[feature] only trace functions in specific files

[Co1lin]

It seems that the current tracer does not support only tracing files in some specific files. The user can of course filter out the results after execution, but I found that this affects efficiency. To trace a large project containing many functions simultaneously, it is hard to specify a fixed depth. Setting it too large will lead to diving into many builtin modules, which is very slow. Instead, using path/filenames as the filtering criteria is more controllable.

I'll implement this for my needs. If you guys think it's useful, I can submit a PR. But which style for the additional parameter is suitable? Welcome any comments to the draft PR, thanks!

[cool-RR]

Good idea. Here's my proposed API. The argument will be called source_paths and will have a default value of None, indicating that there shouldn't be filtering.

You could feed into it an iterable where every item can be a string or a pathlib.Path object. (Be mindful that you're not breaking Python 2.7 compatibility when checking for that.) These paths get canonicalized as you've done with realpath into a string. Then they get put in a tuple (because the user may have used any other kind of sequence or iterable.)

These paths may point to either a folder or a file. If it's a folder, then any file in that folder or its subfolders is included. If it's a file, then just that file.

Additionally, we can add boolean arguments include_stdlib=True and include_site_packages=True. Let's say that we don't allow these arguments to be used in conjuction with source_paths, and we raise an error if someone passes False into them while also passing something into source_paths. For these to work, we need to be sure we're correctly detecting the stdlib and site-packages folders.

What do you think?