Overhaul Formula/Cask JSON generation

- Use constants for placeholders
- Monkeypatch to set `HOMEBREW_PREFIX` consistently to placeholder
- Use environment variable to set `Dir.home` consistently to placeholder
- Use `appdir` short-circuit to set `Cask#appdir` consistently to placeholder
- Use `Cask.generating_hash!` to enable "generating mode" with these patches
- Fix `Formula#caveats` from JSON

Fixes #14505
Fixes #14595

Library/Homebrew/cask/cask.rb

@@ -19,10 +19,48 @@ module Cask
     extend Searchable
     include Metadata
 
-    attr_reader :token, :sourcefile_path, :source, :config, :default_config, :loaded_from_api
+    HOME_PLACEHOLDER = "$HOME"
+    HOMEBREW_PREFIX_PLACEHOLDER = "$HOMEBREW_PREFIX"
+    APPDIR_PLACEHOLDER = "$APPDIR"
+
+    # TODO: can be removed when API JSON is regenerated with HOMEBREW_PREFIX_PLACEHOLDER.
+    HOMEBREW_OLD_PREFIX_PLACEHOLDER = "$(brew --prefix)"
+
+    attr_reader :token, :sourcefile_path, :source, :config, :default_config, :loaded_from_api, :loader
 
     attr_accessor :download, :allow_reassignment
 
+    class << self
+      def generating_hash!
+        return if generating_hash?
+
+        # Apply monkeypatches for API generation
+        @old_homebrew_prefix = HOMEBREW_PREFIX
+        @old_home = Dir.home
+        Object.send(:remove_const, :HOMEBREW_PREFIX)
+        Object.const_set(:HOMEBREW_PREFIX, Pathname(HOMEBREW_PREFIX_PLACEHOLDER))
+        ENV["HOME"] = HOME_PLACEHOLDER
+
+        @generating_hash = true
+      end
+
+      def generated_hash!
+        return unless generating_hash?
+
+        # Revert monkeypatches for API generation
+        Object.send(:remove_const, :HOMEBREW_PREFIX)
+        Object.const_set(:HOMEBREW_PREFIX, @old_homebrew_prefix)
+        ENV["HOME"] = @old_home
+
+        @generating_hash = false
+      end
+
+      def generating_hash?
+        @generating_hash ||= false
+        @generating_hash == true
+      end
+    end
+
     def self.all
       # TODO: ideally avoid using ARGV by moving to e.g. CLI::Parser
       if ARGV.exclude?("--eval-all") && !Homebrew::EnvConfig.eval_all?
@@ -45,13 +83,14 @@ module Cask
     end
 
     def initialize(token, sourcefile_path: nil, source: nil, tap: nil, config: nil,
-                   allow_reassignment: false, loaded_from_api: false, &block)
+                   allow_reassignment: false, loaded_from_api: false, loader: nil, &block)
       @token = token
       @sourcefile_path = sourcefile_path
       @source = source
       @tap = tap
       @allow_reassignment = allow_reassignment
       @loaded_from_api = loaded_from_api
+      @loader = loader
       @block = block
 
       @default_config = config || Config.new
@@ -251,7 +290,7 @@ module Cask
         "outdated"       => outdated?,
         "sha256"         => sha256,
         "artifacts"      => artifacts_list,
-        "caveats"        => (to_h_string_gsubs(caveats) unless caveats.empty?),
+        "caveats"        => (caveats unless caveats.empty?),
         "depends_on"     => depends_on,
         "conflicts_with" => conflicts_with,
         "container"      => container&.pairs,
@@ -315,52 +354,10 @@ module Cask
         when Artifact::AbstractFlightBlock
           # Only indicate whether this block is used as we don't load it from the API
           { artifact.summarize => nil }
-        when Artifact::Relocated
-          # Don't replace the Homebrew prefix in the source path since the source could include /usr/local
-          source, *args = artifact.to_args
-          { artifact.class.dsl_key => [to_h_string_gsubs(source, replace_prefix: false), *to_h_gsubs(args)] }
         else
-          { artifact.class.dsl_key => to_h_gsubs(artifact.to_args) }
+          { artifact.class.dsl_key => artifact.to_args }
         end
       end
     end
-
-    def to_h_string_gsubs(string, replace_prefix: true)
-      string = string.to_s.gsub(Dir.home, "$HOME")
-
-      if replace_prefix
-        string.gsub(HOMEBREW_PREFIX, "$(brew --prefix)")
-      else
-        string.gsub(Caskroom.path, "$(brew --prefix)/Caskroom")
-      end
-    end
-
-    def to_h_array_gsubs(array)
-      array.to_a.map do |value|
-        to_h_gsubs(value)
-      end
-    end
-
-    def to_h_hash_gsubs(hash)
-      hash.to_h.transform_values do |value|
-        to_h_gsubs(value)
-      end
-    rescue TypeError
-      to_h_array_gsubs(hash)
-    end
-
-    def to_h_gsubs(value)
-      return value if value.blank?
-
-      if value.respond_to? :to_h
-        to_h_hash_gsubs(value)
-      elsif value.respond_to? :to_a
-        to_h_array_gsubs(value)
-      elsif [true, false].include? value
-        value
-      else
-        to_h_string_gsubs(value)
-      end
-    end
   end
 end

