Use of document.insertLines is deprecated. Use the…

Error message

Use of document.insertLines is deprecated. Use the insertFullLines method instead.

What it means

A deprecation warning printed by Document.insertLines. The method still works — it delegates to insertFullLines — but the API was renamed to reflect that it inserts complete lines, and callers are expected to migrate.

Solutions

Replace doc.insertLines(row, lines) with doc.insertFullLines(row, lines)
If you want silent text insertion rather than whole-line semantics, use doc.insert(position, text) instead
Audit wrapper libraries for passthrough calls to insertLines
Acknowledge the warning as benign until migration is done — behavior is unchanged

Example fix

// before
doc.insertLines(5, ['foo', 'bar']);
// after
doc.insertFullLines(5, ['foo', 'bar']);

Defensive patterns

Strategy: validation

Validate before calling

if (typeof doc.insertFullLines !== 'function') throw new Error('insertFullLines unavailable; upgrade ace');
doc.insertFullLines(row, lines);

Type guard

function hasFullLinesApi(doc) { return doc && typeof doc.insertFullLines === 'function'; }

Try / catch

try {
  doc.insertFullLines(row, lines);
} catch (e) {
  console.error('line insert failed', e);
}

Prevention

Migrate to insertFullLines/removeFullLines/insertMergedLines across the board
Run tests with console warnings visible so deprecations surface in CI
Avoid wrapping Document methods in your own facade that may lag the API

When it happens

Trigger: Calling session.doc.insertLines(row, lines) or document.insertLines directly in code written against the old Ace Document API.

Common situations: Old editor plugins and legacy codebases ported forward across Ace versions; tutorials or snippets predating the API rename.

Related errors

AI-assisted analysis of ajaxorg/ace@2c1eddc392 (2026-08-30). Data as JSON: /api/errors/63028765d8c17a08. Report an issue: GitHub.

Appendix: source

Thrown at src/document.js:201

            // Handle a multi-line range.
            lines = this.getLines(range.start.row, range.end.row);
            lines[0] = (lines[0] || "").substring(range.start.column);
            var l = lines.length - 1;
            if (range.end.row - range.start.row == l)
                lines[l] = lines[l].substring(0, range.end.column);
        }
        return lines;
    }

    // Deprecated methods retained for backwards compatibility.
    /**
     * @param row
     * @param lines
     
     * @deprecated
     */
    insertLines(row, lines) {
        console.warn("Use of document.insertLines is deprecated. Use the insertFullLines method instead.");
        return this.insertFullLines(row, lines);
    }

    /**
     * @param firstRow
     * @param lastRow
     * @returns {String[]}
     
     * @deprecated
     */
    removeLines(firstRow, lastRow) {
        console.warn("Use of document.removeLines is deprecated. Use the removeFullLines method instead.");
        return this.removeFullLines(firstRow, lastRow);
    }

    /**
     * @param position
     * @returns {Point}

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