fix(sitemap): use latest post's date as <lastmod>

- posts[0] is used instead of posts.first() because first()
is not available after posts.toArray()

themes/chameleon/scripts/sitemap/.sitemap.xml

@@ -4,30 +4,29 @@
   <url>
     <loc>{{ post.permalink }}</loc>
     {% if post.updated %}
-    <lastmod>{{ post.updated }}</lastmod>
+    <lastmod>{{ post.updated | formatDate }}</lastmod>
     {% elif post.date %}
-    <lastmod>{{ post.date }}</lastmod>
+    <lastmod>{{ post.date | formatDate }}</lastmod>
     {% endif %}
   </url>
   {% endfor %}
 
   {# home page #}
   <url>
-      <loc>{{ config.url + config.root }}</loc>
-      <lastmod>{{ sNow }}</lastmod>
-   </url>
+    <loc>{{ config.url + config.root }}</loc>
+    <lastmod>{% if posts[0].updated %}{{ posts[0].updated | formatDate }}{% else %}{{ posts[0].date | formatDate }}{% endif %}</lastmod>
+  </url>
 
   {# archive page #}
   <url>
-      <loc>{{ config.url + '/' + archive_dir + '/' }}</loc>
-      <lastmod>{{ sNow }}</lastmod>
+    <loc>{{ config.url + '/' + config.archive_dir + '/' }}</loc>
+    <lastmod>{% if posts[0].updated %}{{ posts[0].updated | formatDate }}{% else %}{{ posts[0].date | formatDate }}{% endif %}</lastmod>
    </url>
-
-  {# tag pages #}
+  
   {% for tag in tags %}
-    <url>
-      <loc>{{ tag.permalink }}</loc>
-      <lastmod>{{ sNow }}</lastmod>
-    </url>
+  <url>
+    <loc>{{ tag.permalink }}</loc>
+    <lastmod>{% if tag.posts.first().updated %}{{ tag.posts.first().updated | formatDate }}{% else %}{{ tag.posts.first().date | formatDate }}{% endif %}</lastmod>
+  </url>
   {% endfor %}
 </urlset>

themes/chameleon/scripts/sitemap/generator.js

@@ -39,9 +39,7 @@ module.exports = function (locals) {
   // configuration dictionary
   const xmlConfig = {
     config: config,
-    posts: posts,
-    // add current time to <lastmod> of homepage and tags
-    sNow: moment().format('YYYY-MM-DD[T00:00:00.000Z]')
+    posts: posts
   }
 
   if (config.sitemap.tags !== false) {

themes/chameleon/scripts/sitemap/index.js

@@ -9,7 +9,8 @@
 const pathFn = require('path')
 
 const config = hexo.config.sitemap = Object.assign({
-  path: 'sitemap.xml'
+  path: 'sitemap.xml',
+  tags: true
 }, hexo.config.sitemap)
 
 if (!pathFn.extname(config.path)) {

themes/chameleon/scripts/sitemap/template.js

@@ -2,6 +2,7 @@
 
 const { join } = require('path')
 const { readFileSync } = require('fs')
+const moment = require('moment')
 let sitemapTmpl = ''
 
 module.exports = function (config) {
@@ -13,6 +14,11 @@ module.exports = function (config) {
     watch: false
   })
 
+  env.addFilter('formatDate', str => {
+    if (typeof str === 'string') return str.substring(0, 10)
+    return moment(str).format('YYYY-MM-DD[T00:00:00.000Z]').substring(0, 10)
+  })
+
   const sitemapSrc = config.sitemap.template || join(__dirname, '.sitemap.xml')
   sitemapTmpl = nunjucks.compile(readFileSync(sitemapSrc, 'utf8'), env)