StreamParser fails when language tags are split across chunk boundaries

[ddeboer]

Bug: StreamParser fails when language tags are split across chunk boundaries

The StreamParser throws Unexpected "-nl" when a language tag like @nl-nl happens to be split across two HTTP response chunks (e.g. @nl in one chunk, -nl in the next).

Parsing the same data as a complete string with Parser.parse() works fine.

Reproduction

The issue occurs when streaming large SPARQL CONSTRUCT responses (~12 MB+) through StreamParser via fetch-sparql-endpoint. The exact split point varies between runs because HTTP chunking is non-deterministic, making the error intermittent.

import {StreamParser, Parser} from 'n3';

// Non-streaming: always works
const parser = new Parser({format: 'text/turtle'});
const quads = parser.parse(largeTurtleString); // OK

// Streaming: intermittently fails with "Unexpected '-nl'"
const streamParser = new StreamParser({format: 'text/turtle'});
responseStream.pipe(streamParser); // ERROR at random positions

Environment

• n3 v2.0.3
• Node.js v24
• Data contains literals with @nl-nl language tags
• The SPARQL server (QLever) returns N-Triples content with Content-Type: text/turtle, so fetch-sparql-endpoint passes text/turtle as the format to StreamParser. N-Triples is valid Turtle, but the Turtle tokenizer may handle chunk boundaries differently.

Expected behaviour

The StreamParser should buffer incomplete tokens across chunk boundaries, recognising that @nl at the end of a chunk is an incomplete language tag when followed by -nl in the next chunk.

Observed behaviour

The parser treats the chunk boundary as a token boundary, yielding @nl as a complete language tag, then encounters -nl as the start of the next token and throws:

Unexpected "-nl" on line 64895.

The line number and occurrence vary between runs depending on how HTTP chunks are split.