• Stars
    star
    3,628
  • Rank 12,143 (Top 0.3 %)
  • Language
    Java
  • License
    MIT License
  • Created about 7 years ago
  • Updated 3 days ago

Reviews

There are no reviews yet. Be the first to send feedback to the community and the maintainers!

Repository Details

A tool to help eliminate NullPointerExceptions (NPEs) in your Java code with low build-time overhead

NullAway: Fast Annotation-Based Null Checking for Java Build Status Coverage Status

NullAway is a tool to help eliminate NullPointerExceptions (NPEs) in your Java code. To use NullAway, first add @Nullable annotations in your code wherever a field, method parameter, or return value may be null. Given these annotations, NullAway performs a series of type-based, local checks to ensure that any pointer that gets dereferenced in your code cannot be null. NullAway is similar to the type-based nullability checking in the Kotlin and Swift languages, and the Checker Framework and Eradicate null checkers for Java.

NullAway is fast. It is built as a plugin to Error Prone and can run on every single build of your code. In our measurements, the build-time overhead of running NullAway is usually less than 10%. NullAway is also practical: it does not prevent all possible NPEs in your code, but it catches most of the NPEs we have observed in production while imposing a reasonable annotation burden, giving a great "bang for your buck."

Installation

Overview

NullAway requires that you build your code with Error Prone, version 2.10.0 or higher. See the Error Prone documentation for instructions on getting started with Error Prone and integration with your build system. The instructions below assume you are using Gradle; see the docs for discussion of other build systems.

Gradle

Java (non-Android)

To integrate NullAway into your non-Android Java project, add the following to your build.gradle file:

plugins {
  // we assume you are already using the Java plugin
  id "net.ltgt.errorprone" version "<plugin version>"
}

dependencies {
  errorprone "com.uber.nullaway:nullaway:<NullAway version>"

  // Optional, some source of nullability annotations.
  // Not required on Android if you use the support 
  // library nullability annotations.
  compileOnly "com.google.code.findbugs:jsr305:3.0.2"

  errorprone "com.google.errorprone:error_prone_core:<Error Prone version>"
}

import net.ltgt.gradle.errorprone.CheckSeverity

tasks.withType(JavaCompile) {
  // remove the if condition if you want to run NullAway on test code
  if (!name.toLowerCase().contains("test")) {
    options.errorprone {
      check("NullAway", CheckSeverity.ERROR)
      option("NullAway:AnnotatedPackages", "com.uber")
    }
  }
}

Let's walk through this script step by step. The plugins section pulls in the Gradle Error Prone plugin for Error Prone integration.

In dependencies, the first errorprone line loads NullAway, and the compileOnly line loads a JSR 305 library which provides a suitable @Nullable annotation (javax.annotation.Nullable). NullAway allows for any @Nullable annotation to be used, so, e.g., @Nullable from the Android Support Library or JetBrains annotations is also fine. The second errorprone line sets the version of Error Prone is used.

Finally, in the tasks.withType(JavaCompile) section, we pass some configuration options to NullAway. First check("NullAway", CheckSeverity.ERROR) sets NullAway issues to the error level (it's equivalent to the -Xep:NullAway:ERROR standard Error Prone argument); by default NullAway emits warnings. Then, option("NullAway:AnnotatedPackages", "com.uber") (equivalent to the -XepOpt:NullAway:AnnotatedPackages=com.uber standard Error Prone argument) tells NullAway that source code in packages under the com.uber namespace should be checked for null dereferences and proper usage of @Nullable annotations, and that class files in these packages should be assumed to have correct usage of @Nullable (see the docs for more detail). NullAway requires at least the AnnotatedPackages configuration argument to run, in order to distinguish between annotated and unannotated code. See the configuration docs for other useful configuration options. For even simpler configuration of NullAway options, use the Gradle NullAway plugin.

We recommend addressing all the issues that Error Prone reports, particularly those reported as errors (rather than warnings). But, if you'd like to try out NullAway without running other Error Prone checks, you can use options.errorprone.disableAllChecks (equivalent to passing "-XepDisableAllChecks" to the compiler, before the NullAway-specific arguments).

Snapshots of the development version are available in Sonatype's snapshots repository.

Android

Versions 3.0.0 and later of the Gradle Error Prone Plugin no longer support Android. So if you're using a recent version of this plugin, you'll need to add some further configuration to run Error Prone and NullAway. Our sample app build.gradle file shows one way to do this, but your Android project may require tweaks. Alternately, 2.x versions of the Gradle Error Prone Plugin still support Android and may still work with your project.

