Don't compact service_args in FormulaStruct#serialize

[Rylan12]

Fixes the following issue:

$ brew info nginx
==> nginx ✘: stable 1.29.8 (bottled), HEAD
HTTP(S) server and reverse proxy, and IMAP/POP3 proxy server
https://nginx.org/
Not installed
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/n/nginx.rb
License: BSD-2-Clause
==> Dependencies
Required (2): openssl@3 ✔, pcre2 ✔
==> Options
--HEAD
 Install HEAD version
Defining service run_type with argument immediate
Defining service working_dir with argument /opt/homebrew
Defining service keep_alive with argument
Error: Parameter 'value': Expected type T.any(T::Boolean, T::Hash[Symbol, T.untyped]), got type NilClass
Caller: /opt/homebrew/Library/Homebrew/formulary.rb:315
Definition: /opt/homebrew/Library/Homebrew/service.rb:169 (Homebrew::Service#keep_alive)
...

Since service_args are defined by the service DSL and only include methods explicitly called, we shouldn't compact away falsey values. For example:

keep_alive successful_exit: false

Internally, this sets @keep_alive = { successful_exit: false } which has a different effect from @keep_alive = nil which is what you get if you don't call keep_alive at all.

However, the current FormulaStruct serialization filters away all falsey values, reducing this to keep_alive nil which causes a type error. In reality, we need the falsey DSL values to be preserved.

The values passed to service_args are computed by Homebrew::Service.from_hash which only includes DSLs that were explicitly used, so this doesn't add any unnecessary information to the serialized files.

Please merge at the same time or after Homebrew/formulae.brew.sh#2173

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[Copilot]

Pull request overview

This PR adjusts FormulaStruct#serialize to preserve falsy values inside service_args when generating the formula API hash, preventing invalid service DSL reconstruction (e.g., keep_alive successful_exit: false being compacted into keep_alive nil and triggering Sorbet runtime type errors during brew info/API formula loading).

Changes:

• Preserve service_args across Utils.deep_compact_blank so false (and other “blank” values per ActiveSupport) are not dropped from service DSL arguments.
• Return the compacted hash explicitly after restoring service_args.
• Remove now-unneeded service_args arg-pair formatting in FormulaStruct.deserialize.

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[Rylan12]

Note: technically this isn't backward compatible, and in between when this is merged and formulae.brew.sh is regenerated, there is a very small number of formulae¹ that will not be installable. Since I think only me and Mike have this set, I'll just avoid this by merging when you're asleep 😅 (or you can merge it while I'm asleep). As long as it merges with or after Homebrew/formulae.brew.sh#2173, the broken period will be a max of 15 minutes.

Footnotes

1. 34 formulae that set either keep_alive successful_exit: false or keep_alive always: false in service do. It will be a type error, and temporarily unsetting HOMEBREW_REALLY_USE_INTERNAL_API will fix it. ↩

[MikeMcQuaid]

Thanks!