Stackoverflow on circular referenced records.

[WhiteBlackGoose]

First, awesome project!

Second... yes, it's the first thing I tried in it. Here's the repro:

record A(int P1) { public A Node { get; set; } }
var a = new A(5);
a.Node = a;
a

I suspect it's a problem of dotnet/interactive. Should I redirect the issue there?

[Jon Sequeira]

This is actually a bug here. .NET Interactive will handle this correctly because the default formatters will check for recursion correctly. dotnet-repl has different formatter implementations targeting Spectre.Console.

[Jon Sequeira]

This is fixed in version 0.1.30.

[Jon Sequeira]

This is actually not fixed for records.

The underlying issue here is one with ToString when records have reference cycles. See: dotnet/roslyn-analyzers#5068

[WhiteBlackGoose]

@jonsequitur it's more than that. It's not ToString which causes it. Maybe you're calling PrintMembers? Otherwise, here's my output for my lib's records:

[Jon Sequeira]

The formatters do recursive evaluation but they also have built-in recursion controls, e.g.:

Does this repro on the latest version and does it repro in a .NET Interactive notebook?

How can I repro it?

[WhiteBlackGoose]

Updated the tool to 1.44 version.

You are using classes, and I'm using record. In record it is by default overriden to printing its members recurisively => circular reference implies an SO.

But if I add my own overriding,

record A(int P1) { public A Node { get; set; } public override string ToString() => "Quack!"; }
var a = new A(5);
a.Node = a;
a

it results in a similar output you have

Now, if I override PrintMembres too

sealed record A(int P1) { public A Node { get; set; } public override string ToString() => "Quack!";  bool PrintMembers(System.Text.StringBuilder sb) => true; }
var a = new A(5);
a.Node = a;
a.ToString()

But if I don't do ToString in the end, I get

My suggestion is to simply call ToString on a record. Yes, you would get an SO if the author of the record didn't override the necessary methods, but at least it would coincide with the expectations.

[Jon Sequeira]

Here's a non-recursive example comparing the formatter to the ToString output:

The formatter output is definitely a little redundant.

Let's look at the larger goal of using formatters instead of ToString. We wanted to provide something richer than whatever the original developer decided to use ToString for. I agree that records have a more useful default ToString implementation than classes, so maybe a different behavior is warranted in this case. The general expectation in interactive though (analogous for example to F# printers) is that ToString is typically not sufficient.

Take recursive formatting. If you want to format a record with more complex members and those records are of types where you also have custom formatting rules, those will be in effect with the formatter approach: