parse(text: string) -- Модуль
- std.
json → - Получатель
- Неприменимо
- Минимальное число аргументов
- 1
- Максимальное число аргументов
- 1
Declaration and parameters
СсылкаДоступность
Включено по умолчанию · Не определено
Import std.json in language mode 5.21.
The current compiler selects std/json.tpz for this language mode. Availability in other released editions and inclusion in each installed distribution are Pending.
Получатель
Ограничения параметров
parse accepts one complete JSON value with leading and trailing space, tab, CR or LF. An empty input, a byte order mark, comments, trailing commas and trailing nonwhitespace return Err. Scalars are valid roots.
JSON numbers follow the JSON decimal grammar. A leading plus, redundant leading zero, missing fraction or exponent digits, NaN and infinities are invalid. Every accepted lexeme is stored exactly without conversion to binary floating point. Its magnitude need not fit int or float.
Quoted strings decode the JSON escapes and valid UTF 16 surrogate pairs into Unicode scalar values. Unescaped controls, malformed escapes and unpaired surrogates return Err. No Unicode normalization is performed.
Object names are compared after escape decoding. A repeated name returns Err before its value is converted into the object. The second name does not overwrite the first. Arrays preserve source order and object traversal follows the decoded key order.
The root starts at depth zero. Descending into an array element or object value adds one. Depths through 128 are accepted and the first value at depth 129 returns Err with a nesting limit message.
A parse failure returns a record containing a nonempty cause message and one based line and column integers. Columns count Unicode scalar values. CRLF is one line break and a lone CR or LF also starts the next line. The first offending scalar is the location. An invalid escape points to its backslash. A repeated name points to its second opening quote. An incomplete input points immediately after the final scalar.
The text expression is evaluated once before parsing. The parser consumes through trailing whitespace before returning Ok. It performs no I/O, invokes no typed decoder and exposes no partial tree. Malformed data uses the Result error channel rather than a runtime diagnostic.
Результат
The declared result type is Result<JSON.
Эффекты
Ошибки
Result and effects
СсылкаParse a complete JSON document without losing number text. Return a structured cause and scalar position for invalid input.
Related entries
СсылкаParse a complete JSON document
СсылкаParse a complete JSON document
parse accepts one complete JSON value with leading and trailing space, tab, CR or LF. An empty input, a byte order mark, comments, trailing commas and trailing nonwhitespace return Err. Scalars are valid roots.
JSON numbers follow the JSON decimal grammar. A leading plus, redundant leading zero, missing fraction or exponent digits, NaN and infinities are invalid. Every accepted lexeme is stored exactly without conversion to binary floating point. Its magnitude need not fit int or float.
Quoted strings decode the JSON escapes and valid UTF 16 surrogate pairs into Unicode scalar values. Unescaped controls, malformed escapes and unpaired surrogates return Err. No Unicode normalization is performed.
Object names are compared after escape decoding. A repeated name returns Err before its value is converted into the object. The second name does not overwrite the first. Arrays preserve source order and object traversal follows the decoded key order.
The root starts at depth zero. Descending into an array element or object value adds one. Depths through 128 are accepted and the first value at depth 129 returns Err with a nesting limit message.
A parse failure returns a record containing a nonempty cause message and one based line and column integers. Columns count Unicode scalar values. CRLF is one line break and a lone CR or LF also starts the next line. The first offending scalar is the location. An invalid escape points to its backslash. A repeated name points to its second opening quote. An incomplete input points immediately after the final scalar.
The text expression is evaluated once before parsing. The parser consumes through trailing whitespace before returning Ok. It performs no I/O, invokes no typed decoder and exposes no partial tree. Malformed data uses the Result error channel rather than a runtime diagnostic.
Причина
Exact number storage avoids losing document data before a caller chooses a numeric type. Rejecting duplicate names prevents source order from silently selecting a value. A single scalar based location rule makes errors actionable across Unicode text and newline styles.
Retain numbers beyond binary and integer precision
Ссылкаimport std.jsonimport std.testimport std.iofor text in (["9007199254740993", "9223372036854775808", "-0", "1.2300e+03", "1e9999"]) {let value = test.assertOk(json.parse(text))io.writeLine(test.assertSome(value.numberText()))}
9007199254740993
9223372036854775808
-0
1.2300e+03
1e9999
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
90071992547409939223372036854775808-01.2300e+031e9999
Locate the first invalid scalar and end of input
Ссылкаimport std.jsonimport std.iofor text in (["", "true false", "[1,]", "[1 x]", "[\rtrue,\r?]"]) {match (json.parse(text)) {case Ok(_) => io.writeLine("accepted")case Err(error) => io.writeLine("{error.line},{error.column}")}}
1,1
1,6
1,4
1,4
3,1
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
1,11,61,41,43,1
Reject a repeated decoded key at its opening quote
Ссылкаimport std.jsonimport std.iomatch (json.parse("\{\"a\":1,\"\\u0061\":2\}")) {case Ok(_) => io.writeLine("accepted")case Err(error) => io.writeLine("{error.line},{error.column}")}
1,8
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
1,8
Decode surrogate pairs and reject malformed JSON spellings
Ссылкаimport std.jsonimport std.testimport std.iolet value = test.assertOk(json.parse("\"\\uD83D\\uDE00\""))test.assertEq(test.assertSome(value.asString()), "😀")for text in (["01", "+1", "1.", "1e", "NaN", "\"\\uD800\"", "\"\\uDC00\""]) {match (json.parse(text)) {case Ok(_) => io.writeLine("accepted")case Err(_) => io.writeLine("invalid")}}
invalid
invalid
invalid
invalid
invalid
invalid
invalid
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
invalidinvalidinvalidinvalidinvalidinvalidinvalid
Accept depth 128 and reject the next child
Ссылкаimport std.jsonimport std.iolet mut text = "0"for level in (0 ..< 128) {text = "[" + text + "]"}match (json.parse(text)) {case Ok(_) => io.writeLine("depth 128 accepted")case Err(_) => io.writeLine("depth 128 rejected")}match (json.parse("[" + text + "]")) {case Ok(_) => io.writeLine("depth 129 accepted")case Err(_) => io.writeLine("depth 129 rejected")}
depth 128 accepted
depth 129 rejected
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
depth 128 accepteddepth 129 rejected