eslint-plugin-formatjs

This eslint plugin allows you to enforce certain rules in your ICU message. This is currently under development

Usage

npm install eslint-plugin-formatjs

Then in your eslint config:

{
"plugins": ["formatjs"],
"rules": {
"formatjs/no-offset": "error"
}
}

Currently this uses intl.formatMessage, defineMessage, defineMessages, <FormattedMessage> from react-intl as hooks to verify the message. Therefore, in your code use 1 of the following mechanisms:

import {defineMessages, defineMessage} from 'react-intl';
const messages = defineMessages({
foo: {
defaultMessage: 'foo',
description: 'bar',
},
});
defineMessage({
defaultMessage: 'single message',
});
import {FormattedMessage} from 'react-intl';
<FormattedMessage defaultMessage="foo" description="bar" />;
function foo() {
intl.formatMessage({
defaultMessage: 'foo',
});
}

Available Rules

blacklist-elements

This blacklists usage of specific elements in ICU message.

Why

  • Certain translation vendors cannot handle things like selectordinal

Available elements

enum Element {
// literal text, like `defaultMessage: 'some text'`
literal = 'literal',
// placeholder, like `defaultMessage: '{placeholder} var'`
argument = 'argument',
// number, like `defaultMessage: '{placeholder, number} var'`
number = 'number',
// date, like `defaultMessage: '{placeholder, date} var'`
date = 'date',
// time, like `defaultMessage: '{placeholder, time} var'`
time = 'time',
// select, like `defaultMessage: '{var, select, foo{one} bar{two}} var'`
select = 'select',
// selectordinal, like `defaultMessage: '{var, selectordinal, one{one} other{two}} var'`
selectordinal = 'selectordinal',
// plural, like `defaultMessage: '{var, plural, one{one} other{two}} var'`
plural = 'plural',
}

Example

{
"plugins": ["formatjs"],
"rules": {
"formatjs/blacklist-elements": [2, ["selectordinal"]]
}
}

enforce-description

This enforces description in the message descriptor.

Why

  • Description provides helpful context for translators
import {defineMessages} from 'react-intl';
const messages = defineMessages({
// WORKS
foo: {
defaultMessage: 'foo',
description: 'bar',
},
// FAILS
bar: {
defaultMessage: 'bar',
},
});

Options

{
"plugins": ["formatjs"],
"rules": {
"formatjs/enforce-description": ["error", "literal"]
}
}

Setting literal forces description to always be a string literal instead of function calls or variables. This is helpful for extraction tools that expects description to always be a literal

enforce-default-message

This enforces defaultMessage in the message descriptor.

Why

  • Can be useful in case we want to extract messages for translations from source code. This way can make sure people won't forget about defaultMessage
import {defineMessages} from 'react-intl';
const messages = defineMessages({
// WORKS
foo: {
defaultMessage: 'This is default message',
description: 'bar',
},
// FAILS
bar: {
description: 'bar',
},
});

Options

{
"plugins": ["formatjs"],
"rules": {
"formatjs/enforce-default-message": ["error", "literal"]
}
}

Setting literal forces defaultMessage to always be a string literal instead of function calls or variables. This is helpful for extraction tools that expects defaultMessage to always be a literal

enforce-placeholders

Makes sure all values are passed in if message has placeholders (number/date/time/plural/select/selectordinal). This requires values to be passed in as literal object (not a variable).

// WORKS, no error
<FormattedMessage
defaultMessage="this is a {placeholder}"
values={{placeholder: 'dog'}}
/>
// WORKS, no error
intl.formatMessage({
defaultMessage: 'this is a {placeholder}'
}, {placeholder: 'dog'})
// WORKS, error bc no values were provided
<FormattedMessage
defaultMessage="this is a {placeholder}"
/>
// WORKS, error bc no values were provided
intl.formatMessage({
defaultMessage: 'this is a {placeholder}'
})
// WORKS, error bc `placeholder` is not passed in
<FormattedMessage
defaultMessage="this is a {placeholder}"
values={{foo: 1}}
/>
// WORKS, error bc `placeholder` is not passed in
intl.formatMessage({
defaultMessage: 'this is a {placeholder}'
}, {foo: 1})
// DOESN'T WORK
<FormattedMessage
defaultMessage="this is a {placeholder}"
values={someVar}
/>
// DOESN'T WORK
intl.formatMessage({
defaultMessage: 'this is a {placeholder}'
}, values)

enforce-plural-rules

Enforce certain plural rules to always be specified/forbidden in a message.

