Possible Unhandled Promise Rejection (id: 3):
Error: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
The cause appears to be that displayName on Contact is initialized to null, and if name is also null it will remain null. Then in the sort comparator, we do not verify that displayName is not null. This is in sortContactsBy method of ContactsModule.java.
Also, the exception will sometimes manifest as Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference instead.
Environment - output of expo diagnostics & the platform(s) you're targeting
Expo CLI 3.13.1 environment info:

System:

OS: macOS 10.15.2

Shell: 5.8 - /usr/local/bin/zsh

Binaries:

Node: 13.14.0 - ~/.nvm/versions/node/v13.14.0/bin/node

Yarn: 1.22.4 - /usr/local/bin/yarn

npm: 6.14.4 - ~/.nvm/versions/node/v13.14.0/bin/npm

Watchman: 4.9.0 - /usr/local/bin/watchman

IDEs:

Android Studio: 4.0 AI-193.6911.18.40.6626763

Xcode: 11.6/11E708 - /usr/bin/xcodebuild

npmPackages:

@sentry/react-native: ^1.6.1 => 1.6.1

@types/react: ^16.8.22 => 16.9.11

@types/react-native: 0.62.2 => 0.62.2

react: 16.11.0 => 16.11.0

react-native: 0.62.2 => 0.62.2
Steps to Reproduce
Reproduced on a Samsung A10, though I've also seen it occur on a variety of Samsung, Motorola, LG devices. To reproduce, do the following:
Create a contact with no name set (can have just phone number).
Make the following call to fetch and sort contacts:
await Contacts.getContactsAsync({
                fields: [
                    'image',
                    'phoneNumbers',
                    'firstName',
                    'lastName',
                    'name',
                    'nickname',
                pageOffset: offset,
                pageSize: 100,
                sort: 'firstName',
Note: If you remove the sort parameter, then the exception will not be thrown.
      changed the title
Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
Attempt to invoke virtual method 'int java.lang.String.compareToIgnoreCase(java.lang.String)' on a null object reference
    Aug 4, 2020
          
When both firstName and lastName are null - they fall back to displayName.
How did you create contact with null displayName too? Even if I create empty contact with only phone number - it's display name is set to that number.
Is your no-name contact visible on Android built-in Contacts app?
And which version of Expo SDK are you using?
          
I still haven't found a way to create contact with all firstName, lastName and displayName being null. They're at least empty strings.
Arabic should not be a reason, however you can paste here that name - I'll try it
          
Oh okay, cool then. Actually, this issue only happens on one Android so far. It doesn't happen for two other Androids that I've tested. But then, I'm still a bit sceptical so that it doesn't happen in Production. But would this issue happen when the user's contacts have some weird names or something? I just wanna be sure
          
It may be dependent on currently installed and used Android Contact app and how it saves contacts with no name. I tested it on two devices and two emulator API versions and couldn't reproduce, however I cannot deny possibility of catching null on any device. I'll think of securing it more.
If you want to be sure that it never happens to your users, make a simple fallback - catch your promise rejection and try again without sorting. Then you can sort it on your own.
          
@barthap I created the contact with just a phone number only, using the default Contacts app on Samsung. It doesn't even appear in the Contacts app after creating it (which brings up a dilemma of how to delete it).
I've only seen the issue on Android, and mostly on Samsung devices, but I've also seen it for Pixel 3 XL and several Motorola devices (G4/G7/Z4).
For now, I've just turned off the sort, as a work-around.
          
Okay, great. Thanks
Our production build would have to be delayed a bit then. Any ETA for the
fix on expo-contacts, please?
On Thu, Aug 6, 2020 at 2:58 PM Bartłomiej Klocek ***@***.***> wrote:
 It'll be available in the client with next SDK release. However,
 standalone expo-contacts package can possibly have this fix released
 sooner.
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 <#9556 (comment)>, or
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Best Regards.
Oluwafemi E. Akinde
Fixes #9556 
There are rare situations, when Android Contacts app can save contact, which has all `firstName`, `lastName` and `displayName` fields being `null`.
Expo Contacts module mostly handles these situations by falling back to empty strings, or taking the name from elsewhere (e.g. phone number, company name etc.), but there's a place where sorting by name can crash because of `NullPointerException`.
# How
`Contacts.getContactsAsync({ sort: 'firstName' }) //or 'lastName'` in order to sort, calls Java `Contact.getFirstName()` which in extreme cases returns `null`. Adding another null-check fixes the issue. Empty string is used as fallback, because initially all `Contact` fields are initialized this way.
# Test Plan
Tested with a few combinations of unnamed contacts.