Adopt exception unification #8002

tgoyne · 2022-10-24T23:26:45Z

This isn't mergeable yet as it depends on realm/realm-core#5911 (and also a core release with exception unification merged), but I think the code changes here are complete and ready for review.

There's currently a few failing tests due to core bugs which have been fixed on master but not merged into the branch yet.

leemaguire · 2022-11-07T10:20:47Z

Realm/ObjectServerTests/SwiftObjectServerTests.swift

-            if p.transferredBytes > 0 && p.isTransferComplete && !hasBeenFulfilled {
-                ex.fulfill()
-                hasBeenFulfilled = true
+            DispatchQueue.main.async {


Why is there a need to wrap this is a dispatch block?

I think it was a race condition at the end of the test? Without this we can return from the test function while the sync thread is still in the progress notification callback, and maybe that was an issue?

I clearly should have written a comment saying why because I don't remember and there isn't an obvious reason. Might just be incorrect.

dianaafanador3

LGTM!, Just some minor changes and some questions.

dianaafanador3 · 2022-11-10T22:38:27Z

Realm/RLMError.mm

+    return translateSystemError(exception.code(), exception.what());
+}
+
+__attribute__((objc_direct_members))


I read that marking something as direct doesn't translate into a noticeable performance advantage, as it turns out that objc_msgSend is very fast indeed. Is there any other reason for this or it is a performance and code size reduction decision.

It's just for the minor compiled size benefits.

Realm/RLMError.h

dianaafanador3 · 2022-11-11T13:51:35Z

Realm/RLMError.h

+
+/// A user info key containing the error code. This is provided for backwards
+/// compatiblity only and should not be used.
+extern NSString *const RLMErrorCodeKey __attribute((deprecated("use -[NSError code]")));


Should we add this to the CHANGELOG?

It was never actually documented anywhere afaict so it wasn't really part of the public API.

Realm/RLMError.h

dianaafanador3 · 2022-11-14T15:43:44Z

Realm/RLMRealm.mm

-            *error = [NSError errorWithDomain:NSCocoaErrorDomain code:NSFileWriteNoPermissionError
-                                     userInfo:@{NSLocalizedDescriptionKey: @(e.what()),
-                                                NSFilePathErrorKey: @(e.get_path().c_str())}];
+            // For backwards compatiblity, but this should go away in 11.0


I don't if this been tried before, but we could have a label or tag to identify changes that need to occur in the next major release (11.0) which would make it so much easier to do clean up when we do this in the future.

@dianaafanador3 Other teams create issues with a "NextMajor" label.

dianaafanador3 · 2022-11-14T16:12:22Z

Realm/RLMResults.mm

    try {
        throw;
    }
-    catch (realm::InvalidTransactionException const&) {
-        @throw RLMException(@"Cannot modify Results outside of a write transaction.");
+    catch (realm::WrongTransactionState const&) {


Why some of this exceptions were converted to LogicError in core an some left out to be handled by the SDKs like this one WrongTransactionState

Most of the exception messages from core are now fine to use as-is, and the two cases we're catching are where we want a different message. WrongTransactionState doesn't know what thing was being modified so it has a slightly less useful error message, and for OutOfBounds we're exactly mirroring NSArray's error message, mostly to simplify tests which check error messages on both managed and unmanaged collections.

dianaafanador3 · 2022-11-14T16:34:31Z

Realm/RLMSyncSubscription.mm

-    if (_mutableSubscriptionSet != nil) {
-        @throw RLMException(@"Cannot initiate a write transaction on subscription set that is already been updated.");
+    if (_mutableSubscriptionSet) {
+        @throw RLMException(@"Cannot initiate a write transaction on subscription set that is already being updated.");


Suggested change

@throw RLMException(@"Cannot initiate a write transaction on subscription set that is already being updated.");

@throw RLMException(@"Cannot initiate a write transaction on a subscription set that is already being updated.");

dianaafanador3 · 2022-11-14T16:41:13Z

Realm/RLMSyncSubscription.mm

    }
    _mutableSubscriptionSet = std::make_unique<realm::sync::MutableSubscriptionSet>(_subscriptionSet->make_mutable_copy());
+    realm::util::ScopeExit cleanup([&]() noexcept {


When this is executed? trying to understand this deeper. Seems like this returns the mutableSubscriptionSet to null even after an error?

