Troubleshooting¶

Reading error messages¶

Every parse error names a zero-based byte offset, at position N. The first byte of the input is position 0.

Expected , or } or newline but found Eof at position 5

This message, for the input {a: 1, means the parser reached the end of the input (Eof) at byte 5 while it still expected a comma, a closing brace or a newline. Common messages:

Message	Usual cause
`Expected , or } or newline but found Eof`	The input ends inside an object
`Expected , or ] or newline but found …`	A missing comma or a wrong closing bracket in an array
`Expected string key but found UnquotedString`	An unquoted key while `allow_unquoted_keys` is off
`Expected : but found RightBrace`	An unquoted value with spaces, such as `{a: two words}`
`Unexpected character 'a'`	A bare word while the lexer is in strict mode (see below)
`Trailing comma at position N`	A trailing comma while `allow_trailing_commas` is off
`Expected end of input but found …`	Two top-level values, such as `{"a":1}{"b":2}`
`Depth limit exceeded at position N`	Nesting deeper than `max_depth`

To see the line and column in the CLI, add --verbose-errors. For a file it also prints the lines around the error with a ^ under the column.

"Unexpected character" after turning off comments¶

--no-comments (or allow_comments: false) puts the lexer in strict mode. Strict mode rejects unquoted keys, unquoted values and single-quoted strings even though their own options are still on. If you need to reject comments but keep the other extensions, there is no combination of options for that in this version; strip comments before parsing instead.

Object keys come out in a different order¶

Value::Object is a hash map (FxHashMap). Key order is not kept in Rust, in the CLI output, in the WebAssembly output or in the C output, and Python dicts built by vexy_json.parse can list keys in a different order too. If order matters, sort the keys after parsing.

The CLI writes nothing for empty input¶

For empty standard input, vexy-json prints No input provided to standard error and exits with status 0. With --validate it prints nothing. The library returns null for empty input.

`--repair` refuses to repair¶

The CLI only closes open brackets and braces at the very end of the input. It refuses when that would invent data, for example when the input stops in the middle of a string, after a comma or inside a comment. The message says which case applied. See Repairing incomplete input.

WebAssembly: errors on strings with escapes¶

parse_json and the other WebAssembly functions fail on strings that contain an escaped quote (\") or a control character such as \n:

control character (\u0000-\u001F) found while parsing a string at line 2 column 0

The parser itself accepts these strings; the failure happens when the WebAssembly wrapper converts the result to a JSON string. Until this is fixed, parse such input with the CLI, the Python package or the Rust library.

Python: `dumps` output is not valid JSON¶

vexy_json.dumps(obj) without indent does not escape quotes or control characters inside strings. Pass indent=2 (which escapes) or use the standard library's json.dumps.

C: the output is wrapped in type names¶

The C functions return Serde's tagged form of the value, such as {"Object":{"a":{"Number":{"Integer":1}}}}, not plain JSON. See C and C++.

The demo shows "JSON.parse" behaviour¶

The interactive demo falls back to the browser's JSON.parse when the WebAssembly module fails to load, and then rejects every extension. Open the browser console: a Failed to load WASM message names the cause. Serve the demo over HTTP; browsers do not load WebAssembly modules from file:// pages.

Very large or deeply nested input¶

The default max_depth is 128. Raise it for legitimately deep data.
For files with one JSON value per line, use --ndjson (CLI), NdJsonParser (Rust) or StreamingParser.parse_lines (Python) instead of parsing the whole file as one value.
--parallel-parse splits one large input into chunks of at least --chunk-size bytes and parses them on several threads.

Reporting a problem¶

Open an issue at github.com/vexyart/vexy-json/issues with the smallest input that shows the problem, the interface you used, the version (vexy-json --version or vexy_json.__version__) and the full error message.