Process.WaitForExitAsync doesn't wait for the reditected output to be read #42556
Description
Description
In #34294, @scalablecory said that Process.WaitForExitAsync is semantically equivalent to Process.WaitForExit. However, it seems that it is not the case when the process has exited before calling BeginOutputReadLine.
The following test succeeds. It is not expected as Assert.Empty(logs) should fail. Calling WaitForExit correctly raises the OutputDataReceived event, so the second assert succeeds as expected.
[Fact]
public async Task Test1()
{
var logs = new List<string>();
var psi = new ProcessStartInfo("cmd", "/C echo test")
{
UseShellExecute = false,
RedirectStandardOutput = true,
};
using var process = new Process();
process.StartInfo = psi;
process.OutputDataReceived += (sender, e) => { if (e.Data != null) logs.Add(e.Data); };
Assert.True(process.Start());
// Give time for the process (cmd) to terminate
Thread.Sleep(1000);
process.BeginOutputReadLine();
await process.WaitForExitAsync();
Assert.Empty(logs); // The collection is empty, but it should contain 1 item
process.WaitForExit();
Assert.Equal(new[] { "test" }, logs); // ok
}Configuration
Host (useful for support):
Version: 5.0.0-rc.1.20451.14
Commit: 38017c3935
.NET SDKs installed:
3.1.300 [C:\Program Files\dotnet\sdk]
5.0.100-preview.7.20366.6 [C:\Program Files\dotnet\sdk]
5.0.100-rc.1.20452.10 [C:\Program Files\dotnet\sdk]
.NET runtimes installed:
Microsoft.AspNetCore.All 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.0-preview.7.20365.19 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.0-rc.1.20451.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.0-preview.7.20364.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.0-rc.1.20451.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.0-preview.7.20366.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.0-rc.1.20452.2 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]