fix(dates): rss date fixes

Explicitly define Content Index types to improve type checking.

Make rss feed and sitemap use the appropriate date type:
published and modified, respectively.

quartz/plugins/emitters/contentIndex.ts

@@ -1,7 +1,6 @@
 import { Root } from "hast"
 import { DateTime } from "luxon"
 import { GlobalConfiguration } from "../../cfg"
-import { getDate } from "../../components/Date"
 import { escapeHTML } from "../../util/escape"
 import { FilePath, FullSlug, SimpleSlug, joinSegments, simplifySlug } from "../../util/path"
 import { QuartzEmitterPlugin } from "../types"
@@ -9,7 +8,9 @@ import { toHtml } from "hast-util-to-html"
 import { write } from "./helpers"
 import { i18n } from "../../i18n"
 import DepGraph from "../../depgraph"
+import { QuartzPluginData } from "../vfile"
 
+// Describes the content index (.json) that this plugin produces, to be consumed downstream
 export type ContentIndex = Map<FullSlug, ContentDetails>
 export type ContentDetails = {
   title: string
@@ -17,8 +18,13 @@ export type ContentDetails = {
   tags: string[]
   content: string
   richContent?: string
-  date?: DateTime
-  description?: string
+}
+
+// The content index fields only used within this plugin and will not be written to the final index
+type FullContentIndex = Map<FullSlug, FullContentDetails>
+type FullContentDetails = ContentDetails & {
+  dates: QuartzPluginData["dates"]
+  description: string
 }
 
 interface Options {
@@ -37,42 +43,65 @@ const defaultOptions: Options = {
   includeEmptyFiles: true,
 }
 
-function generateSiteMap(cfg: GlobalConfiguration, idx: ContentIndex): string {
+function generateSiteMap(cfg: GlobalConfiguration, idx: FullContentIndex): string {
   const base = cfg.baseUrl ?? ""
-  const createURLEntry = (slug: SimpleSlug, content: ContentDetails): string => `<url>
+  const createURLEntry = (slug: SimpleSlug, modified?: DateTime): string => {
+    // sitemap protocol specifies that lastmod should *not* be time of sitemap generation; see: https://sitemaps.org/protocol.html#lastmoddef
+    // so we only include explicitly set modified dates
+    return `  <url>
     <loc>https://${joinSegments(base, encodeURI(slug))}</loc>
-    ${content.date && `<lastmod>${content.date.toISO()}</lastmod>`}
+    ${modified == null ? "" : `<lastmod>${modified.toISO()}</lastmod>`}
   </url>`
+  }
   const urls = Array.from(idx)
-    .map(([slug, content]) => createURLEntry(simplifySlug(slug), content))
+    .map(([slug, content]) => createURLEntry(simplifySlug(slug), content.dates?.modified))
     .join("")
   return `<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:xhtml="http://www.w3.org/1999/xhtml">${urls}</urlset>`
 }
 
-function generateRSSFeed(cfg: GlobalConfiguration, idx: ContentIndex, limit?: number): string {
+function generateRSSFeed(cfg: GlobalConfiguration, idx: FullContentIndex, limit?: number): string {
   const base = cfg.baseUrl ?? ""
+  const buildDate = DateTime.now()
 
