JsonPath not using last frame during continuation

[steveharter]

Fixes#39055

The test failure reports in that issue reference PathForChildDictionaryFails however only for .NET framework 461. However, the refactored PathForChildDictionaryFails test now repros on net6 as well. I believe the 461 ArrayPool was returning just the right size pooled buffer from a previous test that caused the continuation issue, and net6 returned a larger pool (likely on a boundary).

This also occurs in 5.0.

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Issue Details

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Fixes #39055

The test failure reports in that issue reference PathForChildDictionaryFails however only for .NET framework 461. However, the refactored PathForChildDictionaryFails test now repros on net6 as well. I believe the 461 ArrayPool was returning just the right size pooled buffer from a previous test that caused the continuation issue, and net6 returned a larger pool (likely on a boundary).

This appears to be a regression from #54420 where the "continuation count" is now 1 less than before.

Author:	steveharter
Assignees:	steveharter
Labels:	area-System.Text.Json
Milestone:	6.0.0

[eiriktsarpalis]

Thanks. Out of curiosity why did this only repro in netfx? Should we backport this to release/6.0?

[steveharter]

Thanks. Out of curiosity why did this only repro in netfx? Should we backport this to release/6.0?

Actually this did repro in 5.0. I don't think it makes the bar for back-porting. Also, I don't think it meets the bar for 6.0 porting to main either (no customer reports + not a regression + used for debugging bad JSON and not runtime functionality).

Here's a standalone repro:

for(inti=1;i<30;i++){stringjson=@"{""Child"":{""MyDictionary"":{""Key"": bad]";JsonSerializerOptionsoptions=new(){DefaultBufferSize=i};MemoryStreamms=newMemoryStream(System.Text.Encoding.ASCII.GetBytes(json));try{awaitJsonSerializer.DeserializeAsync<RootClass>(ms,options);}catch(JsonExceptionex){Console.WriteLine($"{i}:"+ex.Path);// should be "$.Child.MyDictionary.Key"}}publicclassRootClass{publicChildClassChild{get;set;}}publicclassChildClass{publicintMyInt{get;set;}publicint[]MyIntArray{get;set;}publicDictionary<string,ChildClass>MyDictionary{get;set;}publicChildClass[]Children{get;set;}}

[eiriktsarpalis]

Should we backport this to release/6.0?

Depending on how often this happens in CI, it might actually meet the bar citing build stability issues.

Nevermind, it seems like #57834 should be a sufficient intervention.