For my own understanding, it kinda seems like most Pants subprocess should be using

immutable_input_digests

as most won't be mutating inputs (save for

fmt

?) Is that true? Should we consider swapping the "default" so we have

input_digests

be immutable and

mutable_input_digest

for the alternative?

"immutable" really means that the

immutable_input_digest

is something to be reused over multiple

Process

invocations

Oh hmmm, so immutable over time, not immutable in a sandbox?

right

Yeah we have some large resources I'd love to "materialize" much faster 🙂

then might be an idea to think about for Pants but it would still be a separate idea from

immutable_input_digest

which is geared to things like unpacking the Go SDK once and then re-using it

Makes sense

(although re Go SDK, we used to merge it in as an input digest and switched to requiring it to be installed locally because immutable_input_digest support had not been implemented yet)

I also want this feature for

GeneratedSources

We indeed should likely be using immutable_input_digests in more places than we are now, e.g. https://github.com/pantsbuild/pants/issues/14070 Stu has only proposed that we should simplify the API before we port a bunch of stuff

I'm happy to be a sounding board/extra brain on the topic.

at one extreme, we could take the idea from https://github.com/pantsbuild/pants/issues/14070 (includelist paths that should be immutable) and invert it to excludelisting paths which should be mutable

Not that it would speed anything up, but is there already the ability to create a sandbox with

ro

properties on files?

but the current implementation would leave a lot of garbage behind… there is some amount of a hint around re-use inherent in marking something

immutable

currently, because we keep it on disk for the lifetime of

pantsd

I just started thinking about 3rd party deps tools being good citizens in the sandbox, and basically enforcing that with attrs, and maybe even users

mmm, so! there is another potential change here as of late. the

brfs

filesystem hosts digests as a FUSE filesystem. we discussed using it as an alternative to implementing something like immutable inputs, but at the time, FUSE was far too unstable on macOS to be a solution. in the last week or so though, https://www.fuse-t.org/ was announced, which replaces the unstable portion on macOS, and apparently improves performance