Yes. Whenever possible a function which throws an exception should leave an object in exactly the state it was in before the function call (in C++ terminology this is the "strong exception guarantee"). The refresh() means we don't quite hit this, but the important thing is that regardless of how we leave update:, update: should not leave the subscription set in a mid-update state.

Oh, I forgot to answer the first half. The lambda is executed in the ScopeExit object's destructor, meaning that it's run when exiting the scope regardless of if it's via returning normally or due to an exception being thrown. It's the C++ equivalent of finally or defer and is a good place to put cleanup code that needs to be run on both success and error paths.

dianaafanador3 · 2022-11-14T16:53:35Z

Realm/Tests/AsyncTests.mm

@@ -393,54 +393,6 @@ - (void)testCommitInOneNotificationDoesNotCancelOtherNotifications {
    [token2 invalidate];
 }

-#if 0 // Not obvious if there's still any way for notifiers to fail other than memory allocation failure


Changing the error handling should not make this test change instead of deleting it?, why we don't need to test this anymore?

Core removed the error reporting mechanism for notifiers since it's been dead code ever since core 6, so this test is now entirely obsolete.

…ors which retry the job

tgoyne self-assigned this Oct 24, 2022

cla-bot bot added the cla: yes label Oct 24, 2022

tgoyne force-pushed the tg/exception-revamp branch 6 times, most recently from 9116625 to 35cfe06 Compare October 28, 2022 04:18

tgoyne requested review from leemaguire and dianaafanador3 November 4, 2022 22:19

leemaguire reviewed Nov 7, 2022

View reviewed changes

dianaafanador3 approved these changes Nov 15, 2022

View reviewed changes

tgoyne force-pushed the tg/exception-revamp branch 2 times, most recently from 335d975 to c7e609b Compare November 16, 2022 18:45

tgoyne force-pushed the tg/exception-revamp branch from c7e609b to 0951fb4 Compare December 5, 2022 18:39

tgoyne force-pushed the tg/exception-revamp branch 4 times, most recently from b4893df to 6d8d372 Compare February 27, 2023 03:37

Update Core to 13.5.0

db3641e

tgoyne force-pushed the tg/exception-revamp branch from c91ca4e to bfa8cd9 Compare February 28, 2023 16:12

tgoyne added 4 commits February 28, 2023 09:24

Adopt exception unification

383d108

Fix a test which wasn't guaranteed to work

1abe3fa

Set the c++ version to the correct value in the podspec

a79a6c3

Add the "thread is already initializing this class!" error to the err…

def0d51

…ors which retry the job

tgoyne force-pushed the tg/exception-revamp branch from bfa8cd9 to def0d51 Compare February 28, 2023 17:26

tgoyne merged commit 9da26e1 into master Feb 28, 2023

tgoyne deleted the tg/exception-revamp branch February 28, 2023 18:55

nirinchev mentioned this pull request Feb 6, 2024

Could not build Objective-C module 'Realm' #8392

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Adopt exception unification #8002

Adopt exception unification #8002

tgoyne commented Oct 24, 2022 •

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tgoyne Nov 15, 2022

dianaafanador3 Nov 14, 2022 •

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tgoyne Nov 16, 2022

dianaafanador3 Nov 14, 2022

tgoyne Nov 15, 2022

	@throw RLMException(@"Cannot initiate a write transaction on subscription set that is already being updated.");
	@throw RLMException(@"Cannot initiate a write transaction on a subscription set that is already being updated.");

Adopt exception unification #8002

Adopt exception unification #8002

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tgoyne commented Oct 24, 2022 • edited Loading

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dianaafanador3 Nov 14, 2022 • edited Loading

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tgoyne commented Oct 24, 2022 •

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dianaafanador3 Nov 14, 2022 •

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