jgraph/drawio-desktop · error · Error

Invalid file data

Error message

Invalid file data

What it means

saveDraft (src/main/electron.js:3355-3362) refuses to persist a draft whose data fails checkFileContent — i.e. it does not begin with a recognised diagram signature (XML, mxfile/mxGraphModel/mxlibrary, JSON, PDF, PNG, JPG, SVG, VSDX, VSSX). Drafts are autosave artefacts, so refusing malformed content prevents corrupt drafts overwriting good ones.

Source

Thrown at src/main/electron.js:3361

			let stat = await fsProm.lstat(draftsPaths[i]);
			drafts.push({data: await fsProm.readFile(draftsPaths[i], 'utf8'), 
						created: stat.ctimeMs,
						modified: stat.mtimeMs,
						path: draftsPaths[i]});
		}
		catch (e){} // Ignore
	}

	return drafts;
};

async function saveDraft(fileObject, data)
{
	var draftFileName = fileObject.draftFileName || getDraftFileName(fileObject);

	if (!checkFileContent(data))
	{
		throw new Error('Invalid file data');
	}

	await assertWritablePath(draftFileName);

	let draftFh;

	try
	{
		draftFh = await fsProm.open(draftFileName, O_SYNC | O_CREAT | O_WRONLY | O_TRUNC);
		await fsProm.writeFile(draftFh, data, 'utf8');
		await draftFh.sync(); // Flush to disk
	}
	finally
	{
		await draftFh?.close();
	}

	if (isWin)

View on GitHub (pinned to 403a2cb79f)

Solutions

1. Confirm `data` is a non-empty diagram string starting with '<' (mxfile/mxGraphModel) or '['/'{' (JSON) before calling saveDraft.
2. If you intentionally store base64, pass the matching encoding so checkFileContent decodes the header correctly.
3. Suppress autosave when the editor buffer is empty or in an intermediate (non-serialised) state.

Example fix

// before
saveDraft(fileObject, editor.getGraphXmlOrNull());

// after
const xml = editor.getGraphXmlOrNull();
if (xml) saveDraft(fileObject, xml);

function isValidDiagramString(data) {
	return typeof data === 'string' && data.length > 0 &&
		/^[<\[{]/.test(data[0]);
}
if (!isValidDiagramString(data)) throw new Error('nothing to draft');

const isValidDiagramString = (d) => typeof d === 'string' && d.length > 0 && /^[<\[{]/.test(d[0]);

try { await saveDraft(fileObject, data); }
catch (e) {
	if (e.message === 'Invalid file data') { /* skip this autosave cycle, data not ready */ return; }
	throw e;
}

When it happens

Trigger: Autosave fires with data that is null, empty, a fragment that does not start with a known magic byte/signature, or a string whose first 16 chars do not match any allowed header (e.g. plain text that is not XML/JSON, a base64 payload not in 'base64' encoding).

Common situations: Renderer passed an empty string during initial load; an exporter handed a non-diagram blob; encoding mismatch (data is base64 but enc was omitted so checkFileContent decoded it as raw text).

Related errors

• bad arg: ${name}
• path not authorised
• bad arg: fileObject.path
• bad arg: fileObject

AI-assisted analysis of jgraph/drawio-desktop@403a2cb79f (2026-08-13). Data as JSON: /api/errors/02346d3993420b0c. Report an issue: GitHub.