Reject unrecognized struct tags in FromStruct#11
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phinze merged 1 commit intoApr 8, 2026
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mflags silently ignored struct tags it didn't understand, which meant typos and copy-paste mistakes from go-flags (like positional-args:"yes") would compile and run fine but never actually wire anything up. A sweep of the runtime CLI also turned up env and required tags that look intentional but have no effect today. FromStruct now validates every tag key on exported fields against the set of tags it actually reads, and returns an error listing all the unrecognized ones so you can fix them in one pass.
evanphx
approved these changes
Apr 8, 2026
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mflags has always silently ignored struct tags it doesn't recognize. That's how
positional-args:"yes"(a go-flags tag) snuck through in MIR-984 without anyone noticing, and a sweep of the runtime CLI turned upenvandrequiredtags being used on dozens of fields with no effect.FromStruct()now validates every tag key on exported fields against the set of tags it actually reads. If anything doesn't match, it returns an error listing all the unrecognized tags at once so you can fix them in one pass. The allowlist is intentionally strict (only tags mflags implements today), so upgrading mflags in the runtime repo will surface both the go-flags holdovers and the aspirationalenv/requiredtags, prompting us to either add those features or clean up the structs.Closes MIR-985