all: resolve PR comments and add tests

Author: wetor

py/filter.go

@@ -1,4 +1,4 @@
-// Copyright 2018 The go-python Authors.  All rights reserved.
+// Copyright 2023 The go-python Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 

py/map.go

@@ -1,4 +1,4 @@
-// Copyright 2018 The go-python Authors.  All rights reserved.
+// Copyright 2023 The go-python Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 

py/object.go

@@ -23,48 +23,50 @@ func ObjectRepr(o Object) Object {
 }
 
 // Return whether the object is True or not
-func ObjectIsTrue(o Object) (bool, error) {
-	if o == True {
+func ObjectIsTrue(o Object) (cmp bool, err error) {
+	switch o {
+	case True:
 		return true, nil
-	}
-	if o == False {
+	case False:
 		return false, nil
-	}
-
-	if o == None {
+	case None:
 		return false, nil
 	}
 
-	if I, ok := o.(I__bool__); ok {
-		cmp, err := I.M__bool__()
-		if err != nil {
-			return false, err
+	var res Object
+	switch t := o.(type) {
+	case I__bool__:
+		res, err = t.M__bool__()
+	case I__len__:
+		res, err = t.M__len__()
+	case *Type:
+		var ok bool
+		if res, ok, err = TypeCall0(o, "__bool__"); ok {
+			break
 		}
-		if cmp == True {
-			return true, nil
-		} else if cmp == False {
-			return false, nil
+		if res, ok, err = TypeCall0(o, "__len__"); ok {
+			break
 		}
 	}
-	if I, ok := o.(I__len__); ok {
-		l, err := I.M__len__()
-		if err != nil {
-			return false, err
-		}
-		if l.(Int) > 0 {
-			return true, nil
-		} else {
-			return false, nil
-		}
+	if err != nil {
+		return false, err
+	}
+
+	switch t := res.(type) {
+	case Bool:
+		return t == True, nil
+	case Int:
+		return t > 0, nil
 	}
-	return false, nil
+	return true, nil
 }
 
 // Return whether the object is True or not
 func ObjectIsSequence(o Object) bool {
-	if _, ok := o.(I__getitem__); ok {
+	switch t := o.(type) {
+	case I__getitem__:
 		return true
-	} else if t, ok := o.(*Type); ok {
+	case *Type:
 		if t.GetAttrOrNil("__getitem__") != nil {
 			return true
 		}

py/tests/filter.py

@@ -2,6 +2,27 @@
 from libtest import assertRaises
 
 doc="filter"
+class T0:
+    def __bool__(self):
+        return True
+class T1:
+    def __len__(self):
+        return 1
+class T2:
+    def __bool__(self):
+        return False
+class T3:
+    pass
+t0, t1, t2, t3 = T0(), T1(), T2(), T3()
+assert list(filter(None, [t0, t1, t2, t3])) == [t0, t1, t3]
+assert list(filter(None, [1, [], 2, ''])) == [1, 2]
+
+class T3:
+    def __len__(self):
+        raise ValueError
+t3 = T3()
+assertRaises(ValueError, list, filter(None, [t3]))
+
 class Squares:
     def __init__(self, max):
         self.max = max