From b051b131f5ce99ffe1b1bc22a2032ebc886e4e35 Mon Sep 17 00:00:00 2001
From: bfredl <bjorn.linse@gmail.com>
Date: Wed, 30 Aug 2023 11:53:58 +0200
Subject: [PATCH] fix(api): nvim_buf_get_offset in a new buffer with zero or
 one lines

fixes #24930
---
 src/nvim/memline.c                  |  5 +++++
 test/functional/api/buffer_spec.lua | 12 ++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/src/nvim/memline.c b/src/nvim/memline.c
index 5839061aac..123e9d0a0b 100644
--- a/src/nvim/memline.c
+++ b/src/nvim/memline.c
@@ -3934,6 +3934,11 @@ long ml_find_line_or_offset(buf_T *buf, linenr_T lnum, long *offp, bool no_ff)
   if (buf->b_ml.ml_usedchunks == -1
       || buf->b_ml.ml_chunksize == NULL
       || lnum < 0) {
+    // memline is currently empty. Although if it is loaded,
+    // it behaves like there is one empty line.
+    if (!ffdos && buf->b_ml.ml_mfp && (lnum == 1 || lnum == 2)) {
+      return lnum - 1;
+    }
     return -1;
   }
 
diff --git a/test/functional/api/buffer_spec.lua b/test/functional/api/buffer_spec.lua
index aea1f359e6..292e5a2d56 100644
--- a/test/functional/api/buffer_spec.lua
+++ b/test/functional/api/buffer_spec.lua
@@ -1151,6 +1151,18 @@ describe('api/buf', function()
       eq(6, bufmeths.get_offset(1,1))
       command("bunload! 1")
       eq(-1, bufmeths.get_offset(1,1))
+      eq(-1, bufmeths.get_offset(1,0))
+    end)
+
+    it('works in empty buffer', function()
+      eq(0, get_offset(0))
+      eq(1, get_offset(1))
+    end)
+
+    it('works in buffer with one line inserted', function()
+      feed('itext')
+      eq(0, get_offset(0))
+      eq(5, get_offset(1))
     end)
   end)