First pass at SEO tag

cmd/gojekyll/commands.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
-	"reflect"
 	"sort"
 	"strings"
 	"time"
@@ -121,7 +120,7 @@ func varsCommand(site *site.Site) (err error) {
 	var data interface{}
 	switch {
 	case strings.HasPrefix(*variablePath, "site"):
-		data, err = followDots(site, strings.Split(*variablePath, ".")[1:])
+		data, err = utils.FollowDots(site, strings.Split(*variablePath, ".")[1:])
 		if err != nil {
 			return
 		}
@@ -133,7 +132,7 @@ func varsCommand(site *site.Site) (err error) {
 	default:
 		data = site
 	}
-	b, err := yaml.Marshal(toLiquid(data))
+	b, err := yaml.Marshal(liquid.FromDrop(data))
 	if err != nil {
 		return err
 	}
@@ -141,29 +140,3 @@ func varsCommand(site *site.Site) (err error) {
 	fmt.Println(string(b))
 	return nil
 }
-
-func followDots(data interface{}, props []string) (interface{}, error) {
-	for _, name := range props {
-		if drop, ok := data.(liquid.Drop); ok {
-			data = drop.ToLiquid()
-		}
-		if reflect.TypeOf(data).Kind() == reflect.Map {
-			item := reflect.ValueOf(data).MapIndex(reflect.ValueOf(name))
-			if item.CanInterface() && !item.IsNil() {
-				data = item.Interface()
-				continue
-			}
-		}
-		return nil, fmt.Errorf("no such property: %q", name)
-	}
-	return data, nil
-}
-
-func toLiquid(value interface{}) interface{} {
-	switch value := value.(type) {
-	case liquid.Drop:
-		return value.ToLiquid()
-	default:
-		return value
-	}
-}

plugins/feed.go

@@ -26,11 +26,11 @@ func (p *jekyllFeedPlugin) Initialize(s Site) error {
 
 func (p *jekyllFeedPlugin) ConfigureTemplateEngine(e *liquid.Engine) error {
 	e.RegisterTag("feed_meta", p.feedMetaTag)
-	tmpl, err := e.ParseTemplate([]byte(feedTemplateSource))
+	tpl, err := e.ParseTemplate([]byte(feedTemplateSource))
 	if err != nil {
 		panic(err)
 	}
-	p.tpl = tmpl
+	p.tpl = tpl
 	return nil
 }
 
@@ -41,7 +41,6 @@ func (p *jekyllFeedPlugin) PostRead(s Site) error {
 			path = "/" + pp
 		}
 	}
-
 	d := feedDoc{s, p, path}
 	s.AddDocument(&d, true)
 	return nil

plugins/plugins.go

@@ -14,7 +14,6 @@ import (
 	"github.com/osteele/gojekyll/pages"
 	"github.com/osteele/gojekyll/utils"
 	"github.com/osteele/liquid"
-	"github.com/osteele/liquid/render"
 )
 
 // Site is the site interface that is available to a plugin.
@@ -69,7 +68,6 @@ func register(name string, p Plugin) {
 func init() {
 	register("jemoji", jekyllJemojiPlugin{})
 	register("jekyll-mentions", jekyllMentionsPlugin{})
-	register("jekyll-seo-tag", jekyllSEOTagPlugin{})
 
 	// the following plugins are always active
 	// no warning but effect; the server runs in this mode anyway
@@ -102,29 +100,19 @@ func (p jekyllMentionsPlugin) PostRender(b []byte) []byte {
 	})
 }
 
-// jekyll-seo
-
-type jekyllSEOTagPlugin struct{ plugin }
-
-func (p jekyllSEOTagPlugin) ConfigureTemplateEngine(e *liquid.Engine) error {
-	p.stubbed("jekyll-seo-tag")
-	e.RegisterTag("seo", p.makeUnimplementedTag("jekyll-seo-tag"))
-	return nil
-}
-
 // helpers
 
-func (p plugin) stubbed(name string) {
-	fmt.Printf("warning: gojekyll does not emulate the %s plugin. Some tags have been stubbed to prevent errors.\n", name)
-}
+// func (p plugin) stubbed(name string) {
+// 	fmt.Printf("warning: gojekyll does not emulate the %s plugin. Some tags have been stubbed to prevent errors.\n", name)
+// }
 
