frontend: change logic of when doc links are shown in search results

The crate version page uses a fallback to handle crates that don't
define `documentation` keys in their manifests: if docs.rs has
documentation for that crate version, that those docs are used.

The search results do not implement the same logic, so crates that don't
have `documentation` keys don't get the handy documentation link in the
crate row.

This copies the logic from the version model into the crate model, using
the default crate version as the version to look for on docs.rs.

I strongly suspect there is a better way to do this than copying a bunch
of code, and would welcome suggestions from those more familiar with
Ember.

This would eventually fix rust-lang#1484.

app/components/crate-row.hbs

@@ -61,12 +61,12 @@
     {{#if @crate.homepage}}
       <li><a href="{{@crate.homepage}}">Homepage</a></li>
     {{/if}}
-    {{#if @crate.documentation}}
-      <li><a href="{{@crate.documentation}}">Documentation</a></li>
+    {{#if @crate.documentationLink}}
+      <li><a href="{{@crate.documentationLink}}">Documentation</a></li>
     {{/if}}
     {{#if @crate.repository}}
       <li><a href="{{@crate.repository}}">Repository</a></li>
     {{/if}}
   </ul>
 
-</div>
+</div>

app/controllers/search.js

@@ -3,9 +3,10 @@ import { action } from '@ember/object';
 import { inject as service } from '@ember/service';
 import { tracked } from '@glimmer/tracking';
 
-import { restartableTask } from 'ember-concurrency';
+import { all, restartableTask } from 'ember-concurrency';
 import { bool, reads } from 'macro-decorators';
 
+import { AjaxError } from '../utils/ajax';
 import { pagination } from '../utils/pagination';
 import { CATEGORY_PREFIX, processSearchQuery } from '../utils/search';
 
@@ -73,6 +74,22 @@ export default class SearchController extends Controller {
       ? { page, per_page, sort, q: query, all_keywords }
       : { page, per_page, sort, ...processSearchQuery(query) };
 
-    return await this.store.query('crate', searchOptions);
+    const crates = await this.store.query('crate', searchOptions);
+
+    // Prime the docs for the most recent versions of each crate.
+    const docTasks = [];
+    for (const crate of crates) {
+      docTasks.push(crate.loadDocsStatusTask.perform());
+    }
+    try {
+      await all(docTasks);
+    } catch (e) {
+      // report unexpected errors to Sentry and ignore `ajax()` errors
+      if (!didCancel(error) && !(error instanceof AjaxError)) {
+        this.sentry.captureException(error);
+      }
+    }
+
+    return crates;
   });
 }

app/models/crate.js

@@ -1,9 +1,12 @@
 import Model, { attr, hasMany } from '@ember-data/model';
 import { waitForPromise } from '@ember/test-waiters';
 
+import { task } from 'ember-concurrency';
 import { apiAction } from '@mainmatter/ember-api-actions';
 import { cached } from 'tracked-toolbox';
 
+import ajax from '../utils/ajax';
+
 export default class Crate extends Model {
   @attr name;
   @attr downloads;
@@ -42,6 +45,45 @@ export default class Crate extends Model {
     }
   }
 
+  get documentationLink() {
+    let crateDocsLink = this.documentation;
+
+    // if this is *not* a docs.rs link we'll return it directly
+    if (crateDocsLink && !crateDocsLink.startsWith('https://docs.rs/')) {
+      return crateDocsLink;
+    }
+
+    // if we know about a successful docs.rs build, we'll return a link to that
+    let { docsRsLink } = this;
+    if (docsRsLink) {
+      return docsRsLink;
+    }
+
+    // finally, we'll return the specified documentation link, whatever it is
+    if (crateDocsLink) {
+      return crateDocsLink;
+    }
+
+    return null;
+  }
+
+  loadDocsStatusTask = task(async () => {
+    if (!this.documentation) {
+      return await ajax(`https://docs.rs/crate/${this.name}/=${this.defaultVersion}/status.json`);
+    }
+  });
+
+  get hasDocsRsLink() {
+    let docsStatus = this.loadDocsStatusTask.lastSuccessful?.value;
+    return docsStatus?.doc_status === true;
+  }
+
+  get docsRsLink() {
+    if (this.hasDocsRsLink) {
+      return `https://docs.rs/${this.name}`;
+    }
+  }
+
   @cached get versionIdsBySemver() {
     let versions = this.versions.toArray() ?? [];
     return versions.sort(compareVersionBySemver).map(v => v.id);