Improve safety and clarity in getProducer to handle unnamed response properties

[landoncrabtree]

If response entries in a Swagger spec are arrays (and not objects), then when attempting to compile via Restler compile --api_spec, it will throw an error:

ERROR: Compiler failed. See logs in Compile directory for more information.

Task Compile failed.
Collecting logs...

With the following error logs,

Unhandled exception. System.AggregateException: One or more errors occurred. (Object reference not set to an instance of an object.)
 ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at Restler.Dependencies.visitLeaf2@869.Invoke(FSharpList`1 parentAccessPath, LeafProperty p) in C:\restler-fuzzer\src\compiler\Restler.Compiler\Dependencies.fs:line 897
   at Restler.Grammar.Tree.iterCtx[a,LeafData,INodeData](FSharpFunc`2 fLeaf, FSharpFunc`2 fNode, FSharpFunc`2 fCtx, a ctx, Tree`2 tree) in C:\restler-fuzzer\src\compiler\Restler.Compiler\Grammar.fs:line 60
   at Restler.Grammar.Tree.recurse@57-1.Invoke(a ctx, Tree`2 tree)
   at Microsoft.FSharp.Collections.SeqModule.Iterate[T](FSharpFunc`2 action, IEnumerable`1 source) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\seq.fs:line 497
   at Restler.Grammar.Tree.iterCtx[a,LeafData,INodeData](FSharpFunc`2 fLeaf, FSharpFunc`2 fNode, FSharpFunc`2 fCtx, a ctx, Tree`2 tree) in C:\restler-fuzzer\src\compiler\Restler.Compiler\Grammar.fs:line 63
   at Restler.Grammar.Tree.recurse@57-1.Invoke(a ctx, Tree`2 tree)
   at Microsoft.FSharp.Collections.SeqModule.Iterate[T](FSharpFunc`2 action, IEnumerable`1 source) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\seq.fs:line 497
   at Restler.Grammar.Tree.iterCtx[a,LeafData,INodeData](FSharpFunc`2 fLeaf, FSharpFunc`2 fNode, FSharpFunc`2 fCtx, a ctx, Tree`2 tree) in C:\restler-fuzzer\src\compiler\Restler.Compiler\Grammar.fs:line 63
   at Restler.Dependencies.getProducer(RequestId request, Tree`2 response) in C:\restler-fuzzer\src\compiler\Restler.Compiler\Dependencies.fs:line 907
   at Restler.Dependencies.extractDependencies@1286.Invoke(Tuple`2 tupledArg) in C:\restler-fuzzer\src\compiler\Restler.Compiler\Dependencies.fs:line 1290
   at Microsoft.FSharp.Collections.ArrayModule.Parallel.Iterate@1334.Invoke(Int32 i) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\array.fs:line 1334
   at System.Threading.Tasks.Parallel.<>c__DisplayClass19_0`2.<ForWorker>b__1(RangeWorker& currentWorker, Int64 timeout, Boolean& replicationDelegateYieldedBeforeCompletion)
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Parallel.<>c__DisplayClass19_0`2.<ForWorker>b__1(RangeWorker& currentWorker, Int64 timeout, Boolean& replicationDelegateYieldedBeforeCompletion)
   at System.Threading.Tasks.TaskReplicator.Replica.Execute()
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.TaskReplicator.Run[TState](ReplicatableUserAction`1 action, ParallelOptions options, Boolean stopOnFirstFailure)
   at System.Threading.Tasks.Parallel.ForWorker[TLocal,TInt](TInt fromInclusive, TInt toExclusive, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Func`4 bodyWithLocal, Func`1 localInit, Action`1 localFinally)
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Parallel.ForWorker[TLocal,TInt](TInt fromInclusive, TInt toExclusive, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Func`4 bodyWithLocal, Func`1 localInit, Action`1 localFinally)
   at System.Threading.Tasks.Parallel.For(Int32 fromInclusive, Int32 toExclusive, Action`1 body)
   at Microsoft.FSharp.Collections.ArrayModule.Parallel.Iterate[T](FSharpFunc`2 action, T[] array) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\array.fs:line 1334
   at Restler.Dependencies.extractDependencies(Tuple`2[] requestData, IEnumerable`1 globalAnnotations, MutationsDictionary customDictionary, Boolean queryDependencies, Boolean bodyDependencies, Boolean headerDependencies, Boolean allowGetProducers, Boolean dataFuzzing, FSharpMap`2 perResourceDictionaries, FSharpOption`1 namingConvention) in C:\restler-fuzzer\src\compiler\Restler.Compiler\Dependencies.fs:line 1280
   at Restler.Compiler.Main.generateRequestGrammar(FSharpList`1 swaggerDocs, MutationsDictionary dictionary, Config config, FSharpList`1 globalExternalAnnotations, FSharpList`1 userSpecifiedExamples) in C:\restler-fuzzer\src\compiler\Restler.Compiler\Compiler.fs:line 1421
   at Restler.Workflow.generateGrammarFromSwagger(String grammarOutputDirectoryPath, Config config) in C:\restler-fuzzer\src\compiler\Restler.Compiler\Workflow.fs:line 143
   at Restler.Workflow.generateRestlerGrammar(Config config) in C:\restler-fuzzer\src\compiler\Restler.Compiler\Workflow.fs:line 250
   at Program.main(String[] argv) in C:\restler-fuzzer\src\compiler\Restler.CompilerExe\Program.fs:line 43

Here is a simple Swagger spec to reproduce the issue:

{
  "swagger": "2.0",
  "info": { "version": "1.0.0", "title": "PoC API" },
  "paths": {
    "/api/do-something": {
      "get": {
        "responses": {
          "200": {
            "description": "OK",
            "schema": {
              "type": "array",
              "items": {
                "type": "array",
                "items": {
                  "type": "string"
                }
              }
            }
          }
        }
      }
    }
  }
}

The proposed changes add better safety handling in the case there is no top-level object (e.g. nested arrays), where .name could be null. This prevents NullReferenceException, however, it still does not implement the actual producer logic: TODO: support cases where the entire response is an array

[landoncrabtree]

@microsoft-github-policy-service agree company="Microsoft"

[marina-p]

[marina-p]

Thank you for the improvements!

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In reply to: 3138655697