Make apply api-compatible with python (args is not mandatory)

hy/compiler.py

@@ -1255,10 +1255,8 @@ class HyASTCompiler(object):
 
         return ret
 
-    # apply only needs to be defined for python3
-    if sys.version_info[0] >= 3:
     @builds("apply")
-        @checkargs(min=2, max=3)
+    @checkargs(min=1, max=3)
     def compile_apply_expression(self, expr):
         expr.pop(0)  # apply
         call = self.compile(expr.pop(0))
@@ -1271,14 +1269,14 @@ class HyASTCompiler(object):
                         col_offset=expr.start_column)
         ret = call
 
-            #add star args if any
+        if expr:
             stargs = expr.pop(0)
             if stargs is not None:
                 stargs = self.compile(stargs)
                 call.starargs = stargs.force_expr
                 ret = stargs + ret
 
-            if expr != []:
+        if expr:
             kwargs = self.compile(expr.pop(0))
             call.kwargs = kwargs.force_expr
             ret = kwargs + ret

tests/native_tests/language.hy

@@ -168,7 +168,9 @@
   (assert (= (apply sumit [1] {"b" 2 "c" 3}) 6))
   (assert (= (apply sumit [1 2 2]) 5))
   (assert (= (apply sumit [] {"a" 1 "b" 1 "c" 2}) 4))
-  (assert (= (apply sumit ((fn [] [1 1])) {"c" 1}) 3)))
+  (assert (= (apply sumit ((fn [] [1 1])) {"c" 1}) 3))
+  (defn noargs [] [1 2 3])
+  (assert (= (apply noargs) [1 2 3])))
 
 (defn test-dotted []
   "NATIVE: test dotted invocation"