linkedEditing mode incorrectly triggered

[notpeter]

Expected Behavior

textDocument/linkedEditingRange mode is not triggered when typing on empty lines lines

Current Behavior

Duplicated characters are inserted into the buffer on the line below and on the current line.

Possible Solution

I wonder whether is an off-by-one error when mapping the current cursor position in the code to determine whether to enable linkedEditingRange. Have not investigated further.

Steps to Reproduce (for bugs)

Reproducible with both Zed and VSCode.

Zed Steps:
Install the Zed Elm extension (cmd-shift-x, search for Elm, click install.

brew install elm
mkdir /tmp/elm
cd $_
elm init
echo '-- Welcome to hell

viewError : View Msg
viewError = {}
' > src/Main.elm
zed . src/Main.elm:2

Then type something (abc) on line 2.
Use undo (cmd-z) if you want to trigger it multiple times.

Context

End-users trying to edit files can duplicated text inserted a line below after the first character.

Your Environment

• Version used: "@elm-tooling/elm-language-server": "2.8.0" (installed via npm)
• Editor used: Zed Nightly 0.167.0
• Environment name and version node-v18.15.0-darwin-arm64
• Operating System and version: macOS Sonoma 14.7

Extra info

See also:

• Editing elm code incorrectly triggers linkedEditingRange mode with elm-language-server zed-industries/zed#21843

zed video

Screen.Recording.2024-12-15.at.21.43.53.mov

vscode video

Screen.Recording.2024-12-16.at.14.13.04.mov

---

elm-language-server LSP logs: rpc messages

// Send:
{
  "jsonrpc": "2.0",
  "method": "textDocument/didChange",
  "params": {
    "textDocument": {
      "uri": "file:///private/tmp/elm/src/Main.elm",
      "version": 48
    },
    "contentChanges": [
      {
        "range": {
          "start": {
            "line": 1,
            "character": 0
          },
          "end": {
            "line": 1,
            "character": 0
          }
        },
        "text": "a"
      }
    ]
  }
}
// Receive:
{
  "jsonrpc": "2.0",
  "method": "window/logMessage",
  "params": {
    "type": 3,
    "message": "Changed text document, going to parse it. file:///private/tmp/elm/src/Main.elm"
  }
}
// Send
{
  "jsonrpc": "2.0",
  "id": 135,
  "method": "textDocument/linkedEditingRange",
  "params": {
    "textDocument": {
      "uri": "file:///private/tmp/elm/src/Main.elm"
    },
    "position": {
      "line": 1,
      "character": 1
    }
  }
}
// Receive
{
  "jsonrpc": "2.0",
  "id": 135,
  "result": {
    "ranges": [
      {
        "start": {
          "line": 1,
          "character": 0
        },
        "end": {
          "line": 1,
          "character": 1
        }
      },
      {
        "start": {
          "line": 2,
          "character": 0
        },
        "end": {
          "line": 2,
          "character": 1
        }
      }
    ]
  }
}

Thanks!