Macros

Lingui Macro provides powerful macros to transform JavaScript objects and JSX elements into ICU MessageFormat messages at compile time. It provides a more efficient and developer-friendly way to handle internationalization in your project.

The benefits of using macros:

• You don't have to learn ICU MessageFormat syntax. You always use familiar JS and JSX code.
• Components and functions are type checked.
• Short IDs are generated for your messages.
• Additional validation of plural rules is performed during transformation.
• Non-essential data is removed from the production build (e.g. comments and default messages) to save a few bytes.

There are two types of macros: Core Macros (JS) and React Macros (JSX).

Installation

Babel

Lingui macros require @lingui/babel-plugin-lingui-macro or babel-plugin-macros to work.

The recommended way is to use @lingui/babel-plugin-lingui-macro directly. If you are using a framework that doesn't allow you to change the Babel configuration (e.g. Create React App > 2.0), these frameworks may support babel-plugin-macros out of the box.

1. Install @lingui/babel-plugin-lingui-macro as a dev dependency:

   npm

   npm install --save-dev @lingui/babel-plugin-lingui-macro

   Yarn

   yarn add --dev @lingui/babel-plugin-lingui-macro

   pnpm

   pnpm add --save-dev @lingui/babel-plugin-lingui-macro

2. Add @lingui/babel-plugin-lingui-macro to the top of the plugins section in your Babel config:

   {
     "plugins": ["@lingui/babel-plugin-lingui-macro"]
   }

When using a preset, first check if it includes the macros plugin. For example, react-scripts already includes the macros plugin.

SWC

1. Install @lingui/swc-plugin as a dev dependency and @lingui/macro as production dependency:

   npm

   npm install --save-dev @lingui/swc-plugin
   npm install --save @lingui/macro

   Yarn

   yarn add --dev @lingui/swc-plugin
   yarn add @lingui/macro

   pnpm

   pnpm add --save-dev @lingui/swc-plugin
   pnpm add @lingui/macro

2. Add necessary configurations.

tip

Don't miss the Lingui ESLint Plugin which can help you find and prevent common l10n mistakes in your code.

Core Macros

Core (JS) Macros can be used in any JavaScript context (e.g. outside of JSX). All JS macros are transformed into a Message Descriptor wrapped inside of i18n._ call:

import { t } from "@lingui/core/macro";
t`Attachment ${name} saved`;

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
i18n._(
  /*i18n*/ {
    id: "nwR43V",
    message: "Attachment {name} saved",
    values: { name },
  }
);

/*i18n*/ comment

In the example above you may notice the /*i18n*/ comment in the macro output. This comment tells the extract plugin that the following object should be collected into the message catalog.

Message Descriptor is an object with a message ID, default message and other parameters:

type MessageDescriptor = {
  id: string;
  message?: string;
  values?: Record<string, any>;
  comment?: string;
};

The id is the message ID and is the only parameter required. The id and message are extracted into the message catalog. Only id and values are used at runtime, all other attributes are removed from the production code for size optimization.

You don't need to specify the ID manually. By default, Macro will automatically create a short ID from your message. However, you can explicitly specify a custom ID. Read more about Explicit vs Generated IDs.

t

The most common macro for messages. It transforms tagged template literal into message in ICU MessageFormat:

import { t } from "@lingui/core/macro";
const message = t`Hello World`;

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "mY42CM",
    message: "Hello World",
  }
);

Message variables are supported:

import { t } from "@lingui/core/macro";
const message = t`My name is ${name}`;

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "mVmaLu",
    message: "My name is {name}",
    values: { name },
  }
);

In fact, any expression can be used inside template literal. However, only simple variables are referenced by name in a transformed message. All other expressions are referenced by their numeric index:

import { t } from "@lingui/core/macro";
const message = t`Today is ${new Date()}`;

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";

const message = i18n._(
  /*i18n*/ {
    id: "2aJT27",
    message: "Today is {0}",
    values: { 0: new Date() },
  }
);

Optionally, a custom i18n instance can be passed that can be used instead of the global instance:

note

Deprecated in V5, would be removed in v6

import { t } from "@lingui/core/macro";
import { i18nCustom } from "./lingui";
const message = t(i18nCustom)`Hello World`;

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18nCustom } from "./lingui";
const message = i18nCustom._(
  /*i18n*/ {
    id: "mY42CM",
    message: "Hello World",
  }
);

info

By default the i18n object is imported from @lingui/core. If you are using a custom instance of the i18n object, you need to set runtimeConfigModule or pass a custom instance to t.