Beyond that, compared to the Java configuration, the com.google.code.findbugs:jsr305:3.0.2 dependency can be removed; you can use the android.support.annotation.Nullable annotation from the Android Support library instead.

Annotation Processors / Generated Code

Some annotation processors like Dagger and AutoValue generate code into the same package namespace as your own code. This can cause problems when setting NullAway to the ERROR level as suggested above, since errors in this generated code will block the build. Currently the best solution to this problem is to completely disable Error Prone on generated code, using the -XepExcludedPaths option added in Error Prone 2.1.3 (documented here, use options.errorprone.excludedPaths= in Gradle). To use, figure out which directory contains the generated code, and add that directory to the excluded path regex.

Note for Dagger users: Dagger versions older than 2.12 can have bad interactions with NullAway; see here. Please update to Dagger 2.12 to fix the problem.

Lombok

Unlike other annotation processors above, Lombok modifies the in-memory AST of the code it processes, which is the source of numerous incompatibilities with Error Prone and, consequently, NullAway.

We do not particularly recommend using NullAway with Lombok. However, NullAway encodes some knowledge of common Lombok annotations and we do try for best-effort compatibility. In particular, common usages like @lombok.Builder and @Data classes should be supported.

In order for NullAway to successfully detect Lombok generated code within the in-memory Java AST, the following configuration option must be passed to Lombok as part of an applicable lombok.config file:

lombok.addLombokGeneratedAnnotation = true

This causes Lombok to add @lombok.Generated to the methods/classes it generates. NullAway will ignore (i.e. not check) the implementation of this generated code, treating it as unannotated.

Code Example

Let's see how NullAway works on a simple code example:

static void log(Object x) {
    System.out.println(x.toString());
}
static void foo() {
    log(null);
}

This code is buggy: when foo() is called, the subsequent call to log() will fail with an NPE. You can see this error in the NullAway sample app by running:

cp sample/src/main/java/com/uber/mylib/MyClass.java.buggy sample/src/main/java/com/uber/mylib/MyClass.java
./gradlew build

By default, NullAway assumes every method parameter, return value, and field is non-null, i.e., it can never be assigned a null value. In the above code, the x parameter of log() is assumed to be non-null. So, NullAway reports the following error:

warning: [NullAway] passing @Nullable parameter 'null' where @NonNull is required
    log(null);
        ^

We can fix this error by allowing null to be passed to log(), with a @Nullable annotation:

static void log(@Nullable Object x) {
    System.out.println(x.toString());
}

With this annotation, NullAway points out the possible null dereference:

warning: [NullAway] dereferenced expression x is @Nullable
    System.out.println(x.toString());
                        ^

We can fix this warning by adding a null check:

static void log(@Nullable Object x) {
    if (x != null) {
        System.out.println(x.toString());
    }
}

With this change, all the NullAway warnings are fixed.

For more details on NullAway's checks, error messages, and limitations, see our detailed guide.

Support

Please feel free to open a GitHub issue if you have any questions on how to use NullAway. Or, you can join the NullAway Discord server and ask us a question there.

Contributors

We'd love for you to contribute to NullAway! Please note that once you create a pull request, you will be asked to sign our Uber Contributor License Agreement.

License

NullAway is licensed under the MIT license. See the LICENSE.txt file for more information.

More Repositories

1

react-vis

Data Visualization Components
JavaScript
8,728
star
2

baseweb

A React Component library implementing the Base design language
TypeScript
8,717
star
3

cadence

Cadence is a distributed, scalable, durable, and highly available orchestration engine to execute asynchronous long-running business logic in a scalable and resilient way.
Go
8,231
star
4

