Use delete_files from core when deleting a Realm.

[DominicFrei]

Description

This moves the DeleteRealm function into our Core since it's a shared functionality.
The Core PR enables all SDKs to use the same DeleteRealm instead of having duplicated and/or differing implementations of it across the SDKs.

Fixes #386
Fixes #2455

TODO

• Changelog entry
• Tests (if applicable)

Both not really necessary because the point of moving this does include not changing anything on the user API level.
The expectation would be to have all tests still pass even after deleting the function and just calling it's Core equivalent.

[DominicFrei]

Update on the status here: Core PR is merged, waiting for the v11 merge now.

[nirinchev]

One thing I noticed as I was working on #2423 is that delete_files in Core will just go ahead and try to delete the files without first checking if the Realm exists:

https://github.com/realm/realm-core/blob/8765b60e5b4db7bcb4a14d4c22854f12e592b4ec/src/realm/object-store/shared_realm.cpp#L915-L916

It might be a good idea to do the check and perhaps do nothing if the Realm doesn't exist.

[DominicFrei]

One thing I noticed as I was working on #2423 is that delete_files in Core will just go ahead and try to delete the files without first checking if the Realm exists:

https://github.com/realm/realm-core/blob/8765b60e5b4db7bcb4a14d4c22854f12e592b4ec/src/realm/object-store/shared_realm.cpp#L915-L916

It might be a good idea to do the check and perhaps do nothing if the Realm doesn't exist.

This is what happens at the moment. call_with_lock will successfully lock the lockfile (because opening seems to also create it if it does not exist) and then tries to delete all files which succeeds if they don't exist.

Delete on an empty folder will therefore return true as well == succeed without doing anything.

Would that suffice your intention? @nirinchev

[DominicFrei]

One thing I noticed as I was working on #2423 is that delete_files in Core will just go ahead and try to delete the files without first checking if the Realm exists:
https://github.com/realm/realm-core/blob/8765b60e5b4db7bcb4a14d4c22854f12e592b4ec/src/realm/object-store/shared_realm.cpp#L915-L916
It might be a good idea to do the check and perhaps do nothing if the Realm doesn't exist.

This is what happens at the moment. call_with_lock will successfully lock the lockfile (because opening seems to also create it if it does not exist) and then tries to delete all files which succeeds if they don't exist.

Delete on an empty folder will therefore return true as well == succeed without doing anything.

Would that suffice your intention? @nirinchev

@nirinchev Added with 3dc9251. It does not fail locally for me though. Let's see what CI thinks about it. 💪

[DominicFrei]

Summary of the Android crash analysis so far:
https://ci.realm.io/blue/organizations/jenkins/realm%2Frealm-dotnet/detail/PR-2401/14/pipeline/445 shows that the process crashes during the Xamarin Android tests (the last successful test being SynchronizedInstanceTests.GetInstance_WhenDynamic_ReadsSchemaFromDisk right before the crash).

The android-logcat.zip (https://ci.realm.io/blue/organizations/jenkins/realm%2Frealm-dotnet/detail/PR-2401/14/artifacts) mentioned in the crash message shows:

06-10 17:36:06.097 E/libc++abi(13473): terminating with uncaught exception of type
 realm::util::File::NotFound: open("/data/data/io.realm.xamarintests/cache/rt-$13473/mongodb-realm/
 myapp-123/8e98563c-c188-43d2-9812-49bcd53b28dc/
 s_fe4873eb-028d-4fbf-bcbe-2ec70155ff4a.realm.management/access_control.write.mx") 
failed: No such file or directory 
Path: /data/data/io.realm.xamarintests/cache/rt-$13473/mongodb-realm/
 myapp-123/8e98563c-c188-43d2-9812-49bcd53b28dc/
 s_fe4873eb-028d-4fbf-bcbe-2ec70155ff4a.realm.management/access_control.write.mx

access_control.write.mx seems to be the write access mutex created in https://github.com/realm/realm-core/blob/master/src/realm/db.cpp#L951 (also see https://github.com/realm/realm-core/blob/master/src/realm/db.cpp#L770).

It is then used in https://github.com/realm/realm-core/blob/master/src/realm/db.cpp#L1774 and https://github.com/realm/realm-core/blob/master/src/realm/db.cpp#L2046.

It's unclear what exactly causes the crash. It does seem to only happen in this PR which is based on realm/realm-core#4701.

[DominicFrei]

@nirinchev Jenkins is finally happy. 👍 Ready for review again.

[nirinchev]

Looks good, mostly nits from me.

[nirinchev]

Once the File.Exists check is moved to OS, this should be good to go.