Fix duplicate special dependencies in tools/getrealdeps.rb (#12760)

tests/tools/getrealdeps.rb

@@ -203,7 +203,6 @@ class GetRealDepsTest < Minitest::Test
     test_wrapper(input_file, expected_pkg_file, deps)
   end
 
-  # TODO: The expected output in this case could be improved.
   def test_add_special_duplicate_dependency
     deps = ['python3']
     input_file = <<~EOF
@@ -220,7 +219,6 @@ class GetRealDepsTest < Minitest::Test
 
         depends_on 'libnftnl'
         depends_on 'python3' # R
-        depends_on 'python3' # R
       end
     EOF
     pkg_class = Pip

tools/getrealdeps.rb

@@ -44,19 +44,19 @@ end
 
 # Write the missing dependencies to the package file.
 def write_deps(pkg_file, pkgdeps, pkg)
-  # Look for missing runtime dependencies, ignoring build and optional deps.
-  missingpkgdeps = pkgdeps.reject { |i| File.read(pkg_file).include?("depends_on '#{i}'") unless File.read(pkg_file).include?("depends_on '#{i}' => :build") || File.read(pkg_file).include?("# depends_on '#{i}' # R (optional)") }
-
   # Add special deps for perl, pip, python, and ruby gem packages.
   case pkg.superclass.to_s
   when 'PERL'
-    missingpkgdeps << 'perl'
+    pkgdeps << 'perl'
   when 'Pip', 'Python'
-    missingpkgdeps << 'python3'
+    pkgdeps << 'python3'
   when 'RUBY'
-    missingpkgdeps << 'ruby'
+    pkgdeps << 'ruby'
   end
 
+  # Look for missing runtime dependencies, ignoring build and optional deps.
+  missingpkgdeps = pkgdeps.reject { |i| File.read(pkg_file).include?("depends_on '#{i}'") unless File.read(pkg_file).include?("depends_on '#{i}' => :build") || File.read(pkg_file).include?("# depends_on '#{i}' # R (optional)") }
+
   # These deps are sometimes architecture dependent or should not be
   # removed for other reasons.
   privileged_deps = %w[glibc glibc_lib gcc_lib perl python3 ruby]