Library/Homebrew/json_api_postinstall_preflight_postflight_plan.md
This plan tracks repeated Ruby-only install behaviours that can be expressed as structured DSL data and exposed through the JSON APIs.
Install step data is stored as an ordered array of step hashes. Ruby hashes preserve insertion order, but the outer array makes JSON ordering explicit for API consumers in any language.
The first implemented high-level DSL is named steps, exposed as
post_install_steps for formulae and as preflight_steps, postflight_steps,
uninstall_preflight_steps and uninstall_postflight_steps for casks. The
blocks are deliberately narrow: they may only contain literal calls to the
step DSL, with no wider Ruby execution and no access to the surrounding formula
or cask DSL.
The initial step methods shadow common FileUtils naming where practical:
mkdir/mkdir_p, touch, move/mv, move_children and
symlink/ln_s/ln_sf. Formula steps default mkdir and touch paths to
var, and source/target paths to prefix. Cask steps default base,
source_base and target_base to staged_path.
Formula post_install_steps may temporarily coexist with post_install so tap
conversions can peel supported repeated statements out of larger hooks. Runtime
handling runs formula steps first and then runs post_install last for the
remaining Ruby work. Cask *flight_steps still replace the matching legacy
flight block because cask artifacts already carry replacement semantics and
warn when both forms are present. Post-install or postflight steps are not
sandboxed for this iteration because they run only Homebrew-owned structured
operations. The runner shape leaves room to sandbox future step types that
invoke non-Homebrew code. Future cask work should sandbox all *flight run
scripts from non-Homebrew and non-system sources, for example scripts shipped
by upstream artifacts.
The final target is not to keep legacy hooks and structured steps side by side.
Once homebrew/core and homebrew/cask have been converted, all
homebrew/core post_install blocks and all homebrew/cask legacy
preflight, postflight, uninstall_preflight and uninstall_postflight
blocks should be removed for cases covered by structured steps. After that,
Homebrew/brew should reject side-by-side usage again and deprecate
post_install and legacy cask flight blocks for third-party tap usage.
During the temporary bridge, structured steps must appear before the matching
legacy block to make the runtime order obvious: post_install_steps before
post_install, and each cask *flight_steps stanza before its matching legacy
*flight stanza.
For each future operation type, check homebrew/core and homebrew/cask
separately and add formula support only when needed by homebrew/core or cask
support only when needed by homebrew/cask.
Specialised method variants, such as using: :postgresql_initdb, require at
least 3 current usages across homebrew/core and homebrew/cask before
being added to the structured DSL.
When adding install step DSL methods, update the matching RuboCop allow-list so formula or cask tap syntax checks accept the new method in the same context.
RuboCop autocorrection converts the simplest existing post_install and
*flight Ruby blocks to steps blocks when every statement is a supported file
preparation operation with literal paths and known bases. Future post-install
and *flight DSLs should include the same style of conservative autocorrection
from the matching legacy Ruby pattern where possible.
Before opening follow-up PRs, run bundle exec rake lint from docs/ to catch
markdown lint issues and run brew style homebrew/core homebrew/cask to catch
tap-wide formula or cask opportunities exposed by the new DSLs.
From PR 5 onwards each new DSL step type ships as four separate commits/branches/PRs rather than one combined change:
Homebrew/brew: the step method(s), runner execution,
shared step block allow-list entries so tap syntax checks accept the method,
JSON API round-tripping, tests and docs. No legacy-to-steps autocorrection.Homebrew/brew that enforce and audit the DSL:
conflict checks against legacy blocks when the step form replaces them, and
conservative autocorrection from the matching legacy Ruby pattern.homebrew/core: convert formulae to the new DSL.homebrew/cask: convert casks to the new DSL.Merge order is 1, 3, 4, 2. PR 1 ships the DSL and its allow-list so
taps can adopt it; PR 2 (the enforcing/autocorrecting cops) merges last so it
does not flag formulae or casks before the DSL is widely available. After PR 1
is merged and before PRs 3 and 4 are merged, cut a new Homebrew/brew
stable release so homebrew/core and homebrew/cask CI have the new DSL.
