cpp-tree-sitter

... is a simple C++ and CMake wrapper around tree-sitter. This project provides CMake definitions and a C++ wrapper that help with

• managing tree-sitter and tree-sitter grammars as dependencies
• accessing basic tree-sitter APIs for parse tree inspection

Using in a CMake project

... requires the CPM CMake module for fetching and managing dependencies from github. Adding cpp-tree-sitter as a CPM dependency makes cpp-tree-sitter available as a library and provides a function, add_grammar_from_repo, that will download and make available a standard tree-sitter grammar on GitHub as a library.

The tree-sitter parser example can be reproduced in a CMake project with CPM by including the following in CMakeLists.txt:

include(cmake/CPM.cmake)

# Downloads this wrapper library and tree-sitter.
# Makes them available via the `cpp-tree-sitter` CMake library target.
CPMAddPackage(
  NAME cpp-tree-sitter
  GIT_REPOSITORY https://github.com/nsumner/cpp-tree-sitter.git
  GIT_TAG v0.0.1
)

# Downloads a tree-sitter grammar from github and makes it available as a
# cmake library target.
add_grammar_from_repo(tree-sitter-json                 # Defines the library name for a grammar
  https://github.com/tree-sitter/tree-sitter-json.git  # Repository URL of a tree-sitter grammar
  0.19.0                                               # Version tag for the grammar
)

# Use the library in a demo program.
add_executable(demo)
target_sources(demo
  PRIVATE
    demo.cpp
)
target_link_libraries(demo
  tree-sitter-json
  cpp-tree-sitter
)

Translating the parsing and tree inspection operations from the example to use the C++ wrappers then yields a demo.cpp like:

#include <cassert>
#include <cstdio>
#include <memory>
#include <string>

#include <cpp-tree-sitter.h>


extern "C" {
TSLanguage* tree_sitter_json();
}


int main() {
  // Create a language and parser.
  ts::Language language = tree_sitter_json();
  ts::Parser parser{language};

  // Parse the provided string into a syntax tree.
  std::string sourcecode = "[1, null]";
  ts::Tree tree = parser.parseString(sourcecode);

  // Get the root node of the syntax tree. 
  ts::Node root = tree.getRootNode();

  // Get some child nodes.
  ts::Node array = root.getNamedChild(0);
  ts::Node number = array.getNamedChild(0);

  // Check that the nodes have the expected types.
  assert(root.getType() == "document");
  assert(array.getType() == "array");
  assert(number.getType() == "number");

  // Check that the nodes have the expected child counts.
  assert(root.getNumChildren() == 1);
  assert(array.getNumChildren() == 5);
  assert(array.getNumNamedChildren() == 2);
  assert(number.getNumChildren() == 0);

  // Print the syntax tree as an S-expression.
  auto treestring = root.getSExpr();
  printf("Syntax tree: %s\n", treestring.get());

  return 0;
}

In particular, some of the underlying APIs now use method calls for easier discoverability, and resource cleaning is automatic.