Async promise print + async/await support (#406)

Author: borkdude

CHANGELOG.md

@@ -4,6 +4,11 @@ For a list of breaking changes, check [here](#breaking-changes).
 
 [Nbb](https://github.com/babashka/nbb): Scripting in Clojure on Node.js using [SCI](https://github.com/babashka/sci)
 
+## 1.4.206 (2026-02-07)
+
+- Support async/await. See [docs](https://github.com/babashka/sci/blob/master/doc/async-await.md) for syntax.
+- Print promise result value in REPL/nREPL: `(js/Promise.resolve 1) ;;=> #<Promise 1>`
+
 ## 1.3.205 (2025-12-19)
 
 - [#395](https://github.com/babashka/nbb/issues/395): fix `vim-fireplace` infinite loop on nREPL session close.

deps.edn

@@ -1,6 +1,6 @@
 {:paths ["src"]
  :aliases {:test {:extra-paths ["test"]}}
- :deps {thheller/shadow-cljs {:mvn/version "3.3.4"}
+ :deps {thheller/shadow-cljs {:mvn/version "3.3.5"}
         #_#_org.clojure/clojurescript {:mvn/version "1.11.51"}
         ;; reagent/reagent {:mvn/version "1.0.0"}
         cljsjs/react {:mvn/version "18.2.0-1"}
@@ -14,8 +14,8 @@
         cljs-bean/cljs-bean {:mvn/version "1.9.0"}
         org.babashka/sci
         #_{:local/root "../babashka/sci"}
-        #_{:mvn/version "0.9.44"}
-        {:git/url "https://github.com/babashka/sci"
+        {:mvn/version "0.12.51"}
+        #_{:git/url "https://github.com/babashka/sci"
          :git/sha "33995afb71d58dae270f1a8035e21196ea2157f0"}
         org.clojure/tools.cli {:mvn/version "1.0.214"}
         com.cognitect/transit-cljs {:mvn/version "0.8.280"}

package.json

@@ -1,6 +1,6 @@
 {
   "name": "nbb",
-  "version": "1.3.205",
+  "version": "1.4.205",
   "type": "module",
   "main": "index.mjs",
   "bin": {

shadow-cljs.edn

@@ -7,6 +7,7 @@
    :target :esm
    :runtime :node
    :output-dir "lib"
+   :devtools {:enabled false}
    :modules
    {:nbb_core {:init-fn nbb.core/init}
     :nbb_goog_string {:init-fn nbb.impl.gstring/init

src/nbb/impl/nrepl_server.cljs

@@ -96,11 +96,15 @@
     (sci/alter-var-root sci/*3 (constantly @sci/*2))
     (sci/alter-var-root sci/*2 (constantly @sci/*1))
     (sci/alter-var-root sci/*1 (constantly v))
-    (let [v (format-value (:nrepl.middleware.print/print request)
-                          (:nrepl.middleware.print/options request)
-                          v)]
-      (send-fn request {"value" v
-                        "ns" (str sci-ns)}))))
+    (if (instance? js/Promise v)
+      (.then v (fn [resolved]
+                 (send-fn request {"value" (str "#<Promise " (pr-str resolved) ">")
+                                   "ns" (str sci-ns)})))
+      (let [v (format-value (:nrepl.middleware.print/print request)
+                            (:nrepl.middleware.print/options request)
+                            v)]
+        (send-fn request {"value" v
+                          "ns" (str sci-ns)})))))
 
 (defn handle-error [send-fn request e]
   (sci/alter-var-root sci/*e (constantly e))
@@ -126,8 +130,8 @@
                              (.then v
                                     (fn [v]
                                      ;; (prn :v v)
-                                      (send-value request send-fn v)
-                                      (loop-fn v))))))
+                                      (-> (js/Promise.resolve (send-value request send-fn v))
+                                          (.then #(loop-fn v))))))))
                        (catch :default e
                          (handle-error send-fn request e)
                          (loop-fn nil))))]

src/nbb/impl/repl.cljs

@@ -72,8 +72,12 @@
                    (let [ctx #js {:f (if socket (fn [] wrapper)
                                          (fn []
                                            (let [v (first wrapper)]
-                                             (prn v)
-                                             wrapper)))}
+                                             (if (instance? js/Promise v)
+                                               (.then v (fn [resolved]
+                                                          (println (str "#<Promise " (pr-str resolved) ">"))
+                                                          wrapper))
+                                               (do (prn v)
+                                                   wrapper)))))}
                          _ (.createContext vm ctx)]
                      (.runInContext vm "f()" ctx
                                     #js {:displayErrors true
@@ -121,10 +125,13 @@
                                    (sci/alter-var-root sci/*3 (constantly @sci/*2))
                                    (sci/alter-var-root sci/*2 (constantly @sci/*1))
                                    (sci/alter-var-root sci/*1 (constantly val))
-                                   (when socket
-                                     (.write socket (prn-str val))
-                                     #_(prn val))
-                                   (continue rl socket))))
+                                   (if (and socket (instance? js/Promise val))
+                                     (.then val (fn [resolved]
+                                                  (.write socket (str "#<Promise " (pr-str resolved) ">\n"))
+                                                  (continue rl socket)))
+                                     (do (when socket
+                                           (.write socket (prn-str val)))
+                                         (continue rl socket))))))
                         (.catch (fn [err]
                                   (prn (str err))
                                   (sci/alter-var-root sci/*e (constantly err))

test/nbb/test_test.cljs

@@ -16,7 +16,8 @@
     (defmethod t/report [:cljs.test/default :end-run-tests] [m])
     (t/deftest foo (t/is (= 1 2))) (t/run-tests 'foo0)"))
         (.then (fn [_]
-                 (is (str/includes? @output "expected: (= 1 2)  actual: (not (= 1 2))")))))))
+                 (is (str/includes? @output "expected: (= 1 2)"))
+                 (is (str/includes? @output "actual: (not (= 1 2))")))))))
 
 (deftest-async cljs-test-test
   (let [output (atom "")]
@@ -29,7 +30,8 @@
     (t/deftest foo (t/is (= 1 2)))
     (cljs.test/deftest bar (t/is (= 1 2))) (t/run-tests 'foo01)"))
         (.then (fn [_]
-                 (is (str/includes? @output "expected: (= 1 2)  actual: (not (= 1 2))")))))))
+                 (is (str/includes? @output "expected: (= 1 2)"))
+                 (is (str/includes? @output "actual: (not (= 1 2))")))))))
 
 (deftest-async refer-macros-test
   (let [output (atom "")]
@@ -41,7 +43,8 @@
     (defmethod t/report [:cljs.test/default :end-run-tests] [m])
     (deftest foo (is (= 1 2))) (t/run-tests 'foo02)"))
         (.then (fn [_]
-                 (is (str/includes? @output "expected: (= 1 2)  actual: (not (= 1 2))")))))))
+                 (is (str/includes? @output "expected: (= 1 2)"))
+                 (is (str/includes? @output "actual: (not (= 1 2))")))))))
 
 (deftest-async are-test
   (let [output (atom "")]
@@ -54,7 +57,8 @@
     (defmethod t/report [:cljs.test/default :end-run-tests] [m])
     (t/deftest foo (t/are [x] (= x 2) 1 2 3)) (t/run-tests 'foo-are)")
        (.then (fn [_]
-                (is (str/includes? @output "expected: (= 3 2)  actual: (not (= 3 2))"))))
+                (is (str/includes? @output "expected: (= 3 2)"))
+                (is (str/includes? @output "actual: (not (= 3 2))"))))
        (.then (fn [_]
                 (reset! output "")
                 (nbb/load-string "