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Exceptions thrown from c# iterators (yield) cannot be caught #475

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sirwhinesalot opened this issue May 29, 2017 · 3 comments
Closed

Exceptions thrown from c# iterators (yield) cannot be caught #475

sirwhinesalot opened this issue May 29, 2017 · 3 comments
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bug
Milestone
2.4.0

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@sirwhinesalot
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sirwhinesalot commented May 29, 2017 •
edited by den-run-ai
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Environment

  • Pythonnet version: 2.3.0
  • Python version: 2.7.10
  • Operating System: Windows 7

Details

  • Describe what you were trying to get done.

Catch an exception thrown from a C# iterator (done with yield return) in a python script.

using System;
using System.Collections;
using System.Collections.Generic;
namespace Example
{
	public class Script 
	{
	    public static IEnumerable<int> Test()
	    {
	        for (var i = 0; i < 10; i++)
	        {
	            if (i == 5)
	                throw new Exception("Ooops!");
	            yield return i;
	        }
	    }
	}
}

compile:

"C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc.exe" /t:library bad_yield.cs
import clr
clr.AddReference(...)
import System
import Example


try:
    for r in Example.Script.Test():
        print r
except System.Exception as e:
    print e.Message
except Exception as e:
    print e.message
except:
    print "Unfortunately this one doesn't work either"
  • If there was a crash, please include the traceback here.
Unhandled Exception: System.Exception: Ooops!
    at Example.Script.<Test>d__13.MoveNext() in ...
    at Python.Runtime.Iterator.tp_iternext(IntPtr ob)
@den-run-ai
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@drlagos thanks for detailed report. I edited your response for full example.

@filmor filmor added the bug label Jun 6, 2017
@iantDev
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iantDev commented Jul 10, 2017 •
edited
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  • Python 3.6.1
  • Pythonnet 2.3
  • Windows 7

Similar issue with SqlDataReader:

   dbComm = SqlCommand(query, Conn)
    Conn.Open()        
    sqlReader = dbComm.ExecuteReader()
    sqlReader.Read() 
    sqlReader.Close()

I have tried the following as subsequent code before closing the reader:

while sqlReader.Read():
   pass

but same error.

Error message:

Unhandled Exception: System.InvalidOperationException: Inlvaid attempt to call FieldCount when reader is closed.
     at System.Data.SqlClient.SqlDataReader.get_FieldCount()
     at System.Data.Common.DbEnumerator.BuildSchemaInfo()
     at System.Data.Common.DbEnumerator.MoveNext()
     at Python.Runtime.Iterator.tp_iternext(IntPtr ob)

@filmor filmor added this to the 2.4.0 milestone Jul 11, 2017
This was referenced Aug 9, 2017
Closed
Closed
@ArvidJB ArvidJB mentioned this issue Jun 25, 2018
Merged
4 tasks
filmor added a commit that referenced this issue Jun 26, 2018
@filmor
Merge pull request #693 from ArvidJB/issue-475
3eb7e58 
Catching exceptions from iterator MoveNext(), additional testing (issue #475, original pull request #523)
@den-run-ai
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fixed via #693 and #523

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@filmor @sirwhinesalot @iantDev @den-run-ai