Is mergeItem mock correct for value initialisation case?

[matt-dalton]

What happened?

I'm using the library mock to unit test some logic I've written that uses mergeItem. My function and test are:

const mergeProperties =  async (properties: { [a: string]: any }) => {
        const propsStr = JSON.stringify(properties)

        await AsyncStorage.mergeItem(MY_KEY_CONST, propsStr)
}

it('should initialise the property correctly', async () => {
                const properties = { property: 'hopefully set' }

                await mergeProperties(properties)
                const savedValue = await AsyncStorage.getItem(MY_KEY_CONST)
                expect(savedValue).to.eql('{"property":"hopefully set"}')
})

This tests the case where MY_KEY_CONST has not yet been set.

When I test my code on the simulator, it seems to initialise the value correctly, so I assume I don't need to first initialise with setItem like in the docs example.

However, the unit test crashes with

SyntaxError: Unexpected token u in JSON at position 0
        at JSON.parse (<anonymous>)

The line that crashes in the mock is this one, because asMock.__INTERNAL_MOCK_STORAGE__[key] is undefined.

Is the mock incorrect? Should line 100 look like const oldValue = JSON.parse(asMock.__INTERNAL_MOCK_STORAGE__[key] || '{}');? Or is there a problem with what I'm trying to do?

Version

1.15.9

What platforms are you seeing this issue on?

• Android
• iOS
• macOS
• Windows
• web

System Information

System:
    OS: macOS 11.6
    CPU: (4) x64 Intel(R) Core(TM) i7-7567U CPU @ 3.50GHz
    Memory: 22.23 MB / 16.00 GB
    Shell: 3.2.57 - /bin/bash
  Binaries:
    Node: 10.24.1 - /usr/local/Cellar/nvm/0.30.1/versions/node/v10.24.1/bin/node
    Yarn: 1.17.3 - ~/.yarn/bin/yarn
    npm: 6.14.12 - /usr/local/Cellar/nvm/0.30.1/versions/node/v10.24.1/bin/npm
    Watchman: Not Found
  Managers:
    CocoaPods: 1.11.2 - /Users/me/.rvm/rubies/ruby-2.6.3/bin/pod
  SDKs:
    iOS SDK:
      Platforms: iOS 14.5, DriverKit 20.4, macOS 11.3, tvOS 14.5, watchOS 7.4
    Android SDK:
      API Levels: 23, 27, 28, 29, 30
      Build Tools: 28.0.3, 29.0.0, 29.0.2, 30.0.2
      System Images: android-28 | Intel x86 Atom, android-28 | Google Play Intel x86 Atom, android-R | Google APIs Intel x86 Atom
      Android NDK: Not Found
  IDEs:
    Android Studio: 3.5 AI-191.8026.42.35.5791312
    Xcode: 12.5.1/12E507 - /usr/bin/xcodebuild
  Languages:
    Java: 10.0.1 - /usr/bin/javac
    Python: 2.7.16 - /usr/bin/python
  npmPackages:
    @react-native-community/cli: Not Found
    react: 16.13.1 => 16.13.1 
    react-native: 0.63.4 => 0.63.4 
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

Steps to Reproduce

Use the mock function and unit test above

[tido64]

I don't think you can assume that getItem will always return something. Looking at the native code, null is returned if the key doesn't exist. If this worked in the Simulator, you probably already have something there from before.

[matt-dalton]

So mergeItem won't initialise the value if it's currently set as null? I tested this on the iOS simulator (I cleared the variable using removeItem first to make sure it was null) and it seemed to work.

Looking at the native code, null is returned if the key doesn't exist - You mean mergeItem will set the value as null if it hasn't already been set?

[tido64]

Actually, I misunderstood your initial question. I think the correct behaviour should be something like

const oldValue = asMock.__INTERNAL_MOCK_STORAGE__[key];
asMock.__INTERNAL_MOCK_STORAGE__[key] = oldValue != null
  ? JSON.stringify(merge(JSON.parse(oldValue), value))
  : JSON.stringify(value); 

Tagging @krizzu in case I'm completely mistaken.

[krizzu]

Yes you're correct, the mock should follow the same behavior as the platform does

[krizzu]

🎉 This issue has been resolved in version 1.15.15 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