1 files changed, 231 insertions, 40 deletions
diff --git a/spec/ruby/core/io/set_encoding_by_bom_spec.rb b/spec/ruby/core/io/set_encoding_by_bom_spec.rb
index c551042bee..92433d6640 100644
--- a/spec/ruby/core/io/set_encoding_by_bom_spec.rb
+++ b/spec/ruby/core/io/set_encoding_by_bom_spec.rb
@@ -12,60 +12,251 @@ describe "IO#set_encoding_by_bom" do
     rm_r @name
   end
 
-  ruby_version_is "2.7" do
-    it "returns the result encoding if found BOM UTF-8 sequence" do
-      File.binwrite(@name, "\u{FEFF}abc")
+  it "returns nil if not readable" do
+    not_readable_io = new_io(@name, 'wb')
 
-      @io.set_encoding_by_bom.should == Encoding::UTF_8
-      @io.external_encoding.should == Encoding::UTF_8
-    end
+    not_readable_io.set_encoding_by_bom.should be_nil
+    not_readable_io.external_encoding.should == Encoding::ASCII_8BIT
+  ensure
+    not_readable_io.close
+  end
+
+  it "returns the result encoding if found BOM UTF-8 sequence" do
+    File.binwrite(@name, "\u{FEFF}")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_8
+    @io.external_encoding.should == Encoding::UTF_8
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.binwrite(@name, "\u{FEFF}abc")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_8
+    @io.external_encoding.should == Encoding::UTF_8
+    @io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_16LE sequence" do
+    File.binwrite(@name, "\xFF\xFE")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    @io.external_encoding.should == Encoding::UTF_16LE
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.binwrite(@name, "\xFF\xFEabc")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    @io.external_encoding.should == Encoding::UTF_16LE
+    @io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_16BE sequence" do
+    File.binwrite(@name, "\xFE\xFF")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16BE
+    @io.external_encoding.should == Encoding::UTF_16BE
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.binwrite(@name, "\xFE\xFFabc")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16BE
+    @io.external_encoding.should == Encoding::UTF_16BE
+    @io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_32LE sequence" do
+    File.binwrite(@name, "\xFF\xFE\x00\x00")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_32LE
+    @io.external_encoding.should == Encoding::UTF_32LE
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.binwrite(@name, "\xFF\xFE\x00\x00abc")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_32LE
+    @io.external_encoding.should == Encoding::UTF_32LE
+    @io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_32BE sequence" do
+    File.binwrite(@name, "\x00\x00\xFE\xFF")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_32BE
+    @io.external_encoding.should == Encoding::UTF_32BE
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.binwrite(@name, "\x00\x00\xFE\xFFabc")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_32BE
+    @io.external_encoding.should == Encoding::UTF_32BE
+    @io.read.b.should == "abc".b
+  end
+
+  it "returns nil if io is empty" do
+    @io.set_encoding_by_bom.should be_nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+  end
+
+  it "returns nil if UTF-8 BOM sequence is incomplete" do
+    File.write(@name, "\xEF")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xEF".b
+    @io.rewind
+
+    File.write(@name, "\xEFa")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xEFa".b
+    @io.rewind
 
-    it "returns the result encoding if found BOM UTF_16LE sequence" do
-      File.binwrite(@name, "\xFF\xFEabc")
+    File.write(@name, "\xEF\xBB")
 
-      @io.set_encoding_by_bom.should == Encoding::UTF_16LE
-      @io.external_encoding.should == Encoding::UTF_16LE
-    end
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xEF\xBB".b
+    @io.rewind
 
-    it "returns the result encoding if found BOM UTF_16BE sequence" do
-      File.binwrite(@name, "\xFE\xFFabc")
+    File.write(@name, "\xEF\xBBa")
 
