tpl/collections: Add collections.Complement

Fixes #5400

tpl/collections/complement_test.go

@@ -0,0 +1,84 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package collections
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+
+	"github.com/gohugoio/hugo/deps"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestComplement(t *testing.T) {
+	t.Parallel()
+
+	assert := require.New(t)
+
+	ns := New(&deps.Deps{})
+
+	s1 := []TstX{TstX{A: "a"}, TstX{A: "b"}, TstX{A: "d"}, TstX{A: "e"}}
+	s2 := []TstX{TstX{A: "b"}, TstX{A: "e"}}
+
+	xa, xd := &TstX{A: "a"}, &TstX{A: "d"}
+
+	sp1 := []*TstX{xa, &TstX{A: "b"}, xd, &TstX{A: "e"}}
+	sp2 := []*TstX{&TstX{A: "b"}, &TstX{A: "e"}}
+
+	for i, test := range []struct {
+		s        interface{}
+		t        []interface{}
+		expected interface{}
+	}{
+		{[]string{"a", "b", "c"}, []interface{}{[]string{"c", "d"}}, []string{"a", "b"}},
+		{[]string{"a", "b", "c"}, []interface{}{[]string{"c", "d"}, []string{"a", "b"}}, []string{}},
+		{[]interface{}{"a", "b", nil}, []interface{}{[]string{"a", "d"}}, []interface{}{"b", nil}},
+		{[]int{1, 2, 3, 4, 5}, []interface{}{[]int{1, 3}, []string{"a", "b"}, []int{1, 2}}, []int{4, 5}},
+		{[]int{1, 2, 3, 4, 5}, []interface{}{[]int64{1, 3}}, []int{2, 4, 5}},
+		{s1, []interface{}{s2}, []TstX{TstX{A: "a"}, TstX{A: "d"}}},
+		{sp1, []interface{}{sp2}, []*TstX{xa, xd}},
+
+		// Errors
+		{[]string{"a", "b", "c"}, []interface{}{"error"}, false},
+		{"error", []interface{}{[]string{"c", "d"}, []string{"a", "b"}}, false},
+		{[]string{"a", "b", "c"}, []interface{}{[][]string{[]string{"c", "d"}}}, false},
+		{[]interface{}{[][]string{[]string{"c", "d"}}}, []interface{}{[]string{"c", "d"}, []string{"a", "b"}}, false},
+	} {
+
+		errMsg := fmt.Sprintf("[%d]", i)
+
+		args := append(test.t, test.s)
+
+		result, err := ns.Complement(args...)
+
+		if b, ok := test.expected.(bool); ok && !b {
+			require.Error(t, err, errMsg)
+			continue
+		}
+
+		require.NoError(t, err, errMsg)
+
+		if !reflect.DeepEqual(test.expected, result) {
+			t.Fatalf("%s got\n%T: %v\nexpected\n%T: %v", errMsg, result, result, test.expected, test.expected)
+		}
+	}
+
+	_, err := ns.Complement()
+	assert.Error(err)
+	_, err = ns.Complement([]string{"a", "b"})
+	assert.Error(err)
+
+}