tpl: Add uniq function

Author: adiabatic

docs/content/templates/functions.md

@@ -373,6 +373,15 @@ e.g.
        {{ .Content }}
     {{ end }}
 
+
+### uniq
+
+Takes in a slice or array and returns a slice with subsequent duplicate elements removed.
+
+    {{ uniq (slice 1 2 3 2) }}
+    {{ slice 1 2 3 2 | uniq }}
+    <!-- both return [1 2 3] -->
+
 ## Files
 
 ### readDir

tpl/collections/collections.go

@@ -587,3 +587,41 @@ func (ns *Namespace) Union(l1, l2 interface{}) (interface{}, error) {
 		return nil, errors.New("can't iterate over " + reflect.ValueOf(l1).Type().String())
 	}
 }
+
+// Uniq takes in a slice or array and returns a slice with subsequent
+// duplicate elements removed.
+func (ns *Namespace) Uniq(l interface{}) (interface{}, error) {
+	if l == nil {
+		return make([]interface{}, 0), nil
+	}
+
+	lv := reflect.ValueOf(l)
+	lv, isNil := indirect(lv)
+	if isNil {
+		return nil, errors.New("invalid nil argument to Uniq")
+	}
+
+	var ret reflect.Value
+
+	switch lv.Kind() {
+	case reflect.Slice:
+		ret = reflect.MakeSlice(lv.Type(), 0, 0)
+	case reflect.Array:
+		ret = reflect.MakeSlice(reflect.SliceOf(lv.Type().Elem()), 0, 0)
+	default:
+		return nil, errors.New("Can't use Uniq on " + reflect.ValueOf(lv).Type().String())
+	}
+
+	for i := 0; i != lv.Len(); i++ {
+		lvv := lv.Index(i)
+		lvv, isNil := indirect(lvv)
+		if isNil {
+			continue
+		}
+
+		if !ns.In(ret.Interface(), lvv.Interface()) {
+			ret = reflect.Append(ret, lvv)
+		}
+	}
+	return ret.Interface(), nil
+}

tpl/collections/collections_test.go

@@ -603,6 +603,42 @@ func TestUnion(t *testing.T) {
 	}
 }
 
+func TestUniq(t *testing.T) {
+	t.Parallel()
+
+	ns := New(&deps.Deps{})
+	for i, test := range []struct {
+		l      interface{}
+		expect interface{}
+		isErr  bool
+	}{
+		{[]string{"a", "b", "c"}, []string{"a", "b", "c"}, false},
+		{[]string{"a", "b", "c", "c"}, []string{"a", "b", "c"}, false},
+		{[]string{"a", "b", "b", "c"}, []string{"a", "b", "c"}, false},
+		{[]string{"a", "b", "c", "b"}, []string{"a", "b", "c"}, false},
+		{[]int{1, 2, 3}, []int{1, 2, 3}, false},
+		{[]int{1, 2, 3, 3}, []int{1, 2, 3}, false},
+		{[]int{1, 2, 2, 3}, []int{1, 2, 3}, false},
+		{[]int{1, 2, 3, 2}, []int{1, 2, 3}, false},
+		{[4]int{1, 2, 3, 2}, []int{1, 2, 3}, false},
+		{nil, make([]interface{}, 0), false},
+		// should-errors
+		{1, 1, true},
+		{"foo", "fo", true},
+	} {
+		errMsg := fmt.Sprintf("[%d] %v", i, test)
+
+		result, err := ns.Uniq(test.l)
+		if test.isErr {
+			assert.Error(t, err, errMsg)
+			continue
+		}
+
+		assert.NoError(t, err, errMsg)
+		assert.Equal(t, test.expect, result, errMsg)
+	}
+}
+
 func (x *TstX) TstRp() string {
 	return "r" + x.A
 }

tpl/collections/init.go

@@ -137,6 +137,12 @@ func init() {
 				{`{{ seq 3 }}`, `[1 2 3]`},
 			},
 		)
+		ns.AddMethodMapping(ctx.Uniq,
+			[]string{"uniq"},
+			[][2]string{
+				{`{{ slice 1 2 3 2 | uniq }}`, `[1 2 3]`},
+			},
+		)
 
 		return ns