formula: add any_installed_version

Library/Homebrew/cmd/install.rb

@@ -219,8 +219,7 @@ module Homebrew
         end
         opoo msg if msg
       elsif !f.any_version_installed? && old_formula = f.old_installed_formulae.first
-        installed_version = old_formula.any_installed_keg.version
-        msg = "#{old_formula.full_name} #{installed_version} already installed"
+        msg = "#{old_formula.full_name} #{old_formula.any_installed_version} already installed"
         if !old_formula.linked? && !old_formula.keg_only?
           msg = <<~EOS
             #{msg}, it's just not linked.

Library/Homebrew/formula.rb

@@ -1625,6 +1625,10 @@ class Formula
     end
   end
 
+  def any_installed_version
+    any_installed_keg&.version
+  end
+
   # Returns a list of Dependency objects that are required at runtime.
   # @private
   def runtime_dependencies(read_from_tab: true, undeclared: true)

Library/Homebrew/language/java.rb

@@ -14,7 +14,7 @@ module Language
         next false unless f.any_version_installed?
 
         unless version.zero?
-          major = f.any_installed_keg.version.major
+          major = f.any_installed_version.major
           next false if major < version
           next false if major > version && !can_be_newer
         end

Library/Homebrew/livecheck/livecheck.rb

@@ -81,7 +81,7 @@ module Homebrew
         formula.head.downloader.shutup! if formula.head?
 
         current = if formula.head?
-          formula.any_installed_keg.version.version.commit
+          formula.any_installed_version.version.commit
         else
           formula.version
         end

Library/Homebrew/test/formula_spec.rb

@@ -1344,4 +1344,22 @@ describe Formula do
       end
     end
   end
+
+  describe "#any_installed_version" do
+    let(:f) do
+      Class.new(Testball) do
+        version "1.0"
+        revision 1
+      end.new
+    end
+
+    it "returns nil when not installed" do
+      expect(f.any_installed_version).to be nil
+    end
+
+    it "returns package version when installed" do
+      f.brew { f.install }
+      expect(f.any_installed_version).to eq(PkgVersion.parse("1.0_1"))
+    end
+  end
 end