-  const createURLEntry = (slug: SimpleSlug, content: ContentDetails): string => `<item>
+  const createRSSItem = (
+    slug: SimpleSlug,
+    content: FullContentDetails,
+    pubDate?: DateTime,
+  ): string => {
+    return `<item>
     <title>${escapeHTML(content.title)}</title>
     <link>https://${joinSegments(base, encodeURI(slug))}</link>
     <guid>https://${joinSegments(base, encodeURI(slug))}</guid>
     <description>${content.richContent ?? content.description}</description>
-    <pubDate>${content.date?.toRFC2822()}</pubDate>
+    ${pubDate == null ? "" : `<pubDate>${pubDate.toRFC2822()}</pubDate>`}
   </item>`
+  }
   const items = Array.from(idx)
-    .sort(([_, f1], [__, f2]) => {
-      if (f1.date && f2.date) {
-        return f2.date.toMillis() - f1.date.toMillis()
-      } else if (f1.date && !f2.date) {
+    .map(([slug, content]): [FullSlug, DateTime | undefined, FullContentDetails] => {
+      // rss clients use pubDate to determine the order of items, and which items are newly-published
+      // so to keep new items at the front, we use the explicitly set published date and fall back
+      // to the earliest other date known for the file
+      const { published, ...otherDates } = content.dates ?? {}
+      const pubDate =
+        published ??
+        Object.values(otherDates)
+          .sort((d1, d2) => d1.toMillis() - d2.toMillis())
+          .find((d) => d)
+      return [slug, pubDate, content]
+    })
+    .sort(([, d1, f1], [, d2, f2]) => {
+      // sort primarily by date (descending), then break ties with titles
+      if (d1 && d2) {
+        return d2.toMillis() - d1.toMillis() || f1.title.localeCompare(f2.title)
+      } else if (d1 && !d2) {
         return -1
-      } else if (!f1.date && f2.date) {
+      } else if (!d1 && d2) {
         return 1
       }
-
       return f1.title.localeCompare(f2.title)
     })
-    .map(([slug, content]) => createURLEntry(simplifySlug(slug), content))
     .slice(0, limit ?? idx.size)
+    .map(([slug, pubDate, content]) => createRSSItem(simplifySlug(slug), content, pubDate))
     .join("")
 
   return `<?xml version="1.0" encoding="UTF-8" ?>
@@ -83,6 +112,7 @@ function generateRSSFeed(cfg: GlobalConfiguration, idx: ContentIndex, limit?: nu
       <description>${!!limit ? i18n(cfg.locale).pages.rss.lastFewNotes({ count: limit }) : i18n(cfg.locale).pages.rss.recentNotes} on ${escapeHTML(
         cfg.pageTitle,
       )}</description>
+      <lastBuildDate>${buildDate.toRFC2822()}</lastBuildDate>
       <generator>Quartz -- quartz.jzhao.xyz</generator>
       ${items}
     </channel>
@@ -116,10 +146,9 @@ export const ContentIndex: QuartzEmitterPlugin<Partial<Options>> = (opts) => {
     async emit(ctx, content, _resources) {
       const cfg = ctx.cfg.configuration
       const emitted: FilePath[] = []
-      const linkIndex: ContentIndex = new Map()
+      const linkIndex: FullContentIndex = new Map()
       for (const [tree, file] of content) {
         const slug = file.data.slug!
-        const date = getDate(ctx.cfg.configuration, file.data) ?? DateTime.now()
         if (opts?.includeEmptyFiles || (file.data.text && file.data.text !== "")) {
           linkIndex.set(slug, {
             title: file.data.frontmatter?.title!,
@@ -129,7 +158,7 @@ export const ContentIndex: QuartzEmitterPlugin<Partial<Options>> = (opts) => {
             richContent: opts?.rssFullHtml
               ? escapeHTML(toHtml(tree as Root, { allowDangerousHtml: true }))
               : undefined,
-            date: date,
+            dates: file.data.dates,
             description: file.data.description ?? "",
           })
         }
@@ -158,13 +187,13 @@ export const ContentIndex: QuartzEmitterPlugin<Partial<Options>> = (opts) => {
       }
 
       const fp = joinSegments("static", "contentIndex") as FullSlug
-      const simplifiedIndex = Object.fromEntries(
-        Array.from(linkIndex).map(([slug, content]) => {
+      // explicitly annotate the type of simplifiedIndex to typecheck output file contents
+      const simplifiedIndex: ContentIndex = new Map(
+        Array.from(linkIndex, ([slug, fullContent]) => {
           // remove description and from content index as nothing downstream
           // actually uses it. we only keep it in the index as we need it
           // for the RSS feed
-          delete content.description
-          delete content.date
+          const { description, dates, ...content } = fullContent
           return [slug, content]
         }),
       )
@@ -172,7 +201,7 @@ export const ContentIndex: QuartzEmitterPlugin<Partial<Options>> = (opts) => {
       emitted.push(
         await write({
           ctx,
-          content: JSON.stringify(simplifiedIndex),
+          content: JSON.stringify(Object.fromEntries(simplifiedIndex)),
           slug: fp,
           ext: ".json",
         }),