Each operation PR should also clone, or create clean local worktrees for,
homebrew/core and homebrew/cask, make the corresponding tap changes and
verify the changed taps with ./bin/brew style, ./bin/brew audit and
./bin/brew readall. The local-tap workflow is:
./bin/brew tap --force homebrew/core../bin/brew tap --force homebrew/cask../bin/brew --repository homebrew/core and
./bin/brew --repository homebrew/cask../bin/brew style and ./bin/brew audit for changed formulae
or casks, then tap-wide ./bin/brew readall homebrew/core and
./bin/brew readall homebrew/cask.If one tap has no applicable changes for an operation, record that with filenames from the scan rather than leaving the tap unchecked.
Long-term success for each operation PR means a tap conversion can remove the
whole legacy hook for the case it targets. For formulae, the temporary bridge
also allows partial conversions: move the supported repeated statements into
post_install_steps, leave the remaining Ruby in post_install and rely on
post_install running last. For casks, the matching *flight block should
still disappear because cask steps continue to replace legacy flight blocks. If
a candidate formula step only covers one statement in a current hook, either
include the remaining repeated behaviour as named steps for the same case or
document the remaining legacy work with filenames and use the bridge only while
the follow-up named step is being built.
Local all-file scan source: homebrew/core at ced17121766b. The scan read
all 8,459 files under Formula/. Pattern buckets overlap because one
post_install can create directories, write files and run commands.
144 of 8,459 formulae define post_install.post_install_defined is the only install-time Ruby execution flag exposed
through the formula JSON API for bottle installs. I did not find a
caskfile-only-style source download gate for other formula DSL at bottle
install time; formula source downloads for API-loaded formulae are used for
source builds, local patches and resources rather than post-install metadata
gaps.79 create shared directories in var, etc or HOMEBREW_PREFIX.
Examples: Formula/g/glib.rb, Formula/l/languagetool.rb and
Formula/m/mecab.rb.112 write or patch default configuration/data files.
Examples: Formula/n/[email protected], Formula/w/wemux.rb and
Formula/p/php.rb.27 rebuild desktop/cache databases.
Examples: Formula/g/gjs.rb, Formula/g/geocode-glib.rb and
Formula/e/efl.rb.19 initialise service data directories.
Examples: Formula/m/mariadb.rb, Formula/m/mysql.rb,
Formula/p/[email protected] and Formula/p/percona-server.rb.17 update certificate/trust state.
Examples: Formula/o/[email protected], Formula/lib/libressl.rb and
Formula/g/gnutls.rb.Formula/i/icecast.rb already uses post_install_steps. Remaining touch
examples such as Formula/r/r.rb and Formula/n/nethack.rb also contain
symlink or permission work, so they need full-hook coverage before
conversion.Refresh the formula buckets with:
rg -n 'def post_install|\.mkpath|mkdir_p|FileUtils\.mkdir|\bmkdir\b' Library/Taps/homebrew/homebrew-core/Formula
rg -n 'def post_install|\.write\b|\.atomic_write\b|File\.write|\binreplace\b' Library/Taps/homebrew/homebrew-core/Formula
rg -n 'glib-compile-schemas|gio-querymodules|gdk-pixbuf-query-loaders|gtk.*update-icon-cache|update-mime-database|update-desktop-database' Library/Taps/homebrew/homebrew-core/Formula
rg -n 'initdb|mysqld.*initialize-insecure|mysql_install_db|PG_VERSION|general_log\.CSM|mysql/user\.frm' Library/Taps/homebrew/homebrew-core/Formula
rg -n 'c_rehash|cert\.pem|openssl.*rehash|\btrust\b|certifi|ca-certificates' Library/Taps/homebrew/homebrew-core/Formula
rg -n 'FileUtils\.touch|\.touch\b|\btouch\b' Library/Taps/homebrew/homebrew-core/Formula
Local all-file scan source: homebrew/cask at 4eee0394c96c. The scan read
all 7,741 files under Casks/. Pattern buckets overlap because one flight
block can prepare files, change permissions and run commands.
193 of 7,741 casks currently require the Ruby source at install time
through Cask#caskfile_only?: 170 because of legacy *flight blocks and
23 because of language blocks only. 27 casks have language blocks in
total, so 4 have both language blocks and legacy *flight blocks.on_* variations are serialised through API data. *_steps artifacts are
also serialised and should not make caskfile_only? true.68 flight blocks create directories, touch files or write small files.
Examples: Casks/a/android-ndk.rb, Casks/b/blender.rb and
Casks/c/chromium.rb.13 move, copy or symlink files during install or uninstall.
