tpl: Add urls.Parse function

Add a urls.Parse template function that front-ends url.Parse from the Go
stdlib.

Fixes #3849

tpl/urls/urls.go

@@ -15,7 +15,9 @@ package urls
 
 import (
 	"errors"
+	"fmt"
 	"html/template"
+	"net/url"
 
 	"github.com/gohugoio/hugo/deps"
 	"github.com/spf13/cast"
@@ -43,6 +45,17 @@ func (ns *Namespace) AbsURL(a interface{}) (template.HTML, error) {
 	return template.HTML(ns.deps.PathSpec.AbsURL(s, false)), nil
 }
 
+// Parse parses rawurl into a URL structure. The rawurl may be relative or
+// absolute.
+func (ns *Namespace) Parse(rawurl interface{}) (*url.URL, error) {
+	s, err := cast.ToStringE(rawurl)
+	if err != nil {
+		return nil, fmt.Errorf("Error in Parse: %s", err)
+	}
+
+	return url.Parse(s)
+}
+
 // RelURL takes a given string and prepends the relative path according to a
 // page's position in the project directory structure.
 func (ns *Namespace) RelURL(a interface{}) (template.HTML, error) {

tpl/urls/urls_test.go

@@ -0,0 +1,68 @@
+// 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 urls
+
+import (
+	"fmt"
+	"net/url"
+	"testing"
+
+	"github.com/gohugoio/hugo/deps"
+	"github.com/spf13/viper"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+var ns = New(&deps.Deps{Cfg: viper.New()})
+
+type tstNoStringer struct{}
+
+func TestParse(t *testing.T) {
+	t.Parallel()
+
+	for i, test := range []struct {
+		rawurl interface{}
+		expect interface{}
+	}{
+		{
+			"http://www.google.com",
+			&url.URL{
+				Scheme: "http",
+				Host:   "www.google.com",
+			},
+		},
+		{
+			"http://j@ne:password@google.com",
+			&url.URL{
+				Scheme: "http",
+				User:   url.UserPassword("j@ne", "password"),
+				Host:   "google.com",
+			},
+		},
+		// errors
+		{tstNoStringer{}, false},
+	} {
+		errMsg := fmt.Sprintf("[%d] %v", i, test)
+
+		result, err := ns.Parse(test.rawurl)
+
+		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)
+	}
+}