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Taoensso open-source

CHANGELOG | API | current Break Version:

[com.taoensso/tempura "1.5.3"] ; See CHANGELOG for details

See here if to help support my open-source work, thanks! - Peter Taoussanis

Tempura: a pure Clojure/Script i18n translations library


  • Tiny (single fn), cross-platform all-Clojure API for providing multilingual content.
  • Match gettext's convenience for embedding default content directly in code (optional).
  • Exceed gettext's ability to handle versioned content through unique content ids.
  • Work out-the-box with plain text, Hiccup, Reactjs, ...
  • Easy, optional platform-appropriate support for simple Markdown styles.
  • Flexibility: completely open/pluggable resource compiler.
  • Performance: match or exceed format performance through compilation + smart caching.
  • All-Clojure (edn) dictionary format for ease of use, easy compile-and-runtime manipulation, etc.
  • Focus only on common-case translation and no other aspects of i18n/L10n.

10-second example

(require '[taoensso.tempura :as tempura :refer [tr]]))

(tr ; For "translate"
    {:dict ; Dictionary of translations
     {:sw {:missing "sw/?" :r1 "sw/r1" :r2 "sw/r2"}
      :en {:missing "en/?" :r1 "en/r1" :r2 "en/r2"}}}

    [:sw :en <...>] ; Locales   (desc priority)
    [:r1 :r2 <...>  ; Resources (desc priority)
     <?fallback-str> ; Optional final fallback string

;; =>

  sw/r1 sw/r2  <...> ; Descending-priority resources in priority-1 locale
  en/r1 en/r2  <...> ; ''                            in priority-2 locale

  ?fallback-str ; Optional fallback string (as last element in resources vec)

  sw/? ; Missing (error) resource in priority-1 locale
  en/? ; ''                          priority-2 locale

  nil  ; If none of the above exist

;; etc.

;; Note that ?fallback-str is super handy for development before you
;; have translations ready, e.g.:

(tr {:dict {}} [:en] [:sign-in-btn "Sign in here!"])
;; => "Sign in here!"

;; Tempura also supports Hiccup with Markdown-like styles, e.g.:

(tr {:dict {}} [:en] [:sign-in-btn ["**Sign in** here!"]])
;; => [:span [:strong "Sign in"] " here!"]

See the wiki docs for a more detailed discussion of Tempura's resource search behaviour.


Add the necessary dependency to your project:

Leiningen: [com.taoensso/tempura "1.5.3"] ; or
deps.edn:   com.taoensso/tempura {:mvn/version "1.5.3"}

Setup your namespace imports:

(def my-clj-or-cljs-ns
  (:require [taoensso.tempura :as tempura :refer [tr]]))

Define a dictionary for translation resources:

(def my-tempura-dictionary
  {:en-GB ; Locale
   {:missing ":en-GB missing text" ; Fallback for missing resources
    :example ; You can nest ids if you like
    {:greet "Good day %1!" ; Note Clojure fn-style %1 args

   :en ; A second locale
   {:missing ":en missing text"
    {:greet "Hello %1"
     :farewell "Goodbye %1"
     :foo "foo"
     :bar "bar"
     :bar-copy :en.example/bar ; Can alias entries
     :baz [:div "This is a **Hiccup** form"]

     ;; Can use arbitrary fns as resources
     :qux (fn [[arg1 arg2]] (str arg1 " and " arg2))}

    :example-copy :en/example ; Can alias entire subtrees

    {:__load-resource ; Inline edn content loaded from disk/resource

And we're ready to go:

(tr ; Just a functional call
  {:dict my-tempura-dictionary} ; Opts map, see docstring for details
  [:en-GB :fr] ; Vector of descending-preference locales to search
  [:example/foo] ; Vector of descending-preference resource-ids to search
  ) ; => "foo"

(def opts {:dict my-tempura-dictionary})
(def tr (partial tr opts [:en])) ; You'll typically use a partial like this

;; Grab a resource
(tr [:example/foo]) ; => "foo"

;; Missing resource
(tr [:example/invalid])                       ; => ":en missing text"
(tr [:example/invalid "inline-fallback"])     ; => "inline-fallback"
(tr [:example/invalid :bar "final-fallback"]) ; => "bar"

;; Let's try some argument interpolation
(tr [:example/greet] ["Steve"]) ; => "Hello Steve"

;; With inline fallback
(tr [:example/invalid "Hi %1"] ["Steve"]) ; => "Hi Steve"

;; Example of a deeply-nested resource id
(tr [:example.buttons/login-button "Login!"]) ; => "Login!"

