gohugoio/hugo · error · Error

Error parsing JSON ' ' from stdin

Error message

Error parsing JSON '${new TextDecoder().decode(arr)}' from stdin: ${e.message}

What it means

Each newline-delimited chunk read from stdin is decoded and passed to JSON.parse (common.js:55). If the chunk is not valid JSON, the parse error is rethrown with the offending text included so the malformed line is visible in the error message.

Solutions

1. Validate the producer emits strict JSONL: one JSON object per line, UTF-8, no BOM
2. Capture the offending line printed in the error and fix the producer
3. Ensure 0x0A newlines separate each message as the splitter expects

function isValidJsonl(line) { try { JSON.parse(line); return true; } catch { return false; } }
// producer: assert isValidJsonl(line) before writing to the pipe

try { message = JSON.parse(text); } catch (e) { logBadLine(text, e); continue; }

When it happens

Trigger: A line in the JSONL stream that is not valid JSON (truncated, non-JSON, mixed encoding, or split incorrectly) reaches JSON.parse.

Common situations: The producer writes non-JSONL or partial JSON; a BOM/encoding mismatch; an incomplete chunk because newlines were absent; debug logging interleaved into the stream.

Related errors

• Error reading from stdin
• ${value}
• {}
• timeout
• {}

AI-assisted analysis of gohugoio/hugo@52c9bd7908 (2026-08-09). Data as JSON: /api/errors/3172e3f554a64fe5. Report an issue: GitHub.

Appendix: source

Thrown at internal/warpc/js/common.js:57

		currentLine = [...currentLine, ...buffer.subarray(0, bytesRead)];

		// Check for newline. If not, we need to read more data.
		if (!currentLine.includes(10)) {
			continue;
		}

		// Split array into chunks by newline.
		let i = 0;
		for (let j = 0; i < currentLine.length; i++) {
			if (currentLine[i] === 10) {
				const chunk = currentLine.splice(j, i + 1);
				const arr = new Uint8Array(chunk);
				let message;
				try {
					message = JSON.parse(new TextDecoder().decode(arr));
				} catch (e) {
					throw new Error(`Error parsing JSON '${new TextDecoder().decode(arr)}' from stdin: ${e.message}`);
				}

				try {
					handle(message);
				} catch (e) {
					let header = message.header;
					header.err = e.message;
					writeOutput({ header: header });
				}

				j = i + 1;
			}
		}
		// Remove processed data.
		currentLine = currentLine.slice(i);
	}
}

View on GitHub (pinned to 52c9bd7908)