Vue I18n

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Breaking Changes in v10 ​

NOTICE

Vue I18n v10 is still an alpha version.

APIs ​

Change $t and t overloaded signature for Legacy API mode ​

In Vue I18n v9, it has a different interface from the Composition API mode and Legacy API mode of $t and t overloaded signature.

Especially, $t and t signature in Legacy API mode has fewer overloaded signatures than in Composition API mode, as shown below:

$t and t overloaded signaturesLegacy API v9Legacy API v10Composition API v9 & v10
$t(key: Key): TranslateResult;✅✅✅
$t(key: Key, locale: Locale): TranslateResult;✅--
$t(key: Key, locale: Locale, list: unknown[]): TranslateResult;✅--
$t(key: Key, locale: Locale, named: NamedValue): TranslateResult;✅--
$t(key: Key, plural: number): TranslateResult;-✅✅
$t(key: Key, plural: number, options: TranslateOptions): TranslateResult;-✅✅
$t(key: Key, defaultMsg: string): TranslateResult;-✅✅
$t(key: Key, defaultMsg: string, options: TranslateOptions): TranslateResult;-✅✅
$t(key: Key, list: unknown[]): TranslateResult;✅✅✅
$t(key: Key, list: unknown[], plural: number): TranslateResult;-✅✅
$t(key: Key, list: unknown[], defaultMsg: string): TranslateResult;-✅✅
$t(key: Key, list: unknown[], options: TranslateOptions): TranslateResult;-✅✅
$t(key: Key, named: Record<string, unknown>): TranslateResult;✅✅✅
$t(key: Key, named: NamedValue, plural: number): TranslateResult;-✅✅
$t(key: Key, named: NamedValue, defaultMsg: string): TranslateResult;-✅✅
$t(key: Key, named: NamedValue, options: TranslateOptions): TranslateResult;-✅✅
t(key: Key): TranslateResult;✅✅✅
t(key: Key, locale: Locale): TranslateResult;✅--
t(key: Key, locale: Locale, list: unknown[]): TranslateResult;✅--
t(key: Key, locale: Locale, named: Record<string, unknown>): TranslateResult;✅--
t(key: Key, plural: number): TranslateResult; -✅✅
t(key: Key, plural: number, options: TranslateOptions<Locales>): TranslateResult; -✅✅
t(key: Key, defaultMsg: string): TranslateResult;-✅✅
t(key: Key, defaultMsg: string, options: TranslateOptions<Locales>): TranslateResult;-✅✅
t(key: Key, list: unknown[]): TranslateResult;✅✅✅
t(key: Key, list: unknown[], plural: number): TranslateResult;-✅✅
t(key: Key, list: unknown[], defaultMsg: string): TranslateResult;-✅✅
t(key: Key, list: unknown[], options: TranslateOptions<Locales>): TranslateResult;-✅✅
t(key: Key, named: Record<string, unknown>): TranslateResult;✅✅✅
t(key: Key, named: NamedValue, plural: number): TranslateResult;-✅✅
t(key: Key, named: NamedValue, defaultMsg: string): TranslateResult;-✅✅
t(key: Key, named: NamedValue, options: TranslateOptions<Locales>): TranslateResult;-✅✅

Starting from v10, Legacy API mode can use the same $t and t overload signature as Composition API mode.

Reason: After that migration, when migrating to Composition API mode, we sometimes fall into a pitfall due to the different signature.

If you are using the following APIs in Legacy API mode, you must change to another signature because of the breaking changes:

  • $t(key: Key, locale: Locale): TranslateResult;
  • $t(key: Key, locale: Locale, list: unknown[]): TranslateResult;
  • $t(key: Key, locale: Locale, named: NamedValue): TranslateResult;
  • t(key: Key, locale: Locale): TranslateResult;
  • t(key: Key, locale: Locale, list: unknown[]): TranslateResult;
  • t(key: Key, locale: Locale, named: NamedValue): TranslateResult;

$t(key: Key, locale: Locale): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $t('message.hello', 'ja') }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, list: unknown[], options: TranslateOptions): TranslateResult; or $t(key: Key, named: NamedValue, options: TranslateOptions): TranslateResult;

vue
<template>
  <p>{{ $t('message.hello', {}, { locale: 'ja' }) }}</p>
</template>

