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eslint-plugin-formatjs

This eslint plugin allows you to enforce certain rules in your ICU message.

Usage

npm i -D eslint-plugin-formatjs

Then in your eslint config:

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

React

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',
})
}

Vue

This will check against intl.formatMessage, $formatMessage function calls in both your JS/TS & your SFC .vue files. For example:

<template>
<p>
{{
$formatMessage({
defaultMessage: 'today is {now, date}',
})
}}
</p>
</template>

Shared Settings

These settings are applied globally to all formatjs rules once specified. See Shared Settings for more details on how to set them.

additionalFunctionNames

Similar to babel-plugin-formatjs & @formatjs/ts-transformer, this allows you to specify additional function names to check besides formatMessage & $formatMessage.

additionalComponentNames

Similar to babel-plugin-formatjs & @formatjs/ts-transformer, this allows you to specify additional component names to check besides FormattedMessage.

Available Rules

blocklist-elements

This blocklists 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/blocklist-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)

Options

{
"plugins": ["formatjs"],
"rules": {
"formatjs/enforce-placeholders": [
"error",
{
"ignoreList": ["foo"]
}
]
}
}
  • ignoreList: List of placeholder names to ignore. This works with defaultRichTextElements in react-intl so we don't provide false positive for ambient global tag formatting

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}}',
},
})

enforce-id

This enforces generated ID to be set in MessageDescriptor.

Why

Pipelines can enforce automatic/manual 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",
{
"idInterpolationPattern": "[sha512:contenthash:base64:6]"
}
]
}
}
  • idInterpolationPattern: Pattern to verify ID against
  • idWhitelist: An array of strings with regular expressions. This array allows allowlist custom ids for messages. For example '\\.' allows any id which has dot; '^payment_.*' - allows any custom id which has prefix payment_. Be aware that any backslash \ provided via string must be escaped with an additional backslash.

no-id

This bans explicit ID in MessageDescriptor.

Why

We generally encourage automatic ID generation due to these reasons. This makes sure no explicit IDs are set.

no-complex-selectors

Make sure a sentence is not too complex. Complexity is determined by how many strings are produced when we try to flatten the sentence given its selectors. For example:

I have {count, plural, one{a dog} other{many dogs}}

has the complexity of 2 because flattening the plural selector results in 2 sentences: I have a dog & I have many dogs. Default complexity limit is 20 (using Smartling as a reference)

Options

{
"plugins": ["formatjs"],
"rules": {
"formatjs/no-complex-selectors": [
"error",
{
"limit": 3
}
]
}
}