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, 333 insertions, 0 deletions

diff --git a/tpl/transform/transform.go b/tpl/transform/transform.go
new file mode 100644
index 000000000..7e3b81bed
--- /dev/null
+++ b/tpl/transform/transform.go
@@ -0,0 +1,119 @@
+// 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 transform
+
+import (
+	"bytes"
+	"html"
+	"html/template"
+
+	"github.com/spf13/cast"
+	"github.com/spf13/hugo/deps"
+	"github.com/spf13/hugo/helpers"
+)
+
+// New returns a new instance of the transform-namespaced template functions.
+func New(deps *deps.Deps) *Namespace {
+	return &Namespace{
+		deps: deps,
+	}
+}
+
+// Namespace provides template functions for the "transform" namespace.
+type Namespace struct {
+	deps *deps.Deps
+}
+
+// Namespace returns a pointer to the current namespace instance.
+func (ns *Namespace) Namespace() *Namespace {
+	return ns
+}
+
+// Emojify returns a copy of s with all emoji codes replaced with actual emojis.
+//
+// See http://www.emoji-cheat-sheet.com/
+func (ns *Namespace) Emojify(s interface{}) (template.HTML, error) {
+	ss, err := cast.ToStringE(s)
+	if err != nil {
+		return "", err
+	}
+
+	return template.HTML(helpers.Emojify([]byte(ss))), nil
+}
+
+// Highlight returns a copy of s as an HTML string with syntax
+// highlighting applied.
+func (ns *Namespace) Highlight(s interface{}, lang, opts string) (template.HTML, error) {
+	ss, err := cast.ToStringE(s)
+	if err != nil {
+		return "", err
+	}
+
+	return template.HTML(helpers.Highlight(ns.deps.Cfg, html.UnescapeString(ss), lang, opts)), nil
+}
+
+// HTMLEscape returns a copy of s with reserved HTML characters escaped.
+func (ns *Namespace) HTMLEscape(s interface{}) (string, error) {
+	ss, err := cast.ToStringE(s)
+	if err != nil {
+		return "", err
+	}
+
+	return html.EscapeString(ss), nil
+}
+
+// HTMLUnescape returns a copy of with HTML escape requences converted to plain
+// text.
+func (ns *Namespace) HTMLUnescape(s interface{}) (string, error) {
+	ss, err := cast.ToStringE(s)
+	if err != nil {
+		return "", err
+	}
+
+	return html.UnescapeString(ss), nil
+}
+
+var markdownTrimPrefix = []byte("<p>")
+var markdownTrimSuffix = []byte("</p>\n")
+
+// Markdownify renders a given input from Markdown to HTML.
+func (ns *Namespace) Markdownify(s interface{}) (template.HTML, error) {
+	ss, err := cast.ToStringE(s)
+	if err != nil {
+		return "", err
+	}
+
+	m := ns.deps.ContentSpec.RenderBytes(
+		&helpers.RenderingContext{
+			Cfg:     ns.deps.Cfg,
+			Content: []byte(ss),
+			PageFmt: "markdown",
+			Config:  ns.deps.ContentSpec.NewBlackfriday(),
+		},
+	)
+	m = bytes.TrimPrefix(m, markdownTrimPrefix)
+	m = bytes.TrimSuffix(m, markdownTrimSuffix)
+
+	return template.HTML(m), nil
+}
+
+// Plainify returns a copy of s with all HTML tags removed.