-      @io.set_encoding_by_bom.should == Encoding::UTF_16BE
-      @io.external_encoding.should == Encoding::UTF_16BE
-    end
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xEF\xBBa".b
+  end
+
+  it "returns nil if UTF-16BE BOM sequence is incomplete" do
+    File.write(@name, "\xFE")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xFE".b
+    @io.rewind
+
+    File.write(@name, "\xFEa")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xFEa".b
+  end
+
+  it "returns nil if UTF-16LE/UTF-32LE BOM sequence is incomplete" do
+    File.write(@name, "\xFF")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xFF".b
+    @io.rewind
+
+    File.write(@name, "\xFFa")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xFFa".b
+  end
+
+  it "returns UTF-16LE if UTF-32LE BOM sequence is incomplete" do
+    File.write(@name, "\xFF\xFE")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    @io.external_encoding.should == Encoding::UTF_16LE
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.write(@name, "\xFF\xFE\x00")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    @io.external_encoding.should == Encoding::UTF_16LE
+    @io.read.b.should == "\x00".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.write(@name, "\xFF\xFE\x00a")
 
-    it "returns the result encoding if found BOM UTF_32LE sequence" do
-      File.binwrite(@name, "\xFF\xFE\x00\x00abc")
+    @io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    @io.external_encoding.should == Encoding::UTF_16LE
+    @io.read.b.should == "\x00a".b
+  end
+
+  it "returns nil if UTF-32BE BOM sequence is incomplete" do
+    File.write(@name, "\x00")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00".b
+    @io.rewind
+
+    File.write(@name, "\x00a")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00a".b
+    @io.rewind
+
+    File.write(@name, "\x00\x00")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00\x00".b
+    @io.rewind
+
+    File.write(@name, "\x00\x00a")
 
-      @io.set_encoding_by_bom.should == Encoding::UTF_32LE
-      @io.external_encoding.should == Encoding::UTF_32LE
-    end
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00\x00a".b
+    @io.rewind
 
-    it "returns the result encoding if found BOM UTF_32BE sequence" do
-      File.binwrite(@name, "\x00\x00\xFE\xFFabc")
+    File.write(@name, "\x00\x00\xFE")
 
-      @io.set_encoding_by_bom.should == Encoding::UTF_32BE
-      @io.external_encoding.should == Encoding::UTF_32BE
-    end
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00\x00\xFE".b
+    @io.rewind
 
-    it "returns nil if found BOM sequence not provided" do
-      File.write(@name, "abc")
+    File.write(@name, "\x00\x00\xFEa")
 
-      @io.set_encoding_by_bom.should == nil
-    end
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00\x00\xFEa".b
+  end
+
+  it "returns nil if found BOM sequence not provided" do
+    File.write(@name, "abc")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read(3).should == "abc".b
+  end
 
-    it 'returns exception if io not in binary mode' do
-      not_binary_io = new_io(@name, 'r')
+  it 'returns exception if io not in binary mode' do
+    not_binary_io = new_io(@name, 'r')
 
-      -> { not_binary_io.set_encoding_by_bom }.should raise_error(ArgumentError, 'ASCII incompatible encoding needs binmode')
-    ensure
-      not_binary_io.close
-    end
+    -> { not_binary_io.set_encoding_by_bom }.should raise_error(ArgumentError, 'ASCII incompatible encoding needs binmode')
+  ensure
+    not_binary_io.close
+  end
+
+  it 'returns exception if encoding already set' do
+    @io.set_encoding("utf-8")
+
+    -> { @io.set_encoding_by_bom }.should raise_error(ArgumentError, 'encoding is set to UTF-8 already')
+  end
 
-    it 'returns exception if encoding already set' do
-      @io.set_encoding("utf-8")
+  it 'returns exception if encoding conversion is already set' do
+    @io.set_encoding(Encoding::UTF_8, Encoding::UTF_16BE)
 
-      -> { @io.set_encoding_by_bom }.should raise_error(ArgumentError, 'encoding is set to UTF-8 already')
-    end
+    -> { @io.set_encoding_by_bom }.should raise_error(ArgumentError, 'encoding conversion is set')
   end
 end