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@erickoledadevrel The default configuration does not contain trailing slashes: https://github.com/google/google-api-php-client/blob/master/src/Google/Config.php#L52 therefore, I took the approach to strip the trailing slash here and then add it at the combination step. I could add it back in the line above, but not really sure the benefit either way...

The rootUrl field in the discovery document does contains the slash by default, and since you are naming this field root_url instead of base_path it's probably better to have it respect the format of rootUrl and contain the trailing slash.