Customize `StrictnessLevel`

[rvhonorato]

I'm using pdbtbx to validate input PDBs in our new frontend via wasm.

While implementing it I've came acrross the StrictnessLevel which is a nice way to be more or less permissive in the format. For our application in specific, some of the things that are marked as InvalidatingError can actually be handled by the molecular engine (CNS).

Before I write something to automatically fix these so that they pass the pdbtbx validation I think its best to ask first if; is there a way to customize the strictness to allow for certain errors?

[douweschulte]

There currently is not. But with PR #126 more fine grained control is added to the opening of files, if something like this is useful we could think about a way of allowing control here.

The point of invalidation errors though is that I found them to be so bad I could not unambiguously parse the file, this judgement is just my own though so changes can be made. Maybe the easiest way would be to add a strictnesslevel in between two already present and allow some of the warnings there. Or potentially if we want to go the full control via OpenOptions route we could give a list of errors/warnings to ignore there.

[OWissett]

I think that this is possible, we could potentially change how we use the strictness level, and make it work more like a bitfield options approach that you'd use in C/C++. I'm not sure how idiomatic bitfields are in Rust, I think fine for internal usage?

The idea would be that we keep the current StrictnessLevels, but make it so that that type actually sits on top of a bitfield which controls which types of errors are raised. So the current levels will have certain default bits set, but we also then expose an API for constructing custom StrictnessLevels, where in some contexts people want certain checks but not others.

The next thing I wanted to ask, is would it make sense to have it so that PDBTBX can automatically fix simple issues with PDBs? We could have that as a setting on the new ReadOptions mechanism, e.g. ReadOptions::auto_fix()

[douweschulte]

Bitfields do not have built in support but there are crates for it. Keeping it internal sounds good.

I like the sound of auto_fix but some fine grained control might be needed here as well. Right now I mainly have the renumber function which could become part of the auto_fix.

[OWissett]

My lab has a PDB fixing script in python which performs lots of corrections for PDB files, it might be interesting to add some of them to PDBTBX?

Again, I think this comes down to what do we want from PDBTBX? I think that this is also potential feature creep (I know I am the one who suggested the auto_fix function).

[OWissett]

I do think that having PDB validation and fixing tools would make sense for this crate, but it might be a good idea to add them behind a feature flag, depending on how much code it takes.

[rvhonorato]

+1 for auto_fix!

[OWissett]

I will checkout a branch to have a look at implementing it. @rvhonorato are you able to give me a list of which checks you care most about and want changing?

[OWissett]

I am currently blocked by #126 since I will need to use what this adds.

[rvhonorato]

I will checkout a branch to have a look at implementing it. @rvhonorato are you able to give me a list of which checks you care most about and want changing?

The ones I've found more frequently are:

• TER after chain break and after chain changes
• Truncate/Pad lines to 80 chars
• add END record to the end of the file