[THRIFT-4715] C# union "data" should be strongly-typed

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.12.0
• Fix Version/s: 0.13.0
• Component/s: C# - Compiler
• Patch Info: Patch Available
• Assignee: Jens Geyer
• Reporter: J W
• Created: 04/Jan/19 05:54
• Updated: 16/Oct/19 22:27
• Resolved: 24/Jan/19 17:29

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:

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:

// 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`:

public class Play : RequestMsg{ 
    public PlayMsg Data { get; private set; }
    public Play(PlayMsg data) : base(true)
    { this.Data = data; }
//SNIP

 

 

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?

Issue Links

• Dependency: THRIFT-1786 C# Union Typing
• is related to: THRIFT-4722 Netcore union "data" should be strongly-typed
• links to: GitHub Pull Request #1704