[benma-agent]

Let size-sensitive applications omit fragment strings from type-checking
errors so otherwise unused fragment-formatting code can be removed from
the binary.

Add an opt-in compact-errors feature that leaves Error::fragment_string
empty while preserving ErrorKind and all parsing and validation behavior.
Reuse the existing error wrapper for threshold errors so both paths follow
the same feature setting. Display still includes the error reason with an
empty fragment; detailed diagnostics remain the default.

Assisted-by: OpenAI Codex (GPT-6)

[benma]

We use this dep in the BitBox02 firmware and would appreciate this (or something similar) being included, as it would significantly reduce binary size.

[apoelstra]

Yeah, I think this is fine. Does it really reduce your binary size though? It just removes a runtime descriptor serialization.

[benma]

Yeah, I think this is fine. Does it really reduce your binary size though? It just removes a runtime descriptor serialization.

Yes, it reduces the binary size by about 6.3kb (Rust 1.96.0, opt-level = "z" and LTO).

From the agent:

The runtime fragment.to_string() call keeps the fragment serialization implementation reachable in the binary. Replacing it with String::new() lets the optimizer/linker discard the formatting and tree-traversal code that becomes unused.

I also checked the linked symbols: the DisplayNode traversal helpers and Terminal::fragment_name instantiations for both String and bitcoin::PublicKey are present with the feature disabled and disappear with it enabled.

[apoelstra]

Yeah, my guess was that this was eliminating the only callsite to Descriptor::fmt.

So, this seems pretty fragile. Like, if anybody formats a descriptor anywhere in your codebase then the formatting code would be reintroduced and the feature gate would be negated.

A better approach might be to directly feature-gate the formatting logic. But then, I wonder if the formatting logic is the best target. It seems like there are lots of "big algorithms" in this codebase and different users might like to avoid different subsets of them.