tpl: Add template function namespaces

This commit moves almost all of the template functions into separate
packages under tpl/ and adds a namespace framework.  All changes should
be backward compatible for end users, as all existing function names in
the template funcMap are left intact.

Seq and DoArithmatic have been moved out of the helpers package and into
template namespaces.

Most of the tests involved have been refactored, and many new tests have
been written.  There's still work to do, but this is a big improvement.

I got a little overzealous and added some new functions along the way:

- strings.Contains
- strings.ContainsAny
- strings.HasSuffix
- strings.TrimPrefix
- strings.TrimSuffix

Documentation is forthcoming.

Fixes #3042

2 files changed, 395 insertions, 0 deletions

diff --git a/tpl/compare/compare.go b/tpl/compare/compare.go
new file mode 100644
index 000000000..8b7a96bf0
--- /dev/null
+++ b/tpl/compare/compare.go
@@ -0,0 +1,198 @@
+// Copyright 2017 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 compare
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"time"
+)
+
+// Default checks whether a given value is set and returns a default value if it
+// is not.  "Set" in this context means non-zero for numeric types and times;
+// non-zero length for strings, arrays, slices, and maps;
+// any boolean or struct value; or non-nil for any other types.
+func Default(dflt interface{}, given ...interface{}) (interface{}, error) {
+	// given is variadic because the following construct will not pass a piped
+	// argument when the key is missing:  {{ index . "key" | default "foo" }}
+	// The Go template will complain that we got 1 argument when we expectd 2.
+
+	if len(given) == 0 {
+		return dflt, nil
+	}
+	if len(given) != 1 {
+		return nil, fmt.Errorf("wrong number of args for default: want 2 got %d", len(given)+1)
+	}
+
+	g := reflect.ValueOf(given[0])
+	if !g.IsValid() {
+		return dflt, nil
+	}
+
+	set := false
+
+	switch g.Kind() {
+	case reflect.Bool:
+		set = true
+	case reflect.String, reflect.Array, reflect.Slice, reflect.Map:
+		set = g.Len() != 0
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		set = g.Int() != 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		set = g.Uint() != 0
+	case reflect.Float32, reflect.Float64:
+		set = g.Float() != 0
+	case reflect.Complex64, reflect.Complex128:
+		set = g.Complex() != 0
+	case reflect.Struct:
+		switch actual := given[0].(type) {
+		case time.Time:
+			set = !actual.IsZero()
+		default:
+			set = true
+		}
+	default:
+		set = !g.IsNil()
+	}
+
+	if set {
+		return given[0], nil
+	}
+
+	return dflt, nil
+}
+
+// Eq returns the boolean truth of arg1 == arg2.
+func Eq(x, y interface{}) bool {
+	normalize := func(v interface{}) interface{} {
+		vv := reflect.ValueOf(v)
+		switch vv.Kind() {
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			return vv.Int()
+		case reflect.Float32, reflect.Float64:
+			return vv.Float()
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+			return vv.Uint()
+		default:
+			return v
+		}
+	}
+	x = normalize(x)
+	y = normalize(y)
+	return reflect.DeepEqual(x, y)
+}
+
+// Ne returns the boolean truth of arg1 != arg2.
+func Ne(x, y interface{}) bool {
+	return !Eq(x, y)
+}
+
+// Ge returns the boolean truth of arg1 >= arg2.
+func Ge(a, b interface{}) bool {
+	left, right := compareGetFloat(a, b)
+	return left >= right
+}
+
+// Gt returns the boolean truth of arg1 > arg2.
