In magento 2.3.5 Swagger is not working (Failed to load API definition.)

Question

I had upgraded the magento version to 2.3.5 after that swagger is not working in my setup

Image Reference :

To debug the i click invalid button it shows

{"schemaValidationMessages":[{"level":"error","message":"Can't read from file http://My Domain/rest/all/schema?services=all"}]}

The below errors i got in the debug.log

[2020-06-30 08:50:34] main.ERROR: Unable to resolve the source file for 'frontend/Vendor/child-theme/en_US/Magento_Swagger/swagger-ui/js/swagger-ui-bundle.js.map' [] []
[2020-06-30 08:50:34] main.CRITICAL: Unable to resolve the source file for 'frontend/Vendor/child-theme/en_US/Magento_Swagger/swagger-ui/js/swagger-ui-bundle.js.map' [] []
[2020-06-30 08:50:34] main.ERROR: Unable to resolve the source file for 'frontend/Vendor/child-theme/en_US/Magento_Swagger/swagger-ui/css/swagger-ui.css.map' [] []
[2020-06-30 08:50:34] main.CRITICAL: Unable to resolve the source file for 'frontend/Vendor/child-theme/en_US/Magento_Swagger/swagger-ui/css/swagger-ui.css.map' [] []
[2020-06-30 08:50:34] main.ERROR: Unable to resolve the source file for 'frontend/Vendor/child-theme/en_US/Magento_Swagger/swagger-ui/js/swagger-ui-standalone-preset.js.map' [] []
[2020-06-30 08:50:34] main.CRITICAL: Unable to resolve the source file for 'frontend/Vendor/child-theme/en_US/Magento_Swagger/swagger-ui/js/swagger-ui-standalone-preset.js.map' [] []

I ran the below commands and tested

1. bin/magento deploy:mode:set developer - (Set the store to developer mode)
2. Removed the pub/static frontend and adminhtml
3. php bin/magento setup:upgrade
4. php bin/magento setup:static-content:deploy -f
5. php bin/magento setup:di:compile
6. chmod -R 777 root_file/*

Answer 1

There is a \Datetime error breaking SOAP 2.3.5 so it is affecting swagger tool. Run command below to resolve that issue.

php bin/magento module:disable --clear-static-content Dotdigitalgroup_Email Dotdigitalgroup_Chat Dotdigitalgroup_Enterprise

It may be possible other installed extensions may break swagger so have to debug on browser console level to check further.

NOTE: Only disable these modules if you do not need in your system or else if required then upgrade dotdigital modules because it may be the case that upgraded versions already have fix for that.

Reference Commit

Answer 2

This errors could be happened by phpdoc on function declarations.

Wrong

/**
* @param $id
**/
public function myFuncitonHere(){}

Right

/**
* @param int $id
**/
public function myFuncitonHere(){}

Swagger uses phpdocs as complement to assemble the service contract to webservices REST/SOAP, and the class (as in/out on function delaration) needs to be declared with full path in return / params phpdocs.

Wrong

/**
* @param MyInterface $myInterface
**/
public function myFuncitonHere(){}

Right

/**
* @param \MyVendor\MyModule\Api\Data\MyInterface $myInterface
**/
public function myFuncitonHere(){}

Answer 3

This error is throw because one of your apis declare. Try to remove your recently added api and try again, if you can get swagger now, it mean your api is wrong about syntax or structure.

Consider this post: https://meetanshi.com/blog/solved-failed-to-load-api-definition-in-magento-2-swagger/

To debug what is wrong you cant visit the url that is expose: https://magento.test/rest/all/schema?services=all