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, 135 insertions, 0 deletions

diff --git a/tpl/inflect/inflect.go b/tpl/inflect/inflect.go
new file mode 100644
index 000000000..9c13238b5
--- /dev/null
+++ b/tpl/inflect/inflect.go
@@ -0,0 +1,79 @@
+// 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 inflect
+
+import (
+	"strconv"
+
+	_inflect "github.com/bep/inflect"
+	"github.com/spf13/cast"
+)
+
+// New returns a new instance of the inflect-namespaced template functions.
+func New() *Namespace {
+	return &Namespace{}
+}
+
+// Namespace provides template functions for the "inflect" namespace.
+type Namespace struct{}
+
+// Namespace returns a pointer to the current namespace instance.
+func (ns *Namespace) Namespace() *Namespace { return ns }
+
+// Humanize returns the humanized form of a single parameter.
+//
+// If the parameter is either an integer or a string containing an integer
+// value, the behavior is to add the appropriate ordinal.
+//
+//     Example:  "my-first-post" -> "My first post"
+//     Example:  "103" -> "103rd"
+//     Example:  52 -> "52nd"
+func (ns *Namespace) Humanize(in interface{}) (string, error) {
+	word, err := cast.ToStringE(in)
+	if err != nil {
+		return "", err
+	}
+
+	if word == "" {
+		return "", nil
+	}
+
+	_, ok := in.(int)           // original param was literal int value
+	_, err = strconv.Atoi(word) // original param was string containing an int value
+	if ok || err == nil {
+		return _inflect.Ordinalize(word), nil
+	}
+
+	return _inflect.Humanize(word), nil
+}
+
+// Pluralize returns the plural form of a single word.
+func (ns *Namespace) Pluralize(in interface{}) (string, error) {
+	word, err := cast.ToStringE(in)
+	if err != nil {
+		return "", err
+	}
+
+	return _inflect.Pluralize(word), nil
+}
+
+// Singularize returns the singular form of a single word.
+func (ns *Namespace) Singularize(in interface{}) (string, error) {
+	word, err := cast.ToStringE(in)
+	if err != nil {
+		return "", err
+	}
+
+	return _inflect.Singularize(word), nil
+}
diff --git a/tpl/inflect/inflect_test.go b/tpl/inflect/inflect_test.go
new file mode 100644
index 000000000..028d5d9af
--- /dev/null
+++ b/tpl/inflect/inflect_test.go
@@ -0,0 +1,56 @@
+package inflect
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNamespace(t *testing.T) {
+	t.Parallel()
+
+	ns := New()
+
+	assert.Equal(t, ns, ns.Namespace(), "object pointers should match")
+}
+
+func TestInflect(t *testing.T) {
+	t.Parallel()
+
+	ns := New()
+
+	for i, test := range []struct {
+		fn     func(i interface{}) (string, error)
+		in     interface{}
+		expect interface{}
+	}{
+		{ns.Humanize, "MyCamel", "My camel"},
+		{ns.Humanize, "", ""},
+		{ns.Humanize, "103", "103rd"},
+		{ns.Humanize, "41", "41st"},
+		{ns.Humanize, 103, "103rd"},
+		{ns.Humanize, int64(92), "92nd"},
+		{ns.Humanize, "5.5", "5.5"},
+		{ns.Humanize, t, false},
+		{ns.Pluralize, "cat", "cats"},
+		{ns.Pluralize, "", ""},
+		{ns.Pluralize, t, false},
+		{ns.Singularize, "cats", "cat"},
+		{ns.Singularize, "", ""},
+		{ns.Singularize, t, false},
+	} {
+		errMsg := fmt.Sprintf("[%d] %v", i, test)
+
+		result, err := test.fn(test.in)
+
+		if b, ok := test.expect.(bool); ok && !b {
+			require.Error(t, err, errMsg)
+			continue
+		}
+
+		require.NoError(t, err, errMsg)
+		assert.Equal(t, test.expect, result, errMsg)
+	}
+}