add Keg#empty_installation?

Avoid using `FormulaAuditor` in `FormulaInstaller`.

Closes Homebrew/homebrew#47887.

Signed-off-by: Xu Cheng <xucheng@me.com>

Library/Homebrew/cmd/audit.rb

@@ -883,20 +883,14 @@ class FormulaAuditor
   def audit_prefix_has_contents
     return unless formula.prefix.directory?
 
-    Pathname.glob("#{formula.prefix}/**/*") do |file|
-      next if file.directory?
-      basename = file.basename.to_s
-      next if Metafiles.copy?(basename)
-      next if %w[.DS_Store INSTALL_RECEIPT.json].include?(basename)
-      return
-    end
-
+    if Keg.new(formula.prefix).empty_installation?
       problem <<-EOS.undent
         The installation seems to be empty. Please ensure the prefix
         is set correctly and expected files are installed.
         The prefix configure/make argument may be case-sensitive.
       EOS
     end
+  end
 
   def audit_conditional_dep(dep, condition, line)
     quoted_dep = quote_dep(dep)

Library/Homebrew/formula_installer.rb

@@ -8,7 +8,6 @@ require "caveats"
 require "cleaner"
 require "formula_cellar_checks"
 require "install_renamed"
-require "cmd/audit"
 require "cmd/postinstall"
 require "hooks/bottles"
 require "debrew"
@@ -573,9 +572,7 @@ class FormulaInstaller
       end
     end
 
-    auditor = FormulaAuditor.new(formula)
-    auditor.audit_prefix_has_contents
-    unless formula.prefix.exist? && auditor.problems.empty?
+    if !formula.prefix.directory? || Keg.new(formula.prefix).empty_installation?
       raise "Empty installation"
     end
 

Library/Homebrew/keg.rb

@@ -150,6 +150,18 @@ class Keg
     path.exist?
   end
 
+  def empty_installation?
+    Pathname.glob("#{path}/**/*") do |file|
+      next if file.directory?
+      basename = file.basename.to_s
+      next if Metafiles.copy?(basename)
+      next if %w[.DS_Store INSTALL_RECEIPT.json].include?(basename)
+      return false
+    end
+
+    true
+  end
+
   def /(other)
     path / other
   end