$t(key: Key, locale: Locale, list: unknown[]): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $t('message.hello', 'ja', ['dio']) }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, list: unknown[], options: TranslateOptions): TranslateResult;

vue
<template>
  <p>{{ $t('message.hello', ['dio'], { locale: 'ja' }) }}</p>
</template>

$t(key: Key, locale: Locale, named: NamedValue): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $t('message.hello', 'ja', { name: 'dio' }) }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, named: NamedValue, options: TranslateOptions): TranslateResult;

vue
<template>
  <p>{{ $t('message.hello', { name: 'dio' }, { locale: 'ja' }) }}</p>
</template>

t(key: Key, locale: Locale): TranslateResult; ​

Vue I18n v9.x:

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})

console.log(i18n.global.t('message.hello', 'ja'))

Vue I18n v10 or later:

use t(key: Key, list: unknown[], options: TranslateOptions): TranslateResult; or t(key: Key, named: NamedValue, options: TranslateOptions): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})

console.log(i18n.global.t('message.hello', {}, { locale: 'ja' })

t(key: Key, locale: Locale, list: unknown[]): TranslateResult; ​

Vue I18n v9.x:

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})

console.log(i18n.global.t('message.hello', 'ja', ['dio']))

Vue I18n v10 or later:

use t(key: Key, list: unknown[], options: TranslateOptions): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})

console.log(i18n.global.t('message.hello', ['dio'], { locale: 'ja' }))

t(key: Key, locale: Locale, named: NamedValue): TranslateResult; ​

Vue I18n v9.x:

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})

console.log(i18n.global.t('message.hello', 'ja', { name: 'dio' }))

Vue I18n v10 or later:

use t(key: Key, named: NamedValue, options: TranslateOptions): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})

console.log(i18n.global.t('message.hello', { name: 'dio' }, { locale: 'ja' }))

Deprecate tc and $tc for Legacy API mode ​

The following APIs are deprecated in v10:

  • tc(key: Key | ResourceKeys): TranslateResult;
  • tc(key: Key | ResourceKeys, locale: Locales | Locale): TranslateResult;
  • tc(key: Key | ResourceKeys, list: unknown[]): TranslateResult;
  • tc(key: Key | ResourceKeys, named: Record<string, unknown>): TranslateResult;
  • tc(key: Key | ResourceKeys, choice: number): TranslateResult;
  • tc(key: Key | ResourceKeys, choice: number, locale: Locales | Locale): TranslateResult;
  • tc(key: Key | ResourceKeys, choice: number, list: unknown[]): TranslateResult;
  • tc(key: Key | ResourceKeys, choice: number, named: Record<string, unknown>): TranslateResult;
  • $tc(key: Key): TranslateResult;
  • $tc(key: Key, locale: Locale): TranslateResult;
  • $tc(key: Key, list: unknown[]): TranslateResult;
  • $tc(key: Key, named: Record<string, unknown>): TranslateResult;
  • $tc(key: Key, choice: number): TranslateResult;
  • $tc(key: Key, choice: number, locale: Locale): TranslateResult;
  • $tc(key: Key, choice: number, list: unknown[]): TranslateResult;
  • $tc(key: Key, choice: number, named: Record<string, unknown>): TranslateResult;

Reason: Legacy API mode has t and $t support plural interfaces, so they can be replaced.

In v10, tc and $tc still exist to give benefit migration. These will be dropped completely in v11.