-func (p plugin) makeUnimplementedTag(pluginName string) liquid.Renderer {
-	warned := false
-	return func(ctx render.Context) (string, error) {
-		if !warned {
-			fmt.Printf("The %q tag in the %q plugin has not been implemented.\n", ctx.TagName(), pluginName)
-			warned = true
-		}
-		return fmt.Sprintf(`<!-- unimplemented tag: %q -->`, ctx.TagName()), nil
-	}
-}
+// func (p plugin) makeUnimplementedTag(pluginName string) liquid.Renderer {
+// 	warned := false
+// 	return func(ctx render.Context) (string, error) {
+// 		if !warned {
+// 			fmt.Printf("The %q tag in the %q plugin has not been implemented.\n", ctx.TagName(), pluginName)
+// 			warned = true
+// 		}
+// 		return fmt.Sprintf(`<!-- unimplemented tag: %q -->`, ctx.TagName()), nil
+// 	}
+// }

plugins/seo_tag.go

@@ -0,0 +1,219 @@
+package plugins
+
+import (
+	"fmt"
+	"regexp"
+
+	"github.com/osteele/gojekyll/utils"
+	"github.com/osteele/liquid"
+	"github.com/osteele/liquid/render"
+)
+
+type jekyllSEOTagPlugin struct {
+	plugin
+	site Site
+	tpl  *liquid.Template
+}
+
+func init() {
+	register("jekyll-seo-tag", &jekyllSEOTagPlugin{})
+}
+
+func (p *jekyllSEOTagPlugin) Initialize(s Site) error {
+	p.site = s
+	return nil
+}
+
+func (p *jekyllSEOTagPlugin) ConfigureTemplateEngine(e *liquid.Engine) error {
+	e.RegisterTag("seo", p.seoTag)
+	tpl, err := e.ParseTemplate([]byte(seoTagTemplateSource))
+	if err != nil {
+		panic(err)
+	}
+	p.tpl = tpl
+	return nil
+}
+
+var seoSiteFields = []string{"description", "url", "twitter", "facebook", "logo", "social", "google_site_verification", "lang"}
+var seoPageOrSiteFields = []string{"author", "description", "image", "author", "lang"}
+var seoTagMultipleLinesPattern = regexp.MustCompile(`( *\n)+`)
+
+func (p *jekyllSEOTagPlugin) seoTag(ctx render.Context) (string, error) {
+	var (
+		site         = liquid.FromDrop(ctx.Get("site")).(map[string]interface{})
+		page         = liquid.FromDrop(ctx.Get("page")).(map[string]interface{})
+		pageTitle    = page["title"]
+		siteTitle    = site["title"]
+		canonicalURL = fmt.Sprintf("%s%s", site["url"], page["url"])
+	)
+	if siteTitle == nil && site["name"] != nil {
+		siteTitle = site["name"]
+	}
+	seoTag := map[string]interface{}{
+		"title?": true,
+		"title":  siteTitle,
+		// the following are not doc'ed, but evident from inspection:
+		// FIXME canonical w|w/out site.url and site.prefix
+		"canonical_url": canonicalURL,
+		"page_lang":     "en_US",
+		"page_title":    pageTitle,
+	}
+	copyFields(seoTag, site, append(seoSiteFields, seoPageOrSiteFields...))
+	copyFields(seoTag, page, seoPageOrSiteFields)
+	if pageTitle != nil && siteTitle != nil && pageTitle != siteTitle {
+		seoTag["title"] = fmt.Sprintf("%s | %s", pageTitle, siteTitle)
+	}
+	if author, ok := seoTag["author"].(string); ok {
+		if data, _ := utils.FollowDots(site, []string{"data", "authors", author}); data != nil {
+			seoTag["author"] = data
+		}
+	}
+	seoTag["json_ld"] = makeJSONLD(seoTag)
+	bindings := map[string]interface{}{
+		"page":    page,
+		"site":    site,
+		"seo_tag": seoTag,
+	}
+	b, err := p.tpl.Render(bindings)
+	if err != nil {
+		return "", err
+	}
+	return string(seoTagMultipleLinesPattern.ReplaceAll(b, []byte{'\n'})), nil
+}
+
+func copyFields(to, from map[string]interface{}, fields []string) {
+	for _, name := range fields {
+		if value := from[name]; value != nil {
+			to[name] = value
+		}
+	}
+}
+
+func makeJSONLD(seoTag map[string]interface{}) interface{} {
+	var authorRecord interface{}
+	if author := seoTag["author"]; author != nil {
+		if m, ok := author.(map[string]interface{}); ok {
+			author = m["name"]
+		}
+		authorRecord = map[string]interface{}{
+			"@type": "Person",
+			"name":  author,
+		}
+	}
+	return map[string]interface{}{
+		// TODO publisher
+		"@context":    "http://schema.org",
+		"@type":       "WebPage",
+		"author":      authorRecord,
+		"headline":    seoTag["page_title"],
+		"description": seoTag["description"],
+		"url":         seoTag["canonical_url"],
+	}
+}
+
+// Taken verbatim from https://github.com/jekyll/jekyll-seo-tag/
+const seoTagTemplateSource = `<!-- Begin emulated Jekyll SEO tag -->
+<!-- Adapted from github.com/jekyll/jekyll-seo-tag. Used according to the MIT License. -->
