Catch panic when using go-spew

[ccoVeille]

Summary

Avoid panic on go-spew errors

Changes

wrap the calls to go-spew into a call to didPanic

Motivation

go-spew can panic when trying to diff certain types of values, there are open issues about this on their GitHub repository.

go-spew is unfortunately unmaintained, we cannot expect a fix any time soon. Also, because of go-spew's design, there are multiple causes for a panic, and fixing all of them would be a huge undertaking.

We already return an empty diff when the types are not comparable, or when the values are not from types that can be easily diffed by go-spew.

Let's hide the panic by recovering from it, and returning an empty diff instead. This is not ideal, but at least it prevents the entire program from crashing. The expected/actual values will still be printed, just without the diff.

Related issues

Closes #480

• Panic in assert/require.Equal when calling into go-spew #480

Related to

• don't panic on unexported struct key in map #1816 It provides a different approach but don't panic on unexported struct key in map #1816 could be still be considered cc @HaraldNordgren
• assert.Equal panic on diff unexported map with array as key #1813 Provide a solution for the panic issues without changing the diff lib cc @olitez