Formatting of document not working

[ydaveluy]

Hello,

I have some formatting issues with my dsl.

Before calling AbstractFormatter.avoidOverlappingEdits I have the following edits:

  newText:'', start:'1:1', end:'1:1'
  newText:' ', start:'1:10', end:'1:11'
  newText:'', start:'2:1', end:'2:2'
  newText:'', start:'3:1', end:'3:1'
  newText:'', start:'2:1', end:'2:2'
  newText:'', start:'3:1', end:'3:1'

and after:

  newText:'', start:'1:1', end:'1:1'
  newText:' ', start:'1:10', end:'1:11'
  newText:'', start:'2:1', end:'2:2'
  newText:'', start:'2:1', end:'2:2'
  newText:'', start:'3:1', end:'3:1'

The newText:'', start:'2:1', end:'2:2' edit is duplicated which prevent from formatting the whole file.

As a workaround I overrode the avoidOverlappingEdits method:

    protected override avoidOverlappingEdits(textDocument: TextDocument, textEdits: TextEdit[]): TextEdit[] {
        const edits: TextEdit[] = [];
        for (const edit of textEdits) {
            let last = edits[edits.length - 1];
            while (last) {
                const currentStart = textDocument.offsetAt(edit.range.start);
                const lastEnd = textDocument.offsetAt(last.range.end);
                if (currentStart < lastEnd) {
                    edits.pop();
                    last = edits[edits.length - 1];
                }
                else {
                    break;
                }
            }
            edits.push(edit);
        }
        return edits;
    }

Is it an issue in AbstractFormatter.avoidOverlappingEdits or somewhere else ?

[msujew]

@ydaveluy Can you please open an issue for this? While the formatter implementation (i.e. your formatter) shouldn't generate duplicate formattings in the first place (since the formatting can become non-deterministic), the avoidOverlappingEdits method should avoid such errors even if they exist.

[ydaveluy]

Issues opened.

In my case the duplicated edit is on a hidden ML_COMMENT rule.
This is the text that produce the duplicate formatting

catalogue Test           
 /**
*/

I don't perform any operation in my formatter on the ML_COMMENT rule.
I will have a look on createHiddenTextEdits to see if creates the duplicates.

[ydaveluy]

The createHiddenTextEdits is called twice for the same node:

A firts time here (nextNode is hidden) :

langium/packages/langium/src/lsp/formatter.ts

Line 243 in b2c40e3

const nodeEdits = this.createTextEdit(node, nextNode, appendFormatting, context);

And a second time here:

langium/packages/langium/src/lsp/formatter.ts

Line 253 in b2c40e3

const hiddenEdits = this.createHiddenTextEdits(lastNode, node, undefined, context);

I locally changed

langium/packages/langium/src/lsp/formatter.ts

Line 242 in b2c40e3

if (nextNode) {

to

if (nextNode && !nextNode.hidden)

With this change hidden nodes are formatted on the next iteration only