Fix Dir.glob returning a blank string entry in some cases

When the first part of the glob is '**'
and the base keyword argument is provided.

Add several additional tests to ensure compatibility.

Author: rwstauner

CHANGELOG.md

@@ -5,6 +5,7 @@ New features:
 
 Bug fixes:
 
+* Fix `Dir.glob` returning blank string entry with leading `**/` in glob and `base:` argument (@rwstauner).
 
 Compatibility:
 

spec/ruby/core/dir/glob_spec.rb

@@ -182,6 +182,90 @@
     Dir.glob('**/**/**').should_not.empty?
   end
 
+  it "handles **/** with base keyword argument" do
+    Dir.glob('**/**', base: "dir").should == ["filename_ordering"]
+
+    expected = %w[
+      directory
+      directory/structure
+      directory/structure/bar
+      directory/structure/baz
+      directory/structure/file_one
+      directory/structure/file_one.ext
+      directory/structure/foo
+    ].sort
+
+    Dir.glob('**/**', base: "deeply/nested").sort.should == expected
+  end
+
+  it "handles **/ with base keyword argument" do
+    expected = %w[
+      /
+      directory/
+      directory/structure/
+    ]
+    Dir.glob('**/', base: "deeply/nested").sort.should == expected
+  end
+
+  # 2.7 and 3.0 include a "." entry for every dir: ["directory/.", "directory/structure/.", ...]
+  guard_not -> { ruby_version_is ''...'3.1' } do
+    it "handles **/.* with base keyword argument" do
+      expected = %w[
+        .dotfile.ext
+        directory/structure/.ext
+      ].sort
+
+      Dir.glob('**/.*', base: "deeply/nested").sort.should == expected
+    end
+
+    it "handles **/.* with base keyword argument and FNM_DOTMATCH" do
+      expected = %w[
+        .
+        .dotfile.ext
+        directory/structure/.ext
+      ].sort
+
+      Dir.glob('**/.*', File::FNM_DOTMATCH, base: "deeply/nested").sort.should == expected
+    end
+
+    it "handles **/** with base keyword argument and FNM_DOTMATCH" do
+      expected = %w[
+        .
+        .dotfile.ext
+        directory
+        directory/structure
+        directory/structure/.ext
+        directory/structure/bar
+        directory/structure/baz
+        directory/structure/file_one
+        directory/structure/file_one.ext
+        directory/structure/foo
+      ].sort
+
+      Dir.glob('**/**', File::FNM_DOTMATCH, base: "deeply/nested").sort.should == expected
+    end
+  end
+
+  it "handles **/*pattern* with base keyword argument and FNM_DOTMATCH" do
+    expected = %w[
+      .dotfile.ext
+      directory/structure/file_one
+      directory/structure/file_one.ext
+    ]
+
+    Dir.glob('**/*file*', File::FNM_DOTMATCH, base: "deeply/nested").sort.should == expected
+  end
+
+  it "handles **/glob with base keyword argument and FNM_EXTGLOB" do
+    expected = %w[
+      directory/structure/bar
+      directory/structure/file_one
+      directory/structure/file_one.ext
+    ]
+
+    Dir.glob('**/*{file,bar}*', File::FNM_EXTGLOB, base: "deeply/nested").sort.should == expected
+  end
+
   it "handles simple filename patterns" do
     Dir.glob('.dotfile').should == ['.dotfile']
   end

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

@@ -225,18 +225,18 @@ class StartRecursiveDirectories < Node
       def process_directory(matches, parent, entry, glob_base_dir)
         raise 'invalid usage' if parent || entry
 
-        # Even though the recursive entry is zero width
-        # in this case, its left separator is still the
-        # dominant one, so we fix things up to use it.
-        if @separator
-        else
-          @next.process_entry '', Truffle::DirOperations::DT_DIR, matches, parent, glob_base_dir if glob_base_dir
-        end
-
         stack = [[nil, subdir_entries(glob_base_dir, nil)]]
 
         allow_dots = ((@flags & File::FNM_DOTMATCH) != 0)
 
+        if glob_base_dir
+          if Primitive.is_a?(@next, DirectoriesOnly)
+            @next.process_entry '', Truffle::DirOperations::DT_DIR, matches, parent, glob_base_dir
+          else
+            @next.process_entry '.', Truffle::DirOperations::DT_DIR, matches, parent, glob_base_dir if allow_dots
+          end
+        end
+
         until stack.empty?
           path, dir_entries = *stack.pop
 
@@ -245,13 +245,15 @@ def process_directory(matches, parent, entry, glob_base_dir)
             type = entry.type
 
             full = path_join(path, ent)
-            if (type == Truffle::DirOperations::DT_DIR) and (allow_dots or ent.getbyte(0) != 46) # ?.
-              @next.process_entry ent, type, matches, path, glob_base_dir
-
-              stack << [path, dir_entries]
-              path = full
-              dir_entries = subdir_entries(glob_base_dir, full)
-            elsif (allow_dots or ent.getbyte(0) != 46) # ?.
+            if (type == Truffle::DirOperations::DT_DIR)
+              if (allow_dots or ent.getbyte(0) != 46) # ?.
+                @next.process_entry ent, type, matches, path, glob_base_dir
+
+                stack << [path, dir_entries]
+                path = full
+                dir_entries = subdir_entries(glob_base_dir, full)
+              end
+            else
               @next.process_entry ent, type, matches, path, glob_base_dir
             end
           end