Use HOMEBREW_CELLAR_PLACEHOLDER

Similarly to HOMEBREW_PREFIX_PLACEHOLDER, this allows the substitution
of HOMEBREW_CELLAR in JSON output when using the API.

Fixes #15668.

Library/Homebrew/cask/cask_loader.rb

@@ -349,6 +349,7 @@ module Cask
         string.to_s
               .gsub(HOMEBREW_HOME_PLACEHOLDER, Dir.home)
               .gsub(HOMEBREW_PREFIX_PLACEHOLDER, HOMEBREW_PREFIX)
+              .gsub(HOMEBREW_CELLAR_PLACEHOLDER, HOMEBREW_CELLAR)
               .gsub(HOMEBREW_CASK_APPDIR_PLACEHOLDER, appdir)
       end
 

Library/Homebrew/extend/api_hashable.rb

@@ -8,9 +8,11 @@ module APIHashable
 
     # Apply monkeypatches for API generation
     @old_homebrew_prefix = HOMEBREW_PREFIX
+    @old_homebrew_cellar = HOMEBREW_CELLAR
     @old_home = Dir.home
     Object.send(:remove_const, :HOMEBREW_PREFIX)
     Object.const_set(:HOMEBREW_PREFIX, Pathname.new(HOMEBREW_PREFIX_PLACEHOLDER))
+    Object.const_set(:HOMEBREW_CELLAR, Pathname.new(HOMEBREW_CELLAR_PLACEHOLDER))
     ENV["HOME"] = HOMEBREW_HOME_PLACEHOLDER
 
     @generating_hash = true
@@ -22,6 +24,8 @@ module APIHashable
     # Revert monkeypatches for API generation
     Object.send(:remove_const, :HOMEBREW_PREFIX)
     Object.const_set(:HOMEBREW_PREFIX, @old_homebrew_prefix)
+    Object.send(:remove_const, :HOMEBREW_CELLAR)
+    Object.const_set(:HOMEBREW_CELLAR, @old_homebrew_cellar)
     ENV["HOME"] = @old_home
 
     @generating_hash = false

Library/Homebrew/formula.rb

@@ -2173,7 +2173,8 @@ class Formula
       "conflicts_with"           => conflicts.map(&:name),
       "conflicts_with_reasons"   => conflicts.map(&:reason),
       "link_overwrite"           => self.class.link_overwrite_paths.to_a,
-      "caveats"                  => caveats&.gsub(HOMEBREW_PREFIX, HOMEBREW_PREFIX_PLACEHOLDER),
+      "caveats"                  => caveats&.gsub(HOMEBREW_PREFIX, HOMEBREW_PREFIX_PLACEHOLDER)
+                                           &.gsub(HOMEBREW_CELLAR, HOMEBREW_CELLAR_PLACEHOLDER),
       "installed"                => [],
       "linked_keg"               => linked_version&.to_s,
       "pinned"                   => pinned?,

Library/Homebrew/formulary.rb

@@ -342,6 +342,7 @@ module Formulary
       def caveats
         self.class.instance_variable_get(:@caveats_string)
             &.gsub(HOMEBREW_PREFIX_PLACEHOLDER, HOMEBREW_PREFIX)
+            &.gsub(HOMEBREW_CELLAR_PLACEHOLDER, HOMEBREW_CELLAR)
             &.gsub(HOMEBREW_HOME_PLACEHOLDER, Dir.home)
       end
 

Library/Homebrew/global.rb

@@ -57,6 +57,7 @@ HOMEBREW_MACOS_ARM_DEFAULT_REPOSITORY = ENV.fetch("HOMEBREW_MACOS_ARM_DEFAULT_RE
 HOMEBREW_LINUX_DEFAULT_PREFIX = ENV.fetch("HOMEBREW_LINUX_DEFAULT_PREFIX").freeze
 HOMEBREW_LINUX_DEFAULT_REPOSITORY = ENV.fetch("HOMEBREW_LINUX_DEFAULT_REPOSITORY").freeze
 HOMEBREW_PREFIX_PLACEHOLDER = "$HOMEBREW_PREFIX"
+HOMEBREW_CELLAR_PLACEHOLDER = "$HOMEBREW_CELLAR"
 # Needs a leading slash to avoid `File.expand.path` complaining about non-absolute home.
 HOMEBREW_HOME_PLACEHOLDER = "/$HOME"
 HOMEBREW_CASK_APPDIR_PLACEHOLDER = "$APPDIR"

Library/Homebrew/service.rb

@@ -633,6 +633,7 @@ module Homebrew
     sig { params(string: String).returns(String) }
     def self.replace_placeholders(string)
       string.gsub(HOMEBREW_PREFIX_PLACEHOLDER, HOMEBREW_PREFIX)
+            .gsub(HOMEBREW_CELLAR_PLACEHOLDER, HOMEBREW_CELLAR)
             .gsub(HOMEBREW_HOME_PLACEHOLDER, Dir.home)
     end
   end

Library/Homebrew/sorbet/rbi/hidden-definitions/hidden.rbi

@@ -5174,6 +5174,7 @@ class Object
   HOMEBREW_CASK_APPDIR_PLACEHOLDER = ::T.let(nil, ::T.untyped)
   HOMEBREW_CASK_TAP_CASK_REGEX = ::T.let(nil, ::T.untyped)
   HOMEBREW_CELLAR = ::T.let(nil, ::T.untyped)
+  HOMEBREW_CELLAR_PLACEHOLDER = ::T.let(nil, ::T.untyped)
   HOMEBREW_CORE_DEFAULT_GIT_REMOTE = ::T.let(nil, ::T.untyped)
   HOMEBREW_DATA_PATH = ::T.let(nil, ::T.untyped)
   HOMEBREW_DEFAULT_CACHE = ::T.let(nil, ::T.untyped)