Why

  • It is recommended to always specify other as fallback in the message.
  • Some translation vendors only accept certain rules.

Available rules

enum LDML {
zero = 'zero',
one = 'one',
two = 'two',
few = 'few',
many = 'many',
other = 'other',
}

Example

{
"plugins": ["formatjs"],
"rules": {
"formatjs/enforce-plural-rules": [
2,
{
"one": true,
"other": true,
"zero": false
}
]
}
}

no-camel-case

This make sure placeholders are not camel-case.

Why

  • This is to prevent case-sensitivity issue in certain translation vendors.
import {defineMessages} from 'react-intl';
const messages = defineMessages({
// WORKS
foo: {
defaultMessage: 'foo {snake_case} {nothing}',
},
// FAILS
bar: {
defaultMessage: 'foo {camelCase}',
},
});

no-emoji

This prevents usage of emoji in message.

Why

  • Certain translation vendors cannot handle emojis.
  • Cross-platform encoding for emojis are faulty.
import {defineMessages} from 'react-intl';
const messages = defineMessages({
// WORKS
foo: {
defaultMessage: 'Smileys & People',
},
// FAILS
bar: {
defaultMessage: '😃 Smileys & People',
},
});

no-multiple-whitespaces

This prevents usage of multiple consecutive whitespaces in message.

Why

  • Consecutive whitespaces are handled differently in different locales.
  • Prevents \ linebreaks in JS string which results in awkward whitespaces.
import {defineMessages} from 'react-intl';
const messages = defineMessages({
// WORKS
foo: {
defaultMessage: 'Smileys & People',
},
// FAILS
bar: {
defaultMessage: 'Smileys & People',
},
// FAILS
baz: {
defaultMessage: 'this message is too long \
so I wanna line break it.',
},
});

no-multiple-plurals

This prevents specifying multiple plurals in your message.

Why

  • Nested plurals are hard to translate across languages so some translation vendors don't allow it.
import {defineMessages} from 'react-intl'
const messages = defineMessages({
// WORKS
foo: {
defaultMessage: '{p1, plural, one{one}}',
},
// FAILS
bar: {
defaultMessage: '{p1, plural, one{one}} {p2, plural, one{two}}',
}
// ALSO FAILS
bar2: {
defaultMessage: '{p1, plural, one{{p2, plural, one{two}}}}',
}
})

no-offset

This prevents specifying offset in plural rules in your message.

Why

  • Offset has complicated logic implication so some translation vendors don't allow it.
import {defineMessages} from 'react-intl';
const messages = defineMessages({
// PASS
foo: {
defaultMessage: '{var, plural, one{one} other{other}}',
},
// FAILS
bar: {
defaultMessage: '{var, plural, offset:1 one{one} other{other}}',
},
});

supported-datetime-skeleton

Since formatjs only supports a subset of DateTime Skeleton. This rule exists to make sure you don't use a unsupported pattern.

no-id

This prevents specifying manual ID in MessageDescriptor.

Why

Some pipelines enforces automatic ID generation during transpilation using babel-plugin-react-intl or @formatjs/ts-transformer so manual IDs cause issues of mismatching during runtime.

import {defineMessages} from 'react-intl';
const messages = defineMessages({
// PASS
foo: {
defaultMessage: '{var, plural, one{one} other{other}}',
},
// FAILS
bar: {
id: 'something',
defaultMessage: '{var, plural, offset:1 one{one} other{other}}',
},
});

enforce-id

This enforces generated ID to be set in MessageDescriptor.

Why

Pipelines can enforce automatic ID generation at the linter level (autofix to insert autogen ID) so this guarantees that.

import {defineMessages} from 'react-intl';
const messages = defineMessages({
// PASS
foo: {
id: '19shaf'
defaultMessage: '{var, plural, one{one} other{other}}',
},
// FAILS
bar: {
id: 'something',
defaultMessage: '{var, plural, offset:1 one{one} other{other}}',
},
// FAILS
bar: {
defaultMessage: '{var, plural, offset:1 one{one} other{other}}',
},
});

Options

{
"plugins": ["formatjs"],
"rules": {
"formatjs/enforce-id": [
"error",
{
// THIS IS REQUIRED
"idInterpolationPattern": "[sha512:contenthash:base64:6]"
}
]
}
}