Replace tera filters with macros

Zola doesn't support adding custom filters, but macros will work.

Author: senekor

src/lib.rs

@@ -9,7 +9,6 @@ use rayon::prelude::*;
 use sass_rs::{Options, compile_file};
 use serde::Serialize;
 use serde_json::{Value, json};
-use std::collections::HashMap;
 use std::fs::{self, File};
 use std::io::{self, Write};
 use std::path::{Path, PathBuf};
@@ -33,53 +32,12 @@ struct ReleasePost {
     url: String,
 }
 
-fn month_name(month_num: &Value, _args: &HashMap<String, Value>) -> tera::Result<Value> {
-    let month_num = month_num
-        .as_u64()
-        .expect("month_num should be an unsigned integer");
-    let name = match month_num {
-        1 => "Jan.",
-        2 => "Feb.",
-        3 => "Mar.",
-        4 => "Apr.",
-        5 => "May",
-        6 => "June",
-        7 => "July",
-        8 => "Aug.",
-        9 => "Sept.",
-        10 => "Oct.",
-        11 => "Nov.",
-        12 => "Dec.",
-        _ => panic!("invalid month! ({month_num})"),
-    };
-    Ok(name.into())
-}
-
-// Tera and Handlebars escape HTML differently by default.
-// Tera:       &<>"'/
-// Handlebars: &<>"'`=
-// To make the transition testable, this function escapes just like Handlebars.
-fn escape_hbs(input: &Value, _args: &HashMap<String, Value>) -> tera::Result<Value> {
-    let input = input.as_str().expect("input should be a string");
-    Ok(input
-        .replace("&", "&amp;")
-        .replace("<", "&lt;")
-        .replace(">", "&gt;")
-        .replace("\"", "&quot;")
-        .replace("'", "&#x27;")
-        .replace("`", "&#x60;")
-        .replace("=", "&#x3D;")
-        .into())
-}
-
 impl Generator {
     fn new(
         out_directory: impl AsRef<Path>,
         posts_directory: impl AsRef<Path>,
     ) -> eyre::Result<Self> {
         let mut tera = Tera::new("templates/*")?;
-        tera.register_filter("month_name", month_name);
-        tera.register_filter("escape_hbs", escape_hbs);
         tera.autoescape_on(vec![]); // disable auto-escape for .html templates
         Ok(Generator {
             tera,

templates/feed.xml

@@ -1,3 +1,4 @@
+{% import "macros.tera" as macros %}
 <?xml version="1.0" encoding="utf-8"?>
 <feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en">
     <generator uri="https://blog.rust-lang.org/{{blog.prefix}}" version="0.1.0">{{blog.title}}</generator>
@@ -14,15 +15,15 @@
 
     {% for post in posts %}
     <entry>
-        <title>{{post.title | escape_hbs}}</title>
-        <link rel="alternate" href="https://blog.rust-lang.org/{{blog.prefix}}{{post.url | escape_hbs}}" type="text/html" title="{{post.title | escape_hbs}}" />
-        <published>{{post.published | escape_hbs}}</published>
-        <updated>{{post.updated | escape_hbs}}</updated>
-        <id>https://blog.rust-lang.org/{{blog.prefix}}{{post.url | escape_hbs}}</id>
-        <content type="html" xml:base="https://blog.rust-lang.org/{{blog.prefix}}{{post.url | escape_hbs}}">{{post.contents | escape_hbs}}</content>
+        <title>{{ macros::escape_hbs(input=post.title) }}</title>
+        <link rel="alternate" href="https://blog.rust-lang.org/{{blog.prefix}}{{ macros::escape_hbs(input=post.url) }}" type="text/html" title="{{ macros::escape_hbs(input=post.title) }}" />
+        <published>{{ macros::escape_hbs(input=post.published) }}</published>
+        <updated>{{ macros::escape_hbs(input=post.updated) }}</updated>
+        <id>https://blog.rust-lang.org/{{blog.prefix}}{{ macros::escape_hbs(input=post.url) }}</id>
+        <content type="html" xml:base="https://blog.rust-lang.org/{{blog.prefix}}{{ macros::escape_hbs(input=post.url) }}">{{ macros::escape_hbs(input=post.contents) }}</content>
 
         <author>
-            <name>{{post.author | escape_hbs}}</name>
+            <name>{{ macros::escape_hbs(input=post.author) }}</name>
         </author>
     </entry>
     {%- endfor %}

templates/headers.html

@@ -3,12 +3,12 @@
  <meta name="twitter:card" content="summary">
  <meta name="twitter:site" content="@rustlang">
  <meta name="twitter:creator" content="@rustlang">
- <meta name="twitter:title" content="{{title | escape_hbs}}">
+ <meta name="twitter:title" content="{{ macros::escape_hbs(input=title) }}">
  <meta name="twitter:description" content="{{blog.description}}">
 <meta name="twitter:image" content="https://www.rust-lang.org/static/images/rust-social.jpg">
 