It's also possible to pass custom id and comment for translators by calling t macro with a message descriptor:

import { t } from "@lingui/core/macro";
const message = t({
  id: "msg.hello",
  comment: "Greetings at the homepage",
  message: `Hello ${name}`,
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "msg.hello",
    comment: "Greetings at the homepage",
    message: "Hello {name}",
    values: { name },
  }
);

In this case, message is used as the default message, and it's transformed as if it were wrapped in a t macro. message also accepts any other macros:

import { t } from "@lingui/core/macro";
const message = t({
  id: "msg.plural",
  message: plural(value, { one: "...", other: "..." }),
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "msg.plural",
    message: "{value, plural, one {...} other {...}}",
    values: { value },
  }
);

plural

Pluralization is a common problem in i18n. Different languages have different rules for plural form (e.g. English has only one and other, while Czech has one, few, many and other). The plural macro is used to handle this.

plural(value: string | number, options: Object)

The value specifies the plural form or cardinal number. The second argument, options, is an object with available plural forms:

import { plural } from "@lingui/core/macro";
const message = plural(count, {
  one: "# Book",
  other: "# Books",
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "V/M0Vc",
    message: "{count, plural, one {# Book} other {# Books}}",
    values: { count },
  }
);

tip

Choose the plural forms used in your source code based on the pluralization rules of your source locale.

If you need to add variables in plural form, you can use template string literals. This time you don't need the t macro, because template strings are transformed automatically:

import { plural } from "@lingui/core/macro";
const message = plural(count, {
  one: `${name} has # friend`,
  other: `${name} has # friends`,
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "CvuUwE",
    message: "{count, plural, one {{name} has # friend} other {{name} has # friends}}",
    values: { count, name },
  }
);

Plurals can also be nested to form complex messages. Here's an example using two counters:

import { plural } from "@lingui/core/macro";
const message = plural(numBooks, {
  one: plural(numArticles, {
    one: `1 book and 1 article`,
    other: `1 book and ${numArticles} articles`,
  }),
  other: plural(numArticles, {
    one: `${numBooks} books and 1 article`,
    other: `${numBooks} books and ${numArticles} articles`,
  }),
});

// ↓ ↓ ↓ ↓ ↓ ↓
// Generated message was wrapped for better readability

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "XnUh4j",
    message: `{numBooks, plural,
         one {{numArticles, plural,
            one {1 book and 1 article}
            other {1 book and {numArticles} articles}
         }}
         other {{numArticles, plural,
            one {{numBooks} books and 1 article}
            other {{numBooks} books and {numArticles} articles}
         }}
      }`,
    values: { numBooks, numArticles },
  }
);

This is just one example of how macros can be combined to create a complex message. However, simple is better, because in the end it's the translator who has to translate these long and complex strings.

tip

Use plural inside t or defineMessage macro if you want to add custom id, context or comment for translators.

const message = t({
  id: "my.custom.id",
  comment: "My Comment",
  message: plural(count, {
    one: "# Book",
    other: "# Books",
  }),
});

selectOrdinal

SelectOrdinal is a variation of the plural macro. It's used to handle ordinal numbers (e.g. 1st, 2nd, 3rd, 4th, etc.).

selectOrdinal(value: string | number, options: Object)

The value specifies the ordinal number. The second argument, options, is an object with available ordinal forms:

import { selectOrdinal } from "@lingui/core/macro";
const message = selectOrdinal(count, {
  one: "#st",
  two: "#nd",
  few: "#rd",
  other: "#th",
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "V8xI3w",
    message: "{count, selectOrdinal, one {#st} two {#nd} few {#rd} other {#th}}",
    values: { count },
  }
);

tip

Use selectOrdinal inside t or defineMessage macro if you want to add custom id, context or comment for translators.

const message = t({
  id: "my.custom.id",
  comment: "My Comment",
  message: selectOrdinal(count, {
    one: "#st",
    two: "#nd",
    few: "#rd",
    other: "#th",
  }),
});

select

The select macro is used to handle different forms of a message based on a value.

select(value: string | number, options: Object)

It works like a switch statement - it selects one of the forms provided in the options object based on the value:

import { select } from "@lingui/core/macro";
const message = select(gender, {
  male: "he",
  female: "she",
  other: "they",
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";

const message = i18n._(
  /*i18n*/ {
    id: "VRptzI",
    message: "{gender, select, male {he} female {she} other {they}}",
    values: { gender },
  }
);

tip

Use select inside t or defineMessage macro if you want to add custom id, context or comment for translators.

const message = t({
  id: "my.custom.id",
  comment: "My Comment",
  message: select(gender, {
    male: "he",
    female: "she",
    other: "they",
  }),
});

defineMessage / msg

The defineMessage (alias: msg) macro allows to define a message for later use. It has the same signature as t and returns a MessageDescriptor that you can pass to i18n._ to get a translated string at any time later. This is useful for lazy translations.

