Checking translations

To check that the translations of the app are correct at compile time, set the check_translations parameter in the leptos_fluent! macro to a glob pattern that matches the Rust files that you want to check.

The pattern must be relative to the location of the Cargo.toml file.

For single crate projects, it would be something like:

leptos_fluent! {
    check_translations: "./src/**/*.rs",
}

For workspace projects, it could be something like:

leptos_fluent! {
    check_translations: "../{app,components}/src/**/*.rs",
}

Translations error messages

When the translations stop being synchronized, you will see errors like:

error: Translations check failed:
       - Message "select-a-language" defined at `move_tr!("select-a-language")` macro call in src/lib.rs not found in files for locale "en".
       - Message "select-a-lang" of locale "en" not found in any `tr!` or `move_tr!` macro calls.
  --> examples/csr-complete/src/lib.rs:18:29
   |
18 |         check_translations: "./src/**/*.rs",
   |                             ^^^^^^^^^^^^^^^

If placeable are missing in the translations, you will see errors like:

error: Translations check failed:
       - Variable "dir" defined at `move_tr!("html-tag-dir-is", { ... })` macro call in src/lib.rs not found in message "html-tag-dir-is" of locale "en".
       - Variable "name" defined in message "html-tag-dir-is" of locale "en" not found in arguments of `move_tr!("html-tag-dir-is", { ... })` macro call at file src/lib.rs.
  --> examples/csr-complete/src/lib.rs:18:29
   |
18 |         check_translations: "./src/**/*.rs",
   |                             ^^^^^^^^^^^^^^^

Why glob patterns to Rust files?

leptos-fluent provides a I18n context to Leptos when the macro leptos_fluent! is called. So multiple instances of a context with different localization files and strategies can be initialized in different component trees. This is useful, for example, in a multi page app.

The mechanism of translations checking needs to know where reside the calls to tr! and move_tr! macros to extract the messages that need to be checked. This is performed by parsing the source code looking for these macros invocations.

The only limitation for checking translations with glob patterns is that the tr! and move_tr! macros that consume each context must be in different file trees, but this enforces anyway a good practice of file-level separation of contexts in the codebase.