Examples: Casks/g/gcloud-cli.rb, Casks/l/libcblite.rb and
Casks/m/miniconda.rb.21 change permissions and 36 change ownership.
Examples: Casks/b/bitcoin-core.rb, Casks/a/anaconda.rb and
Casks/p/parallels.rb.8 legacy flight blocks directly invoke /usr/bin/security for keychain
certificate cleanup.
Examples: Casks/c/charles.rb, Casks/a/autofirma.rb and
Casks/b/betwixt.rb.27 casks use language blocks. Large examples include
Casks/f/firefox.rb, Casks/l/libreoffice-language-pack.rb and
Casks/t/thunderbird.rb.Refresh the cask buckets with:
rg -n 'preflight|postflight|FileUtils\.mkdir|mkdir_p|\.mkpath|FileUtils\.touch|\.touch\b|\.write\b|File\.write|atomic_write' Library/Taps/homebrew/homebrew-cask/Casks
rg -n 'FileUtils\.(mv|cp|cp_r|ln_s|ln_sf)|\b(mv|cp|cp_r|ln_s|ln_sf)\b|make_symlink|File\.symlink' Library/Taps/homebrew/homebrew-cask/Casks
rg -n 'set_permissions|chmod|FileUtils\.chmod|set_ownership|chown|FileUtils\.chown' Library/Taps/homebrew/homebrew-cask/Casks
rg -n '/usr/bin/security|system_command\s+"/usr/bin/security"|security\s+(delete|add|find)-' Library/Taps/homebrew/homebrew-cask/Casks
rg -n '^\s*language\b' Library/Taps/homebrew/homebrew-cask/Casks
Formula JSON API installs need to preserve post_install because it is the
only install-time Ruby hook recorded for bottle installs. The hook runs from
the formula stored in the installed keg, while source builds and local patch
handling use Homebrew::API::Formula.source_download_formula for build-time
reasons outside this post-install DSL work.
Cask JSON API installs use Homebrew::API::Cask.source_download_cask when
Cask#caskfile_only? is true. Today that is true when a cask has any legacy
preflight, postflight, uninstall_preflight or uninstall_postflight
block, or when it has language blocks. Legacy flight blocks need the source
because API data only records that a block exists, not the Ruby body. Language
blocks need the source because the API stores available language codes, but not
the selected block return value or stanza effects; language-specific URLs must
be resolved before the download can be enqueued.
Store supported installed cask metadata as regular <token>.json, not Ruby
caskfiles or internal JSON. Casks with uninstall_preflight or
uninstall_postflight Ruby blocks should keep using Ruby caskfiles in the
Caskroom until those blocks are ported to structured JSON data. The installed
caskfile is a post-install snapshot, so it should only retain data that can be
useful after installation has finished. This lets future uninstall, reinstall,
upgrade and zap runs reload supported installed metadata without evaluating the
original Ruby caskfile.
The installed JSON is deliberately minimal. It relies on
INSTALL_RECEIPT.json for receipt-owned data such as the installed cask
version and uninstallable artifacts, and only keeps data not otherwise
available after installation, such as url_specs.only_path when needed to
reconstruct staged artifact sources. It omits the full API snapshot so future
JSON API or DSL changes cannot affect post-install operations through fields
that are not needed after installation.
The installed JSON omits legacy preflight and postflight Ruby block
placeholders because JSON cannot represent their block bodies and they are not
needed after installation. Casks with uninstall_preflight or
uninstall_postflight Ruby blocks must remain backed by Ruby metadata so those
blocks continue to run on uninstall, zap, reinstall and upgrade. The goal is to
replace those Ruby blocks with structured uninstall step DSLs so they can be
migrated to JSON too.
The brew update migration should convert existing supported Caskroom .rb
and .internal.json caskfiles to regular .json caskfiles.
As the cask step DSLs grow, keep migrating post-install behaviour from legacy Ruby flight blocks into structured JSON data so less installed cask behaviour is stripped during metadata serialisation.
