` renders when the field is `touched && invalid`.
- **To Create:**
- `tests/frontend/admin-general-page-title-error.spec.ts` — pure-function unit tests covering the new `pageTitleError` branches the component will rely on (already partially covered, but we extend them to lock down the specific "whitespace-only" → `'required'` message that drives the actionable UX).
(No backend changes, no schema migration, no new routes, no DTO changes.)
## 3. Proposed Changes
### 3.1 Backend / API
None. The `PUT /api/v1/admin/general/settings` route, DTO, and `general.service.ts` are unchanged. The server-side trim + `1–120` validation already returns `400 VALIDATION_FAILED` and preserves the stored value — exactly the behavior the Job reports on the negative path. The bug is purely client-side rendering of the error message.
### 3.2 Frontend Logic — `frontend/src/app/features/admin/general.component.ts`
The root cause is that `computed()` does not re-evaluate when reactive-form control flags change. Replace the non-reactive reads with signal-backed local state that IS subscribed to `valueChanges` and `statusChanges`.
Concrete edits:
1. **Add explicit reactive signals for the pageTitle control**, declared at the top of the class alongside the other signals:
```ts
private readonly pageTitleValue = signal
('');
private readonly pageTitleInvalid = signal(false);
private readonly pageTitleTouchedOrDirty = signal(false);
```
2. **Wire the control to those signals** in the existing constructor, right after the `welcomeMarkdown.valueChanges` subscription (using the same `takeUntilDestroyed(this.destroyRef)` pattern already in the file):
```ts
const pt = this.form.controls.pageTitle;
this.pageTitleValue.set(pt.value);
this.pageTitleInvalid.set(pt.invalid);
pt.valueChanges
.pipe(takeUntilDestroyed(this.destroyRef))
.subscribe((v) => this.pageTitleValue.set(v));
pt.statusChanges
.pipe(takeUntilDestroyed(this.destroyRef))
.subscribe(() => {
this.pageTitleInvalid.set(pt.invalid);
this.pageTitleTouchedOrDirty.set(pt.touched || pt.dirty);
});
pt.events
?.pipe(takeUntilDestroyed(this.destroyRef))
?.subscribe?.(); // no-op safety; see note below
```
Note: do NOT introduce a third subscription — the `blur`/`input` events that flip `touched`/`dirty` are dispatched by the DOM and re-validate via Angular's value sync, which already emits a `statusChanges` (and, when the value changes, a `valueChanges`). If `touched`/`dirty` flips without a status change (rare — e.g. focus loss while value is unchanged), also subscribe to the Angular `events` observable filtered by `EventType.Blur`:
```ts
import { EventType } from '@angular/forms';
...
pt.events
.pipe(
filter((e) => e.type === EventType.Blur),
takeUntilDestroyed(this.destroyRef),
)
.subscribe(() => this.pageTitleTouchedOrDirty.set(pt.touched || pt.dirty));
```
Confirm with a quick grep that `EventType` is exported from `@angular/forms` in the installed Angular version before relying on it; if not available in this version, fall back to a `focusout` listener bound via `@HostListener('focusout')` on a directive, OR simply call `this.pageTitleTouchedOrDirty.set(pt.touched || pt.dirty)` after every `valueChanges` AND `statusChanges` emission — both reliably fire on input/blur in modern Angular reactive forms. **Preferred approach (no extra imports):** set `pageTitleTouchedOrDirty` inside the existing `statusChanges` subscription AND inside the existing `valueChanges` subscription (covering both dirty/touched transitions).
