Change JsonSerializer to require all non-optional fields

[eddyashton]

I was surprised by how permissive the JSON deserialization is, and it resulted in error messages hiding useful information.

My motivating use case was an annotations file like this:

{
  "x-restler-global-annotations": [
    { }
  ]
}

Trying to compile a grammar with that produces an extremely generic null-reference message:

Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object. at Restler.Annotations.getAnnotationsFromJson(JToken annotationJson) in /data/src/restler-fuzzer/src/compiler/Restler.Compiler/Annotations.fs:line 168 at Restler.Annotations.getGlobalAnnotationsFromFile(String filePath) in /data/src/restler-fuzzer/src/compiler/Restler.Compiler/Annotations.fs:line 220 at Restler.Workflow.generateGrammarFromSwagger(String grammarOutputDirectoryPath, Config config) in /data/src/restler-fuzzer/src/compiler/Restler.Compiler/Workflow.fs:line 104 at Restler.Workflow.generateRestlerGrammar(Config config) in /data/src/restler-fuzzer/src/compiler/Restler.Compiler/Workflow.fs:line 250 at Program.main(String[] argv) in /data/src/restler-fuzzer/src/compiler/Restler.CompilerExe/Program.fs:line 43

It turns out that even though ProducerConsumerUserAnnotation says producer_endpoint : string (implying a non-optional field), it will parse {} and produce an object with {producer_endpoint: null}. Despite sensible checks on the result of tryDeserialize, this is missed and blows up later. I think this should be a parsing error, caught by all callers of Utilities.JsonSerialization.tryDeserialize and reported correctly.

This PR makes that change, by specifying a ContractResolver from FSharpLu.Json. The original example now produces a descriptive error:

Unhandled exception. Newtonsoft.Json.JsonSerializationException: Required property 'producer_endpoint' not found in JSON. Path '', line 1, position 2. ...

(Disclaimer - I'm not familiar with F# or .NET, and I've only just started experimenting with restler, so this is a purely speculative change from a bit of docs-probing. Please let me know if there's a better way to achieve this, or some reason that the original behaviour is required)

[eddyashton]

CI failed, but it looks like this was due to a race condition, concurrently accessing files:

  Failed Restler.Test.Dictionary+DictionaryTests.quoting is correct in the grammar [1 s]
  Error Message:
   System.IO.IOException : The process cannot access the file 'C:\Users\VssAdministrator\AppData\Local\Temp\restlerTest\202142\grammar.json' because it is being used by another process.
  Stack Trace:
    ...
  Failed Restler.Test.Dictionary+DictionaryTests.path and body parameter set to the same uuid suffix payload [30 ms]
  Error Message:
   System.IO.IOException : The process cannot access the file 'C:\Users\VssAdministrator\AppData\Local\Temp\restlerTest\202142\grammar.json' because it is being used by another process.

Is this a known flaky test? Should the CI simply be re-run?

[marina-p]

CI failed, but it looks like this was due to a race condition, concurrently accessing files:

  Failed Restler.Test.Dictionary+DictionaryTests.quoting is correct in the grammar [1 s]
  Error Message:
   System.IO.IOException : The process cannot access the file 'C:\Users\VssAdministrator\AppData\Local\Temp\restlerTest\202142\grammar.json' because it is being used by another process.
  Stack Trace:
    ...
  Failed Restler.Test.Dictionary+DictionaryTests.path and body parameter set to the same uuid suffix payload [30 ms]
  Error Message:
   System.IO.IOException : The process cannot access the file 'C:\Users\VssAdministrator\AppData\Local\Temp\restlerTest\202142\grammar.json' because it is being used by another process.

Is this a known flaky test? Should the CI simply be re-run?

Correct, this failure is a known race condition and it's fine to merge if the test passes on re-run.