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    <h3>Editing: ConditionallyLoadsAttributes.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

namespace Illuminate\Http\Resources;

use Illuminate\Support\Arr;

trait ConditionallyLoadsAttributes
{
    /**
     * Filter the given data, removing any optional values.
     *
     * @param  array  $data
     * @return array
     */
    protected function filter($data)
    {
        $index = -1;

        foreach ($data as $key =&gt; $value) {
            $index++;

            if (is_array($value)) {
                $data[$key] = $this-&gt;filter($value);

                continue;
            }

            if (is_numeric($key) &amp;&amp; $value instanceof MergeValue) {
                return $this-&gt;mergeData(
                    $data, $index, $this-&gt;filter($value-&gt;data),
                    array_values($value-&gt;data) === $value-&gt;data
                );
            }

            if ($value instanceof self &amp;&amp; is_null($value-&gt;resource)) {
                $data[$key] = null;
            }
        }

        return $this-&gt;removeMissingValues($data);
    }

    /**
     * Merge the given data in at the given index.
     *
     * @param  array  $data
     * @param  int  $index
     * @param  array  $merge
     * @param  bool  $numericKeys
     * @return array
     */
    protected function mergeData($data, $index, $merge, $numericKeys)
    {
        if ($numericKeys) {
            return $this-&gt;removeMissingValues(array_merge(
                array_merge(array_slice($data, 0, $index, true), $merge),
                $this-&gt;filter(array_values(array_slice($data, $index + 1, null, true)))
            ));
        }

        return $this-&gt;removeMissingValues(array_slice($data, 0, $index, true) +
                $merge +
                $this-&gt;filter(array_slice($data, $index + 1, null, true)));
    }

    /**
     * Remove the missing values from the filtered data.
     *
     * @param  array  $data
     * @return array
     */
    protected function removeMissingValues($data)
    {
        $numericKeys = true;

        foreach ($data as $key =&gt; $value) {
            if (($value instanceof PotentiallyMissing &amp;&amp; $value-&gt;isMissing()) ||
                ($value instanceof self &amp;&amp;
                $value-&gt;resource instanceof PotentiallyMissing &amp;&amp;
                $value-&gt;isMissing())) {
                unset($data[$key]);
            } else {
                $numericKeys = $numericKeys &amp;&amp; is_numeric($key);
            }
        }

        if (property_exists($this, 'preserveKeys') &amp;&amp; $this-&gt;preserveKeys === true) {
            return $data;
        }

        return $numericKeys ? array_values($data) : $data;
    }

    /**
     * Retrieve a value based on a given condition.
     *
     * @param  bool  $condition
     * @param  mixed  $value
     * @param  mixed  $default
     * @return \Illuminate\Http\Resources\MissingValue|mixed
     */
    protected function when($condition, $value, $default = null)
    {
        if ($condition) {
            return value($value);
        }

        return func_num_args() === 3 ? value($default) : new MissingValue;
    }

    /**
     * Merge a value into the array.
     *
     * @param  mixed  $value
     * @return \Illuminate\Http\Resources\MergeValue|mixed
     */
    protected function merge($value)
    {
        return $this-&gt;mergeWhen(true, $value);
    }

    /**
     * Merge a value based on a given condition.
     *
     * @param  bool  $condition
     * @param  mixed  $value
     * @return \Illuminate\Http\Resources\MergeValue|mixed
     */
    protected function mergeWhen($condition, $value)
    {
        return $condition ? new MergeValue(value($value)) : new MissingValue;
    }

    /**
     * Merge the given attributes.
     *
     * @param  array  $attributes
     * @return \Illuminate\Http\Resources\MergeValue
     */
    protected function attributes($attributes)
    {
        return new MergeValue(
            Arr::only($this-&gt;resource-&gt;toArray(), $attributes)
        );
    }

    /**
     * Retrieve an accessor when it has been appended.
     *
     * @param  string  $attribute
     * @param  mixed  $value
     * @param  mixed  $default
     * @return \Illuminate\Http\Resources\MissingValue|mixed
     */
    protected function whenAppended($attribute, $value = null, $default = null)
    {
        if ($this-&gt;resource-&gt;hasAppended($attribute)) {
            return func_num_args() &gt;= 2 ? value($value) : $this-&gt;resource-&gt;$attribute;
        }

        return func_num_args() === 3 ? value($default) : new MissingValue;
    }

    /**
     * Retrieve a relationship if it has been loaded.
     *
     * @param  string  $relationship
     * @param  mixed  $value
     * @param  mixed  $default
     * @return \Illuminate\Http\Resources\MissingValue|mixed
     */
    protected function whenLoaded($relationship, $value = null, $default = null)
    {
        if (func_num_args() &lt; 3) {
            $default = new MissingValue;
        }

        if (! $this-&gt;resource-&gt;relationLoaded($relationship)) {
            return value($default);
        }

        if (func_num_args() === 1) {
            return $this-&gt;resource-&gt;{$relationship};
        }

        if ($this-&gt;resource-&gt;{$relationship} === null) {
            return;
        }

        return value($value);
    }

    /**
     * Execute a callback if the given pivot table has been loaded.
     *
     * @param  string  $table
     * @param  mixed  $value
     * @param  mixed  $default
     * @return \Illuminate\Http\Resources\MissingValue|mixed
     */
    protected function whenPivotLoaded($table, $value, $default = null)
    {
        return $this-&gt;whenPivotLoadedAs('pivot', ...func_get_args());
    }

    /**
     * Execute a callback if the given pivot table with a custom accessor has been loaded.
     *
     * @param  string  $accessor
     * @param  string  $table
     * @param  mixed  $value
     * @param  mixed  $default
     * @return \Illuminate\Http\Resources\MissingValue|mixed
     */
    protected function whenPivotLoadedAs($accessor, $table, $value, $default = null)
    {
        if (func_num_args() === 3) {
            $default = new MissingValue;
        }

        return $this-&gt;when(
            $this-&gt;resource-&gt;$accessor &amp;&amp;
            ($this-&gt;resource-&gt;$accessor instanceof $table ||
            $this-&gt;resource-&gt;$accessor-&gt;getTable() === $table),
            ...[$value, $default]
        );
    }

    /**
     * Transform the given value if it is present.
     *
     * @param  mixed  $value
     * @param  callable  $callback
     * @param  mixed  $default
     * @return mixed
     */
    protected function transform($value, callable $callback, $default = null)
    {
        return transform(
            $value, $callback, func_num_args() === 3 ? $default : new MissingValue
        );
    }
}
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