Webapi Swager schema generation fail in case when Get endpoint has param with Extension Attributes

[swnsma]

Preconditions (*)

1. Magento 2.3.1 & 2.3-develop
2. Created and enabled custom module 'DreamVendor\DreamModule'.

Steps to reproduce (*)

1. Create php interface which will be used for the endpoint. E.g.

namespace DreamVendor\DreamModule\Api;

use Magento\Framework\Api\Search\SearchResultInterface;

/**
 * My Custom Endpoint API.
 */
interface MyCustomEndpointInterface
{
    /**
     * Get some awesome stuff!
     *
     * @param \DreamVendor\DreamModule\Api\Data\SearchRequestInterface $searchRequest
     *
     * @return \Magento\Framework\Api\Search\SearchResultInterface
     */
    public function execute(\DreamVendor\DreamModule\Api\Data\SearchRequestInterface $searchRequest): SearchResultInterface;
}

2. Create SearchRequestInterface. Make it extensible with extension attributes.

namespace DreamVendor\DreamModule\Api\Data;

use Magento\Framework\Api\ExtensibleDataInterface;

/**
 * Search Request Data Object.
 */
interface SearchRequestInterface extends ExtensibleDataInterface
{
    /**
     * Get Extension Attributes.
     *
     * @return \DreamVendor\DreamModule\Api\Data\SearchRequestExtensionInterface|null
     */
    public function getExtensionAttributes(): ?\DreamVendor\DreamModule\Api\Data\SearchRequestExtensionInterface;

    /**
     * Set Extension Attributes.
     *
     * @param \DreamVendor\DreamModule\Api\Data\SearchRequestExtensionInterface|null $extension
     */
    public function setExtensionAttributes(?\DreamVendor\DreamModule\Api\Data\SearchRequestExtensionInterface $extension): void;

3. Declare your endpoint via webapi.xml in etc folder of your module.

<routes xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Webapi:etc/webapi.xsd">
    <route url="/V1/my-custom-endpoint" method="GET">
        <service class="DreamVendor\DreamModule\Api\MyCustomEndpointInterface" method="execute"/>
        <resources>
            <resource ref="anonymous" />
        </resources>
    </route>
</routes>

4. Flush caches.
5. Try to generate schema. Go to your.website.com/swagger/.

Expected result (*)

1. The page has been opened.
2. You can see your new endpoint.

Actual result (*)

1. You can see message like Failed to load API definition. Internal Server Error http://magento2.local/rest/all/schema?services=all
2. Error message Notice: Undefined index: parameters in Magento/Webapi/Model/Rest/Swagger/Generator.php on line 741

[m2-assistant]

Hi @swnsma. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

• Summary of the issue
• Information on your environment
• Steps to reproduce
• Expected and actual results

Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

@magento give me 2.3-develop instance - upcoming 2.3.x release

For more details, please, review the Magento Contributor Assistant documentation.

@swnsma do you confirm that you were able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• yes
• no

---

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[m2-assistant]

Hi @engcom-Charlie. Thank you for working on this issue.
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[magento-engcom-team]

✅ Confirmed by @engcom-Charlie
Thank you for verifying the issue. Based on the provided information internal tickets MC-19179 were created

Issue Available: @engcom-Charlie, You will be automatically unassigned. Contributors/Maintainers can claim this issue to continue. To reclaim and continue work, reassign the ticket to yourself.