Bd Presenter

better-data: Extending the Presenter

For library maintainers adding output transformations to the better-data Presenter — a new fluent builder method (mask, formatPhone, hideIfBlank), a PresentationContext flag (admin vs REST vs export), or a Formatter helper. The Presenter is the read-side projection layer between a DataObject and whatever consumes it (admin UI, REST response, audit log).

Misconception this skill corrects

> "The Presenter is readonly like the DataObject — every fluent method must clone and return a new instance."

Wrong. The DataObject is readonly, the Presenter is intentionally a mutable builder. Look at [src/Presenter/Presenter.php:65-89](Presenter.php) — class Presenter (not final readonly class), with private mutable properties $only, $hidden, $rename, $computed, $presets, $includeSensitive. Each fluent method assigns to $this->... and returns $this. This is deliberate — chained calls share state, repeated calls override, and there's no clone overhead.

What IS immutable: $this->dto is protected readonly DataObject and never gets reassigned. The builder mutates ITS state to control HOW the DTO is rendered; the DTO itself stays untouched.

The "don't mutate permanently" rule from older docs means: don't introduce a method whose effect can't be reset by a subsequent method or context swap. A method that pushes to a private array is fine; a method that writes to a static cache or to the wrapped DTO would be a regression.

Other AI-prone misconceptions:

• "I'll add getSecretRevealed() so consumers don't need ->reveal() boilerplate." Wrong — the explicit $dto->field->reveal() inside a compute() closure IS the security audit point. Adding a bypass method is the same regression as a debug-mode log of secrets.
• "CollectionPresenter is a separate Presenter; I just add the method there too with copy/paste logic." Wrong — CollectionPresenter records each configurer as a closure on $this->configurers ([src/Presenter/CollectionPresenter.php:30-44](CollectionPresenter.php)) and replays it on every item via the per-item Presenter. The pattern is $this->configurers[] = static fn (Presenter $p) => $p->yourMethod(...);. No business logic on the collection side.

When to use this skill

Trigger when ANY of the following is true:

• Adding a fluent method to Presenter / CollectionPresenter (hideIfBlank, truncate, defaultIfNull).
• Adding a flag / accessor to PresentationContext (isExport(), currentUserId()).
• Adding a Formatter helper under src/Presenter/Formatter/.
• Reviewing a PR that emits DTO values without going through sensitiveFieldNames() redaction.

Workflow

1. Decide: per-call (Presenter) or per-context (PresentationContext)

• Per-call (fluent method): the caller decides each invocation. Examples: only(['email']), hide('apiKey'), formatDate('createdAt', 'Y-m-d'). Lives on Presenter + mirrored on CollectionPresenter.
• Per-context (PresentationContext): the entire rendering environment changes. Examples: REST response vs admin table vs export CSV. Lives on PresentationContext.

Most additions are per-call. Per-context additions are rarer and require updating PresentationContext::rest(), ::admin(), ::none(), etc.

2. Per-call method shape

Look at existing methods like hide ([Presenter.php:164](Presenter.php)) or rename ([Presenter.php:204](Presenter.php)):

public function hideIfBlank(string|array $field): static
{
    $fields = (array) $field;
    foreach ($fields as $f) {
        $this->hidden[$f] = static fn (PresentationContext $ctx, mixed $value): bool
            => $value === null || $value === '' || $value === [];
    }
    return $this;
}

Six structural rules:

1. Return static (not self, not Presenter) so subclasses chain correctly.
2. Parameter naming follows existing conventions — $field for single, $fields for list, $capability for cap names, $as for output-key rename.
3. Mutate $this->... private state. Don't add new public mutable state.
4. Return $this at the end of every fluent method.
5. Single concern per method. hideIfBlank doesn't also rename. Compose at the call site: ->hideIfBlank('foo')->rename('foo', 'bar').
6. Resettable. A subsequent call to a related method (or a context() swap) should be able to undo the effect. Methods that push to $this->hidden[$field] work; methods that mutate the wrapped $this->dto would not.

3. Mirror the method on CollectionPresenter

Every per-call method gets a mirror at [src/Presenter/CollectionPresenter.php](CollectionPresenter.php) that records a configurer:

public function hideIfBlank(string|array $field): self
{
    $this->configurers[] = static fn (Presenter $p): Presenter => $p->hideIfBlank($field);
    return $this;
}

Reason: CollectionPresenter::toArray ([line 142-155](CollectionPresenter.php)) creates a fresh Presenter per DTO and replays every configurer on it. The configurers must be closures (not method references) so they bind the args at the time of the collection-level call, not at the per-item replay.