+func (ns *Namespace) Plainify(s interface{}) (string, error) {
+	ss, err := cast.ToStringE(s)
+	if err != nil {
+		return "", err
+	}
+
+	return helpers.StripHTML(ss), nil
+}
diff --git a/tpl/transform/transform_test.go b/tpl/transform/transform_test.go
new file mode 100644
index 000000000..528697469
--- /dev/null
+++ b/tpl/transform/transform_test.go
@@ -0,0 +1,214 @@
+// 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 transform
+
+import (
+	"fmt"
+	"html/template"
+	"testing"
+
+	"github.com/spf13/hugo/config"
+	"github.com/spf13/hugo/deps"
+	"github.com/spf13/hugo/helpers"
+	"github.com/spf13/hugo/hugofs"
+	"github.com/spf13/viper"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type tstNoStringer struct{}
+
+func TestNamespace(t *testing.T) {
+	t.Parallel()
+
+	ns := New(newDeps(viper.New()))
+
+	assert.Equal(t, ns, ns.Namespace(), "object pointers should match")
+}
+
+func TestEmojify(t *testing.T) {
+	t.Parallel()
+
+	ns := New(newDeps(viper.New()))
+
+	for i, test := range []struct {
+		s      interface{}
+		expect interface{}
+	}{
+		{":notamoji:", template.HTML(":notamoji:")},
+		{"I :heart: Hugo", template.HTML("I ❤️ Hugo")},
+		// errors
+		{tstNoStringer{}, false},
+	} {
+		errMsg := fmt.Sprintf("[%d] %s", i, test.s)
+
+		result, err := ns.Emojify(test.s)
+
+		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)
+	}
+}
+
+func TestHighlight(t *testing.T) {
+	t.Parallel()
+
+	ns := New(newDeps(viper.New()))
+
+	for i, test := range []struct {
+		s      interface{}
+		lang   string
+		opts   string
+		expect interface{}
+	}{
+		{"func boo() {}", "go", "", "boo"},
+		{tstNoStringer{}, "go", "", false},
+	} {
+		errMsg := fmt.Sprintf("[%d]", i)
+
+		result, err := ns.Highlight(test.s, test.lang, test.opts)
+
+		if b, ok := test.expect.(bool); ok && !b {
+			require.Error(t, err, errMsg)
+			continue
+		}
+
+		require.NoError(t, err, errMsg)
+		assert.Contains(t, result, "boo", errMsg)
+	}
+}
+
+func TestHTMLEscape(t *testing.T) {
+	t.Parallel()
+
+	ns := New(newDeps(viper.New()))
+
+	for i, test := range []struct {
+		s      interface{}
+		expect interface{}
+	}{
+		{`"Foo & Bar's Diner" <y@z>`, `&#34;Foo &amp; Bar&#39;s Diner&#34; &lt;y@z&gt;`},
+		{"Hugo & Caddy > Wordpress & Apache", "Hugo &amp; Caddy &gt; Wordpress &amp; Apache"},
+		// errors
+		{tstNoStringer{}, false},
+	} {
+		errMsg := fmt.Sprintf("[%d] %s", i, test.s)
+
+		result, err := ns.HTMLEscape(test.s)
+
+		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)
+	}
+}
+
+func TestHTMLUnescape(t *testing.T) {
+	t.Parallel()
+
+	ns := New(newDeps(viper.New()))
+
+	for i, test := range []struct {
+		s      interface{}
+		expect interface{}
+	}{
+		{`&quot;Foo &amp; Bar&#39;s Diner&quot; &lt;y@z&gt;`, `"Foo & Bar's Diner" <y@z>`},
+		{"Hugo &amp; Caddy &gt; Wordpress &amp; Apache", "Hugo & Caddy > Wordpress & Apache"},
+		// errors
+		{tstNoStringer{}, false},
+	} {
+		errMsg := fmt.Sprintf("[%d] %s", i, test.s)
+
+		result, err := ns.HTMLUnescape(test.s)
+
+		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)
+	}
+}
+
+func TestMarkdownify(t *testing.T) {
+	t.Parallel()
+
+	ns := New(newDeps(viper.New()))
+
+	for i, test := range []struct {
+		s      interface{}
+		expect interface{}
+	}{
+		{"Hello **World!**", template.HTML("Hello <strong>World!</strong>")},
+		{[]byte("Hello Bytes **World!**"), template.HTML("Hello Bytes <strong>World!</strong>")},
+		{tstNoStringer{}, false},
+	} {
+		errMsg := fmt.Sprintf("[%d] %s", i, test.s)
+
+		result, err := ns.Markdownify(test.s)
+
+		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)
+	}
+}
+
+func TestPlainify(t *testing.T) {
+	t.Parallel()
+
+	ns := New(newDeps(viper.New()))
+
+	for i, test := range []struct {
+		s      interface{}
+		expect interface{}
+	}{
+		{"<em>Note:</em> blah <b>blah</b>", "Note: blah blah"},
+		// errors
+		{tstNoStringer{}, false},
+	} {
+		errMsg := fmt.Sprintf("[%d] %s", i, test.s)
+
+		result, err := ns.Plainify(test.s)
+
+		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)
+	}
+}
+
+func newDeps(cfg config.Provider) *deps.Deps {
+	l := helpers.NewLanguage("en", cfg)
+	l.Set("i18nDir", "i18n")
+	return &deps.Deps{
+		Cfg:         cfg,
+		Fs:          hugofs.NewMem(l),
+		ContentSpec: helpers.NewContentSpec(l),
+	}
+}