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BasePurchasesTests: fixed leak detection #2534

Merged
merged 2 commits into from
May 24, 2023
Merged

BasePurchasesTests: fixed leak detection #2534

merged 2 commits into from
May 24, 2023

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NachoSoto
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While working on #2533, I knew that my proof of concept had a retain cycle. I however was very confused when it wasn't detected by this mechanism introduced first introduced in #2104.

Turns out that this had been wrong the whole time: the current implementation, as explained by the comment, was executing those blocks in LIFO order, which meant that the references were being set to nil before the assertions could be created.
This meant that by the time the except { [weak purchases = self.purchases] ... } lines were called, self.purchases itself was nil, so nothing was being checked.

This simplifies the implementation by inlining the checks, and saving a weak reference before clearing the singleton and all the local references.

Luckily there was only one failing test that had to do with how Purchases was being created, and implementation details of expectFatalError. To avoid this, I changed the test to use the Purchases.init method directly.

While working on #2533, I knew that my proof of concept had a retain cycle. I however was very confused when it wasn't detected by this mechanism introduced first introduced in #2104.

Turns out that this had been wrong the whole time: the current implementation, as explained by the comment, was executing those blocks in LIFO order, which meant that the references were being set to `nil` before the assertions could be created.
This meant that by the time the `except { [weak purchases = self.purchases] ... }` lines were called, `self.purchases` itself was `nil`, so nothing was being checked.

This simplifies the implementation by inlining the checks, and saving a `weak` reference before clearing the singleton and all the local references.

Luckily there was only one failing test that had to do with how `Purchases` was being created, and implementation details of `expectFatalError`. To avoid this, I changed the test to use the `Purchases.init` method directly.
@NachoSoto NachoSoto added the test label May 23, 2023
@NachoSoto NachoSoto requested a review from a team May 23, 2023 23:34
@NachoSoto
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And now this correctly detects the retain cycle I introduced 🎉

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codecov bot commented May 23, 2023

Codecov Report

Merging #2534 (6954eff) into main (c390a66) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2534   +/-   ##
=======================================
  Coverage   87.76%   87.77%           
=======================================
  Files         199      199           
  Lines       13710    13721   +11     
=======================================
+ Hits        12032    12043   +11     
  Misses       1678     1678           
Impacted Files Coverage Δ
Sources/Logging/Strings/PurchaseStrings.swift 88.66% <100.00%> (+0.34%) ⬆️
...s/Purchasing/Purchases/PurchasesOrchestrator.swift 86.50% <100.00%> (+0.07%) ⬆️

... and 2 files with indirect coverage changes

}
weak var purchases = self.purchases
weak var orchestrator = self.purchasesOrchestrator
weak var deviceCache = self.deviceCache
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Should we rename these 3 so there is less confusion with the global variables?

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You'd rename them to weakPurchases, etc?

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They're limited to the scope of this method so I think it's clear that they're shadowing those variables. But let me know if you disagree.

@NachoSoto NachoSoto merged commit 01e31ef into main May 24, 2023
@NachoSoto NachoSoto deleted the leak-detection-fix branch May 24, 2023 16:50
NachoSoto added a commit that referenced this pull request May 30, 2023
…2533)

This fixes the last edge-case for offline entitlements. Solves the
following scenario:
```swift
func testPurchaseWhileServerIsDownPostsReceiptWhenForegroundingApp() async throws {
    let logger = TestLogHandler()

    // 1. Purchase while server is down
    self.serverDown()
    try await self.purchaseMonthlyProduct()

    logger.verifyMessageWasNotLogged("Finishing transaction")

    // 2. Server is back
    self.serverUp()

    // 3. Request current CustomerInfo
    let info1 = try await Purchases.shared.customerInfo()
    try await self.verifyEntitlementWentThrough(info1)

    // 4. Ensure transaction is finished
    logger.verifyMessageWasLogged("Finishing transaction", level: .info)

    // 5. Restart app
    Purchases.shared.invalidateCustomerInfoCache()
    await self.resetSingleton()

    // 6. To ensure (with a clean cache) that the receipt was posted
    let info2 = try await Purchases.shared.customerInfo()
    try await self.verifyEntitlementWentThrough(info2)
}
```

This race condition happened when fetching `CustomerInfo` after we had
computed an offline `CustomerInfo` with a purchase: if the server is
still not aware of the purchase, then we lose that until some arbitrary
amount of time when `StoreKit` might decide to send the pending
transactions in the queue.
For that reason, instead of waiting, we proactively check now whenever
`CustomerInfoManager` fetches new info.

The refactors #2540 and #2542 where required to break a retain cycle.
Also thanks to #2534 we know for sure that there aren't any cycles.