3. **Replace the broken `computed`s** so they read from the new signals:
```ts
readonly showPageTitleError = computed(
() => this.pageTitleTouchedOrDirty() && this.pageTitleInvalid(),
);
readonly pageTitleMessage = computed(() => {
const err = pageTitleError(this.pageTitleValue());
if (err === 'required') return 'Page title is required and cannot contain only whitespace.';
if (err === 'maxlength') return 'Page title must be 120 characters or fewer.';
// fallback to the raw control errors so the {whitespace:true} branch from
// the custom validator still surfaces the same human-readable text
const controlErrors = this.form.controls.pageTitle.errors;
if (controlErrors?.['whitespace']) return 'Page title is required and cannot contain only whitespace.';
return null;
});
```
The existing `pageTitleError` helper in `general.pure.ts:3-8` already returns `'required'` for both empty and whitespace-only strings (line 5: `if (v.trim().length === 0) return 'required';`), so the actionable message will fire for `''`, `' '`, `'\t\n '`, etc., exactly as the Job requires.
4. **Patch the form after load** — extend the existing `applySettings()` (line 250) to also call `this.pageTitleTouchedOrDirty.set(false)` so loading valid settings from the backend does not flash the error on first paint. After patching the value, also sync `this.pageTitleValue` (a single `pt.setValue(...)` will trigger `valueChanges`, which already updates `pageTitleValue`).
5. **No template change** — `{{ pageTitleMessage() }}
` at line 53 already lives inside the `@if (showPageTitleError())` block; once the computeds are reactive it will render with the actionable text and the `data-testid` will appear in the DOM (matching the negative-case expectation in the Job description).
### 3.3 Pure helper — `frontend/src/app/features/admin/general.pure.ts`
No changes needed. `pageTitleError()` already returns `'required'` for both empty and whitespace-only strings (verified at line 5). Existing tests in `tests/frontend/admin-general-pure.spec.ts:91-114` already lock down this behavior — we extend that suite, not the helper.
## 4. Test Strategy
Per the project's existing convention (all `tests/frontend/*.spec.ts` are pure-function tests against `*.pure.ts` modules), and per the Job's "minimal, focused tests" rule, **we do not introduce a TestBed-based component test**. The existing `admin-general-pure.spec.ts` is the right home.
- **Target test files:**
- **Extend** `tests/frontend/admin-general-pure.spec.ts` with two new `describe` blocks:
1. `describe('pageTitleMessage')` — pure-function mapping (the same mapping the component's computed now uses). Asserts:
- `pageTitleMessage('')` → required message
- `pageTitleMessage(' ')` → required message (the Job's specific edge case)
- `pageTitleMessage('\t\n ')` → required message
- `pageTitleMessage('OpenVelo')` → `null`
- `pageTitleMessage('a'.repeat(121))` → maxlength message
2. To keep this pure-function-friendly, **extract** the message-mapping function out of the component into `general.pure.ts` as `export function pageTitleMessage(value, errors?): string | null`, export it, and import it from the test. This is the minimal refactor that lets us assert the exact user-visible text without spinning up TestBed. The component's `pageTitleMessage` `computed` becomes a one-liner that calls this pure function.
- **Add (new file)** `tests/frontend/admin-general-page-title-error.spec.ts` only if the extracted helper's behavior isn't already covered by extending `admin-general-pure.spec.ts`. Per "minimal tests, single command", **prefer extending the existing file** to avoid duplicate test setup.
- **Mocking strategy:** No mocks needed. The new pure function has no dependencies on `FormControl`, `HttpClient`, or Angular DI. It is a pure `(value: string, errors?: ValidationErrors | null) => string | null` mapping. The reactive plumbing inside the component is exercised manually per the Job description (no automated UI tests, per the Job rules).
- **Run command:** `npm test` (from `/repo`) executes `jest --config tests/jest.config.js --selectProjects frontend` (and backend). Single command, no UI required, fully headless under jsdom.
## 5. Out of Scope / Non-Goals
- Backend DTO, `general.service.ts`, controller, or `setting` table — all already correct.
- Adding new validators (the existing `pageTitleNotBlankValidator` + `Validators.required` + `Validators.maxLength(120)` are sufficient).
- Visual / CSS changes — the existing `.field-error` style and red color tokens are already correct.
- Component-harness / TestBed tests — explicitly out per Job rules (minimal infra, no visual confirmation).
- Refactoring other admin pages — not requested.