crate/settings: Add warning banner when trustpub_only blocks publishing

Shows a warning alert above the trusted publishing section when
`trustpub_only` is enabled but no trusted publisher configs exist.
The warning text: "Trusted publishing is required but no publishers
are configured. Publishing to this crate is currently blocked."

Author: Turbo87

app/controllers/crate/settings/index.js

@@ -20,9 +20,16 @@ export default class CrateSettingsController extends Controller {
    */
   trustpubOnlyCheckboxWasVisible = false;
 
+  get #hasConfigs() {
+    return this.githubConfigs?.length > 0 || this.gitlabConfigs?.length > 0;
+  }
+
   get showTrustpubOnlyCheckbox() {
-    let hasConfigs = this.githubConfigs?.length > 0 || this.gitlabConfigs?.length > 0;
-    return hasConfigs || this.crate?.trustpub_only || this.trustpubOnlyCheckboxWasVisible;
+    return this.#hasConfigs || this.crate?.trustpub_only || this.trustpubOnlyCheckboxWasVisible;
+  }
+
+  get showTrustpubOnlyWarning() {
+    return this.crate?.trustpub_only && !this.#hasConfigs;
   }
 
   @action showAddOwnerForm() {

app/templates/crate/settings/index.css

@@ -114,6 +114,10 @@
     }
 }
 
+.trustpub-only-warning {
+    margin-bottom: var(--space-s);
+}
+
 .trustpub-only-checkbox {
     border-top: 1px solid light-dark(hsla(51, 90%, 42%, 0.25), #232321);
 }

app/templates/crate/settings/index.gjs

@@ -8,6 +8,7 @@ import pageTitle from 'ember-page-title/helpers/page-title';
 import not from 'ember-truth-helpers/helpers/not';
 import or from 'ember-truth-helpers/helpers/or';
 
+import Alert from 'crates-io/components/alert';
 import CrateHeader from 'crates-io/components/crate-header';
 import Tooltip from 'crates-io/components/tooltip';
 import TrustpubOnlyCheckbox from 'crates-io/components/trustpub-only-checkbox';
@@ -117,6 +118,12 @@ import UserAvatar from 'crates-io/components/user-avatar';
     </div>
   </div>
 
+  {{#if @controller.showTrustpubOnlyWarning}}
+    <Alert @variant='warning' class='trustpub-only-warning' data-test-trustpub-only-warning>
+      Trusted publishing is required but no publishers are configured. Publishing to this crate is currently blocked.
+    </Alert>
+  {{/if}}
+
   <div class='trustpub'>
     <table data-test-trusted-publishing>
       <thead>

tests/routes/crate/settings-test.js

@@ -277,6 +277,86 @@ module('Route | crate.settings', hooks => {
     });
   });
 
+  module('trustpub_only warning banner', function () {
+    test('hidden when flag is false', async function (assert) {
+      const { crate, user } = prepare(this);
+      this.authenticateAs(user);
+
+      await visit(`/crates/${crate.name}/settings`);
+
+      assert.dom('[data-test-trustpub-only-warning]').doesNotExist();
+    });
+
+    test('hidden when flag is true and configs exist', async function (assert) {
+      const { crate, user } = prepare(this);
+      this.db.crate.update({ where: { id: { equals: crate.id } }, data: { trustpubOnly: true } });
+      this.authenticateAs(user);
+
+      this.db.trustpubGithubConfig.create({
+        crate,
+        repository_owner: 'rust-lang',
+        repository_name: 'crates.io',
+        workflow_filename: 'ci.yml',
+      });
+
+      await visit(`/crates/${crate.name}/settings`);
+
+      assert.dom('[data-test-trustpub-only-warning]').doesNotExist();
+    });
+
+    test('shown when flag is true but no configs exist', async function (assert) {
+      const { crate, user } = prepare(this);
+      this.db.crate.update({ where: { id: { equals: crate.id } }, data: { trustpubOnly: true } });
+      this.authenticateAs(user);
+
+      await visit(`/crates/${crate.name}/settings`);
+
+      assert.dom('[data-test-trustpub-only-warning]').exists();
+      assert
+        .dom('[data-test-trustpub-only-warning]')
+        .hasText(
+          'Trusted publishing is required but no publishers are configured. Publishing to this crate is currently blocked.',
+        );
+    });
+
+    test('disappears when checkbox is unchecked', async function (assert) {
+      const { crate, user } = prepare(this);
+      this.db.crate.update({ where: { id: { equals: crate.id } }, data: { trustpubOnly: true } });
+      this.authenticateAs(user);
+
+      await visit(`/crates/${crate.name}/settings`);
+
+      assert.dom('[data-test-trustpub-only-warning]').exists();
+
+      await click('[data-test-trustpub-only-checkbox] [data-test-checkbox]');
+
+      assert.dom('[data-test-trustpub-only-warning]').doesNotExist();
+    });
+
+    test('appears when checkbox is checked with no configs', async function (assert) {
+      const { crate, user } = prepare(this);
+      this.db.crate.update({ where: { id: { equals: crate.id } }, data: { trustpubOnly: true } });
+      this.authenticateAs(user);
+
+      this.db.trustpubGithubConfig.create({
+        crate,
+        repository_owner: 'rust-lang',
+        repository_name: 'crates.io',
+        workflow_filename: 'ci.yml',
+      });
+
+      await visit(`/crates/${crate.name}/settings`);
+
+      assert.dom('[data-test-trustpub-only-warning]').doesNotExist();
+
+      // Remove the config
+      await click('[data-test-github-config="1"] [data-test-remove-config-button]');
+
+      // Warning should now appear
+      assert.dom('[data-test-trustpub-only-warning]').exists();
+    });
+  });
+
   module('trustpub_only checkbox', function () {
     test('hidden when no configs and flag is false', async function (assert) {
       const { crate, user } = prepare(this);