DayuanJiang/next-ai-draw-io · error · Error

No encoded data found in the diagram element

Error message

No encoded data found in the diagram element

What it means

A <diagram> element was found, but its textContent is empty, so there is no base64-encoded compressed diagram data to inflate. In draw.io files each <diagram> holds base64 (deflate-raw + urlencode) mxGraphModel data; an empty one means the page exists but has no stored content.

Solutions

1. Skip empty diagrams or treat them as blank pages instead of decoding
2. If constructing pages programmatically, embed the base64 body: '<diagram>' + btoa(deflatedMxGraphModel) + '</diagram>'
3. Validate textContent is non-empty before calling and report which page id/name is empty
4. Regenerate the file from draw.io if the source is corrupt

Example fix

// before
const xml = decodeDiagramFromSvg(dataUri) // '<diagram id="1" name="p"/>'

// after
const diagrams = [...mxfileDoc.querySelectorAll('diagram')].filter(d => d.textContent?.trim())
if (!diagrams.length) throw new Error('file has no pages with content')

const diagrams = [...mxfileDoc.querySelectorAll('diagram')].filter(d => d.textContent?.trim())
if (diagrams.length === 0) throw new Error('mxfile contains no diagram with encoded data')

function diagramHasPayload(d: Element): boolean {
  return Boolean(d.textContent && d.textContent.trim().length > 0)
}

for (const d of diagrams) { if (!diagramHasPayload(d)) continue; results.push(decodeDiagram(d)) }

When it happens

Trigger: Calling the decoder on an <mxfile> whose <diagram> element is self-closing or whitespace-only (e.g. '<diagram id="x" name="p"/>'), or a diagram whose content was stripped during processing.

Common situations: Hand-constructed mxfile XML that adds the diagram element but forgets the encoded body; sanitizers/XML transforms that drop text nodes; empty placeholder pages created by string templating.

Related errors

• No SVG element found in the input string.
• addPageToDoc: opts.xml must be a bare
• No diagram element found
• addPageToDoc: opts.xml must be a bare
• Failed to construct element for new page

AI-assisted analysis of DayuanJiang/next-ai-draw-io@155ef4f7ac (2026-08-27). Data as JSON: /api/errors/a731173693682bea. Report an issue: GitHub.

Appendix: source

Thrown at lib/utils.ts:1713

        function decodeHtmlEntities(str: string) {
            const textarea = document.createElement("textarea") // Use built-in element
            textarea.innerHTML = str
            return textarea.value
        }
        const xmlContent = decodeHtmlEntities(encodedContent)

        // 4. Parse the XML content
        const xmlDoc = parser.parseFromString(xmlContent, "text/xml")
        const diagramElement = xmlDoc.querySelector("diagram")

        if (!diagramElement) {
            throw new Error("No diagram element found")
        }
        // 5. Extract base64 encoded data
        const base64EncodedData = diagramElement.textContent

        if (!base64EncodedData) {
            throw new Error("No encoded data found in the diagram element")
        }

        // 6. Decode base64 data
        const binaryString = atob(base64EncodedData)

        // 7. Convert binary string to Uint8Array
        const len = binaryString.length
        const bytes = new Uint8Array(len)
        for (let i = 0; i < len; i++) {
            bytes[i] = binaryString.charCodeAt(i)
        }

        // 8. Decompress data using pako (equivalent to zlib.decompress with wbits=-15)
        const decompressedData = pako.inflate(bytes, { windowBits: -15 })

        // 9. Convert the decompressed data to a string
        const decoder = new TextDecoder("utf-8")
        const decodedString = decoder.decode(decompressedData)

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