bazel-diff

bazel-diff is a command line tool for Bazel projects that allows users to determine the exact affected set of impacted targets between two Git revisions. Using this set, users can test or build the exact modified set of targets.

bazel-diff offers several key advantages over rolling your own target diffing solution

bazel-diff is designed for very large Bazel projects. We use Java Protobuf's parseDelimitedFrom method alongside Bazel Query's streamed_proto output option. These two together allow you to parse Gigabyte or larger protobuf messages. We have tested it with projects containing tens of thousands of targets.
We avoid usage of large command line query lists when interacting with Bazel, issue here. When you interact with Bazel with thousands of query parameters you can reach an upper maximum limit, seeing this error:

bash: /usr/local/bin/bazel: Argument list too long

bazel-diff is smart enough to prevent these errors

bazel-diff has been tested with file renames, deletions, and modifications. Works on bzl files, WORKSPACE files, BUILD files and regular files

Track the feature request for target diffing in Bazel here

This approach was inspired by the following BazelConf talk by Benjamin Peterson.

There are simpler and faster ways to approximate the affected set of targets. However an incorrect solution can result in a system you can't trust, because tests could be broken at a commit where you didn't select to run them. Then you can't rely on green-to-red (or red-to-green) transitions and lose much of the value from your CI system as breakages can be discovered later on unrelated commits.

Prerequisites

Git
Bazel 3.3.0 or higher
Java 8 JDK or higher (Bazel requires this)

Getting Started

To start using bazel-diff immediately, simply clone down the repo and then run the example shell script:

git clone https://github.com/Tinder/bazel-diff.git
cd bazel-diff
./bazel-diff-example.sh WORKSPACE_PATH BAZEL_PATH START_GIT_REVISION END_GIT_REVISION

Here is a breakdown of those arguments:

WORKSPACE_PATH: Path to directory containing your WORKSPACE file in your Bazel project.
- Note: Your project must use Git for bazel-diff to work!
BAZEL_PATH: Path to your Bazel executable
START_GIT_REVISION: Starting Git Branch or SHA for your desired commit range
END_GIT_REVISION: Final Git Branch or SHA for your desired commit range

You can see the example shell script in action below:

Open bazel-diff-example.sh to see how this is implemented. This is purely an example use-case, but it is a great starting point to using bazel-diff.

How it works

bazel-diff works as follows

The previous revision is checked out, then we run generate-hashes. This gives us the hashmap representation for the entire Bazel graph, then we write this JSON to a file.
Next we checkout the initial revision, then we run generate-hashes and write that JSON to a file. Now we have our final hashmap representation for the Bazel graph.
We run bazel-diff on the starting and final JSON hash filepaths to get our impacted set of targets. This impacted set of targets is written to a file.

CLI Interface

bazel-diff Command

Usage: bazel-diff [-hkV] -b=<bazelPath> [-co=<bazelCommandOptions>]
                  [-fh=<finalHashesJSONPath>] [-o=<outputPath>]
                  [-sh=<startingHashesJSONPath>] [-so=<bazelStartupOptions>]
                  -w=<workspacePath> [COMMAND]
Writes to a file the impacted targets between two Bazel graph JSON files
  -b, --bazelPath=<bazelPath>
                          Path to Bazel binary
      -co, --bazelCommandOptions=<bazelCommandOptions>
                          Additional space separated Bazel command options used
                            when invoking Bazel
      -fh, --finalHashes=<finalHashesJSONPath>
                          The path to the JSON file of target hashes for the
                            final revision. Run 'generate-hashes' to get this
                            value.
  -h, --help              Show this help message and exit.
  -k, --[no-]keep_going   This flag controls if `bazel query` will be executed
                            with the `--keep_going` flag or not. Disabling this
                            flag allows you to catch configuration issues in
                            your Bazel graph, but may not work for some Bazel
                            setups. Defaults to `true`
  -o, --output=<outputPath>
                          Filepath to write the impacted Bazel targets to,
                            newline separated
      -sh, --startingHashes=<startingHashesJSONPath>
                          The path to the JSON file of target hashes for the
                            initial revision. Run 'generate-hashes' to get this
                            value.
      -so, --bazelStartupOptions=<bazelStartupOptions>
                          Additional space separated Bazel client startup
                            options used when invoking Bazel
  -V, --version           Print version information and exit.
  -w, --workspacePath=<workspacePath>
                          Path to Bazel workspace directory.

