render HeapGraph in ASCII art for test harness

[nikomatsakis]

Right now we dump the DOT format but that's unreadable. It'd be cool to use something like https://dot-to-ascii.ggerganov.com/ and save the ASCII format.

Relevant research into how this can be done

• https://stackoverflow.com/questions/3211801/graphviz-and-ascii-output
• https://metacpan.org/release/TELS/Graph-Easy-0.64

Using perl seems fine but we'd have to make sure the installation is super easy and automatic and works everywhere. We could also setup a webserver do it or hand-code something similar (e.g., maybe not a "true" rendering but just extracting the foo --my--> bar edges or something).

[nikomatsakis]

@lqd, I'm responding to this comment on this thread:

ASCII output would be super cool, but maybe svg or another image format would be easier and acceptable in the meantime ? It's not really easily readable as text, but neither is a sufficiently large/complicated .dot file. We can easily do svg output in pure rust via https://github.com/nadavrot/layout.

I think what we really want is the ability to specify the "interesting bits" of the heap-graph dump in the #? annotation.

[nikomatsakis]

e.g. "it ought to show this variable in this state"

[nikomatsakis]

so maybe the right way to think about this is more about looking at the things we're trying to test and how to express them