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gojekyll/plugins/seo_tag.go

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package plugins
import (
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"bytes"
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"fmt"
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"text/template"
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"github.com/osteele/gojekyll/utils"
"github.com/osteele/liquid"
"github.com/osteele/liquid/render"
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"github.com/osteele/liquid/tags"
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"github.com/tdewolff/minify"
"github.com/tdewolff/minify/html"
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)
type jekyllSEOTagPlugin struct {
plugin
site Site
tpl *liquid.Template
}
func init() {
register("jekyll-seo-tag", &jekyllSEOTagPlugin{})
}
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func (p *jekyllSEOTagPlugin) AfterInitSite(s Site) error {
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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
}
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func (p *jekyllSEOTagPlugin) seoTag(ctx render.Context) (string, error) {
buf := new(bytes.Buffer)
e := seoTagTemplate.Execute(buf, seoTag{p.tpl, ctx})
return buf.String(), e
}
type seoTag struct {
tpl *liquid.Template
ctx render.Context
}
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var seoSiteFields = []string{"url", "twitter", "facebook", "logo", "social", "google_site_verification", "lang"}
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var seoPageOrSiteFields = []string{"author", "description", "image", "author", "lang"}
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func (p seoTag) TagBody() (string, error) {
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var (
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ctx = p.ctx
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site = liquid.FromDrop(ctx.Get("site")).(tags.IterationKeyedMap)
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page = liquid.FromDrop(ctx.Get("page")).(tags.IterationKeyedMap)
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pageTitle = page["title"]
siteTitle = site["title"]
canonicalURL = fmt.Sprintf("%s%s", site["url"], page["url"])
)
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if siteTitle == nil {
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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,
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"site_title": siteTitle,
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}
copyFields(seoTag, site, append(seoSiteFields, seoPageOrSiteFields...))
copyFields(seoTag, page, seoPageOrSiteFields)
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// seoTag["description"] = page["excerpt"] FIXME appears to behave something like following, but excerpt should not be processed
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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
}
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m := minify.New()
m.AddFunc("text/html", html.Minify)
min := bytes.NewBuffer(make([]byte, 0, len(b)))
if err := m.Minify("text/html", min, bytes.NewBuffer(b)); err != nil {
return "", err
}
return min.String(), nil
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}
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{} {
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jsonLD := map[string]interface{}{
// TODO dateModified, datePublished, publisher, mainEntityOfPage
"@context": "http://schema.org",
"@type": "WebPage", // FIXME this is BlogPosting for a blog page
"headline": seoTag["page_title"],
"description": seoTag["description"],
"url": seoTag["canonical_url"],
}
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if author := seoTag["author"]; author != nil {
if m, ok := author.(map[string]interface{}); ok {
author = m["name"]
}
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jsonLD["author"] = map[string]interface{}{
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"@type": "Person",
"name": author,
}
}
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return jsonLD
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}
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// This is a separate template so it isn't minimized away.
var seoTagTemplate = template.Must(template.New("SEO tag").Parse(
`<!-- Begin Jekyll SEO tag -->
{{.TagBody}}
<!-- End Jekyll SEO tag -->`))
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// Taken verbatim from https://github.com/jekyll/jekyll-seo-tag/
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// Adapted from github.com/jekyll/jekyll-seo-tag. Used according to the MIT License.
const seoTagTemplateSource = `{% if seo_tag.title? %}
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<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 }}
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</script>`