generate-hashes Command

Usage: bazel-diff generate-hashes [-hkV] -b=<bazelPath>
                                  [-co=<bazelCommandOptions>]
                                  [-s=<seedFilepaths>]
                                  [-so=<bazelStartupOptions>]
                                  -w=<workspacePath> <outputPath>
Writes to a file the SHA256 hashes for each Bazel Target in the provided
workspace.
      <outputPath>        The filepath to write the resulting JSON of
                            dictionary target => SHA-256 values
  -b, --bazelPath=<bazelPath>
                          Path to Bazel binary
      -co, --bazelCommandOptions=<bazelCommandOptions>
                          Additional space separated Bazel command options used
                            when invoking Bazel
  -h, --help              Show this help message and exit.
  -k, --[no-]keep_going   This flag controls if `bazel query` will be executed
                            with the `--keep_going` flag or not. Disabling this
                            flag allows you to catch configuration issues in
                            your Bazel graph, but may not work for some Bazel
                            setups. Defaults to `true`
  -s, --seed-filepaths=<seedFilepaths>
                          A text file containing a newline separated list of
                            filepaths, each of these filepaths will be read and
                            used as a seed for all targets.
      -so, --bazelStartupOptions=<bazelStartupOptions>
                          Additional space separated Bazel client startup
                            options used when invoking Bazel
  -V, --version           Print version information and exit.
  -w, --workspacePath=<workspacePath>
                          Path to Bazel workspace directory.

Installing

Integrate into your project (recommended)

Add to your WORKSPACE file:

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_jar")

http_jar(
    name = "bazel_diff",
    urls = [
        "https://github.com/Tinder/bazel-diff/releases/download/3.3.0/bazel-diff_deploy.jar",
    ],
    sha256 = "0dc9166097c181796cfcbde4d16ab304e70cc853c536257c3dfa9af60ddd31e6",
)

and then in your root BUILD.bazel file:

load("@rules_java//java:defs.bzl", "java_binary")

java_binary(
    name = "bazel-diff",
    main_class = "com.bazel_diff.BazelDiff",
    runtime_deps = ["@bazel_diff//jar"],
)

now run the tool with

bazel run //:bazel-diff

Note, in releases prior to 2.0.0 the value for the main_class attribute is just BazelDiff

Run Via JAR Release

curl -LO bazel-diff.jar GITHUB_RELEASE_JAR_URL
java -jar bazel-diff.jar -h

Build from Source

After cloning down the repo, you are good to go, Bazel will handle the rest

To run the project

bazel run :bazel-diff -- bazel-diff -h

Debugging (when running from source)

To run bazel-diff with debug logging, run your commands with the verbose config like so:

bazel run :bazel-diff --config=verbose -- bazel-diff -h

Build your own deployable JAR

bazel build //src/main/java/com/bazel_diff:bazel-diff_deploy.jar
java -jar bazel-bin/src/main/java/com/bazel_diff/bazel-diff_deploy.jar # This JAR can be run anywhere

Build from source in your Bazel Project

Add the following to your WORKSPACE file to add the external repositories, replacing the RELEASE_ARCHIVE_URL with the archive url of the bazel-diff release you wish to depend on:

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
  name = "bazel_diff",
  urls = [
        "RELEASE_ARCHIVE_URL",
    ],
    sha256 = "UPDATE_ME",
    strip_prefix = "UPDATE_ME"
)

load("@bazel_diff//:repositories.bzl", "bazel_diff_dependencies")

bazel_diff_dependencies()

load("@rules_jvm_external//:defs.bzl", "maven_install")
load("@bazel_diff//:artifacts.bzl", "BAZEL_DIFF_MAVEN_ARTIFACTS")

maven_install(
    name = "bazel_diff_maven",
    artifacts = BAZEL_DIFF_MAVEN_ARTIFACTS,
    repositories = [
        "http://uk.maven.org/maven2",
        "https://jcenter.bintray.com/",
    ],
)

Now you can simply run bazel-diff from your project:

bazel run @bazel_diff//:bazel-diff -- bazel-diff -h

Running the tests

To run the tests simply run

bazel test //test/...

Versioning

We use SemVer for versioning. For the versions available, see the tags on this repository.

License

Copyright (c) 2020, Match Group, LLC
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of Match Group, LLC nor the names of its contributors
      may be used to endorse or promote products derived from this software
      without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL MATCH GROUP, LLC BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Name		Name	Last commit message	Last commit date
Latest commit History 159 Commits
.github/workflows		.github/workflows
integration		integration
src/main/java/com/bazel_diff		src/main/java/com/bazel_diff
test/java/com/bazel_diff		test/java/com/bazel_diff
.bazelrc		.bazelrc
.gitignore		.gitignore
BUILD		BUILD
LICENSE		LICENSE
README.md		README.md
WORKSPACE		WORKSPACE
artifacts.bzl		artifacts.bzl
bazel-diff-example.sh		bazel-diff-example.sh
constants.bzl		constants.bzl
demo.gif		demo.gif
repositories.bzl		repositories.bzl

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bazel-diff

Prerequisites

Getting Started

How it works

CLI Interface

Installing

Integrate into your project (recommended)

Run Via JAR Release

Build from Source

Debugging (when running from source)

Build your own deployable JAR

Build from source in your Bazel Project

Running the tests

Versioning

License

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bazel-diff

Prerequisites

Getting Started

How it works

CLI Interface

Installing

Integrate into your project (recommended)

Run Via JAR Release

Build from Source

Debugging (when running from source)

Build your own deployable JAR

Build from source in your Bazel Project

Running the tests

Versioning

License

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