 <!-- Facebook OpenGraph -->
-<meta property="og:title" content="{{title | escape_hbs}}" />
+<meta property="og:title" content="{{ macros::escape_hbs(input=title) }}" />
 <meta property="og:description" content="{{blog.description}}">
 <meta property="og:image" content="https://www.rust-lang.org/static/images/rust-social-wide.jpg" />
 <meta property="og:type" content="website" />

templates/index.html

@@ -1,3 +1,4 @@
+{% import "macros.tera" as macros %}
 {% extends "layout.html" %}
 {% block page %}
 <header class="mt3 mt0-ns mb4-ns">
@@ -11,7 +12,7 @@
       <p>
       <b>See also:</b>
       {%- for other in other_blogs %}
-              <a href="/{{other.url}}">{{other.link_text | escape_hbs}}</a>
+              <a href="/{{other.url}}">{{ macros::escape_hbs(input=other.link_text) }}</a>
       {%- endfor %}
       </p>
     </div>
@@ -28,8 +29,8 @@
         <td class="bn"><h3 class="f0-l f1-m f2-s mt4 mb0">Posts in {{post.year}}</h3></td>
       </tr>{% endif %}
       <tr>
-        <td class="tr o-60 pr4 pr5-l bn">{{post.month | month_name}}&nbsp;{{post.day}}</td>
-        <td class="bn"><a href="{{post.url}}">{{post.title | escape_hbs}}</a></td>
+        <td class="tr o-60 pr4 pr5-l bn">{{ macros::month_name(num=post.month) }}&nbsp;{{post.day}}</td>
+        <td class="bn"><a href="{{post.url}}">{{ macros::escape_hbs(input=post.title) }}</a></td>
       </tr>
     {%- endfor %}
     </table>

templates/layout.html

@@ -1,11 +1,12 @@
+{% import "macros.tera" as macros %}
 {% import "headers.html" as headers %}
 {% import "nav.html" as nav %}
 {% import "footer.html" as footer %}
 <!DOCTYPE html>
 <html lang="en">
   <head>
     <meta charset="utf-8">
-    <title>{{ title | escape_hbs }}</title>
+    <title>{{ macros::escape_hbs(input=title) }}</title>
     <meta name="viewport" content="width=device-width,initial-scale=1.0">
 <meta name="description" content="Empowering everyone to build reliable and efficient software.">
      {{ headers::headers(title=title, blog=blog) | indent(prefix="    ", blank=true) }}

templates/macros.tera

@@ -0,0 +1,35 @@
+{% macro month_name(num) %}
+    {%- if     num == 1 %}Jan.
+    {%- elif num == 2 %}Feb.
+    {%- elif num == 3 %}Mar.
+    {%- elif num == 4 %}Apr.
+    {%- elif num == 5 %}May
+    {%- elif num == 6 %}June
+    {%- elif num == 7 %}July
+    {%- elif num == 8 %}Aug.
+    {%- elif num == 9 %}Sept.
+    {%- elif num == 10 %}Oct.
+    {%- elif num == 11 %}Nov.
+    {%- elif num == 12 %}Dec.
+    {%- else %}{{ throw(message="invalid month! " ~ num) }}
+    {%- endif %}
+{% endmacro month_name %}
+
+{#
+    The blog templates used to be written in Handlebars, but Tera and Handlebars
+    escape HTML differently by default:
+    Tera:       &<>"'/
+    Handlebars: &<>"'`=
+    To keep the output identical, this macro matches the behavior of Handlebars.
+#}
+{% macro escape_hbs(input) %}
+    {{ input
+        | replace(from="&", to="&amp;")
+        | replace(from="<", to="&lt;")
+        | replace(from=">", to="&gt;")
+        | replace(from='"', to="&quot;")
+        | replace(from="'", to="&#x27;")
+        | replace(from="`", to="&#x60;")
+        | replace(from="=", to="&#x3D;")
+    }}
+{% endmacro escape_hbs %}

templates/post.html

@@ -1,13 +1,14 @@
+{% import "macros.tera" as macros %}
 {% extends "layout.html" %}
 {% block page %}
-<section id="{{post.title | escape_hbs}}" class="white">
+<section id="{{ macros::escape_hbs(input=post.title) }}" class="white">
   <div class="w-100 mw-none ph3 mw8-m mw8-l center f3">
     <header>
-      <h2>{{ post.title | escape_hbs }}</h2>
+      <h2>{{ macros::escape_hbs(input=post.title) }}</h2>
       <div class="highlight mt2 mb3"></div>
     </header>
 
-    <div class="publish-date-author">{{post.month | month_name}} {{post.day}}, {{post.year}} &middot; {{post.author | escape_hbs}}
+    <div class="publish-date-author">{{ macros::month_name(num=post.month) }} {{post.day}}, {{post.year}} &middot; {{ macros::escape_hbs(input=post.author) }}
     {% if post.has_team %} on behalf of <a href="{{post.team_url}}">{{post.team}}</a> {% endif %}
     </div>