RIBs

Uber's cross-platform mobile architecture framework.
Kotlin
7,744
star
5

kraken

P2P Docker registry capable of distributing TBs of data in seconds
Go
6,071
star
6

prototool

Your Swiss Army Knife for Protocol Buffers
Go
5,044
star
7

causalml

Uplift modeling and causal inference with machine learning algorithms
Python
5,018
star
8

h3

Hexagonal hierarchical geospatial indexing system
C
4,877
star
9

AutoDispose

Automatic binding+disposal of RxJava streams.
Java
3,367
star
10

aresdb

A GPU-powered real-time analytics storage and query engine.
Go
3,022
star
11

react-digraph

A library for creating directed graph editors
JavaScript
2,621
star
12

piranha

A tool for refactoring code related to feature flag APIs
Rust
2,273
star
13

orbit

A Python package for Bayesian forecasting with object-oriented design and probabilistic models under the hood.
Python
1,861
star
14

needle

Compile-time safe Swift dependency injection framework
Swift
1,810
star
15

ios-snapshot-test-case

Snapshot view unit tests for iOS
Objective-C
1,790
star
16

petastorm

Petastorm library enables single machine or distributed training and evaluation of deep learning models from datasets in Apache Parquet format. It supports ML frameworks such as Tensorflow, Pytorch, and PySpark and can be used from pure Python code.
Python
1,785
star
17

manifold

A model-agnostic visual debugging tool for machine learning
JavaScript
1,648
star
18

okbuck

OkBuck is a gradle plugin that lets developers utilize the Buck build system on a gradle project.
Java
1,537
star
19

UberSignature

Provides an iOS view controller allowing a user to draw their signature with their finger in a realistic style.
Objective-C
1,286
star
20

nanoscope

An extremely accurate Android method tracing tool.
HTML
1,250
star
21

tchannel

network multiplexing and framing protocol for RPC
Thrift
1,153
star
22

queryparser

Parsing and analysis of Vertica, Hive, and Presto SQL.
Haskell
1,074
star
23

fiber

Distributed Computing for AI Made Simple
Python
1,043
star
24

neuropod

A uniform interface to run deep learning models from multiple frameworks
C++
937
star
25

uReplicator

Improvement of Apache Kafka Mirrormaker
Java
913
star
26

h3-js

h3-js provides a JavaScript version of H3, a hexagon-based geospatial indexing system.
JavaScript
856
star
27

pam-ussh

uber's ssh certificate pam module
Go
844
star
28

ringpop-go

Scalable, fault-tolerant application-layer sharding for Go applications
Go
828
star
29

h3-py

Python bindings for H3, a hierarchical hexagonal geospatial indexing system
Python
816
star
30

mockolo

Efficient Mock Generator for Swift
Swift
813
star
31

xviz

A protocol for real-time transfer and visualization of autonomy data
JavaScript
760
star
32

streetscape.gl

Visualization framework for autonomy and robotics data encoded in XVIZ
JavaScript
702
star
33

react-view

React View is an interactive playground, documentation and code generator for your components.
TypeScript
697
star
34

nebula.gl

A suite of 3D-enabled data editing overlays, suitable for deck.gl
TypeScript
688
star
35

RxDogTag

Automatic tagging of RxJava 2+ originating subscribe points for onError() investigation.
Java
645
star
36

peloton

Unified Resource Scheduler to co-schedule mixed types of workloads such as batch, stateless and stateful jobs in a single cluster for better resource utilization.
Go
641
star
37

motif

A simple DI API for Android / Java
Kotlin
532
star
38

signals-ios

Typeful eventing
Objective-C
528
star
39

grafana-dash-gen

grafana dash dash dash gen
JavaScript
490
star
40

tchannel-go

Go implementation of a multiplexing and framing protocol for RPC calls
Go
484
star
41

marmaray

Generic Data Ingestion & Dispersal Library for Hadoop
Java
479
star
42

zanzibar

A build system & configuration system to generate versioned API gateways.
Go
460
star
43

clay

Clay is a framework for building RESTful backend services using best practices. It’s a wrapper around Flask.
Python
441
star
44

astro

Astro is a tool for managing multiple Terraform executions as a single command
Go
434
star
45

NEAL

🔎🐞 A language-agnostic linting platform
OCaml
429
star
46

react-vis-force

d3-force graphs as React Components.
JavaScript
403
star
47

arachne

An always-on framework that performs end-to-end functional network testing for reachability, latency, and packet loss
Go
394
star
48

cadence-web

Web UI for visualizing workflows on Cadence
JavaScript
389
star
49

Python-Sample-Application

Python
377
star
50

uber-ios-sdk

Uber iOS SDK (beta)
Swift
375
star
51

stylist

A stylist creates cool styles. Stylist is a Gradle plugin that codegens a base set of Android XML themes.
Kotlin
358
star
52

storagetapper

StorageTapper is a scalable realtime MySQL change data streaming, logical backup and logical replication service
Go
339
star
53

swift-concurrency

Concurrency utilities for Swift
Swift
327
star
54

RemoteShuffleService

Remote shuffle service for Apache Spark to store shuffle data on remote servers.
Java
322
star
55

