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).
Core Macros
Core (JS) Macros can be used in any JavaScript context (e.g. outside 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*/
commentIn 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:
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",
}
);
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 ${name}`,
});
// ↓ ↓ ↓ ↓ ↓ ↓
import { i18n } from "@lingui/core";
const message = i18n._(
/*i18n*/ {
id: "msg.hello",
comment: "Greetings at the homepage",
message: "Hello {name}",
values: { name },
}
);
In this case, message
is used as the default message, and it's transformed as if it were wrapped in a t
macro. message
also accepts any other macros:
import { t } from "@lingui/core/macro";
const message = t({
id: "msg.plural",
message: plural(value, { one: "...", other: "..." }),
});
// ↓ ↓ ↓ ↓ ↓ ↓
import { i18n } from "@lingui/core";
const message = i18n._(
/*i18n*/ {
id: "msg.plural",
message: "{value, plural, one {...} other {...}}",
values: { value },
}
);
plural
Pluralization is a common problem in i18n. Different languages have different rules for plural form (e.g. English has only one
and other
, while Czech has one
, few
, many
and other
). The plural
macro is used to handle this.
plural(value: string | number, options: Object)
The value
specifies the plural form or cardinal number. The second argument, options
, is an object with available plural forms:
import { plural } from "@lingui/core/macro";
const message = plural(count, {
one: "# Book",
other: "# Books",
});
// ↓ ↓ ↓ ↓ ↓ ↓
import { i18n } from "@lingui/core";
const message = i18n._(
/*i18n*/ {
id: "V/M0Vc",
message: "{count, plural, one {# Book} other {# Books}}",
values: { count },
}
);
Choose the plural forms used in your source code based on the pluralization rules of your source locale.
If you need to add variables in plural form, you can use template string literals. This time you don't need the t
macro, because template strings are transformed automatically:
import { plural } from "@lingui/core/macro";
const message = plural(count, {
one: `${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.
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 },
}
);
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 },
}
);
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",
};
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}}
*/
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 |
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
.
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",
}
);
}
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"
/>