@messageformat/parser
v5.1.0
Published
An AST parser for ICU MessageFormat strings
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@messageformat/parser
An AST parser for ICU MessageFormat strings – part of messageformat.
The parse(src, [options])
function takes two parameters, first the
string to be parsed, and a second optional parameter options
, an object with
the following possible keys:
cardinal
andordinal
– Arrays of valid plural categories for the current locale, used to validateplural
andselectordinal
keys. If these are missing or set to false, the full set of valid Unicode CLDR keys is used:'zero', 'one', 'two', 'few', 'many', 'other'
. To disable this check, pass in an empty array.strict
– By default, the parsing applies a few relaxations to the ICU MessageFormat spec. Settingstrict: true
will disable these relaxations:- The
argType
ofsimpleArg
formatting functions will be restricted to the set ofnumber
,date
,time
,spellout
,ordinal
, andduration
, rather than accepting any lower-case identifier that does not start with a number. - The optional
argStyle
ofsimpleArg
formatting functions will not be parsed as any other text, but instead as the spec requires: "In argStyleText, every single ASCII apostrophe begins and ends quoted literal text, and unquoted {curly braces} must occur in matched pairs." - Inside a
plural
orselectordinal
statement, a pound symbol (#
) is replaced with the input number. By default,#
is also parsed as a special character in nested statements too, and can be escaped using apostrophes ('#'
). In strict mode#
will be parsed as a special character only directly inside aplural
orselectordinal
statement. Outside those,#
and'#'
will be parsed as literal text.
- The
The parser only supports the default DOUBLE_OPTIONAL
apostrophe mode, in
which a single apostrophe only starts quoted literal text if it immediately
precedes a curly brace {}
, or a pound symbol #
if inside a plural format. A
literal apostrophe '
is represented by either a single '
or a doubled ''
apostrophe character.
This package was previously named messageformat-parser.
Installation
npm install @messageformat/parser
Usage
> const { parse } = require('@messageformat/parser')
// For clarity, the examples below do not show the ctx object included for each token
> parse('So {wow}.')
[ { type: 'content', value: 'So ' },
{ type: 'argument', arg: 'wow' },
{ type: 'content', value: '.' } ]
> parse('Such { thing }. { count, selectordinal, one {First} two {Second}' +
' few {Third} other {#th} } word.')
[ { type: 'content', value: 'Such ' },
{ type: 'argument', arg: 'thing' },
{ type: 'content', value: '. ' },
{ type: 'selectordinal',
arg: 'count',
cases: [
{ key: 'one', tokens: [ { type: 'content', value: 'First' } ] },
{ key: 'two', tokens: [ { type: 'content', value: 'Second' } ] },
{ key: 'few', tokens: [ { type: 'content', value: 'Third' } ] },
{ key: 'other',
tokens: [ { type: 'octothorpe' }, { type: 'content', value: 'th' } ] }
] },
{ type: 'content', value: ' word.' } ]
> parse('Many{type,select,plural{ numbers}selectordinal{ counting}' +
'select{ choices}other{ some {type}}}.')
[ { type: 'content', value: 'Many' },
{ type: 'select',
arg: 'type',
cases: [
{ key: 'plural', tokens: [ { type: 'content', value: 'numbers' } ] },
{ key: 'selectordinal', tokens: [ { type: 'content', value: 'counting' } ] },
{ key: 'select', tokens: [ { type: 'content', value: 'choices' } ] },
{ key: 'other',
tokens: [ { type: 'content', value: 'some ' }, { type: 'argument', arg: 'type' } ] }
] },
{ type: 'content', value: '.' } ]
> parse('{Such compliance')
// ParseError: invalid syntax at line 1 col 7:
//
// {Such compliance
// ^
> const msg = '{words, plural, zero{No words} one{One word} other{# words}}'
> parse(msg)
[ { type: 'plural',
arg: 'words',
cases: [
{ key: 'zero', tokens: [ { type: 'content', value: 'No words' } ] },
{ key: 'one', tokens: [ { type: 'content', value: 'One word' } ] },
{ key: 'other',
tokens: [ { type: 'octothorpe' }, { type: 'content', value: ' words' } ] }
] } ]
> parse(msg, { cardinal: [ 'one', 'other' ], ordinal: [ 'one', 'two', 'few', 'other' ] })
// ParseError: The plural case zero is not valid in this locale at line 1 col 17:
//
// {words, plural, zero{
// ^
For more example usage, please take a look at our test suite.
Structure
The output of parse()
is an array of tokens, Array<Content | PlainArg | FunctionArg | Select>
:
interface Content {
type: 'content'
value: string
ctx: Context
}
interface PlainArg {
type: 'argument'
arg: string
ctx: Context
}
interface FunctionArg {
type: 'function'
arg: string
key: string
param?: Array<Content | PlainArg | FunctionArg | Select | Octothorpe>
ctx: Context
}
interface Select {
type: 'plural' | 'select' | 'selectordinal'
arg: string
cases: Array<SelectCase>
pluralOffset?: number
ctx: Context
}
interface SelectCase {
key: string
tokens: Array<Content | PlainArg | FunctionArg | Select | Octothorpe>
ctx: Context
}
interface Octothorpe {
type: 'octothorpe'
ctx: Context
}
interface Context {
offset: number
line: number
col: number
text: string
lineBreaks: number
}
Messageformat is an OpenJS Foundation project, and we follow its Code of Conduct.