Wrong object type on FIRCLSURLSessionConfiguration creation

[makadaw]

[REQUIRED] Step 1: Describe your environment

• Xcode version: 11.5
• Firebase SDK version: 6.29.0
• Firebase Component: Crashlytics
• Component version: 4.3.1
• Installation method: CocoaPods

[REQUIRED] Step 2: Describe the problem

+ (NSURLSessionConfiguration *)defaultSessionConfiguration and + (NSURLSessionConfiguration *)ephemeralSessionConfiguration method of FIRCLSURLSessionConfiguration class required return type to be NSURLSessionConfiguration.
https://github.com/firebase/firebase-ios-sdk/blob/master/Crashlytics/Crashlytics/FIRCLSURLSession/FIRCLSURLSessionConfiguration.m#L34
But in some cases it returns instance of FIRCLSURLSessionConfiguration (return [self new];). FIRCLSURLSessionConfiguration is not subclass of the NSURLSessionConfiguration https://github.com/firebase/firebase-ios-sdk/blob/master/Crashlytics/Crashlytics/FIRCLSURLSession/FIRCLSURLSessionConfiguration.h#L21.
During the build, Xcode complained that types are mismatched. This can be suppressed by explicit cast to NSURLSessionConfiguration.

Steps to reproduce:

Build with Xcode and check warnings

[morganchen12]

Based on this code that method should always return a valid NSURLSessionConfiguration object on iOS versions that have NSURLSession support (8+).

@samedson can we get rid of FIRCLSURLSessionConfiguration since our support floor is above iOS 8, or does it need to remain for legacy reasons?

[samedson]

I believe we can get rid of FIRCLSURLSessionConfiguration now - we are following Firebase's support floor.