Babashka and the Small Clojure Interpreter @ ClojureD 2020

Transcript

1. And the Small Clojure Interpreter
   Michiel Borkent
   
   @borkdude
   
   2020-02-29
   
   

   View Slide

2. • CLI tools with instant startup! (< 10ms)
   
   • clj-kondo: a linter for Clojure that sparks joy
   
   • jet: convert between JSON, EDN and Transit
   
   • Jan Stępień, ClojureD 2019
   
   • No eval: dynamic classloader not supported!
   +
   

   View Slide

3. DSL -> scripting
   • Added a query DSL to jet, a GraalVM CLI:

   

   $ jet --query '(map :id)' <<< '[{:id 1} {:id 2}]'

   [1 2]
   
   • Extend this DSL to significant subset of Clojure?

   

   $ ??? '(->> [{:id 1} {:id 2}] (map :id))'

   (1 2)

   

   View Slide

4. • Native Clojure scripting tool, single binary, no JVM
   
   • Can be used to replace “the grey areas” of bash
   
   • Installable via script, brew (macOS, linux), aur (linux), scoop
   (Windows)
   $ time bb '(+ 1 2 3)'

   6

   0.00s user 0.00s system 67% cpu 0.013 total
   

   View Slide

5. CLJ scripting
   Runtime Impl Startup* Interop Windows Execution Threads
   clojure JVM Java ~1.5s + + Compiled +
   planck JSCore CLJS / JS ~ 1s + - Compiled -
   joker Native Go ~50ms** - + Interpreted -
   babashka Native GraalVM ~13ms + + Interpreted +
   *) https://stuartsierra.com/2019/12/21/clojure-start-time-in-2019 **) faster startup in progress
   

   View Slide

6. Babashka goals
   • Low latency Clojure scripting alternative for JVM Clojure
   
   • Easy installation: README ⟶ grab binary ⟶ run within seconds
   • Familiar and portable: JVM clojure ⟷ bb, #{linux, macOS, Windows}
   • Interop with commonly used classes (System, File, java.time.*, java.nio.*)
   
   • Multi-threading support (pmap, future)
   
   • Batteries included (tools.cli, cheshire) + external libraries
   

   View Slide

7. Shell interaction
   $ ls | bb -i '(filter #(-> % io/file .isDirectory) *input*)'
   ("doc" "examples" "logo" ...)
   

   View Slide

8. Predefine functions
   $ export BABASHKA_PRELOADS="(defn is-dir? [f] (-> f io/file .isDirectory))"

   

   $ ls | bb -i '(filter is-dir? *input*)'
   ("doc" "examples" "logo" ...)
   

   View Slide

9. Scripts
   $ pst.clj

   04:58
   #!/usr/bin/env bb
   (def now (java.time.ZonedDateTime/now))
   (def LA-timezone (java.time.ZoneId/of "America/Los_Angeles"))
   (def LA-time (.withZoneSameInstant now LA-timezone))
   (def pattern (java.time.format.DateTimeFormatter/ofPattern "HH:mm"))
   (println (.format LA-time pattern))
   

   View Slide

10. Also works on Windows
    

    View Slide

11. Included libs / namespaces
    • clojure.{core, edn, java.shell, java.io, set, string, test, walk}
    
    • clojure.tools.cli
    
    • clojure.core.async (thread ops work, go WIP)
    
    • clojure.data.csv
    
    • cheshire.core (JSON)
    
    • babashka.{wait, signal} (wait for port to open or file to exist)
    
    • TBD: clojure.xml, yaml, http client, ...
    

    View Slide

12. Compatible libs and scripts
    • spartan.spec: clojure.spec.alpha (1) for bb
    
    • deps.clj: a port of the clojure bash script to babashka
    
    • clj-http-lite: lighter fork of cli-http-lite
    
    • medley: "missing" clojure utility functions
    
    • regal: create regular expressions from EDN/hiccup
    
    • limit-break: REPL debugging tool
    
    • clojure-csv: another CSV library
    

    View Slide

13. Classpath
    ;; spec.clj

    (require '[spartan.spec :as s])

    (s/explain (s/cat :x int? :y keyword?) [1 #{:foo}])
    $ BABASHKA_CLASSPATH=$(clojure -Spath ...)
    $ bb spec.clj

    #{:foo} - failed: keyword? in: [1] at: [:y]
    

    View Slide

14. Decomplecting babashka
    Libraries coming out of babashka:
    
    • edamame: EDN/Clojure parser
    
    • sci: a Small Clojure Interpreter
    

    View Slide

15. edamame
    (def parsed (edamame/parse-string "#(+ 1 2 %)" {:fn true}))
    ;;=> (fn* [%1] (+ 1 2 %1))
    (meta parsed)
    ;;=> {:row 1, :col 1, :end-row 1, :end-col 11}
    - EDN/code parser
    - GraalVM compatible (no eval!)
    - location metadata
    - opt-in code-like features
    

    View Slide

16. Small Clojure Interpreter
    (def f (sci/eval-string "#(+ 1 2 %)"))
    (f 1)
    ;;=> 4
    - Clojure interpreter
    - Works on JVM / GraalVM / JS
    - Sandboxing

    - Works in CLJS advanced compiled apps

    - Comes with Java and JS APIs (available on NPM)
    

    View Slide

17. Malli: serializable schemas
    (def my-schema
    [:and
    [:map
    [:x int?]
    [:y int?]]
    [:fn '(fn [{:keys [x y]}] (> x y))]])
    (m/validate my-schema {:x 1, :y 0})
    ; => true
    (m/validate my-schema {:x 1, :y 2})
    ; => false
    

    View Slide

18. Function CLI args
    $ jet --edn-reader-opts "{:readers {'foo (fn [x] [:foo x])}}" \

    <<< '#foo{:a 1}'

    [:foo {:a 1}]
    $ jet --from json --keywordize '(comp keyword str/upper-case)' \

    <<< '{"a": 1}'
    {:A 1}
    

    View Slide

19. Sci from JavaScript
    https://observablehq.com/@jeroenvandijk/untitled/5
    $ npm install @borkdude/sci

    $ node

    > const { evalString, toJS } = require('@borkdude/sci');

    > x = evalString("(assoc {:a 1} :b 2)")

    > toJS(x)
    { a: 1, b: 2 }
    

    View Slide

20. Sci: adding libs
    (require '[cheshire.core :as json])

    

    (def sci-opts

    {:namespaces

    {'cheshire.core

    {'generate-string json/generate-string}}})
    

    (sci/eval-string
    "(require '[cheshire.core :as json])
    (json/generate-string {:a 1})"
    sci-opts)

    ;;=> "{\"a\":1}"
    

    View Slide

21. Projects using sci
    

    View Slide

22. Companies* using**
    babashka / sci
    Github #254
    Add your company to the list:
    * At least one person

    ** Or evaluating
    

    View Slide

23. Conclusion
    Clojure might not be the best language for everything, like
    scripting
    
    Clojure is the best language for scripting.
    

    View Slide

24. Thank you
    https://github.com/borkdude/babashka

    https://github.com/borkdude/sci
    And the Small Clojure Interpreter
    

    View Slide