Fix cache for missing keys and empty collections

[janicduplessis]

Details

I found 2 cases where onyx component do not properly cache their data and cause it to be fetched from storage every time it mounts, even if it mounted before.

The first case is when the key does not exist in storage. In that case we never end up calling the get function and just send null to the connection. This means that we never cache that this key doesn't exist. To fix that we can manually set null in the cache for this code path.

The 2nd case is when we have an empty collection. Currently tryGetCachedValue always returns undefined when the collection is empty, but we always have all keys available so it is safe to just return an empty collection in that case. The only case where we don't have all keys is if we never called getAllKeys before and in that case cache.getAllKeys will be empty, so that is the only case where we need to return undefined.

Related Issues

N/A

Slack: https://expensify.slack.com/archives/C05LX9D6E07/p1696601323002289

Automated Tests

This adds 3 tests to validate caching behavior of withOnyx. The first one validates a simple case of mounting and unmounting a component. The first time it mounts it should load data from storage and the 2nd time it should be able to synchronously render. This test already passes before these changes.

The 2nd and 3rd test validate behaviors fixed in the PR, missing keys and empty collections. It makes sure that they are also properly cached on remount.

Manual Tests

I tested in expensify app by scrolling to the bottom of the chats list to make sure all data has been loaded in cache, then start profiling with react devtools and scroll back to the top of the list.

Before:

You can see a large number of small renders

They are caused by loading prop change, which should not happen since we already loaded that data.

After:

Only a few bigger renders, seems like there is still an extra render for each chat cell because of a change to the personalDetails prop, we could investigate in a follow up.

Also manually tested the main app screens to make sure it doesn't cause any issues.

Author Checklist

• I linked the correct issue in the ### Related Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android / native
  • Android / Chrome
  • iOS / native
  • iOS / Safari
  • MacOS / Chrome / Safari
  • MacOS / Desktop
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
  • I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick)
  • I verified that the left part of a conditional rendering a React component is a boolean and NOT a string, e.g. myBool && <MyComponent />.
  • I verified that comments were added to code that is not self explanatory
  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified proper file naming conventions were followed for any new files or renamed files. All non-platform specific files are named after what they export and are not named "index.js". All platform-specific files are named for the platform the code supports as outlined in the README.
  • I verified the JSDocs style guidelines (in STYLE.md) were followed
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I followed the guidelines as stated in the Review Guidelines
• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
• I verified all code is DRY (the PR doesn't include any logic written more than once, with the exception of tests)
• I verified any variables that can be defined as constants (ie. in CONST.js or at the top of the file that uses the constant) are defined as such
• I verified that if a function's arguments changed that all usages have also been updated correctly
• If a new component is created I verified that:
  • A similar component doesn't exist in the codebase
  • All props are defined accurately and each prop has a /** comment above it */
  • The file is named correctly
  • The component has a clear name that is non-ambiguous and the purpose of the component can be inferred from the name alone
  • The only data being stored in the state is data necessary for rendering and nothing else
  • If we are not using the full Onyx data that we loaded, I've added the proper selector in order to ensure the component only re-renders when the data it is using changes
  • For Class Components, any internal methods passed to components event handlers are bound to this properly so there are no scoping issues (i.e. for onClick={this.submit} the method this.submit should be bound to this in the constructor)
  • Any internal methods bound to this are necessary to be bound (i.e. avoid this.submit = this.submit.bind(this); if this.submit is never passed to a component event handler like onClick)
  • All JSX used for rendering exists in the render method
  • The component has the minimum amount of code necessary for its purpose, and it is broken down into smaller components in order to separate concerns and functions
• If any new file was added I verified that:
  • The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.
• I have checked off every checkbox in the PR author checklist, including those that don't apply to this PR.

Screenshots/Videos

Web

Mobile Web - Chrome

Mobile Web - Safari

Desktop

iOS

Android

[puneetlath]

I don't have a great understanding of Onyx, so adding a couple more reviewers. The tests seem to make sense to me though.

[tgolen]

How is it possible to not have all keys loaded yet (can you please add this to the code comment)?

[janicduplessis]

If we haven't called getAllKeys yet (from Onyx, not OnyxCache). Not sure if that can actually happen but to be safe this is prob better. I can clarify.

[tgolen]

Ah, I did not notice the subtle difference between getAllKeys from Onyx vs OnyxCache.

[tgolen]

Thinking a little more on this, can you please change allKeys to be renamed to allCacheKeys?

[tgolen]

Is the only way to know that it wasn't rendered immediately because the test doesn't need to add a waitForPromisesToResolve in order for the assertions to pass? If so, can you please clarify that in the comment. It's not very obvious.

[janicduplessis]

Yes, if the assertion passes right away, before waitForPromisesToResolve this means it rendered synchronously since all data is cached. I can clarify.

[mountiny]

+1

[mountiny]

+1

[mountiny]

Curious why do we need to add this key? is it just so there is something in the onyx storage?

[janicduplessis]

Yea to know if all keys are in cache we currently check if the array length is > 0 so if the storage is empty the check never works.

[janicduplessis]

@tgolen @mountiny Thanks for the review, will address the feedback tomorrow!

[janicduplessis]

Updated!

[tgolen]

Thinking a little more on this, can you please change allKeys to be renamed to allCacheKeys?

[tgolen]

Thanks!

[mountiny]

Thank you!