lsp: Fix text edits with the same start position (#12434)

According to the LSP spec[1], multiple edits can have the same starting
position, and if that is the case, they should be applied in the order
as they come in the array.

The implementation uses a reverse sort to not interfere with non applied
edits, but failed to take into account the spec.

[1] https://microsoft.github.io/language-server-protocol/specifications/specification-3-14/#textedit

2 files changed, 25 insertions, 2 deletions

diff --git a/runtime/lua/vim/lsp/util.lua b/runtime/lua/vim/lsp/util.lua
index a4ceeb34e6..4c3c4fa6cb 100644
--- a/runtime/lua/vim/lsp/util.lua
+++ b/runtime/lua/vim/lsp/util.lua
@@ -92,7 +92,7 @@ local function sort_by_key(fn)
   end
 end
 local edit_sort_key = sort_by_key(function(e)
-  return {e.A[1], e.A[2], e.i}
+  return {e.A[1], e.A[2], -e.i}
 end)
 
 --- Position is a https://microsoft.github.io/language-server-protocol/specifications/specification-current/#position
diff --git a/test/functional/plugin/lsp_spec.lua b/test/functional/plugin/lsp_spec.lua
index 5a8a9106a5..1ab81a0ef8 100644
--- a/test/functional/plugin/lsp_spec.lua
+++ b/test/functional/plugin/lsp_spec.lua
@@ -811,10 +811,33 @@ describe('LSP', function()
         'å å ɧ 汉语 ↥ 🤦 🦄';
       }, buf_lines(1))
     end)
+    it('handles edits with the same start position, applying changes in the order in the array', function()
+      local edits = {
+        make_edit(0, 6, 0, 10, {""});
+        make_edit(0, 6, 0, 6, {"REPLACE"});
+        make_edit(1, 0, 1, 3, {""});
+        make_edit(1, 0, 1, 0, {"123"});
+        make_edit(2, 16, 2, 18, {""});
+        make_edit(2, 16, 2, 16, {"XYZ"});
+        make_edit(3, 7, 3, 11, {"this"});
+        make_edit(3, 7, 3, 11, {"will"});
+        make_edit(3, 7, 3, 11, {"not "});
+        make_edit(3, 7, 3, 11, {"show"});
+        make_edit(3, 7, 3, 11, {"(but this will)"});
+      }
+      exec_lua('vim.lsp.util.apply_text_edits(...)', edits, 1)
+      eq({
+        'First REPLACE of text';
+        '123ond line of text';
+        'Third line of teXYZ';
+        'Fourth (but this will) of text';
+        'å å ɧ 汉语 ↥ 🤦 🦄';
+      }, buf_lines(1))
+    end)
     it('applies complex edits', function()
       local edits = {
-        make_edit(0, 0, 0, 0, {"", "12"});
         make_edit(0, 0, 0, 0, {"3", "foo"});
+        make_edit(0, 0, 0, 0, {"", "12"});
         make_edit(0, 1, 0, 1, {"bar", "123"});
         make_edit(0, #"First ", 0, #"First line of text", {"guy"});
         make_edit(1, 0, 1, #'Second', {"baz"});