[Statsig] Don't log extra background events

[gaearon]

Fixes excessive logging of state:background:sampled with secondsActive = 0 on iOS.

The problem is that on iOS, app state goes active -> inactive -> background. As a result, the else branch of this code gets triggered both on inactive and background. It "correctly" counts the time only once (i.e. when going active -> inactive) and reports the other change as secondsActive = 0 (because we weren't active in the first place). But it would be better not to send the event at all. With this change, only actual changes to and from active state emit the event.

Test Plan

--- a/src/lib/statsig/statsig.tsx
+++ b/src/lib/statsig/statsig.tsx
@@ -222,11 +222,13 @@ AppState.addEventListener('change', (state: AppStateStatus) => {
   if (state === 'active') {
     lastActive = performance.now()
     logEvent('state:foreground:sampled', {})
+    console.log('log foreground')
   } else {
     let secondsActive = 0
     if (lastActive != null) {
       secondsActive = Math.round((performance.now() - lastActive) / 1e3)
       lastActive = null
+      console.log('log background', secondsActive)
       logEvent('state:background:sampled', {
         secondsActive,
       })

On iOS, verify logs show up when you switch away from the app and back to it. Verify there is no extra "log background 0" log which would've happened before this change. Verify pulling the notification center and back also gets counted as backgrounding and foregrounding.

On Android, verify logs show up when you switch away from the app and back to it.

On web, it doesn't feel like this setup works reliably at all — not sure if it broke at some point. Concretely, the listener only seems to fire as the tab is about to be closed, but it doesn't seem triggered on tab switch. That's unrelated to this PR though.

[render]

Your Render PR Server URL is https://social-app-pr-5134.onrender.com.

Follow its progress at https://dashboard.render.com/web/srv-crc0kljtq21c73atq1ag.

[github-actions]

Old size	New size	Diff
7.09 MB	7.09 MB	0 B (0.00%)

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[estrattonbailey]

Makes sense to me, code looks good, didn't test but can if you'd like a 2nd look