Skip the mirror only if the method is meaningless for collections (rare).

4. Honor sensitiveFieldNames for any value-emitting method

Verified in [src/Presenter/Presenter.php:481-510](Presenter.php) — sensitiveFieldNames() walks both properties AND constructor parameters, looking for #[Sensitive] attribute OR Secret-typed parameters, and returns the field-name list. The toArray path uses this list to redact ('***' for Secret, omit for Sensitive plain string unless includeSensitive([...]) opted in).

Any new method that emits a value from the DTO must consult this list. Example — a hypothetical mask method:

public function mask(string $field, callable $masker): static
{
    $this->presets[$field] = function (mixed $value, PresentationContext $ctx) use ($field, $masker) {
        // sensitive fields go through normal redaction unless explicitly included
        if (in_array($field, $this->sensitiveFieldNames(), true)
            && !in_array($field, $this->includeSensitive, true)) {
            return $this->redactSensitive($value);  // existing helper, look at toArray for the canonical call
        }
        return $masker($value);
    };
    return $this;
}

A method that bypasses this is a leak path — Secret typed values shouldn't quietly appear via your new fluent helper.

5. Localized strings: wrap through LocaleScope::runIn

If your method emits localized text (e.g. a translated status label, a humanized number with locale-specific separators), wrap the locale-sensitive logic:

public function formatStatus(string $field, ?string $as = null): static
{
    $this->presets[$field] = function (mixed $value, PresentationContext $ctx): string {
        return LocaleScope::runIn(
            $ctx->locale,
            static fn (): string => __( ucfirst((string) $value), 'my-textdomain' )
        );
    };
    if ($as !== null) {
        $this->rename[$field] = $as;
    }
    return $this;
}

Reason: a consumer that calls ->context(PresentationContext::rest()->withLocale('hu_HU')) expects rendered text in Hungarian even if the request came in under another locale. LocaleScope switches WP's locale for the closure scope and restores after.

6. Formatters live in src/Presenter/Formatter/

If the transformation is reusable (date formatting, currency formatting, phone-number formatting), implement the logic in a Formatter class and have the fluent method call it:

src/Presenter/Formatter/
├── DateFormatter.php
├── CurrencyFormatter.php
└── PhoneFormatter.php  ← your new one

The fluent method becomes a thin glue:

public function formatPhone(string $field, ?string $as = null, ?string $region = null): static
{
    $this->presets[$field] = static function (mixed $value, PresentationContext $ctx) use ($region): string {
        return PhoneFormatter::format($value, $region ?? $ctx->locale);
    };
    if ($as !== null) {
        $this->rename[$field] = $as;
    }
    return $this;
}

7. Testing

Per-call methods have unit tests covering:

• Default behavior (no method called).
• Method called once.
• Method called twice (override / append behavior — depends on the method's semantics).
• Interaction with Sensitive / Secret (redaction not bypassed).
• CollectionPresenter replay produces the same per-item output as Presenter directly.

vendor/bin/phpunit --filter Presenter
vendor/bin/phpstan analyse --memory-limit=1G
vendor/bin/php-cs-fixer fix

Critical rules

• Presenter is a mutable builder; the wrapped DTO is readonly. Mutate $this->only, $this->hidden, $this->presets, etc. Never mutate $this->dto or the DTO it points to.
• Fluent methods return static (not self, not Presenter) so subclasses chain.
• Mirror every per-call method on CollectionPresenter as a recorded closure on $this->configurers.
• Honor sensitiveFieldNames() for any value-emitting method. A new path that bypasses redaction is a security regression.
• Secret is revealed only via explicit $dto->field->reveal() inside a compute() closure. Don't add convenience bypasses.
• Wrap localized text in LocaleScope::runIn($ctx->locale, fn () => ...) so withLocale() works.
• Reusable transformations live as Formatter classes under src/Presenter/Formatter/. Fluent method is thin glue.
• Single concern per fluent method. formatDate doesn't also rename — chain ->formatDate(...)->rename(...).

