Deprecate more requirements.

These are ones that were either already deprecated due to audit rules
or are just a simple `which` with a `default_formula` so should just
be a dependency.

4 files changed, 148 insertions, 0 deletions

diff --git a/Library/Homebrew/compat/dependency_collector.rb b/Library/Homebrew/compat/dependency_collector.rb
index fbcf1c2a0..2e97d9d7f 100644
--- a/Library/Homebrew/compat/dependency_collector.rb
+++ b/Library/Homebrew/compat/dependency_collector.rb
@@ -1,6 +1,21 @@
 require "dependency_collector"
 
 class DependencyCollector
+  alias _parse_string_spec parse_string_spec
+
+  # Define the languages that we can handle as external dependencies.
+  LANGUAGE_MODULES = Set[
+    :lua, :lua51, :perl, :python, :python3, :ruby
+  ].freeze
+
+  def parse_string_spec(spec, tags)
+    if (tag = tags.first) && LANGUAGE_MODULES.include?(tag)
+      LanguageModuleRequirement.new(tag, spec, tags[1])
+    else
+      _parse_string_spec(spec, tags)
+    end
+  end
+
   alias _parse_symbol_spec parse_symbol_spec
 
   def parse_symbol_spec(spec, tags)
@@ -20,6 +35,18 @@ class DependencyCollector
       tags << :run
       output_deprecation("libtool", tags)
       Dependency.new("libtool", tags)
+    when :mysql
+      # output_deprecation("mysql", tags)
+      MysqlRequirement.new(tags)
+    when :postgresql
+      # output_deprecation("postgresql", tags)
+      PostgresqlRequirement.new(tags)
+    when :gpg
+      # output_deprecation("gnupg", tags)
+      GPG2Requirement.new(tags)
+    when :rbenv
+      # output_deprecation("rbenv", tags)
+      RbenvRequirement.new(tags)
     else
       _parse_symbol_spec(spec, tags)
     end
diff --git a/Library/Homebrew/compat/requirements.rb b/Library/Homebrew/compat/requirements.rb
index 3886cd7c7..da6d867b3 100644
--- a/Library/Homebrew/compat/requirements.rb
+++ b/Library/Homebrew/compat/requirements.rb
@@ -1,4 +1,42 @@
 require "requirements"
+require "compat/requirements/language_module_requirement"
+require "compat/requirements/tex_requirement"
+
+class MysqlRequirement < Requirement
+  fatal true
+  default_formula "mysql"
+  satisfy { which "mysql_config" }
+end
+
+class PostgresqlRequirement < Requirement
+  fatal true
+  default_formula "postgresql"
+  satisfy { which "pg_config" }
+end
+
+class RbenvRequirement < Requirement
+  fatal true
+  default_formula "rbenv"
+  satisfy { which "rbenv" }
+end
+
+class CVSRequirement < Requirement
+  fatal true
+  default_formula "cvs"
+  satisfy { which "cvs" }
+end
+
+class MercurialRequirement < Requirement
+  fatal true
+  default_formula "mercurial"
+  satisfy { which "hg" }
+end
+
+class GPG2Requirement < Requirement
+  fatal true
+  default_formula "gnupg"
+  satisfy { which "gpg" }
+end
 
 XcodeDependency            = XcodeRequirement
 MysqlDependency            = MysqlRequirement
diff --git a/Library/Homebrew/compat/requirements/language_module_requirement.rb b/Library/Homebrew/compat/requirements/language_module_requirement.rb
new file mode 100644
index 000000000..5ddce7a66
--- /dev/null
+++ b/Library/Homebrew/compat/requirements/language_module_requirement.rb
@@ -0,0 +1,63 @@
+require "requirement"
+
+class LanguageModuleRequirement < Requirement
+  fatal true
+
+  def initialize(language, module_name, import_name = nil)
+    @language = language
+    @module_name = module_name
+    @import_name = import_name || module_name
+    super([language, module_name, import_name])
+  end
+
+  satisfy(build_env: false) { quiet_system(*the_test) }
+
+  def message
+    s = <<~EOS
+      Unsatisfied dependency: #{@module_name}
+      Homebrew does not provide special #{@language.to_s.capitalize} dependencies; install with:
+        `#{command_line} #{@module_name}`
+    EOS
+
+    unless [:python, :perl, :ruby].include? @language
+      s += <<~EOS
+        You may need to: `brew install #{@language}`
+
+      EOS
+    end
+
+    s
+  end
+
+  def the_test
+    case @language
+    when :lua
+      ["/usr/bin/env", "luarocks-5.2", "show", @import_name.to_s]
+    when :lua51
+      ["/usr/bin/env", "luarocks-5.1", "show", @import_name.to_s]
+    when :perl
+      ["/usr/bin/env", "perl", "-e", "use #{@import_name}"]
+    when :python
+      ["/usr/bin/env", "python", "-c", "import #{@import_name}"]
+    when :python3
+      ["/usr/bin/env", "python3", "-c", "import #{@import_name}"]
+    when :ruby
+      ["/usr/bin/env", "ruby", "-rubygems", "-e", "require '#{@import_name}'"]
+    end
+  end
+
+  def command_line
+    case @language
+    when :lua     then "luarocks-5.2 install"
+    when :lua51   then "luarocks-5.1 install"
+    when :perl    then "cpan -i"
+    when :python  then "pip install"
+    when :python3 then "pip3 install"
+    when :ruby    then "gem install"
+    end
+  end
+
+  def display_s
+    "#{@module_name} (#{@language} module)"
+  end
+end
diff --git a/Library/Homebrew/compat/requirements/tex_requirement.rb b/Library/Homebrew/compat/requirements/tex_requirement.rb
new file mode 100644
index 000000000..cb26a8477
--- /dev/null
+++ b/Library/Homebrew/compat/requirements/tex_requirement.rb
@@ -0,0 +1,20 @@
+require "requirement"
+
+class TeXRequirement < Requirement
+  fatal true
+  cask "mactex"
+  download "https://www.tug.org/mactex/"
+
+  satisfy { which("tex") || which("latex") }
+
+  def message
+    s = <<~EOS
+      A LaTeX distribution is required for Homebrew to install this formula.
+
+      Make sure that "/usr/texbin", or the location you installed it to, is in
+      your PATH before proceeding.
+    EOS
+    s += super
+    s
+  end
+end