Note that this is an iOS 15.0+ only feature. It would be useful to
better ensure consistency in older versions, but it's not strictly
required, as those versions don't support offline entitlements either.
This was referenced May 31, 2023
@NachoSoto NachoSoto mentioned this pull request May 31, 2023
NachoSoto added a commit that referenced this pull request Jun 1, 2023
**This is an automatic release.**

### New Features
* `Offline Entitlements`: use offline-computed `CustomerInfo` when
server is down (#2368) via NachoSoto (@NachoSoto)

### Bugfixes
* `AppleReceipt.debugDescription`: don't pretty-print JSON (#2564) via
NachoSoto (@NachoSoto)
* `SK2StoreProduct`: fix crash on iOS 12 (#2565) via NachoSoto
(@NachoSoto)
* `GetCustomerInfo` posts receipts if there are pending transactions
(#2533) via NachoSoto (@NachoSoto)
### Performance Improvements
* `PurchasedProductsFetcher`: cache current entitlements (#2507) via
NachoSoto (@NachoSoto)
* Performance: new check to ensure serialization / deserialization is
done from background thread (#2496) via NachoSoto (@NachoSoto)
### Dependency Updates
* Bump fastlane from 2.212.2 to 2.213.0 (#2544) via dependabot[bot]
(@dependabot[bot])
### Other Changes
* `CustomerInfoManager`: post all unfinished transactions (#2563) via
NachoSoto (@NachoSoto)
* `PostReceiptOperation`: added ability to also post `AdServices` token
(#2566) via NachoSoto (@NachoSoto)
* `Offline Entitlements`: improved computation log (#2562) via NachoSoto
(@NachoSoto)
* Added `TransactionPoster` tests (#2557) via NachoSoto (@NachoSoto)
* Refactored `TransactionPoster`: removed 2 dependencies and abstracted
parameters (#2542) via NachoSoto (@NachoSoto)
* `CustomerInfoManagerTests`: wait for `getAndCacheCustomerInfo` to
finish (#2555) via NachoSoto (@NachoSoto)
* `StoreTransaction`: implemented `description` (#2556) via NachoSoto
(@NachoSoto)
* `Backend.ResponseHandler` is now `@Sendable` (#2541) via NachoSoto
(@NachoSoto)
* Extracted `TransactionPoster` from `PurchasesOrchestrator` (#2540) via
NachoSoto (@NachoSoto)
* `enableAdServicesAttributionTokenCollection`: added integration test
(#2551) via NachoSoto (@NachoSoto)
* `AttributionPoster`: replaced hardcoded strings with constants (#2548)
via NachoSoto (@NachoSoto)
* `DefaultDecodable`: moved to `Misc/Codable/DefaultDecodable.swift`
(#2528) via NachoSoto (@NachoSoto)
* `CircleCI`: specify device to run `backend_integration_tests` (#2547)
via NachoSoto (@NachoSoto)
* Created `StoreKit2TransactionFetcher` (#2539) via NachoSoto
(@NachoSoto)
* Fix load shedder integration tests (#2546) via Josh Holtz
(@joshdholtz)
* Fix doc on `Offering.getMetadataValue` (#2545) via Josh Holtz
(@joshdholtz)
* Extracted and tested `AsyncSequence.extractValues` (#2538) via
NachoSoto (@NachoSoto)
* `Offline Entitlements`: don't compute offline `CustomerInfo` when
purchasing a consumable products (#2522) via NachoSoto (@NachoSoto)
* `OfflineEntitlementsManager`: disable offline `CustomerInfo` in
observer mode (#2520) via NachoSoto (@NachoSoto)
* `BasePurchasesTests`: fixed leak detection (#2534) via NachoSoto
(@NachoSoto)
* `PurchaseTesterSwiftUI`: added `ProxyView` to `iOS` (#2531) via
NachoSoto (@NachoSoto)
* `PurchasedProductsFetcher`: removed `AppStore.sync` call (#2521) via
NachoSoto (@NachoSoto)
* `PurchaseTesterSwiftUI`: added new window on Mac to manage proxy
(#2518) via NachoSoto (@NachoSoto)
* `PurchasedProductsFetcher`: added log if fetching purchased products
is slow (#2515) via NachoSoto (@NachoSoto)
* `Offline Entitlements`: disable for custom entitlements mode (#2509)
via NachoSoto (@NachoSoto)
* `Offline Entitlements`: fixed iOS 12 tests (#2514) via NachoSoto
(@NachoSoto)
* `PurchasedProductsFetcher`: don't throw errors if purchased products
were found (#2506) via NachoSoto (@NachoSoto)
* `Offline Entitlements`: allow creating offline `CustomerInfo` with
empty `ProductEntitlementMapping` (#2504) via NachoSoto (@NachoSoto)
* `Offline Entitlements`: integration tests (#2501) via NachoSoto
(@NachoSoto)
* `CustomerInfoManager`: don't cache offline `CustomerInfo` (#2378) via
NachoSoto (@NachoSoto)
* `DangerousSettings`: debug-only `forceServerErrors` (#2486) via
NachoSoto (@NachoSoto)
* `CocoapodsInstallation`: fixed `Xcode 14.3.0` issue (#2489) via
NachoSoto (@NachoSoto)
* `CarthageInstallation`: removed workaround (#2488) via NachoSoto
(@NachoSoto)

---------

Co-authored-by: NachoSoto <ignaciosoto90@gmail.com>
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2 participants