Auto merge of #2405 - Turbo87:readme, r=locks

Improve README loading code

The `readme_path` property is on the `version` resource, but we currently cache the README file content per crate. This PR cleans up the README loading code to cache the README per version instead, which means that we now show the correct README file corresponding to the selected version.

r? @locks

Author: bors

app/controllers/crate/version.js

@@ -125,27 +125,24 @@ export default Controller.extend({
     return data;
   }),
 
+  readme: alias('loadReadmeTask.last.value'),
+
   loadReadmeTask: task(function* () {
-    if (this.currentVersion.get('readme_path')) {
-      try {
-        let r = yield fetch(this.currentVersion.get('readme_path'));
-        if (r.ok) {
-          this.crate.set('readme', yield r.text());
-
-          if (typeof document !== 'undefined') {
-            setTimeout(() => {
-              let e = document.createEvent('CustomEvent');
-              e.initCustomEvent('hashchange', true, true);
-              window.dispatchEvent(e);
-            });
-          }
-        } else {
-          this.crate.set('readme', null);
-        }
-      } catch (error) {
-        this.crate.set('readme', null);
-      }
+    let version = this.currentVersion;
+
+    let readme = version.loadReadmeTask.lastSuccessful
+      ? version.loadReadmeTask.lastSuccessful.value
+      : yield version.loadReadmeTask.perform();
+
+    if (typeof document !== 'undefined') {
+      setTimeout(() => {
+        let e = document.createEvent('CustomEvent');
+        e.initCustomEvent('hashchange', true, true);
+        window.dispatchEvent(e);
+      });
     }
+
+    return readme;
   }),
 
   documentationLink: computed(

app/models/version.js

@@ -39,4 +39,15 @@ export default Model.extend({
 
     return { normal, build, dev };
   }).keepLatest(),
+
+  loadReadmeTask: task(function* () {
+    if (this.readme_path) {
+      let response = yield fetch(this.readme_path);
+      if (!response.ok) {
+        throw new Error(`README request for ${this.crateName} v${this.num} failed`);
+      }
+
+      return yield response.text();
+    }
+  }).keepLatest(),
 });

app/routes/crate/version.js

@@ -62,7 +62,9 @@ export default Route.extend({
     this._super(...arguments);
 
     model.version.loadDepsTask.perform();
-    controller.loadReadmeTask.perform();
+    controller.loadReadmeTask.perform().catch(() => {
+      // ignored
+    });
 
     let { crate } = model;
     if (!crate.documentation || crate.documentation.startsWith('https://docs.rs/')) {

app/templates/crate/version.hbs

@@ -56,9 +56,9 @@
           <CrateTomlCopy @copyText={{this.crateTomlText}} />
         {{/if}}
       </div>
-      {{#if this.crate.readme}}
+      {{#if this.readme}}
         <section local-class="crate-readme" aria-label="Readme" {{highlight-syntax selector="pre > code"}}>
-          {{html-safe this.crate.readme}}
+          {{html-safe this.readme}}
         </section>
       {{else}}
         {{#if this.crate.description}}