java-tree-sitter

Java bindings for tree-sitter.

Building

Before you can start using java-tree-sitter, you need to build a shared library that Java can load. The included build.py script can facilitate building the library. The first argument is the output file, followed by all of the tree-sitter repositories that you want to be included:

./build.py libjava-tree-sitter tree-sitter-css tree-sitter-python ...

Examples

First, load the shared object somewhere in your application:

public class App {
  static {
    // or on a Mac, libjava-tree-sitter.dylib
    System.load("./path/to/libjava-tree-sitter.so");
  }
}

Then, you can create a Parser, set the language, and parse a string:

try (Parser parser = new Parser()) {
  parser.setLanguage(Languages.python());
  try (Tree tree = parser.parseString("def foo(bar, baz):\n  print(bar)\n  print(baz)")) {
    Node root = tree.getRootNode();
    assertEquals(1, root.getChildCount());
    assertEquals("module", root.getType());
    assertEquals(0, root.getStartByte());
    assertEquals(44, root.getEndByte());

    Node function = root.getChild(0);
    assertEquals("function_definition", function.getType());
    assertEquals(5, function.getChildCount());
  }
}

For debugging, it can be helpful to see a string of the tree:

try (Parser parser = new Parser()) {
  parser.setLanguage(Languages.python());
  try (Tree tree = parser.parseString("print(\"hi\")")) {
    assertEquals(
      "(module (expression_statement (call function: (identifier) arguments: (argument_list (string)))))",
      tree.getRootNode().getNodeString()
    );
  }
}

If you're going to be traversing a tree, then you can use the walk method, which is much more efficient than the above getters:

try (Parser parser = new Parser()) {
  parser.setLanguage(Languages.python());
  try (Tree tree = parser.parseString("def foo(bar, baz):\n  print(bar)\n  print(baz)")) {
    try (TreeCursor cursor = tree.getRootNode().walk()) {
      assertEquals("module", cursor.getCurrentTreeCursorNode().getType());
      cursor.gotoFirstChild();
      assertEquals("function_definition", cursor.getCurrentTreeCursorNode().getType());
      cursor.gotoFirstChild();
      assertEquals("def", cursor.getCurrentTreeCursorNode().getType());
      cursor.gotoNextSibling();
      cursor.gotoParent();
    }
  }

For more examples, see the tests in src/test/java/ai/serenade/treesitter.