py: implement builtin vars

py/method.go

@@ -84,6 +84,7 @@ const (
 	InternalMethodImport
 	InternalMethodEval
 	InternalMethodExec
+	InternalMethodVars
 )
 
 var MethodType = NewType("method", "method object")

stdlib/builtin/builtin.go

@@ -63,7 +63,7 @@ func init() {
 		py.MustNewMethod("setattr", builtin_setattr, 0, setattr_doc),
 		py.MustNewMethod("sorted", builtin_sorted, 0, sorted_doc),
 		py.MustNewMethod("sum", builtin_sum, 0, sum_doc),
-		// py.MustNewMethod("vars", builtin_vars, 0, vars_doc),
+		py.MustNewMethod("vars", py.InternalMethodVars, 0, vars_doc),
 	}
 	globals := py.StringDict{
 		"None":     py.None,
@@ -1189,6 +1189,11 @@ const globals_doc = `globals() -> dictionary
 
 Return the dictionary containing the current scope's global variables.`
 
+const vars_doc = `vars([object]) -> dictionary
+
+Without an argument, equivalent to locals().
+With an argument, equivalent to object.__dict__.`
+
 const sum_doc = `sum($module, iterable, start=0, /)
 --
 Return the sum of a \'start\' value (default: 0) plus an iterable of numbers

stdlib/builtin/tests/builtin.py

@@ -107,6 +107,39 @@ def fn(x):
     assert locals()["x"] == 1
 fn(1)
 
+doc="vars"
+def fn(x):
+    assert vars()["x"] == 1
+fn(1)
+
+# Test vars() with an object that has __dict__ (function objects have __dict__)
+def test_func():
+    pass
+
+assert vars(test_func) == test_func.__dict__
+assert isinstance(vars(test_func), dict)
+
+ok = False
+try:
+    vars(test_func, test_func)
+except TypeError:
+    ok = True
+assert ok, "TypeError not raised for too many arguments"
+
+ok = False
+try:
+    vars(x=1)
+except TypeError:
+    ok = True
+assert ok, "TypeError not raised for keyword arguments"
+
+ok = False
+try:
+    vars(test_func, y=1)
+except TypeError:
+    ok = True
+assert ok, "TypeError not raised for keyword arguments with object"
+
 def func(p):
    return p[1]
 

vm/eval.go

@@ -1599,6 +1599,23 @@ func callInternal(fn py.Object, args py.Tuple, kwargs py.StringDict, f *py.Frame
 		case py.InternalMethodExec:
 			f.FastToLocals()
 			return builtinExec(f.Context, args, kwargs, f.Locals, f.Globals, f.Builtins)
+		case py.InternalMethodVars:
+			if len(kwargs) > 0 {
+				return nil, py.ExceptionNewf(py.TypeError, "vars() takes no keyword arguments")
+			}
+			switch len(args) {
+			case 0:
+				f.FastToLocals()
+				return f.Locals, nil
+			case 1:
+				attr, err := py.GetAttrString(args[0], "__dict__")
+				if err != nil {
+					return nil, err
+				}
+				return attr, nil
+			default:
+				return nil, py.ExceptionNewf(py.TypeError, "vars() takes at most 1 argument (%d given)", len(args))
+			}
 		default:
 			return nil, py.ExceptionNewf(py.SystemError, "Internal method %v not found", x)
 		}