fix(lsp): out of bounds error in lsp.util.apply_text_edits (#20137)

Co-authored-by: Jonas Strittmatter <40792180+smjonas@users.noreply.github.com>

runtime/lua/vim/lsp/util.lua

@@ -459,21 +459,37 @@ function M.apply_text_edits(text_edits, bufnr, offset_encoding)
       text = split(text_edit.newText, '\n', true),
     }
 
-    -- Some LSP servers may return +1 range of the buffer content but nvim_buf_set_text can't accept it so we should fix it here.
     local max = api.nvim_buf_line_count(bufnr)
-    if max <= e.start_row or max <= e.end_row then
-      local len = #(get_line(bufnr, max - 1) or '')
+    -- If the whole edit is after the lines in the buffer we can simply add the new text to the end
+    -- of the buffer.
     if max <= e.start_row then
-        e.start_row = max - 1
-        e.start_col = len
-        table.insert(e.text, 1, '')
-      end
+      api.nvim_buf_set_lines(bufnr, max, max, false, e.text)
+    else
+      local last_line_len = #(get_line(bufnr, math.min(e.end_row, max - 1)) or '')
+      -- Some LSP servers may return +1 range of the buffer content but nvim_buf_set_text can't
+      -- accept it so we should fix it here.
       if max <= e.end_row then
         e.end_row = max - 1
-        e.end_col = len
-      end
+        e.end_col = last_line_len
         has_eol_text_edit = true
+      else
+        -- If the replacement is over the end of a line (i.e. e.end_col is out of bounds and the
+        -- replacement text ends with a newline We can likely assume that the replacement is assumed
+        -- to be meant to replace the newline with another newline and we need to make sure this
+        -- doens't add an extra empty line. E.g. when the last line to be replaced contains a '\r'
+        -- in the file some servers (clangd on windows) will include that character in the line
+        -- while nvim_buf_set_text doesn't count it as part of the line.
+        if
+          e.end_col > last_line_len
+          and #text_edit.newText > 0
+          and string.sub(text_edit.newText, -1) == '\n'
+        then
+          table.remove(e.text, #e.text)
         end
+      end
+      -- Make sure we don't go out of bounds for e.end_col
+      e.end_col = math.min(last_line_len, e.end_col)
+
       api.nvim_buf_set_text(bufnr, e.start_row, e.start_col, e.end_row, e.end_col, e.text)
 
       -- Fix cursor position.
@@ -490,6 +506,7 @@ function M.apply_text_edits(text_edits, bufnr, offset_encoding)
         is_cursor_fixed = true
       end
     end
+  end
 
   local max = api.nvim_buf_line_count(bufnr)
 

test/functional/plugin/lsp_spec.lua

@@ -1719,6 +1719,46 @@ describe('LSP', function()
     end)
   end)
 
+  describe('apply_text_edits regression tests for #20116', function()
+    before_each(function()
+      insert(dedent([[
+      Test line one
+      Test line two 21 char]]))
+    end)
+    describe('with LSP end column out of bounds and start column at 0', function()
+      it('applies edits at the end of the buffer', function()
+        local edits = {
+          make_edit(0, 0, 1, 22, {'#include "whatever.h"\r\n#include <algorithm>\r'});
+        }
+        exec_lua('vim.lsp.util.apply_text_edits(...)', edits, 1, "utf-8")
+        eq({'#include "whatever.h"', '#include <algorithm>'}, buf_lines(1))
+      end)
+      it('applies edits in the middle of the buffer', function()
+        local edits = {
+          make_edit(0, 0, 0, 22, {'#include "whatever.h"\r\n#include <algorithm>\r'});
+        }
+        exec_lua('vim.lsp.util.apply_text_edits(...)', edits, 1, "utf-8")
+        eq({'#include "whatever.h"', '#include <algorithm>', 'Test line two 21 char'}, buf_lines(1))
+      end)
+    end)
+    describe('with LSP end column out of bounds and start column NOT at 0', function()
+      it('applies edits at the end of the buffer', function()
+        local edits = {
+          make_edit(0, 2, 1, 22, {'#include "whatever.h"\r\n#include <algorithm>\r'});
+        }
+        exec_lua('vim.lsp.util.apply_text_edits(...)', edits, 1, "utf-8")
+        eq({'Te#include "whatever.h"', '#include <algorithm>'}, buf_lines(1))
+      end)
+      it('applies edits in the middle of the buffer', function()
+        local edits = {
+          make_edit(0, 2, 0, 22, {'#include "whatever.h"\r\n#include <algorithm>\r'});
+        }
+        exec_lua('vim.lsp.util.apply_text_edits(...)', edits, 1, "utf-8")
+        eq({'Te#include "whatever.h"', '#include <algorithm>', 'Test line two 21 char'}, buf_lines(1))
+      end)
+    end)
+  end)
+
   describe('apply_text_document_edit', function()
     local target_bufnr
     local text_document_edit = function(editVersion)