+{% if seo_tag.title? %}
+  <title>{{ seo_tag.title }}</title>
+{% endif %}
+
+{% if seo_tag.page_title %}
+  <meta property="og:title" content="{{ seo_tag.page_title }}" />
+{% endif %}
+
+{% if seo_tag.author.name %}
+  <meta name="author" content="{{ seo_tag.author.name }}" />
+{% endif %}
+
+<meta property="og:locale" content="{{ seo_tag.page_lang | replace:'-','_' }}" />
+
+{% if seo_tag.description %}
+  <meta name="description" content="{{ seo_tag.description }}" />
+  <meta property="og:description" content="{{ seo_tag.description }}" />
+{% endif %}
+
+{% if site.url %}
+  <link rel="canonical" href="{{ seo_tag.canonical_url }}" />
+  <meta property="og:url" content="{{ seo_tag.canonical_url }}" />
+{% endif %}
+
+{% if seo_tag.site_title %}
+  <meta property="og:site_name" content="{{ seo_tag.site_title }}" />
+{% endif %}
+
+{% if seo_tag.image %}
+  <meta property="og:image" content="{{ seo_tag.image.path }}" />
+  {% if seo_tag.image.height %}
+    <meta property="og:image:height" content="{{ seo_tag.image.height }}" />
+  {% endif %}
+  {% if seo_tag.image.width %}
+    <meta property="og:image:width" content="{{ seo_tag.image.width }}" />
+  {% endif %}
+{% endif %}
+
+{% if page.date %}
+  <meta property="og:type" content="article" />
+  <meta property="article:published_time" content="{{ page.date | date_to_xmlschema }}" />
+{% endif %}
+
+{% if paginator.previous_page %}
+  <link rel="prev" href="{{ paginator.previous_page_path | absolute_url }}">
+{% endif %}
+{% if paginator.next_page %}
+  <link rel="next" href="{{ paginator.next_page_path | absolute_url }}">
+{% endif %}
+
+{% if site.twitter %}
+  {% if seo_tag.image %}
+    <meta name="twitter:card" content="summary_large_image" />
+  {% else %}
+    <meta name="twitter:card" content="summary" />
+  {% endif %}
+
+  <meta name="twitter:site" content="@{{ site.twitter.username | replace:"@","" }}" />
+
+  {% if seo_tag.author.twitter %}
+    <meta name="twitter:creator" content="@{{ seo_tag.author.twitter }}" />
+  {% endif %}
+{% endif %}
+
+{% if site.facebook %}
+  {% if site.facebook.admins %}
+    <meta property="fb:admins" content="{{ site.facebook.admins }}" />
+  {% endif %}
+
+  {% if site.facebook.publisher %}
+    <meta property="article:publisher" content="{{ site.facebook.publisher }}" />
+  {% endif %}
+
+  {% if site.facebook.app_id %}
+    <meta property="fb:app_id" content="{{ site.facebook.app_id }}" />
+  {% endif %}
+{% endif %}
+
+{% if site.webmaster_verifications %}
+  {% if site.webmaster_verifications.google %}
+    <meta name="google-site-verification" content="{{ site.webmaster_verifications.google }}">
+  {% endif %}
+
+  {% if site.webmaster_verifications.bing %}
+    <meta name="msvalidate.01" content="{{ site.webmaster_verifications.bing }}">
+  {% endif %}
+
+  {% if site.webmaster_verifications.alexa %}
+    <meta name="alexaVerifyID" content="{{ site.webmaster_verifications.alexa }}">
+  {% endif %}
+
+  {% if site.webmaster_verifications.yandex %}
+    <meta name="yandex-verification" content="{{ site.webmaster_verifications.yandex }}">
+  {% endif %}
+{% elsif site.google_site_verification %}
+  <meta name="google-site-verification" content="{{ site.google_site_verification }}" />
+{% endif %}
+
+<script type="application/ld+json">
+  {{ seo_tag.json_ld | jsonify }}
+</script>
+
+<!-- End emulated Jekyll SEO tag -->`

utils/liquid.go

@@ -0,0 +1,26 @@
+package utils
+
+import (
+	"fmt"
+	"reflect"
+
+	"github.com/osteele/liquid"
+)
+
+// FollowDots applied to a property list ["a", "b", "c"] is equivalent to
+// the Liquid data expression "data.a.b.c", except without special treatment
+// of "first", "last", and "size".
+func FollowDots(data interface{}, props []string) (interface{}, error) {
+	for _, name := range props {
+		data = liquid.FromDrop(data)
+		if reflect.TypeOf(data).Kind() == reflect.Map {
+			item := reflect.ValueOf(data).MapIndex(reflect.ValueOf(name))
+			if item.IsValid() && !item.IsNil() && item.CanInterface() {
+				data = item.Interface()
+				continue
+			}
+		}
+		return nil, fmt.Errorf("no such property: %q", name)
+	}
+	return data, nil
+}