "C",
+        platform_line(indoc! {"\
+            #[testitem|]#
+            test
+            "})
+        .as_str(),
+    ))
+    .await?;
+
+    // Copy the selection to next line, including the last line in the file
+    test((
+        platform_line(indoc! {"\
+            #[test|]#
+            test
+            "})
+        .as_str(),
+        "C",
+        platform_line(indoc! {"\
+            #(test|)#
+            #[test|]#
+            "})
+        .as_str(),
+    ))
+    .await?;
     Ok(())
 }