Common mistakes

// WRONG — cloning per call (fights the builder pattern)
public function hide(string $field): static
{
    $clone = clone $this;
    $clone->hidden[$field] = ...;
    return $clone;
}

// RIGHT — mutate $this, return $this
public function hide(string $field): static
{
    $this->hidden[$field] = ...;
    return $this;
}

// WRONG — mutating the DTO
public function uppercase(string $field): static
{
    $this->dto->{$field} = strtoupper($this->dto->{$field});  // FATAL — readonly property
    return $this;
}

// RIGHT — preset the rendered value
public function uppercase(string $field): static
{
    $this->presets[$field] = static fn (mixed $value): string => \mb_strtoupper((string) $value);
    return $this;
}

// WRONG — secret bypass
public function revealAllSecrets(): static
{
    $this->includeSensitive = $this->sensitiveFieldNames();  // 🔴 silent reveal of all Secret fields
    return $this;
}

// RIGHT — caller is explicit per field
$presenter->includeSensitive(['apiKey'])->compute('apiKey', fn (Dto $d) => $d->apiKey?->reveal());

// WRONG — forgetting CollectionPresenter mirror
// (added formatPhone to Presenter, didn't add to CollectionPresenter)
// Result: Dto::for($single)->formatPhone(...) works, ::forCollection([...])->formatPhone(...) fatals.

// RIGHT — both sides
// Presenter::formatPhone — implementation
// CollectionPresenter::formatPhone — $this->configurers[] = fn (Presenter $p) => $p->formatPhone(...)

// WRONG — locale unaware string emission
public function formatStatus(string $field): static
{
    $this->presets[$field] = static fn (string $v) => __( ucfirst($v), 'plugin' );
    // Translates in current request locale; ignores ->withLocale('hu_HU') on context.
    return $this;
}

// RIGHT — wrap in LocaleScope::runIn
public function formatStatus(string $field): static
{
    $this->presets[$field] = static function (string $v, PresentationContext $ctx) {
        return LocaleScope::runIn($ctx->locale, fn () => __( ucfirst($v), 'plugin' ));
    };
    return $this;
}

// WRONG — multi-concern method
public function formatDateAndRename(string $field, string $format, string $as): static
{
    // Encourages copy-paste later when consumers want one but not both.
}

// RIGHT — chain instead
->formatDate('createdAt', 'Y-m-d')->rename('createdAt', 'created_at')

// WRONG — closure captures $this->dto by reference and reads through it
public function annotate(string $field): static
{
    $this->presets[$field] = function (mixed $value) {
        return $value . ' (id: ' . $this->dto->id . ')';
    };
    // Works for the immediate render. But $this->dto is the per-item DTO inside CollectionPresenter
    // replay — fine here. If you instead capture $this->dto into a variable before the closure, you
    // freeze the first DTO and apply it to all collection items.
    return $this;
}

// RIGHT — capture inside the closure (lazy bind)
$this->presets[$field] = function (mixed $value): string {
    return $value . ' (id: ' . $this->dto->id . ')';
};

Cross-references

• Run bd-data-object if the new method needs a NEW DTO field (e.g. a presentation-only computed field) — DTO + Presenter design often co-evolve.
• Run bd-attribute if the new method consumes a NEW attribute (e.g. #[Format('Y-m-d')]) — wire the attribute everywhere relevant.
• Run bd-security when the new method emits values from Secret / #[Sensitive] fields — explicit reveal is the audit point.

What this skill does NOT cover

• HTML rendering / Twig integration / view layer. Presenter emits arrays + JSON; HTML is a consumer-side concern.
• Caching the rendered output. Presenter renders fresh; cache at the consumer layer.
• Async / lazy field computation (compute('foo', fn () => Promise::resolve(...))). The Presenter is sync.
• Schema generation for the rendered output. That's RestSchemaBuilder, not Presenter.
• Replacing CollectionPresenter with a streaming variant. Not in scope; sufficient batches keep memory bounded.

References

• Presenter base: [libraries/better-data/src/Presenter/Presenter.php:65](Presenter.php) — class Presenter (mutable builder, NOT readonly), constructor at 99, for() factory at 109, forCollection() at 117.
• Sensitive-field discovery: [libraries/better-data/src/Presenter/Presenter.php:481-510](Presenter.php) — sensitiveFieldNames() walks properties + constructor params for #[Sensitive] or Secret type.
• CollectionPresenter: [libraries/better-data/src/Presenter/CollectionPresenter.php:30-160](CollectionPresenter.php) — $configurers[] per fluent call, replayed in toArray.
• PresentationContext: [libraries/better-data/src/Presenter/PresentationContext.php](PresentationContext.php) — none(), rest(), admin(), withLocale().
• HasPresenter trait: [libraries/better-data/src/Presenter/HasPresenter.php:15-20](HasPresenter.php) — adds ->present() to DTOs.
• Formatters: [libraries/better-data/src/Presenter/Formatter/](Formatter/) — DateFormatter, CurrencyFormatter as templates for new helpers.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Lonsdale201
• Source: Lonsdale201/wp-agent-skills
• License: MIT

Install and usage instructions live in the source repository linked above.