;; Let's get a Hiccup form for Reactjs, etc.
;; Note how the Markdown gets expanded into appropriate Hiccup forms:
(tr [:example/baz]) ; => [:div "This is a " [:strong "Hiccup"] " form"]

;; With inline fallback
(tr [:example/invalid [:div "My **fallback** div"]]) ; => [:div "My " [:strong "fallback"] " div"]

And that's it, you know the API:

(tr [opts locales resource-ids])               ; Without argument interpolation, or
(tr [opts locales resource-ids resource-args]) ; With    argument interpolation

Please see the tr docstring for more info on available opts, etc.

Pattern: adding translations in stages

The support for gettext-like inline fallback content makes it really easy to write your application in stages, without translations becoming a burden until if/when you need them.

Assuming we have a tr partial (tr [resource-ids] [resource-ids resource-args]):

"Please login here"        ; Phase 1: no locale support (avoid)
(tr ["Please login here"]) ; Phase 2: works just like a text literal during dev

;; Phase 3: now supports translations when provided under the `:please-login`
;; resource id, otherwise falls back to the (English) text literal:
(tr [:please-login "Please login here"])

This means:

  • You can write dev/prototype apps w/o worrying about translations or naming resource ids.
  • Once your app design settles down, you can add resource ids.
  • Your translation team can now populate locale dictionaries at their own pace.
  • You can keep the default inline content as context for your developers.

I'll note that since the API is so pleasant, it's actually often much less effort for your developers to use tr than it would be for them to write the equivalent Hiccup structures by hand, etc.:

;; Compare the following two equivalent values:
(tr [["Hi %1, please enter your **login details** below:"]] [user-name])
[:span "Hi " user-name ", please enter your " [:strong "login details"] " below:"]

Note that ["foo"] is an optional resource content shorthand for the common-case [:span "foo"]

If it's easy to use, it'll be easy to get your developers in the habit of writing content this way - which means that there's a trivial path to adding multilingual support whenever it makes sense to do so.

See also the wiki docs for more info.


How's the performance? These seem like expensive transformations.

There's two aspects of performance worth measuring: resource lookup, and resource compilation.

Both are highly optimized, and intelligently cached. In fact, caching is quite easy since most applications have a small number of unique multilingual text assets. Assets are compiled each time they're encountered for the first time, and the compilation cached.

As an example:

`(tr [["Hi %1, please enter your **login details** below:"]] [user-name])`

;; Will compile the inner resource to an optimized function like this:

(fn [user-name] [:span "Hi " user-name ", please enter your " [:strong "login details"] " below:"])

So performance is often on par with the best possible hand-optimized monolingual code.

How would you use this with Reagent, etc.?

Tempura was specifically designed to work with Reactjs applications, and works great with Reagent out-the-box.

  • Step 1: Setup your ns imports so that your client has access to tempura/tr.
  • Step 2: Make sure your client has an appropriate dictionary [1].
  • Step 3: Call tr with the appropriate dictionary.

Couldn't be simpler.

[1] If your dictionaries are small, you could just define them with the rest of your client code. Or you can define them on the server-side and clients can fetch the relevant part/s through an Ajax request, etc. Remember that Tempura dictionaries are just plain Clojure maps, so they're trivially easy to modify/filter.

Ring middleware?

Please see tempura/wrap-ring-request.

Use with XLIFF or other industry standard tools?

Shouldn't be hard to do, you'll just need a conversion tool to/from edn. Haven't had a need for this myself, but PRs welcome.

Contacting me / contributions

Please use the project's GitHub issues page for all questions, ideas, etc. Pull requests welcome. See the project's GitHub contributors page for a list of contributors.

Otherwise, you can reach me at Happy hacking!

- Peter Taoussanis


Distributed under the EPL v1.0 (same as Clojure).
Copyright © 2016-2022 Peter Taoussanis.