Truncate InvalidCallbackReturnValue size

[stdedos]

Truncate the stringified value of bad_val,
in order to avoid excessive output on the debug pop-up.

Fixes #2658

Signed-off-by: Stavros Ntentos 133706+stdedos@users.noreply.github.com

[alexcjohnson]

Looks great, thanks! Would you mind adding a test in test_devtools_error_handling, perhaps modeled off dveh003, where a callback returns a very long value that gets truncated? (No need for the percy snapshot though, just validate the contents of the error

After that, just a changelog entry - make a new ## Unreleased -> ## Fixed section at the top if necessary.

[Coding-with-Adam]

hi @stdedos
Thank you for creating this pull request. We wanted to follow up and encourage you to finalize this PR by adding a test. In case it's helpful, here is an example of a basic Dash test.

[stdedos]

Hello there, both!

I don't think it's feasible for me to do testing for this PR.

It was not a commitment discussed in #2658.
Furthermore, testing dash is problematic for me from start to finish 😓

1. Local testing is impossible to start
2. I cannot find good instructions
3. REPL via CI is too slow

I do not want to spend more headaches trying to bootstrap testing something otherwise easy to spot as working.

[alexcjohnson]

Thanks for giving it a shot @stdedos - sorry to hear it's not working. We'll find a time to finish it up at some point.