gohugoio/hugo · error · Error

Error parsing JSON '${new TextDecoder().decode(arr)}' from s

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.

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)

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

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

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