AST answerer

July 28, 2025 ยท View on GitHub

A Clang-AST based project for understanding the OpenUSD AST and generating code for a Swift interface to Usd

Prerequisites

  1. Clone LLVM
git clone --depth 1 https://github.com/llvm/llvm-project.git

(Per LLVM's instructions, --depth 1 saves storage space and speeds up checkout time by doing a shallow clone.)
Currently, I'm using 60fc4ac67a613e4e36cef019fb2d13d70a06cfe8.

  1. Build LLVM
cd llvm-project

cmake -S llvm -B build -G Ninja \
  -DLLVM_ENABLE_PROJECTS='clang;clang-tools-extra' \
  -DCMAKE_BUILD_TYPE=Release
    
cmake --build build

Note: this will take a while.

  1. Build vanilla OpenUSD without Python
python3 build_scripts/build_usd.py \
    --no-python \
    /opt/local/OpenUSD_no-python

Using AST answerer

  1. Clone AST answerer
git clone git@github.com:apple/SwiftUsd-ast-answerer.git
  1. Run CMake
cd ast-answerer
cmake -S . -B build \
  -G Xcode \
  -DUSD_SOURCE_REPO_PATH=/PATH/TO/YOUR/USD/SOURCE/REPO \
  -DUSD_INSTALL_NO_PYTHON_PATH=/PATH/TO/YOUR/USD/INSTALL/WITHOUT/PYTHON

Replace /PATH/TO/YOUR/USD/SOURCE/REPO with the absolute path to a Usd source repo. Replace /PATH/TO/YOUR/USD/INSTALL/WITHOUT/PYTHON with the absolute path to your no-python install of OpenUSD, e.g. /opt/local/OpenUSD_no-python.

For example,

cmake -S . -B build \
  -G Xcode \
  -DUSD_SOURCE_REPO_PATH=/Users/maddyadams/OpenUSD \
    -DUSD_INSTALL_NO_PYTHON_PATH=/opt/local/OpenUSD_no-python
  1. Build and run the Xcode project
    Open build/ast-answerer.xcodeproj, and run.
    Note: The first time that you run, the compiler will have to parse and build the AST for all the source files in Usd, which takes about one minute. It serializes the AST to disk, so subsequent runs should load it and start processing the AST almost immediately.

Documentation

See DOC.md, and documentation in the source code.