1. Summary
---------------
Optional font ligature is not rendered on Mac OS X when natively loaded 
font is used.
When the same font is loaded in application using java.awt.Font.createFont() method, 
it works fine.

2. How to reproduce
--------------------------
The issue is reproduced on Mac OS X Yosemite version 10.10.5 using latest Java 9 EA:

$ uname -a
Darwin xxx 14.5.0 Darwin Kernel Version 14.5.0: Wed Jul 29 02:26:53 PDT 2015; root:xnu-2782.40.9~1/RELEASE_X86_64 x86_64
$ 

$  ../jdk1.9.0.jdk/Contents/Home/bin/java -version
java version "1.9.0-ea"
Java(TM) SE Runtime Environment (build 1.9.0-ea-b86)
Java HotSpot(TM) 64-Bit Server VM (build 1.9.0-ea-b86, mixed mode)
$ 

To reproduce the issue, please do the following:
(1) compile attached file 'Ligatures1Test.java' and run it.
$  ../jdk1.9.0.jdk/Contents/Home/bin/javac Ligatures1Test.java
$  ../jdk1.9.0.jdk/Contents/Home/bin/java Ligatures1Test &
[1] 4133
$
(2) Actual behaviour:
    The window shows characters that are rendered separately.
    (see attached file 'Ligatures1_OSX.png')

(3) Expected behaviour:
    On Windows, the expected behaviour is shown
    (see attached file 'Ligatures1-Windows.png')

(4) Loading the font in the application using java.awt.Font.createFont() method,
it works fine: 
(unfortunately, this approach is not usable as a workaround, as the font mapping
is too complex.)

(4.1) install attached font 'Hasklig-Regular.noDFLT.otf':
      (copy the file into ~/Library/Fonts folder)
$ cp Hasklig-Regular.noDFLT.otf ../Library/Fonts
$ ls ../Library/Fonts
Hasklig-Regular.noDFLT.otf
$
(4.2) compile attached file 'Ligatures2Test.java' and run it.
The window shows characters that are rendered as a single glyph.
(see attached file 'Ligatures2_OSX.png')

3. Sources
--------------
% more Ligatures1Test.java
import javax.swing.*;
import java.awt.*;
import java.awt.font.TextAttribute;
import java.util.HashMap;
import java.util.Map;

public class Ligatures1Test {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame frame = new JFrame();
            JLabel label = new JLabel("->");
            label.setFont(createFont());
            frame.add(label);
            frame.pack();
            frame.setVisible(true);
            frame.setLocationRelativeTo(null);
            frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        });
    }

    private static Font createFont() {
        try {
            Font font = new Font("Hasklig", Font.PLAIN, 1);
            Map<TextAttribute, Object> attributes = new HashMap<>();
            attributes.put(TextAttribute.SIZE, 30);
            attributes.put(TextAttribute.LIGATURES, TextAttribute.LIGATURES_ON);
            return font.deriveFont(attributes);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}


% more Ligatures2Test.java
import javax.swing.*;
import java.awt.*;
import java.awt.font.TextAttribute;
import java.io.File;
import java.util.HashMap;
import java.util.Map;

public class Ligatures2Test {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame frame = new JFrame();
            JLabel label = new JLabel("->");
            label.setFont(createFont());
            frame.add(label);
            frame.pack();
            frame.setVisible(true);
            frame.setLocationRelativeTo(null);
            frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        });
    }

    private static Font createFont() {
        try {
            Font font = Font.createFont(Font.TRUETYPE_FONT, new File(System.getProperty("user.home"), "Library/Fonts/Hasklig-Regular.noDFLT.otf"));
            Map<TextAttribute, Object> attributes = new HashMap<>();
            attributes.put(TextAttribute.SIZE, 30);
            attributes.put(TextAttribute.LIGATURES, TextAttribute.LIGATURES_ON);
            return font.deriveFont(attributes);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}