Merge pull request #4058 from yglukhov/js-closures-test

Added js closures test. Fixes #3132.

tests/js/tclosures.nim

@@ -0,0 +1,51 @@
+discard """
+  action: run
+"""
+
+import math, strutils
+const consolePrefix = "jsCallbacks"
+
+asm """
+    var callback = []
+    function regCallback (fn) { callback.push (fn); }
+    function runCallbacks () {
+        var result = "\n"
+        var n = 0
+        for (var fn in callback) {
+            n += 1
+            result += "("+String (n)+")"
+            result += callback [fn] ()
+            result += "\n"
+        }
+        return result
+    }
+    function print (text) { console.log (text); }
+"""
+
+proc consoleprint (str:cstring): void {.importc: "print", noDecl.}
+proc print* (a: varargs[string, `$`]) = consoleprint "$1: $2" % [consolePrefix, join (a, " ")]
+
+type CallbackProc {.importc.} = proc () : cstring
+
+proc regCallback (fn:CallbackProc) {.importc.}
+proc runCallbacks ():cstring {.importc.}
+
+proc `*` (s:string, n:Natural) : string = s.repeat (n)
+
+proc outer (i:Natural) : (string, int) =
+    let c = $char (random (93) + 33)
+    let n = random (40)
+    let s = c * n
+    proc inner () : cstring = ("[$1]" % $n) & s & " <--"
+    regCallback (inner)
+    return (s, n)
+
+var expected = "\n"
+for i in 1 .. 10:
+    let (s, n) = outer (i)
+    expected &= ("($1)[$2]" % [$i, $n]) & s & " <--"
+    expected &= "\n"
+
+let results = runCallbacks ()
+
+doAssert(expected == results)