[jira] [Updated] (THRIFT-4715) C# union "data" should be strongly-typed

["J W (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/THRIFT-4715?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

J W updated THRIFT-4715:
------------------------
    Description: 
`union` option for netcore generator was fixed in 0.12, but what it generates doesn't seem very user-friendly.

Following thrift:
```thrift
struct PlayMsg {
 1: string url,
}

union RequestMsg {
 1: PlayMsg Play,
}
```

Generates:
```csharp
public abstract partial class RequestMsg : TAbstractBase {
 public abstract void Write(TProtocol protocol);
 public readonly bool Isset;
 public abstract object Data \{ get; }
 protected RequestMsg(bool isset) {
 Isset = isset;
 }

public class ___undefined : RequestMsg {
 public override object Data \{ get { return null; } }
 public ___undefined() : base(false) {}

public override void Write(TProtocol protocol) {
 throw new TProtocolException( TProtocolException.INVALID_DATA, "Cannot persist an union type which is not set.");
 }

}

public class Play : RequestMsg {
 private PlayMsg _data;
 public override object Data \{ get { return _data; } }
 public Play(PlayMsg data) : base(true) {
 this._data = data;
 }
 // SNIP
```

Usage:
```csharp
// RequestMsg message = ...
switch (message)
{
 case RequestMsg.Play msg:
 // Need a cast here T_T
 PlayMsg play = (PlayMsg)msg.Data;
```

Is there a reason for the `public abstract object Data`?

If we get rid of that and instead generate a strongly-type getter we don't need to cast `Data`:
```csharp
public class Play : RequestMsg {
 public PlayMsg Data \{ get; private set; }
 public Play(PlayMsg data) : base(true) {
 this.Data = data;
 }
```

I could have sworn it worked like that with the "csharp" generator in 0.11.0 but it generates the same now.

Is the intended usage different from what I'm doing?

> C# union "data" should be strongly-typed
> ----------------------------------------
>
>                 Key: THRIFT-4715
>                 URL: https://issues.apache.org/jira/browse/THRIFT-4715
>             Project: Thrift
>          Issue Type: Improvement
>          Components: C# - Compiler, netcore - Compiler
>    Affects Versions: 0.12.0
>            Reporter: J W
>            Priority: Minor
>
> `union` option for netcore generator was fixed in 0.12, but what it generates doesn't seem very user-friendly.
> Following thrift:
> ```thrift
> struct PlayMsg {
>  1: string url,
> }
> union RequestMsg {
>  1: PlayMsg Play,
> }
> ```
> Generates:
> ```csharp
> public abstract partial class RequestMsg : TAbstractBase {
>  public abstract void Write(TProtocol protocol);
>  public readonly bool Isset;
>  public abstract object Data \{ get; }
>  protected RequestMsg(bool isset) {
>  Isset = isset;
>  }
> public class ___undefined : RequestMsg {
>  public override object Data \{ get { return null; } }
>  public ___undefined() : base(false) {}
> public override void Write(TProtocol protocol) {
>  throw new TProtocolException( TProtocolException.INVALID_DATA, "Cannot persist an union type which is not set.");
>  }
> }
> public class Play : RequestMsg {
>  private PlayMsg _data;
>  public override object Data \{ get { return _data; } }
>  public Play(PlayMsg data) : base(true) {
>  this._data = data;
>  }
>  // SNIP
> ```
> Usage:
> ```csharp
> // RequestMsg message = ...
> switch (message)
> {
>  case RequestMsg.Play msg:
>  // Need a cast here T_T
>  PlayMsg play = (PlayMsg)msg.Data;
> ```
> Is there a reason for the `public abstract object Data`?
> If we get rid of that and instead generate a strongly-type getter we don't need to cast `Data`:
> ```csharp
> public class Play : RequestMsg {
>  public PlayMsg Data \{ get; private set; }
>  public Play(PlayMsg data) : base(true) {
>  this.Data = data;
>  }
> ```
> I could have sworn it worked like that with the "csharp" generator in 0.11.0 but it generates the same now.
> Is the intended usage different from what I'm doing?



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