In other words, t returns a translated string at the time when it's called, while msg returns a MessageDescriptor that can produce translated strings later:

import { i18n } from "@lingui/core";
import { defineMessage } from "@lingui/core/macro";

// define message
const message = defineMessage`Hello World`;

// use it later
i18n._(message);

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";

const message = /*i18n*/ {
  id: "mY42CM",
  message: "Hello World",
};

// use it later
i18n._(message);

You can also use a shorter alias of the defineMessage macro:

import { msg } from "@lingui/core/macro";
const message = msg`Hello World`;

// ↓ ↓ ↓ ↓ ↓ ↓

const message = /*i18n*/ {
  id: "mY42CM",
  message: "Hello World",
};

The defineMessage macro also supports a MacroMessageDescriptor object as input. This can be used to provide additional information for the message such as comment or context:

type MacroMessageDescriptor = {
  id?: string;
  message?: string;
  comment?: string;
  context?: string;
};

Either the id or message property is required. id is a custom message ID. If it isn't set, the message (and context if present) will be used to generate an ID. Read more about Explicit vs Generated IDs.

import { defineMessage } from "@lingui/core/macro";
const message = defineMessage({
  id: "Navigation / About",
  message: "About us",
});

// ↓ ↓ ↓ ↓ ↓ ↓

const message = /*i18n*/ {
  id: "Navigation / About",
  message: "About us",
};

The message is a default message. Any JS macro can be used here. Template string literals don't need to be tagged with t.

import { defineMessage } from "@lingui/core/macro";
const name = "Joe";
const message = defineMessage({
  message: `Welcome, ${name}!`,
});

// ↓ ↓ ↓ ↓ ↓ ↓

const message = /*i18n*/ {
  id: "dgJjNB",
  message: "Welcome, {name}",
  values: {
    name,
  },
};

The comment is a comment for translators. It's extracted into the message catalog, and it gives translators additional information about the message. It's removed from the production code:

import { defineMessage } from "@lingui/core/macro";
const message = defineMessage({
  comment: "Link in navigation pointing to About page",
  message: "About us",
});

// ↓ ↓ ↓ ↓ ↓ ↓

const message = /*i18n*/ {
  id: "+mNwru",
  comment: "Link in navigation pointing to About page",
  message: "About us",
};

Note

In the production build, the macro is stripped of message, comment and context properties:

import { defineMessage } from "@lingui/core/macro";
const message = defineMessage({
  id: "msg.navigation.about",
  comment: "Link in navigation pointing to About page",
  message: "About us",
  context: "Context about the link",
});

// process.env.NODE_ENV === "production"
// ↓ ↓ ↓ ↓ ↓ ↓

const message = /*i18n*/ {
  id: "msg.navigation.about",
};

message and comment are used in message catalogs only. context is used only for generating ID and is stripped from the output.

React Macros

React (JSX) Macros are used in JSX elements and are transformed into the Trans component imported from the @lingui/react package.

Trans

The Trans macro is used to translate static messages, messages with variables and messages with inline markup:

import { Trans } from "@lingui/react/macro";
<Trans>Refresh inbox</Trans>;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id="EsCV2T" message="Refresh inbox" />;

Available Props:

Prop Name	Type	Description
id	string	Custom message ID
comment	string	Comment for translators
context	string	Allows to extract the same messages with different IDs
render	func	Render prop function used to render translation

id

Each message in the catalog is identified by a message ID. While macro uses message (and context property if provided) to generate the ID, it's possible to provide custom ID. Read more about Explicit vs Generated IDs.

import { Trans } from "@lingui/react/macro";
<Trans id="message.attachment_saved">Attachment {name} saved.</Trans>;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id="message.attachment_saved" message="Attachment {name} saved." />;

comment

Comment for translators to give them additional information about the message. It will be visible in the TMS if it is supported, and in the catalog format. It will be removed from production code.

context

Allows to extract the same messages with different IDs. It is useful when the same message has different meanings in different contexts. See Context for more details.