Formula/l/languagetool.rb: post_install_steps with
mkdir "log/languagetool", base: :var.Formula/i/icecast.rb: post_install_steps with one mkdir and two
touch steps under var/"log/icecast".Formula/o/[email protected]: post_install_steps with a forced symlink from
ca-certificates pkgetc/"cert.pem" into the formula pkgetc.Casks/8/86box.rb: preflight_steps with a home-directory mkdir for
the shared ROM directory.Casks/k/klayout.rb: preflight_steps with move_children from the
staged root into the nested KLayout directory.Casks/l/libcblite.rb: postflight_steps with relative symlink steps
marked for uninstall cleanup.Add install steps framework.
Scope: shared ordered step data, a confined steps DSL, a shared runner, cask
stanza ordering, RuboCop registration, conflict checks and the refactor plan.
This PR does not wire formula or cask JSON API output or run steps from
install phases.
Estimated existing formulae/casks affected: 0 runtime behaviour changes.
It creates the guardrails for the later 144 formulae with post_install
blocks and 170 casks with flight blocks, but no existing formula or cask
opts into the new DSL yet.
Notes for the next PRs: keep the step payload as an ordered array; keep
_steps blocks literal-only; for formulae, steps run before a remaining
post_install hook during the temporary bridge; for casks, steps win over
the legacy Ruby block with a runtime warning. Add conservative autocorrection
only where every legacy statement maps mechanically.post_install_steps.
Commit: Add formula install steps.
Scope: formula DSL, formula JSON API data, API formula loading, installer and
brew postinstall execution, formula cookbook docs and formula fixture.
Estimated existing formulae affected: 144 formulae currently define
post_install. The first useful conversion surface is roughly 79 formulae
creating shared directories; parts of the 19 service data directory and
17 certificate/trust formulae may also
move once their operations fit the supported step set. Runtime behaviour
changes only for formulae that opt into post_install_steps.
Notes for implementation: default mkdir/touch to var and source/target
paths to prefix; expose the ordered array through FormulaStruct; make
post_install_steps run before any remaining post_install; document that
the two forms may coexist only as an incremental conversion bridge. Keep the
tap-wide autocorrect audit in a follow-up commit so the implementation can
land before converted formulae.Add cask install steps.
Scope: cask artifacts for preflight_steps, postflight_steps,
uninstall_preflight_steps and uninstall_postflight_steps, cask API
serialisation through artifact data, installer casts, cask cookbook docs,
cask fixture/API loader coverage.
Estimated existing casks affected: 170 casks currently use flight blocks.
The first useful conversion surface is roughly 68 casks that create/touch
files or directories and the supported subset of 13 casks that move or
symlink files. Runtime behaviour changes only for casks that opt into the
new *_steps stanzas.
Notes for implementation: default all relative cask paths to staged_path;
keep steps as normal cask artifacts so API loader round-trips work; make
steps remove/override the matching Ruby flight artifact with a warning; keep
uninstall: true symlink cleanup available for install-phase steps. Keep
the tap-wide autocorrect audit in a follow-up commit so the implementation
can land before converted casks.27 formulae run rebuild
tools such as glib-compile-schemas, gtk*-update-icon-cache,
gio-querymodules, gdk-pixbuf-query-loaders, update-mime-database and
update-desktop-database; no cask count was identified in the initial scan.
Scope: shared named action types for GSettings schemas, GIO modules,
GDK Pixbuf loaders, GTK icon caches, MIME databases and desktop databases,
runner dispatch through Homebrew-owned tools and docs.
Notes for implementation: add named action types rather than raw commands;
define idempotence and failure handling; decide whether any action invokes
non-Homebrew code and should be ready for future sandboxing. Land RuboCop
autocorrection and tap-wide conversions in a separate follow-up after the
new DSL methods are available in a stable Homebrew release.112 formulae write or
patch default configuration/data files, and a subset of the 68 file-prep
cask flight blocks write small files.
Notes for implementation: use scoped token expansion instead of arbitrary
Ruby interpolation; require literal templates or API-safe template data;
define overwrite, unless_exists and upgrade semantics before adding
autocorrection.
write DSL in Homebrew/brew.
Commit: Add install step config writes.
Scope: shared write step method with base: and overwrite:, runner
execution that skips existing files unless overwrite is set, formula and
cask step block allow-list entries, non-interpolated heredoc (dstr)
support so write content can use heredocs, runner tests and cookbook
docs. Default behaviour preserves existing files so user edits survive
upgrades. Content stays a literal template in the JSON API but supports a
fixed {{...}} token allow-list (HOMEBREW_PREFIX, prefix, opt_prefix,
bin, var, etc, pkgetc, version, version.major_minor; casks add
staged_path and appdir) expanded at install time; any other {{...}}
is left verbatim. Dynamic interpolation (random cookies, popen-derived
paths, File.read rewrites) is intentionally out of scope and stays as
legacy Ruby.write enforcing RuboCops in Homebrew/brew.