+func Gt(a, b interface{}) bool {
+	left, right := compareGetFloat(a, b)
+	return left > right
+}
+
+// Le returns the boolean truth of arg1 <= arg2.
+func Le(a, b interface{}) bool {
+	left, right := compareGetFloat(a, b)
+	return left <= right
+}
+
+// Lt returns the boolean truth of arg1 < arg2.
+func Lt(a, b interface{}) bool {
+	left, right := compareGetFloat(a, b)
+	return left < right
+}
+
+func compareGetFloat(a interface{}, b interface{}) (float64, float64) {
+	var left, right float64
+	var leftStr, rightStr *string
+	av := reflect.ValueOf(a)
+
+	switch av.Kind() {
+	case reflect.Array, reflect.Chan, reflect.Map, reflect.Slice:
+		left = float64(av.Len())
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		left = float64(av.Int())
+	case reflect.Float32, reflect.Float64:
+		left = av.Float()
+	case reflect.String:
+		var err error
+		left, err = strconv.ParseFloat(av.String(), 64)
+		if err != nil {
+			str := av.String()
+			leftStr = &str
+		}
+	case reflect.Struct:
+		switch av.Type() {
+		case timeType:
+			left = float64(toTimeUnix(av))
+		}
+	}
+
+	bv := reflect.ValueOf(b)
+
+	switch bv.Kind() {
+	case reflect.Array, reflect.Chan, reflect.Map, reflect.Slice:
+		right = float64(bv.Len())
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		right = float64(bv.Int())
+	case reflect.Float32, reflect.Float64:
+		right = bv.Float()
+	case reflect.String:
+		var err error
+		right, err = strconv.ParseFloat(bv.String(), 64)
+		if err != nil {
+			str := bv.String()
+			rightStr = &str
+		}
+	case reflect.Struct:
+		switch bv.Type() {
+		case timeType:
+			right = float64(toTimeUnix(bv))
+		}
+	}
+
+	switch {
+	case leftStr == nil || rightStr == nil:
+	case *leftStr < *rightStr:
+		return 0, 1
+	case *leftStr > *rightStr:
+		return 1, 0
+	default:
+		return 0, 0
+	}
+
+	return left, right
+}
+
+var timeType = reflect.TypeOf((*time.Time)(nil)).Elem()
+
+func toTimeUnix(v reflect.Value) int64 {
+	if v.Kind() == reflect.Interface {
+		return toTimeUnix(v.Elem())
+	}
+	if v.Type() != timeType {
+		panic("coding error: argument must be time.Time type reflect Value")
+	}
+	return v.MethodByName("Unix").Call([]reflect.Value{})[0].Int()
+}
diff --git a/tpl/compare/compare_test.go b/tpl/compare/compare_test.go
new file mode 100644
index 000000000..d40a6fe5f
--- /dev/null
+++ b/tpl/compare/compare_test.go
@@ -0,0 +1,197 @@
+// Copyright 2017 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 compare
+
+import (
+	"fmt"
+	"path"
+	"reflect"
+	"runtime"
+	"testing"
+	"time"
+
+	"github.com/spf13/cast"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type tstCompareType int
+
+const (
+	tstEq tstCompareType = iota
+	tstNe
+	tstGt
+	tstGe
+	tstLt
+	tstLe
+)
+
+func tstIsEq(tp tstCompareType) bool { return tp == tstEq || tp == tstGe || tp == tstLe }
+func tstIsGt(tp tstCompareType) bool { return tp == tstGt || tp == tstGe }
+func tstIsLt(tp tstCompareType) bool { return tp == tstLt || tp == tstLe }
+
+func TestDefaultFunc(t *testing.T) {
+	t.Parallel()
+
+	then := time.Now()
+	now := time.Now()
+
+	for i, test := range []struct {
+		dflt   interface{}
+		given  interface{}
+		expect interface{}
+	}{
+		{true, false, false},
+		{"5", 0, "5"},
+
+		{"test1", "set", "set"},
+		{"test2", "", "test2"},
+		{"test3", nil, "test3"},
+
+		{[2]int{10, 20}, [2]int{1, 2}, [2]int{1, 2}},
+		{[2]int{10, 20}, [0]int{}, [2]int{10, 20}},
