feat(web/blog): Add support for draft & unlisted posts r/521

Posts with either `draft = true;` or `listed = false;` will no longer
be included in index generation and will have a warning callout
inserted at the top of the page urging people not to share the links
to them.

2 files changed, 39 insertions, 8 deletions

diff --git a/web/blog/default.nix b/web/blog/default.nix
index 73b1bc20e3e7..5f97c00bc985 100644
--- a/web/blog/default.nix
+++ b/web/blog/default.nix
@@ -7,6 +7,8 @@
 with pkgs.nix.yants;
 
 let
+  inherit (builtins) filter;
+
   # Type definition for a single blog post.
   post = struct "blog-post" {
     key = string; #
@@ -38,7 +40,12 @@ let
       "cp ${fragments.renderPost post} $out/${post.key}.html"
     ) posts)}
   '';
+
+  includePost = post: !(fragments.isDraft post) && !(fragments.isUnlisted post);
 in {
-  inherit post posts rendered;
+  inherit post rendered;
   static = ./static;
+
+  # Only include listed posts
+  posts = filter includePost posts;
 }
diff --git a/web/blog/fragments.nix b/web/blog/fragments.nix
index c910ac014e5e..b13ba20c6699 100644
--- a/web/blog/fragments.nix
+++ b/web/blog/fragments.nix
@@ -5,13 +5,17 @@
 # An entire post is rendered by `renderPost`, which assembles the
 # fragments together in a runCommand execution.
 #
-# The post overview is rendered by 'postList'.
+# The post index is generated by //web/homepage, not by this code.
 { pkgs, lib, ... }:
 
 let
   inherit (builtins) filter map hasAttr replaceStrings toFile;
   inherit (pkgs.third_party) runCommandNoCC writeText;
 
+  # Generate a post list for all listed, non-draft posts.
+  isDraft = post: (hasAttr "draft" post) && post.draft;
+  isUnlisted = post: (hasAttr "listed" post) && !post.listed;
+
   escape = replaceStrings [ "<" ">" "&" "'" ] [ "&lt;" "&gt;" "&amp;" "&#39;" ];
 
   header = title: ''
@@ -47,6 +51,22 @@ let
   </body>
   '';
 
+  draftWarning = toFile "draft.html" ''
+    <p class="cheddar-callout cheddar-warning">
+      <b>Note:</b> This post is a <b>draft</b>! Please do not share
+      the link to it without asking me first.
+    </p>
+    <hr>
+  '';
+
+  unlistedWarning = toFile "unlisted.html" ''
+    <p class="cheddar-callout cheddar-warning">
+      <b>Note:</b> This post is <b>unlisted</b>! Please do not share
+      the link to it without asking me first.
+    </p>
+    <hr>
+  '';
+
   renderPost = post: runCommandNoCC "${post.key}.html" {} ''
     cat ${toFile "header.html" (header post.title)} > $out
 
@@ -56,17 +76,21 @@ let
     date --date="@${toString post.date}" '+%Y-%m-%d' >> $out
     echo '</aside>' >> $out
 
+    ${
+      # Add a warning to draft/unlisted posts to make it clear that
+      # people should not share the post.
+
+      if (isDraft post) then "cat ${draftWarning} >> $out"
+      else if (isUnlisted post) then "cat ${unlistedWarning} >> $out"
+      else "# Your ads could be here?"
+    }
+
     # Write the actual post through cheddar's about-filter mechanism
     cat ${post.content} | ${pkgs.tools.cheddar}/bin/cheddar --about-filter ${post.content} >> $out
     echo '</article>' >> $out
 
     cat ${toFile "footer.html" footer} >> $out
   '';
-
-  # Generate a post list for all listed, non-draft posts.
-  isDraft = post: (hasAttr "draft" post) && post.draft;
-  isUnlisted = post: (hasAttr "listed" post) && !post.listed;
-  includePost = post: !(isDraft post) && !(isUnlisted post);
 in {
-  inherit renderPost;
+  inherit renderPost isDraft isUnlisted;
 }