format: the sentence saying which words a setting takes is written in one place

[donislawdev]

Two places in the archive package listed the values of a closed set by hand, in the registry's order and the registry's phrasing - compression and entry_owner. The registry builds that sentence from the declared set, so both were copies of it with nothing comparing the two.

Identical copies are the dangerous kind, because nothing goes red while they agree, and they agreed. The day they stop agreeing is the day somebody adds a value to the declaration: the registry lists it, tfg formats prints it, the window offers it, and the hand written line does not.

The second copy arrived through the change that closed the first half of this, in the same week the note warning about copies was written.

What changes for a person using the tool

Nothing. Measured on the built binary: --set compression=TURBO and --set entry_owner=USER are refused by the registry, exit 4, in the registry's own words. Both hand written branches sit behind that check and no surface reaches them - they are there for a direct caller, which is what a guard is. No changelog entry, because there is nothing a person would notice.

Guards

Three, each proven by mutation.

• The sentence is built in one place. Read from string literals through the parser rather than from the file text, so a comment explaining the rule may still name the sentence.
• A refusal quotes the registry. This catches a copy that was reworded rather than repeated, which the first guard cannot see.
• Every word the declaration offers is one its reader accepts. This closes the hole the fix itself opens: Allows says nothing is wrong with a value it allows, so a word added to the set and not handled by the reader would arrive as a refusal with an empty reason.

The first mutation is worth naming: it puts back a sentence identical to the one the registry builds, so the second guard stays green under it. That is the whole shape of the problem.

Checks

Full go test green, preflight --quick green on all twelve checks, staleness clean at 727 entries.

🤖 Generated with Claude Code