The deserialization constructor on type 'FSI_0080 {..}' may not have more than 64 paramete-CodePudding

I am using the library FsHttp to create REST API calls with F#.

I got one API call with returns (potentially) large amount of data. I created records for the JSON responses. In this case the record contains 65 entries.

type Event = {
    policyName: string option
    hash: string
    publisher: string
    eventType: string
    sourceType: string
    ... 60 more paramters
}

With this response I encounter the error:

System.AggregateException: One or more errors occurred. (The deserialization constructor on type 'FSI_0080 Event' may not have more than 64 parameters for deserialization. Path: $.events[0] | LineNumber: 0 | BytePositionInLine: 2087.)
 ---> System.NotSupportedException: The deserialization constructor on type 'FSI_0080 Event' may not have more than 64 parameters for deserialization. Path: $.events[0] | 
LineNumber: 0 | BytePositionInLine: 2087.
 ---> System.NotSupportedException: The deserialization constructor on type 'FSI_0080 Event' may not have more than 64 parameters for deserialization.
   at System.Text.Json.ThrowHelper.ThrowNotSupportedException_ConstructorMaxOf64Parameters(Type type)
   at System.Text.Json.Serialization.Converters.LargeObjectWithParameterizedConstructorConverter`1.CreateObject(ReadStackFrame& frame)
   at System.Text.Json.Serialization.Converters.ObjectWithParameterizedConstructorConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
   at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)        
   at System.Text.Json.Serialization.JsonCollectionConverter`2.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, TCollection& value)
   at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)        
   at System.Text.Json.Serialization.Converters.SmallObjectWithParameterizedConstructorConverter`5.TryRead[TArg](ReadStack& state, Utf8JsonReader& reader, JsonParameterInfo jsonParameterInfo, TArg& arg)
   at System.Text.Json.Serialization.Converters.SmallObjectWithParameterizedConstructorConverter`5.ReadAndCacheConstructorArgument(ReadStack& state, Utf8JsonReader& reader, JsonParameterInfo jsonParameterInfo)
   at System.Text.Json.Serialization.Converters.ObjectWithParameterizedConstructorConverter`1.ReadConstructorArgumentsWithContinuation(ReadStack& state, Utf8JsonReader& reader, JsonSerializerOptions options)
   at System.Text.Json.Serialization.Converters.ObjectWithParameterizedConstructorConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
   at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)        
   at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   --- End of inner exception stack trace ---
   at System.Text.Json.ThrowHelper.ThrowNotSupportedException(ReadStack& state, Utf8JsonReader& reader, NotSupportedException ex)
   at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[TValue](JsonConverter jsonConverter, Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[TValue](JsonReaderState& readerState, Boolean isFinalBlock, ReadOnlySpan`1 buffer, JsonSerializerOptions options, ReadStack& state, JsonConverter converterBase)
   at System.Text.Json.JsonSerializer.ContinueDeserialize[TValue](ReadBufferState& bufferState, JsonReaderState& jsonReaderState, ReadStack& readStack, JsonConverter converter, JsonSerializerOptions options)
   at System.Text.Json.JsonSerializer.ReadAllAsync[TValue](Stream utf8Json, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
   --- End of inner exception stack trace ---
   at Microsoft.FSharp.Control.AsyncResult`1.Commit() in D:\a\_work\1\s\src\fsharp\FSharp.Core\async.fs:line 394
   at Microsoft.FSharp.Control.AsyncPrimitives.QueueAsyncAndWaitForResultSynchronously[a](CancellationToken token, FSharpAsync`1 computation, FSharpOption`1 timeout) in D:\a\_work\1\s\src\fsharp\FSharp.Core\async.fs:line 1045
   at Microsoft.FSharp.Control.AsyncPrimitives.RunSynchronously[T](CancellationToken cancellationToken, FSharpAsync`1 computation, FSharpOption`1 timeout) in D:\a\_work\1\s\src\fsharp\FSharp.Core\async.fs:line 1071
   at Microsoft.FSharp.Control.FSharpAsync.RunSynchronously[T](FSharpAsync`1 computation, FSharpOption`1 timeout, FSharpOption`1 cancellationToken)
   at <StartupCode$FSI_0087>.$FSI_0087.main@() in C:\Users\Alex_P\Documents\PowerShell\stdin:line 606
Stopped due to error

Does JSON deserialization have a limit on parameters?

How to go around this limitation?

CodePudding user response：

This is a known issue in System.Text.Json. It looks like they plan to raise or eliminate the limit. It's not a limit on JSON deserialization in general.

To get around it for now, I think you might have to refactor your type into smaller pieces, or switch to a different JSON library.