Library/Homebrew/cask/cask_loader.rb

@@ -237,13 +237,9 @@ module Cask
           return FromContentLoader.new(cask_source).load(config: config)
         end
 
-        # convert generic string replacements into actual ones
-        json_cask[:artifacts] = json_cask[:artifacts].map(&method(:from_h_hash_gsubs))
-        json_cask[:caveats] = from_h_string_gsubs(json_cask[:caveats])
-
         tap = Tap.fetch(json_cask[:tap]) if json_cask[:tap].to_s.include?("/")
 
-        Cask.new(token, tap: tap, source: cask_source, config: config, loaded_from_api: true) do
+        Cask.new(token, tap: tap, source: cask_source, config: config, loaded_from_api: true, loader: self) do
           version json_cask[:version]
 
           if json_cask[:sha256] == "no_check"
@@ -300,45 +296,53 @@ module Cask
           end
 
           json_cask[:artifacts].each do |artifact|
+            # convert generic string replacements into actual ones
+            artifact = cask.loader.from_h_hash_gsubs(artifact, appdir)
             key = artifact.keys.first
             send(key, *artifact[key])
           end
 
-          caveats json_cask[:caveats] if json_cask[:caveats].present?
+          if json_cask[:caveats].present?
+            # convert generic string replacements into actual ones
+            json_cask[:caveats] = cask.loader.from_h_string_gsubs(json_cask[:caveats], appdir)
+            caveats json_cask[:caveats]
+          end
         end
       end
 
-      private
+      def from_h_string_gsubs(string, appdir)
-
+        # TODO: HOMEBREW_OLD_PREFIX_PLACEHOLDER can be removed when API JSON is
-      def from_h_string_gsubs(string)
+        #       regenerated with HOMEBREW_PREFIX_PLACEHOLDER.
         string.to_s
-              .gsub("$HOME", Dir.home)
+              .gsub(Cask::HOME_PLACEHOLDER, Dir.home)
-              .gsub("$(brew --prefix)", HOMEBREW_PREFIX)
+              .gsub(Cask::HOMEBREW_PREFIX_PLACEHOLDER, HOMEBREW_PREFIX)
+              .gsub(Cask::APPDIR_PLACEHOLDER, appdir)
+              .gsub(Cask::HOMEBREW_OLD_PREFIX_PLACEHOLDER, HOMEBREW_PREFIX)
       end
 
-      def from_h_array_gsubs(array)
+      def from_h_array_gsubs(array, appdir)
         array.to_a.map do |value|
-          from_h_gsubs(value)
+          from_h_gsubs(value, appdir)
         end
       end
 
-      def from_h_hash_gsubs(hash)
+      def from_h_hash_gsubs(hash, appdir)
         hash.to_h.transform_values do |value|
-          from_h_gsubs(value)
+          from_h_gsubs(value, appdir)
         end
       rescue TypeError
-        from_h_array_gsubs(hash)
+        from_h_array_gsubs(hash, appdir)
       end
 
-      def from_h_gsubs(value)
+      def from_h_gsubs(value, appdir)
         return value if value.blank?
 
         if value.respond_to? :to_h
-          from_h_hash_gsubs(value)
+          from_h_hash_gsubs(value, appdir)
         elsif value.respond_to? :to_a
-          from_h_array_gsubs(value)
+          from_h_array_gsubs(value, appdir)
         elsif value.is_a? String
-          from_h_string_gsubs(value)
+          from_h_string_gsubs(value, appdir)
         else
           value
         end

