fix #1216: fix core.async alts example with polyfill

CHANGELOG.md

@@ -12,6 +12,10 @@ A preview of the next release can be installed from
 - [#863](https://github.com/babashka/babashka/issues/863): allow pods to be declared in `bb.edn` and load them when required
   - See [updated pod library docs for details](TODO: link)
 
+### Enhanced
+
+- [#1216](https://github.com/babashka/babashka/issues/1216): support `core.async/alts!` using polyfill
+
 ## 0.7.8 (2022-03-13)
 
 This release improves compatibility with several libraries: [loom](https://github.com/aysylu/loom), [hugsql.core](https://www.hugsql.org) and [specter](https://github.com/redplanetlabs/specter)!

src/babashka/impl/clojure/core/async.clj

@@ -46,7 +46,6 @@
    '<!! (copy-var async/<!! core-async-namespace)
    '>!! (copy-var async/>!! core-async-namespace)
    'admix (copy-var async/admix core-async-namespace)
-   'alts! (copy-var async/alts! core-async-namespace)
    'alts!! (copy-var async/alts!! core-async-namespace)
    'alt!! (macrofy 'alt!! alt!! core-async-namespace)
    'buffer (copy-var async/buffer core-async-namespace)
@@ -107,6 +106,7 @@
    '<! (copy-var async/<!! core-async-namespace)
    '>! (copy-var async/>!! core-async-namespace)
    'alt! (macrofy 'alt! alt!! core-async-namespace)
+   'alts! (copy-var async/alts!! core-async-namespace)
    'go-loop (macrofy 'go-loop go-loop core-async-namespace)})
 
 (def async-protocols-ns (vars/->SciNamespace 'clojure.core.async.impl.protocols nil))

test/babashka/async_test.clj

@@ -33,3 +33,12 @@
   (is (number? (edn/read-string (test-utils/bb nil "
 (def ^:dynamic x 0)
 (binding [x 10] (async/<!! (async/thread x)))")))))
+
+(deftest alts-test
+  (is (true? (edn/read-string (test-utils/bb nil "
+(= 10 (first (async/<!!
+  (async/go
+    (async/alts!
+     [(async/go
+        (async/<! (async/timeout 100))
+        10)])))))")))))