Commit: Add install step write cops.
Scope: formula and cask RuboCops conservatively autocorrect literal,
newline-terminated .write, .atomic_write and File.write legacy
blocks to *_steps write calls with overwrite: true. Writes without
trailing newlines stay as legacy Ruby because the step DSL appends one.homebrew/core formulae to write.
Branch install-steps-config-write, commits
tronbyt-server: use post_install_steps and node@18: use post_install_steps. tronbyt-server mapped with literal content;
node@18 became convertible once {{HOMEBREW_PREFIX}} token expansion
landed (its whole post_install was one atomic_write). All other
.write formulae interpolate paths, interpolate unsupported values, or
run unsupported Ruby (cp_r, inreplace, safe_popen_read, loops).homebrew/cask casks to write.
Branch install-steps-config-write, commit
dnsmonitor: use postflight_steps. Only dnsmonitor had a flight block
with literal content. Token expansion does not unblock more casks: the
{{appdir}}-content flight writes all target a shimscript local that is
also wired to a binary stanza, and the literal-path LibreOffice packs
interpolate an unsupported language token and run system_command.Add install step data directories.
Estimated existing formulae/casks affected: about 19 formulae initialise
service data directories.
Scope: formula init_data_dir step, runner execution, formula step block
allow-list entries, fixture coverage and formula cookbook docs. The step
creates service data directories and supports named bootstrap commands for
PostgreSQL initdb, MySQL mysqld --initialize-insecure and MariaDB
mysql_install_db, including the marker-file and CI-skip guards used by
current homebrew/core formulae. Permission and ownership metadata were
skipped because current tap usages fit future permission/ownership action
work instead. PostgreSQL versioned link maintenance is handled by generic
link_dir and link_children steps. MySQL conflicting configuration
warnings stay as legacy Ruby until a separate named action is added.
Local tap work for this step was prepared with
./bin/brew tap --force homebrew/core and
./bin/brew tap --force homebrew/cask. In this checkout,
./bin/brew --repository homebrew/core resolves to
Library/Taps/homebrew/homebrew-core at 369b5855942, and
./bin/brew --repository homebrew/cask resolves to
Library/Taps/homebrew/homebrew-cask at 16a3a6e4562.
Success target for tap conversions: use the bridge to move database
bootstrap statements out of every current MySQL and PostgreSQL hook, including
Formula/m/mysql.rb, Formula/m/[email protected], Formula/m/[email protected],
Formula/p/[email protected] and Formula/p/[email protected], while their
remaining warning or link maintenance work stays in post_install until
separate named actions cover it. Fully remove post_install from
bootstrap-only formulae such as Formula/m/mariadb.rb,
Formula/m/[email protected], Formula/m/[email protected],
Formula/m/[email protected], Formula/m/[email protected],
Formula/m/[email protected], Formula/p/[email protected],
Formula/p/[email protected], Formula/p/[email protected] and
Formula/p/[email protected]. Verify the homebrew/core conversion with
./bin/brew style homebrew/core, targeted ./bin/brew audit --strict --online --formula ... for the changed formulae and ./bin/brew readall homebrew/core.17 formulae update
certificate/trust state and 8 cask flight blocks invoke
/usr/bin/security for keychain certificate cleanup.
Notes for implementation: separate formula-owned symlinked certificate
actions from keychain mutations; keychain work likely counts as non-Homebrew
code and should be prepared for sandbox policy decisions.21 casks change permissions and
36 change ownership.
Notes for implementation: match the existing flight mini-DSL
set_permissions and set_ownership semantics first; define sudo/root
requirements and uninstall behaviour before adding API output.27 casks use language blocks, with large
examples including Casks/f/firefox.rb,
Casks/l/libreoffice-language-pack.rb and Casks/t/thunderbird.rb.
Notes for implementation: represent language-specific URLs, checksums and
returned values without evaluating cask Ruby before fetch; keep the public API
shape friendly to clients that need to choose one language deterministically.