h3-go

Go bindings for H3, a hierarchical hexagonal geospatial indexing system
Go
304
star
56

cyborg

Display Android Vectordrawables on iOS.
Swift
301
star
57

rides-android-sdk

Uber Rides Android SDK (beta)
Java
292
star
58

hermetic_cc_toolchain

Bazel C/C++ toolchain for cross-compiling C/C++ programs
Starlark
287
star
59

h3-java

Java bindings for H3, a hierarchical hexagonal geospatial indexing system
Java
279
star
60

h3-py-notebooks

Jupyter notebooks for h3-py, a hierarchical hexagonal geospatial indexing system
Jupyter Notebook
260
star
61

geojson2h3

Conversion utilities between H3 indexes and GeoJSON
JavaScript
225
star
62

artist

An artist creates views. Artist is a Gradle plugin that codegens a base set of Android Views.
Kotlin
211
star
63

tchannel-node

JavaScript
203
star
64

RxCentralBle

A reactive, interface-driven central role Bluetooth LE library for Android
Java
199
star
65

uberalls

Track code coverage metrics with Jenkins and Phabricator
Go
186
star
66

SwiftCodeSan

SwiftCodeSan is a tool that "sanitizes" code written in Swift.
Swift
177
star
67

rides-python-sdk

Uber Rides Python SDK (beta)
Python
174
star
68

doubles

Test doubles for Python.
Python
165
star
69

logtron

A logging MACHINE
JavaScript
159
star
70

athenadriver

A fully-featured AWS Athena database driver (+ athenareader https://github.com/uber/athenadriver/tree/master/athenareader)
Go
148
star
71

cadence-java-client

Java framework for Cadence Workflow Service
Java
142
star
72

bayesmark

Benchmark framework to easily compare Bayesian optimization methods on real machine learning tasks
Python
140
star
73

cassette

Store and replay HTTP requests made in your Python app
Python
138
star
74

UBTokenBar

Flexible and extensible UICollectionView based TokenBar written in Swift
Swift
136
star
75

tchannel-java

A Java implementation of the TChannel protocol.
Java
133
star
76

android-template

This template provides a starting point for open source Android projects at Uber.
Java
128
star
77

crumb

An annotation processor for breadcrumbing metadata across compilation boundaries.
Kotlin
124
star
78

py-find-injection

Look for SQL injection attacks in python source code
Python
119
star
79

rides-java-sdk

Uber Rides Java SDK (beta)
Java
104
star
80

startup-reason-reporter

Reports the reason why an iOS App started.
Objective-C
97
star
81

cadence-java-samples

Java
96
star
82

uber-poet

A mock swift project generator & build runner to help benchmark various module dependency graphs.
Python
96
star
83

charlatan

A Python library to efficiently manage and install database fixtures
Python
89
star
84

simple-store

Simple yet performant asynchronous file storage for Android
Java
84
star
85

swift-abstract-class

Compile-time abstract class validation for Swift
Swift
84
star
86

tchannel-python

Python implementation of the TChannel protocol.
Python
76
star
87

lint-checks

A set of opinionated and useful lint checks
Kotlin
72
star
88

client-platform-engineering

A collection of cookbooks, scripts and binaries used to manage our macOS, Ubuntu and Windows endpoints
Ruby
71
star
89

eight-track

Record and playback HTTP requests
JavaScript
70
star
90

multidimensional_urlencode

Python library to urlencode a multidimensional dict
Python
67
star
91

uncaught-exception

Handle uncaught exceptions.
JavaScript
66
star
92

swift-common

Common code used by various Uber open source projects
Swift
66
star
93

uberscriptquery

UberScriptQuery, a SQL-like DSL to make writing Spark jobs super easy
Java
59
star
94

sentry-logger

A Sentry transport for Winston
JavaScript
56
star
95

graph.gl

WebGL2-Powered Visualization Components for Graph Visualization
JavaScript
53
star
96

nanoscope-art

C++
49
star
97

assume-role-cli

CLI for AssumeRole is a tool for running programs with temporary credentials from AWS's AssumeRole API.
Go
47
star
98

airlock

A prober to probe HTTP based backends for health
JavaScript
47
star
99

mutornadomon

Easy-to-install monitor endpoint for Tornado applications
Python
46
star
100

kafka-logger

A kafka logger for winston
JavaScript
45
star