Support optional level argument for File.dirname method

Author: moste00

spec/ruby/core/file/dirname_spec.rb

@@ -25,6 +25,26 @@
     it "raises ArgumentError if the level is negative" do
       -> {File.dirname('/home/jason', -1)}.should raise_error(ArgumentError)
     end
+
+    it "returns the exact same object when passed 0 as the level" do
+      obj = "path"
+      File.dirname(obj,0).should .equal?(obj)
+
+      obj = mock("to_path")
+      def obj.to_path
+        "path"
+      end
+      File.dirname(obj,0).should .equal?(obj)
+
+      obj = Object.new
+      File.dirname(obj,0).should .equal?(obj)
+    end
+
+    it "returns / when passed number of levels exceeds the number of segments in the path" do
+      (3..100).each { |level|
+        File.dirname("/home/jason", level).should == '/'
+      }
+    end
   end
 
   it "returns a String" do

spec/tags/core/file/dirname_tags.txt

@@ -415,37 +415,26 @@ def self.last_nonslash(path, start = nil)
   # the separator used on the local file system.
   #
   #  File.dirname("/home/gumby/work/ruby.rb")   #=> "/home/gumby/work"
-  def self.dirname(path)
-    path = Truffle::Type.coerce_to_path(path)
-
-    # edge case
-    return +'.' if path.empty?
-
-    slash = '/'
-
-    # pull off any /'s at the end to ignore
-    chunk_size = last_nonslash(path)
-    return +'/' unless chunk_size
-
-    if pos = Primitive.find_string_reverse(path, slash, chunk_size)
-      return +'/' if pos == 0
-
-      path = path.byteslice(0, pos)
-
-      return +'/' if path == '/'
-
-      return path unless path.end_with? slash
+  def self.dirname(path,num_levels=1)
+    if num_levels < 0
+      raise ArgumentError, "level can't be negative"
+    end
+    #This must happen before the type coercion to string below, because File.dirname accepts any objects which can respond to a :to_path message
+    #If path was such an object, File.dirname(obj,0) returns it as-is without conversion to string
+    #Tricky, but that's how Matz ruby behave
+    if num_levels == 0
+      return path
+    end
 
-      # prune any trailing /'s
-      idx = last_nonslash(path, pos)
+    path = Truffle::Type.coerce_to_path(path)
 
-      # edge case, only /'s, return /
-      return +'/' unless idx
+    num_levels.times do
+      # edge case
+      return +'.' if path.empty?
 
-      return path.byteslice(0, idx - 1)
+      path = Truffle::FileOperations.remove_last_segment_from_path(path)
     end
-
-    +'.'
+    path
   end
 
   ##

src/main/ruby/truffleruby/core/file.rb

@@ -78,5 +78,34 @@ def self.expand_path(path, dir, expand_tilde)
     def self.exist?(path)
       Truffle::POSIX.truffleposix_stat_mode(path) > 0
     end
+
+    #Helper to File.dirname, extracts the directory of a path (doesn't need to handle the empty string)
+    #This was the original File.dirname, but ruby 3.1 made File.dirname take an optional number of times to do its logic
+    def self.remove_last_segment_from_path(path)
+      slash = '/'
+      # pull off any /'s at the end to ignore
+      chunk_size = File.last_nonslash(path)
+      return +'/' unless chunk_size
+
+      if pos = Primitive.find_string_reverse(path, slash, chunk_size)
+        return +'/' if pos == 0
+
+        path = path.byteslice(0, pos)
+
+        return +'/' if path == '/'
+
+        return path unless path.end_with? slash
+
+        # prune any trailing /'s
+        idx = File.last_nonslash(path, pos)
+
+        # edge case, only /'s, return /
+        return +'/' unless idx
+
+        return path.byteslice(0, idx - 1)
+      end
+
+      +'.'
+    end
   end
 end