UnresolvableAppendedModelAttribute

An Eloquent $appends entry that no accessor or class cast backs. Enabled by default; see How to disable.

Why it matters

Model::attributesToArray() runs mutateAttributeForArray($key, null) for every $appends entry, with no existence guard. That call resolves a value through exactly one of three paths: a class cast (isClassCastable()), a new Attribute-returning accessor, or a legacy getXxxAttribute(). When none of them exist it falls through to $this->{'get'.Str::studly($key).'Attribute'}(), which reaches Model::__call(), forwards to a fresh query builder, and throws BadMethodCallException the moment the model is arrayed or JSON encoded.

So a typo in $appends, or a forgotten accessor, is not a silent null. It is a runtime fatal on toArray() / toJson() (and therefore on any API resource or response()->json($model)).

Example

class User extends Model
{
    protected $appends = ['full_name', 'avatar_url'];

    // Backs `full_name`.
    protected function fullName(): Attribute
    {
        return Attribute::get(fn (): string => "{$this->first_name} {$this->last_name}");
    }

    // `avatar_url` has no accessor and no cast: reported, and User::first()->toArray() throws.
}

How to fix

Add the missing accessor (either form resolves it):

// modern Attribute form
protected function avatarUrl(): Attribute
{
    return Attribute::get(fn (): string => "https://cdn.example.test/{$this->id}.png");
}

// or the legacy form
protected function getAvatarUrlAttribute(): string
{
    return "https://cdn.example.test/{$this->id}.png";
}

A declared cast for the attribute also satisfies the rule (a value object backed by a custom cast computes the appended value the same way an accessor does). If the entry was a mistake, remove it from $appends.

How to disable

<issueHandlers>
    <PluginIssue name="UnresolvableAppendedModelAttribute" errorLevel="suppress" />
</issueHandlers>

Scope

The rule reports an entry only when the model has neither an accessor nor a declared cast for it. A plain column or a relation does NOT back an appended attribute: the serialization loop passes null as the value and ignores the stored attribute, so appending a column name without a matching accessor throws all the same. An entry removed by $hidden, or excluded by a non-empty $visible, is not reported, since Eloquent drops it before that loop runs. At runtime only a class cast (not a primitive one) resolves an appended value, but the rule treats any declared cast as backing, a deliberately conservative choice that keeps it free of false positives (the cost is a rare missed case: a built-in-cast column listed in $appends with no accessor).

Accessor names are matched the way Eloquent resolves them (case-insensitive, with separators stripped), so full_name, fullName, and getFullNameAttribute() all line up. Abstract base classes are validated through their concrete descendants, which carry the complete accessor set (a child can supply the accessor for an attribute a base appends). An accessor the plugin cannot detect statically (for example, one synthesized at runtime) can be silenced with an inline @psalm-suppress UnresolvableAppendedModelAttribute on the model.