A fast, practical, static nullness checker for Java

NullAway takes in code following an intuitive annotation discipline, where values that might be null at runtime, must be annotated with @Nullable. It performs type-based local analysis to ensure that any pointer that gets dereferenced in annotated code cannot be null, and thus prevent NullPointerExceptions (NPEs). In our measurements, the build-time overhead of running NullAway is usually less than 20% of javac, which allows us to use it to analize all of Uber Android Java code on every local compilation.

with Manu Sridharan, Subarno Banerjee, Nima Karimipour, and others at Uber

A fast nilness analyzer for Go requiring no code annotations

NilAway builds upon the lessons of NullAway to build a fast nil dereference checker for Go, which works across packages without requiring any code anotations on functions or fields. It manages this by performing whole-program nilability type inference, modeled as graph reachability. It handles language features like struct initialization, error returns, and contracts between function parameters. It leverages integration with the Bazel build system and nogo to scale to 90+M LoC with minimal overhead over compilation.

I led this project, which means most of the real work is to be credited to Sonal Mahajan, Julia Turcotti, Yuxing Wang and many others at Uber

A polyglot code transformation toolset for automating large scale changes

Piranha began as an automated cross-paltform tool to eliminate stale feature flags in Uber's codebase and related dead code, with three separate language-specific implementations. The current version of the tool is a polyglot (cross-language) code transformation framework built on top of the tree-sitter parsing infrastructure. It provides a lightweight, yet surprisingly flexible, DSL for cascading code transformations.

with Ameya Ketkar, Murali Krishna Ramanathan, and others at Uber

A static analysis tool for preventing UI access off the main thread in stream-based (RxJava/RxAndroid) Android applications.

The RxThreadEffectChecker is built on the Checker Framework, and particularly it works in tandem with their guieffect checker. It extends these checkers with awaraness of the ReactiveX stream-based threading model. We deployed RxThreadEffectChecker at Uber, then later replaced it with a faster (but regrettably not open-source) implementation, using the same type system directly atop the Error Prone framework.

with Benno Stein, Manu Sridharan, and others at Uber