Establish a convention for Requirement names

The name attribute of requirements is used when generating options for
the :optional and :recommended dependency tags.

Unless otherwise specified, the name attribute of a Requirement will be
populated by stripping any module prefixes from the beginning and
"Dependency" or "Requirement" from end of the class name and downcasing
the result.

Closes Homebrew/homebrew#17759.

Library/Homebrew/dependency_collector.rb

@@ -85,9 +85,9 @@ private
       Dependency.new(spec.to_s, tag)
     when :x11        then X11Dependency.new(spec.to_s, tag)
     when :xcode      then XcodeDependency.new(tag)
-    when :mysql      then MysqlInstalled.new(tag)
-    when :postgresql then PostgresqlInstalled.new(tag)
-    when :tex        then TeXInstalled.new(tag)
+    when :mysql      then MysqlDependency.new(tag)
+    when :postgresql then PostgresqlDependency.new(tag)
+    when :tex        then TeXDependency.new(tag)
     when :clt        then CLTDependency.new(tag)
     else
       raise "Unsupported special dependency #{spec}"

Library/Homebrew/requirement.rb

@@ -13,6 +13,7 @@ class Requirement
   def initialize(*tags)
     @tags = tags.flatten.compact
     @tags << :build if self.class.build
+    @name ||= infer_name
   end
 
   # The message to show when the requirement is not met.
@@ -55,6 +56,13 @@ class Requirement
 
   private
 
+  def infer_name
+    klass = self.class.to_s
+    klass.sub!(/(Dependency|Requirement)$/, '')
+    klass.sub!(/^(\w+::){0,}/, '')
+    klass.downcase
+  end
+
   def infer_env_modification(o)
     case o
     when Pathname

Library/Homebrew/requirements.rb

@@ -253,7 +253,7 @@ class XcodeDependency < Requirement
   end
 end
 
-class MysqlInstalled < Requirement
+class MysqlDependency < Requirement
   fatal true
 
   satisfy { which 'mysql_config' }
@@ -274,7 +274,7 @@ class MysqlInstalled < Requirement
   end
 end
 
-class PostgresqlInstalled < Requirement
+class PostgresqlDependency < Requirement
   fatal true
 
   satisfy { which 'pg_config' }
@@ -292,7 +292,7 @@ class PostgresqlInstalled < Requirement
   end
 end
 
-class TeXInstalled < Requirement
+class TeXDependency < Requirement
   fatal true
 
   satisfy { which('tex') || which('latex') }

Library/Homebrew/test/test_requirement.rb

@@ -92,4 +92,12 @@ class RequirementTests < Test::Unit::TestCase
     req = Class.new(Requirement) { build true }.new
     assert req.build?
   end
+
+  def test_infer_name_from_class
+    klass, const = self.class, :FooRequirement
+    klass.const_set(const, Class.new(Requirement))
+    assert_equal "foo", klass.const_get(const).new.name
+  ensure
+    klass.send(:remove_const, const) if klass.const_defined?(const)
+  end
 end