add global alert to notify users about upcoming breaking changes

src/lib.rs

@@ -53,6 +53,15 @@ pub mod utils;
 mod docbuilder;
 mod web;
 
+use web::page::GlobalAlert;
+
+
+// Warning message shown in the navigation bar of every page. Set to `None` to hide it.
+pub(crate) static GLOBAL_ALERT: Option<GlobalAlert> = Some(GlobalAlert {
+    url: "https://blog.rust-lang.org/2019/09/18/upcoming-docsrs-changes.html",
+    text: "Upcoming docs.rs breaking changes!",
+});
+
 
 /// Version string generated at build time contains last git
 /// commit hash and build date

src/web/page.rs

@@ -7,6 +7,21 @@ use iron::response::Response;
 use handlebars_iron::Template;
 
 
+pub(crate) struct GlobalAlert {
+    pub(crate) url: &'static str,
+    pub(crate) text: &'static str,
+}
+
+impl ToJson for GlobalAlert {
+    fn to_json(&self) -> Json {
+        let mut map = BTreeMap::new();
+        map.insert("url".to_string(), self.url.to_json());
+        map.insert("text".to_string(), self.text.to_json());
+        Json::Object(map)
+    }
+}
+
+
 pub struct Page<T: ToJson> {
     title: Option<String>,
     content: T,
@@ -89,6 +104,11 @@ impl<T: ToJson> ToJson for Page<T> {
             tree.insert("title".to_owned(), title.to_json());
         }
 
+        tree.insert("has_global_alert".to_owned(), ::GLOBAL_ALERT.is_some().to_json());
+        if let Some(ref global_alert) = ::GLOBAL_ALERT {
+            tree.insert("global_alert".to_owned(), global_alert.to_json());
+        }
+
         tree.insert("content".to_owned(), self.content.to_json());
         tree.insert("cratesfyi_version".to_owned(), ::BUILD_VERSION.to_json());
         tree.insert("cratesfyi_version_safe".to_owned(),

templates/navigation.hbs

@@ -21,6 +21,7 @@
                 <li class="pure-menu-item"><a href="/about" class="pure-menu-link">About Docs.rs</a></li>
               </ul>
             </li>
+            {{> navigation_global_alert}}
           </ul>
           </form>
         </div>

templates/navigation_global_alert.hbs

@@ -0,0 +1,10 @@
+{{#if ../has_global_alert}}
+<li class="pure-menu-item">
+  <a href="{{../global_alert.url}}" class="pure-menu-link warn">
+    <i class="fa fa-fw fa-warning"></i>
+    {{../global_alert.text}}
+    <i class="fa fa-fw fa-warning"></i>
+  </a>
+</li>
+{{/if}}
+

templates/navigation_rustdoc.hbs

@@ -101,6 +101,7 @@
               </ul>
             </li>
           {{/with}}
+          {{> navigation_global_alert}}
           </ul>
           </form>
         </div>