Library/Homebrew/cask/dsl.rb

@@ -376,6 +376,8 @@ module Cask
 
     # @api public
     def appdir
+      return Cask::APPDIR_PLACEHOLDER if Cask.generating_hash?
+
       cask.config.appdir
     end
   end

Library/Homebrew/formula.rb

@@ -2119,7 +2119,7 @@ class Formula
       "uses_from_macos"          => uses_from_macos_elements.uniq,
       "requirements"             => [],
       "conflicts_with"           => conflicts.map(&:name),
-      "caveats"                  => caveats&.gsub(HOMEBREW_PREFIX, "$(brew --prefix)"),
+      "caveats"                  => caveats&.gsub(HOMEBREW_PREFIX, HOMEBREW_PREFIX_PLACEHOLDER),
       "installed"                => [],
       "linked_keg"               => linked_version&.to_s,
       "pinned"                   => pinned?,

Library/Homebrew/formulary.rb

@@ -251,6 +251,7 @@ module Formulary
       @caveats_string = json_formula["caveats"]
       def caveats
         self.class.instance_variable_get(:@caveats_string)
+            &.gsub(HOMEBREW_PREFIX_PLACEHOLDER, HOMEBREW_PREFIX)
       end
 
       @tap_git_head_string = json_formula["tap_git_head"]

Library/Homebrew/global.rb

@@ -64,6 +64,7 @@ HOMEBREW_MACOS_ARM_DEFAULT_PREFIX = "/opt/homebrew"
 HOMEBREW_MACOS_ARM_DEFAULT_REPOSITORY = HOMEBREW_MACOS_ARM_DEFAULT_PREFIX
 HOMEBREW_LINUX_DEFAULT_PREFIX = "/home/linuxbrew/.linuxbrew"
 HOMEBREW_LINUX_DEFAULT_REPOSITORY = "#{HOMEBREW_LINUX_DEFAULT_PREFIX}/Homebrew"
+HOMEBREW_PREFIX_PLACEHOLDER = "$HOMEBREW_PREFIX"
 
 HOMEBREW_PULL_API_REGEX =
   %r{https://api\.github\.com/repos/([\w-]+)/([\w-]+)?/pulls/(\d+)}.freeze

Library/Homebrew/test/cask/cask_spec.rb

@@ -300,5 +300,18 @@ describe Cask::Cask, :cask do
       expect(h).to be_a(Hash)
       expect(JSON.pretty_generate(h["variations"])).to eq expected_sha256_variations.strip
     end
+
+    it "returns the correct hash placeholders" do
+      described_class.generating_hash!
+      expect(described_class).to be_generating_hash
+      c = Cask::CaskLoader.load("placeholders")
+      h = c.to_hash_with_variations
+      described_class.generated_hash!
+      expect(described_class).not_to be_generating_hash
+
+      expect(h).to be_a(Hash)
+      expect(h["artifacts"].first[:binary].first).to eq "$APPDIR/some/path"
+      expect(h["caveats"]).to eq "$HOMEBREW_PREFIX and $HOME\n"
+    end
   end
 end

Library/Homebrew/test/cask/cmd/list_spec.rb

@@ -117,7 +117,7 @@ describe Cask::Cmd::List, :cask do
               {
                 "zap": [
                   {
-                    "trash": "$HOME/support/fixtures/cask/caffeine/org.example.caffeine.plist"
+                    "trash": "#{TEST_FIXTURE_DIR}/cask/caffeine/org.example.caffeine.plist"
                   }
                 ]
               }

Library/Homebrew/test/support/fixtures/cask/Casks/placeholders.rb

@@ -0,0 +1,11 @@
+cask "placeholders" do
+  version "2.61"
+  sha256 "e44ffa103fbf83f55c8d0b1bea309a43b2880798dae8620b1ee8da5e1095ec68"
+
+  url "file://#{TEST_FIXTURE_DIR}/cask/transmission-2.61.dmg"
+  homepage "https://brew.sh/placeholders"
+
+  binary "#{appdir}/some/path"
+
+  caveats "#{HOMEBREW_PREFIX} and #{Dir.home}"
+end