New class loading safety

The most common failure for our unit tests is a DynamicExpresso bug. It’s quite annoying too.

Every usage of DynamicExpresso is guarded by locks in our case however unit tests still fail. There appears to be a race condition in type loading, something that looks to require a global (app domain?) lock internally.

[xUnit.net 00:00:02.12]       DynamicExpresso.Exceptions.ParseException : No applicable constructor exists in type 'X4BFlow.Test.Nf9.TestTemplatePrototype+TemplateTest' (at index 55).
[xUnit.net 00:00:02.12]       Stack Trace:
[xUnit.net 00:00:02.12]            at DynamicExpresso.Parsing.Parser.ParseNew()

We can make this happen by running tests in xunit which occur in parallel between test fixtures. One interpreter per test case, however the loading of types on first use may still occur in parallel.

[davideicardi]

I think that the problem is that you can have one thread that modify the Interpreter (calling Reference, …) While another thread is calling Compile. This is not supported. For unit testing I suggest to not share the instances. For real usage code I suggest to have an initialization phase where you configure it, and then call only read only functions.

[davideicardi]

I will close the issue, but if you need further assistence feel free to re-open it.

Just a clarification regarding thread safety: All the Interpreter functions that do not modify the instance can be called by multiple threads at the same time. But you cannot call Interpreter.Reference in one thread while calling Interpreter.Parse in another thread. This could result in unexpected errors. So technically Interpreter.Parse is thread safe, but only if used without changing the inner instance… I think this is quite common in .NET classes.