Similarly to comment, it will be added to the message catalog, visible in TMS and will be removed from the production code.

import { Trans } from "@lingui/react/macro";
<Trans context="direction">right</Trans>;
<Trans context="correctness">right</Trans>;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id={"d1wX4r"} message="right" />;
<Trans id={"16eaSK"} message="right" />;

This macro is particularly useful if the message contains inline markup:

import { Trans } from "@lingui/react/macro";

<Trans>
  Read the <a href="/docs">docs</a>.
</Trans>;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id={"mk8bSG"} message="Read the <0>docs</0>." components={{ 0: <a href="/docs" /> }} />;

Components and HTML tags are replaced by dummy indexed tags (<0></0>) which has several advantages:

• Both custom React components and built-in HTML tags are supported.
• Changing component props doesn't break translation.
• The message is extracted as a whole sentence (this seems to be obvious, but most i18n libs simply split the message into pieces by tags and translate them separately).

render

Render prop function used to render translation. This prop is passed directly to the Trans component from the @lingui/react package.

Plural

The Plural JSX macro is used to handle plural forms. It's similar to the plural macro from the core macros, but it's used in JSX elements.

import { Plural } from "@lingui/react/macro";
<Plural value={numBooks} one="Book" other="Books" />;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id={"is7n96"} message="{numBooks, plural, one {Book} other {Books}}" values={{ numBooks }} />;

Available Props:

Prop name	Type	Description
value	number	(required) Value is mapped to plural form below
format	string|Object	Number format passed as options to Intl.NumberFormat
offset	number	Offset of value when calculating plural forms
zero	string	Form for empty value
one	string	Singular form
two	string	Dual form
few	string	Paucal form
many	string	Plural form
other	string	(required) general plural form
_<number>	string	Exact match form, corresponds to =N rule

Exact matches in MessageFormat syntax are expressed as =int (e.g. =0), but in React this isn't a valid prop name. Therefore, exact matches are expressed as _int prop (e.g. _0). This is commonly used in combination with offset prop. offset affects only plural forms, not exact matches.

import { Plural } from "@lingui/react/macro";

<Plural
  value={count}
  offset={1}
  // when value == 0
  _0="Nobody arrived"
  // when value == 1
  _1="Only you arrived"
  // when value == 2
  // value - offset = 1 -> `one` plural form
  one="You and # other guest arrived"
  // when value >= 3
  other="You and # other guests arrived"
/>;

/*
  This is transformed to Trans component with ID:
  {count, plural, offset:1 _0    {Nobody arrived}
                           _1    {Only you arrived}
                           one   {You and # other guest arrived}
                           other {You and # other guests arrived}}
*/

tip

Use <Plural> inside <Trans> macro if you want to add custom id, context or comment for translators.

<Trans context={"my context"}>
  <Plural value={numBooks} one="Book" other="Books" />;
</Trans>

SelectOrdinal

The SelectOrdinal JSX macro is used to handle ordinal numbers. It's similar to the selectOrdinal macro from the core macros, but it's used in JSX elements.

import { SelectOrdinal } from "@lingui/react/macro";

// count == 1 -> 1st
// count == 2 -> 2nd
// count == 3 -> 3rd
// count == 4 -> 4th
<SelectOrdinal value={count} one="#st" two="#nd" few="#rd" other="#th" />;

Available Props:

Prop name	Type	Description
value	number	(required) Value is mapped to plural form below
offset	number	Offset of value for plural forms
zero	string	Form for empty value
one	string	Singular form
two	string	Dual form
few	string	Paucal form
many	string	Plural form
other	string	(required) general plural form
_<number>	string	Exact match form, correspond to =N rule. (e.g: _0, _1)
format	string|Object	Number format passed as options to Intl.NumberFormat

tip

Use <SelectOrdinal> inside <Trans> macro if you want to add custom id, context or comment for translators.

<Trans context={"my context"}>
  <SelectOrdinal value={count} one="#st" two="#nd" few="#rd" other="#th" />
</Trans>

Select

The Select JSX macro is used to handle different forms of a message based on a value. It's similar to the select macro from the core macros, but it's used in JSX elements.

import { Select } from "@lingui/react/macro";

// gender == "female"      -> Her book
// gender == "male"        -> His book
// gender == "non-binary"  -> Their book
<Select value={gender} _male="His book" _female="Her book" other="Their book" />;

Available Props:

Prop name	Type	Description
value	number	(required) Value determines which form is output
_<case>	string	Form for specific case
other	number	(required) Default, catch-all form

The select cases except other should be prefixed with underscore: _male or _female.

tip

Use <Select> inside <Trans> macro if you want to provide id, context or comment.

