Implement debugPrint for built-in file providers

[fmeum]

Simplifies print style debugging.

[comius]

This is only for print, right? Not for str which would be a bigger change.

I'd go for a more Starlark representation, printing those providers as if they were implemented in starlark.

[comius]

cc @brandjon @tetromino @lberki
You might have an opinion about this as well...

[brandjon]

If it doesn't expose non-hermetic / non-deterministic information that we don't want Starlark users to introspect on, then it should be safe for str()/repr() and not just print().

But limiting it to print() is less of a breaking change, if that's what you're worried about. Still, I think a str() breakage in a provider isn't that big a deal.

[fmeum]

I'd go for a more Starlark representation, printing those providers as if they were implemented in starlark.

That's a good point. I've modified the methods to use struct syntax, including alphabetic ordering of keys. A positive side effect of this is that you can use buildifier to prettify the output if you want to.

I noticed that the providers that derive from StructImpl don't print their type (e.g. OutputGroupInfo is just a struct(...)). This has some benefits in terms of consistency, but it also loses information. What would you prefer?

[comius]

That's a good point. I've modified the methods to use struct syntax, including alphabetic ordering of keys. A positive side effect of this is that you can use buildifier to prettify the output if you want to.

Nice.

I noticed that the providers that derive from StructImpl don't print their type (e.g. OutputGroupInfo is just a struct(...)). This has some benefits in terms of consistency, but it also loses information. What would you prefer?

My preference would be to print out the Name in all cases (either native or Starlark). I don't know what's current state.
I'm leaning more to Name, because it matters, i.e. OutputGroupInfo(a=["x"]) != struct(a =["x"])

[fmeum]

@bazel-io fork 8.1.0

[lberki]

(late to the party)

Yes, I do have an opinion, which is that this is a good thing :)