If you will use them, Vue I18n will output the console warning in your application.

tc(key: Key | ResourceKeys): TranslateResult; ​

Vue I18n v9.x:

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.tc('banana'))

Vue I18n v10 or later:

use t(key: Key | ResourceKeys, plural: number): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.t('banana', 1))

tc(key: Key | ResourceKeys, locale: Locales | Locale): TranslateResult; ​

Vue I18n v9.x:

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.tc('banana', 'ja'))

Vue I18n v10 or later:

use t(key: Key | ResourceKeys, plural: number, options: TranslateOptions<Locales>): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.t('banana', 1, { locale: 'ja' }))

tc(key: Key | ResourceKeys, list: unknown[]): TranslateResult; ​

Vue I18n v9.x:

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.tc('banana', ['dio']))

Vue I18n v10 or later:

use t(key: Key | ResourceKeys, list: unknown[], plural: number): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.t('banana', ['dio'], 1))

tc(key: Key | ResourceKeys, named: Record<string, unknown>): TranslateResult; ​

Vue I18n v9.x:

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.tc('banana', { name: 'dio' }))

Vue I18n v10 or later:

use t(key: Key | ResourceKeys, named: NamedValue, plural: number): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.t('banana', { name: 'dio' }, 1))

tc(key: Key | ResourceKeys, choice: number): TranslateResult; ​

Vue I18n v9.x:

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.tc('banana', 2))

Vue I18n v10 or later:

use t(key: Key | ResourceKeys, plural: number): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.t('banana', 2))

tc(key: Key | ResourceKeys, choice: number, locale: Locales | Locale): TranslateResult; ​

Vue I18n v9.x:

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.tc('banana', 2, 'ja'))

Vue I18n v10 or later:

use t(key: Key | ResourceKeys, plural: number, options: TranslateOptions<Locales>): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.t('banana', 2, { locale: 'ja' }))

tc(key: Key | ResourceKeys, choice: number, list: unknown[]): TranslateResult; ​

Vue I18n v9.x:

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.t('banana', 2, ['dio']))

Vue I18n v10 or later:

use t(key: Key | ResourceKeys, list: unknown[], plural: number): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.t('banana', ['dio'], 2))

tc(key: Key | ResourceKeys, choice: number, named: Record<string, unknown>): TranslateResult; ​

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.tc('banana', 2, { name: 'dio' }))

Vue I18n v10 or later:

use t(key: Key | ResourceKeys, named: NamedValue, plural: number): TranslateResult;

ts
const i18n = createI18n({
  legacy: true,
  // something options ...
})
console.log(i18n.global.tc('banana', { name: 'dio' }, 2))

$tc(key: Key): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $tc('banana') }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, plural: number): TranslateResult;

vue
<template>
  <p>{{ $t('banana', 1) }}</p>
</template>

$tc(key: Key, locale: Locale): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $tc('banana', 'ja') }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, plural: number, options: TranslateOptions): TranslateResult;

vue
<template>
  <p>{{ $t('banana', 1, { locale: 'ja' }) }}</p>
</template>

$tc(key: Key, list: unknown[]): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $tc('banana', ['dio']) }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, list: unknown[], plural: number): TranslateResult;

vue
<template>
  <p>{{ $t('banana', ['dio'], 1) }}</p>
</template>

$tc(key: Key, named: Record<string, unknown>): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $tc('banana', { name: 'dio' }) }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, named: NamedValue, plural: number): TranslateResult;

vue
<template>
  <p>{{ $t('banana', { name: 'dio' }, 1) }}</p>
</template>

$tc(key: Key, choice: number): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $tc('banana', 2) }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, plural: number): TranslateResult;

vue
<template>
  <p>{{ $t('banana', 2) }}</p>
</template>

$tc(key: Key, choice: number, locale: Locale): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $tc('banana', 2, 'ja') }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, plural: number, options: TranslateOptions): TranslateResult;

vue
<template>
  <p>{{ $t('banana', 2, { locale: 'ja' }) }}</p>
</template>

$tc(key: Key, choice: number, list: unknown[]): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $tc('banana', 2, ['dio']) }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, list: unknown[], plural: number): TranslateResult;

vue
<template>
  <p>{{ $t('banana', ['dio'], 2) }}</p>
</template>

$tc(key: Key, choice: number, named: Record<string, unknown>): TranslateResult; ​

Vue I18n v9.x:

vue
<template>
  <p>{{ $tc('banana', 2,  { name: 'dio' }) }}</p>
</template>

Vue I18n v10 or later:

use $t(key: Key, named: NamedValue, plural: number): TranslateResult;

vue
<template>
  <p>{{ $t('banana', { name: 'dio' }, 2) }}</p>
</template>

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