<Trans context={"my context"}>
  <Select value={gender} _male="His book" _female="Her book" other="Their book" />
</Trans>

useLingui

The useLingui React macro gives access to a t macro that is bound to the local i18n object passed from the React context.

It returns an object with the following content:

Key	Type	Description
i18n	I18n	The I18n object instance passed to I18nProvider
t	t	Reference to the t macro described above
defaultComponent	React.ComponentType	the same defaultComponent passed to I18nProvider, if provided

Example usage:

import { useLingui } from "@lingui/react/macro";

function MyComponent() {
  const { t } = useLingui();
  const a = t`Text`;
}

// ↓ ↓ ↓ ↓ ↓ ↓
import { useLingui } from "@lingui/react";

function MyComponent() {
  const { _ } = useLingui();
  const a = _(
    /*i18n*/
    {
      id: "xeiujy",
      message: "Text",
    }
  );
}

caution

The useLingui React macro is available from Lingui v5.

More Examples

Examples of JS macros

t`Refresh inbox`;

// ↓ ↓ ↓ ↓ ↓ ↓

i18n._(
  /*i18n*/ {
    id: "EsCV2T",
    message: "Refresh inbox",
  }
);

t(customI18n)`Refresh inbox`;

// ↓ ↓ ↓ ↓ ↓ ↓

customI18n._(
  /*i18n*/ {
    id: "EsCV2T",
    message: "Refresh inbox",
  }
);

t(customI18n)`Attachment ${name} saved`;

// ↓ ↓ ↓ ↓ ↓ ↓

customI18n._(
  /*i18n*/ {
    id: "nwR43V",
    message: "Attachment {name} saved",
    values: { name },
  }
);

plural(count, {
  one: "# Message",
  other: "# Messages",
});

// ↓ ↓ ↓ ↓ ↓ ↓

i18n._(
  /*i18n*/ {
    id: "4w2nim",
    message: "{count, plural, one {# Message} other {# Messages}}",
    values: { count },
  }
);

t({
  id: "msg.refresh",
  message: "Refresh inbox",
});

// ↓ ↓ ↓ ↓ ↓ ↓

i18n._(
  /*i18n*/ {
    id: "msg.refresh",
    message: "Refresh inbox",
  }
);

t(customI18n)({
  id: "msg.refresh",
  message: "Refresh inbox",
});

// ↓ ↓ ↓ ↓ ↓ ↓

customI18n._(
  /*i18n*/ {
    id: "msg.refresh",
    message: "Refresh inbox",
  }
);

const msg = defineMessage`Refresh inbox`;

// ↓ ↓ ↓ ↓ ↓ ↓

const msg = /*i18n*/ {
  id: "EsCV2T",
  message: "Refresh inbox",
};

const msg = defineMessage({
  id: "msg.refresh",
  message: "Refresh inbox",
});

// ↓ ↓ ↓ ↓ ↓ ↓

const msg = /*i18n*/ {
  id: "msg.refresh",
  message: "Refresh inbox",
};

const msg = defineMessage({
  id: "msg.plural",
  message: plural(count, {
    one: "# Message",
    other: "# Messages",
  }),
});

// ↓ ↓ ↓ ↓ ↓ ↓

const msg = /*i18n*/ {
  id: "msg.plural",
  message: "{count, plural, one {# Message} other {# Messages}}",
  values: { count },
};

Examples of JSX macros

<Trans>Attachment {name} saved</Trans>

// ↓ ↓ ↓ ↓ ↓ ↓

<Trans
   id={"nwR43V"}
   message="Attachment {name} saved"
   values={{ name }}
/>

<Plural
   value={count}
   one="# Message"
   other="# Messages"
/>

// ↓ ↓ ↓ ↓ ↓ ↓

<Trans
   id={"4w2nim"}
   message="{count, plural, one {# Message} other {# Messages}}"
   values={{ count }}
/>

<Trans id="msg.refresh">
   Refresh inbox
</Trans>

// ↓ ↓ ↓ ↓ ↓ ↓

<Trans
   id="msg.refresh"
   message="Refresh inbox"
/>