JsonParseError variantv0.1.0

Why parsing stopped, and where.

pub variant JsonParseError {
    Lexical(JsonLexError, uint),
    Unexpected(uint),
    Truncated(uint),
    TrailingContent(uint),
    DuplicateName(uint),
    TooDeep(uint),
    TooManyEntries(uint),
    OutOfMemory(uint),
    BadSurrogate(uint),
    Source(uint)
}

Failure-only: there is no case meaning nothing went wrong, because a parse that did not fail hands back a document instead. Every case carries the zero-based byte offset into the input where the parser stopped, which is the first thing anybody debugging a document asks for and used to live in a separate structure that a caller had to remember to read.

Cases

Name	Description
`Lexical(JsonLexError, uint)`	The lexer refused the input, for the reason carried. Nested rather than reported beside this, so a caller holding the failure cannot be holding half of it.
`Unexpected(uint)`	A token that cannot appear where it did.
`Truncated(uint)`	The document ended in the middle of a value.
`TrailingContent(uint)`	Text after the end of the top-level value. The offset is where that text begins.
`DuplicateName(uint)`	An object contained the same name twice, under the rejecting policy. The offset is the second occurrence.
`TooDeep(uint)`	Containers nested deeper than the limit allowed.
`TooManyEntries(uint)`	A container held more entries than the limit allowed.
`OutOfMemory(uint)`	The allocator refused.
`BadSurrogate(uint)`	A `\u` escape naming half of a surrogate pair with no valid partner. JSON's escapes are UTF-16, and a lone surrogate is not a character; the offset is the escape that has no partner.
`Source(uint)`	The stream a `JsonEventReader` reads from failed with something other than its end. Only a streaming reader reports this; the source's own `IoError` is kept on the reader, through `JsonEventReader::SourceError`.

Implements ParseFailure

JsonParseError conforms to ParseFailure.

`Offset`

pub func Offset(self: &JsonParseError) -> uint

Where in the input parsing stopped. Borrows the failure and leaves it untouched. Cannot fail; runs in constant time and allocates nothing.

Returns: the zero-based byte offset into the document

Source

Implements Display

JsonParseError conforms to Display.

`WriteDisplay`

pub func WriteDisplay(
    self: &JsonParseError,
    writer: &var TextWriter,
    spec: FormatSpec
) -> ! FormatError

Writes the description of why parsing stopped, without the position. The offset is a number a caller renders where it makes sense for them — beside a line and column they computed, or not at all — so it is not written into the middle of a sentence here. Debug carries it. Reports whatever the writer reported, and UnsupportedRequest for any style or precision.

Name	Type	Description
`writer`	`&var TextWriter`	the destination
`spec`	`FormatSpec`	what the placeholder asked for

Returns: success when the whole description was accepted

Source

Implements Debug

JsonParseError conforms to Debug.

`WriteDebug`

pub func WriteDebug(
    self: &JsonParseError,
    writer: &var TextWriter,
    spec: FormatSpec
) -> ! FormatError

Names the case and its position: JsonParseError::Unexpected(12). A lexical failure names both, so nothing about it has to be looked up elsewhere: JsonParseError::Lexical(BadEscape, 12). Reports whatever the writer reported, and UnsupportedRequest for any style or precision.

Name	Type	Description
`writer`	`&var TextWriter`	the destination
`spec`	`FormatSpec`	what the placeholder asked for

Returns: success when the whole name was accepted

Source

JsonNumber

A JSON number, held as the text it was written with.

JsonParser

A parser over a document.

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