+		{[2]int{100, 200}, nil, [2]int{100, 200}},
+
+		{[]string{"one"}, []string{"uno"}, []string{"uno"}},
+		{[]string{"two"}, []string{}, []string{"two"}},
+		{[]string{"three"}, nil, []string{"three"}},
+
+		{map[string]int{"one": 1}, map[string]int{"uno": 1}, map[string]int{"uno": 1}},
+		{map[string]int{"one": 1}, map[string]int{}, map[string]int{"one": 1}},
+		{map[string]int{"two": 2}, nil, map[string]int{"two": 2}},
+
+		{10, 1, 1},
+		{10, 0, 10},
+		{20, nil, 20},
+
+		{float32(10), float32(1), float32(1)},
+		{float32(10), 0, float32(10)},
+		{float32(20), nil, float32(20)},
+
+		{complex(2, -2), complex(1, -1), complex(1, -1)},
+		{complex(2, -2), complex(0, 0), complex(2, -2)},
+		{complex(3, -3), nil, complex(3, -3)},
+
+		{struct{ f string }{f: "one"}, struct{}{}, struct{}{}},
+		{struct{ f string }{f: "two"}, nil, struct{ f string }{f: "two"}},
+
+		{then, now, now},
+		{then, time.Time{}, then},
+	} {
+		errMsg := fmt.Sprintf("[%d] %v", i, test)
+
+		result, err := Default(test.dflt, test.given)
+
+		require.NoError(t, err, errMsg)
+		assert.Equal(t, result, test.expect, errMsg)
+	}
+}
+
+func TestCompare(t *testing.T) {
+	t.Parallel()
+
+	for _, test := range []struct {
+		tstCompareType
+		funcUnderTest func(a, b interface{}) bool
+	}{
+		{tstGt, Gt},
+		{tstLt, Lt},
+		{tstGe, Ge},
+		{tstLe, Le},
+		{tstEq, Eq},
+		{tstNe, Ne},
+	} {
+		doTestCompare(t, test.tstCompareType, test.funcUnderTest)
+	}
+}
+
+func doTestCompare(t *testing.T, tp tstCompareType, funcUnderTest func(a, b interface{}) bool) {
+	for i, test := range []struct {
+		left            interface{}
+		right           interface{}
+		expectIndicator int
+	}{
+		{5, 8, -1},
+		{8, 5, 1},
+		{5, 5, 0},
+		{int(5), int64(5), 0},
+		{int32(5), int(5), 0},
+		{int16(4), int(5), -1},
+		{uint(15), uint64(15), 0},
+		{-2, 1, -1},
+		{2, -5, 1},
+		{0.0, 1.23, -1},
+		{1.1, 1.1, 0},
+		{float32(1.0), float64(1.0), 0},
+		{1.23, 0.0, 1},
+		{"5", "5", 0},
+		{"8", "5", 1},
+		{"5", "0001", 1},
+		{[]int{100, 99}, []int{1, 2, 3, 4}, -1},
+		{cast.ToTime("2015-11-20"), cast.ToTime("2015-11-20"), 0},
+		{cast.ToTime("2015-11-19"), cast.ToTime("2015-11-20"), -1},
+		{cast.ToTime("2015-11-20"), cast.ToTime("2015-11-19"), 1},
+		{"a", "a", 0},
+		{"a", "b", -1},
+		{"b", "a", 1},
+	} {
+		result := funcUnderTest(test.left, test.right)
+		success := false
+
+		if test.expectIndicator == 0 {
+			if tstIsEq(tp) {
+				success = result
+			} else {
+				success = !result
+			}
+		}
+
+		if test.expectIndicator < 0 {
+			success = result && (tstIsLt(tp) || tp == tstNe)
+			success = success || (!result && !tstIsLt(tp))
+		}
+
+		if test.expectIndicator > 0 {
+			success = result && (tstIsGt(tp) || tp == tstNe)
+			success = success || (!result && (!tstIsGt(tp) || tp != tstNe))
+		}
+
+		if !success {
+			t.Errorf("[%d][%s] %v compared to %v: %t", i, path.Base(runtime.FuncForPC(reflect.ValueOf(funcUnderTest).Pointer()).Name()), test.left, test.right, result)
+		}
+	}
+}
+
+func TestTimeUnix(t *testing.T) {
+	t.Parallel()
+	var sec int64 = 1234567890
+	tv := reflect.ValueOf(time.Unix(sec, 0))
+	i := 1
+
+	res := toTimeUnix(tv)
+	if sec != res {
+		t.Errorf("[%d] timeUnix got %v but expected %v", i, res, sec)
+	}
+
+	i++
+	func(t *testing.T) {
+		defer func() {
+			if err := recover(); err == nil {
+				t.Errorf("[%d] timeUnix didn't return an expected error", i)
+			}
+		}()
+		iv := reflect.ValueOf(sec)
+		toTimeUnix(iv)
+	}(t)
+}