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https://github.com/Tinder/bazel-diff

Performs Bazel Target Diffing between two revisions in Git, allowing for Test Target Selection and Selective Building
https://github.com/Tinder/bazel-diff

bazel target-selection test-selection

Last synced: 2 months ago
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Performs Bazel Target Diffing between two revisions in Git, allowing for Test Target Selection and Selective Building

Host: GitHub
URL: https://github.com/Tinder/bazel-diff
Owner: Tinder
License: other
Created: 2020-09-14T17:37:18.000Z (almost 4 years ago)
Default Branch: master
Last Pushed: 2024-04-01T15:30:06.000Z (3 months ago)
Last Synced: 2024-04-01T16:04:49.022Z (3 months ago)
Topics: bazel, target-selection, test-selection
Language: Kotlin
Homepage:
Size: 694 KB
Stars: 365
Watchers: 6
Forks: 51
Open Issues: 9
Metadata Files:
- Readme: README.md
- License: LICENSE

Lists

awesome-bazel - bazel-diff - Bazel Target Diffing between two revisions in Git, allowing for Test Target Selection and Selective Building (Tooling / General)

README

# bazel-diff

[![Build status](https://github.com/Tinder/bazel-diff/actions/workflows/ci.yaml/badge.svg?branch=master)](https://github.com/Tinder/bazel-diff/actions/workflows/ci.yaml)

`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

1. `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.
2. We avoid usage of large command line query lists when interacting with Bazel, [issue here](https://github.com/bazelbuild/bazel/issues/8609). 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 avoid these errors.
3. `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](https://github.com/bazelbuild/bazel/issues/7962)

This approach was inspired by the [following BazelConf talk](https://www.youtube.com/watch?v=9Dk7mtIm7_A) 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:

```terminal
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:

![Demo](demo.gif)

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

```terminal
Usage: bazel-diff [-hvV] [COMMAND]
Writes to a file the impacted targets between two Bazel graph JSON files
-h, --help Show this help message and exit.
-v, --verbose Display query string, missing files and elapsed time
-V, --version Print version information and exit.
Commands:
generate-hashes Writes to a file the SHA256 hashes for each Bazel
Target in the provided workspace.
get-impacted-targets Command-line utility to analyze the state of the bazel
build graph
```

### `generate-hashes` command

```terminal
Usage: bazel-diff generate-hashes [-hkvV] [--[no-]useCquery] [-b=]
[--[no-]includeTargetType]
[--contentHashPath=]
[-s=] -w=
[-co=]...
[--cqueryCommandOptions=
]...
[--fineGrainedHashExternalRepos=]...
[-so=]...
Writes to a file the SHA256 hashes for each Bazel Target in the provided
workspace.
The filepath to write the resulting JSON to.
If not specified, the JSON will be written to STDOUT.

By default the JSON schema is a dictionary of target => SHA-256 values.
Example:
{
"//cli:bazel-diff_deploy.jar": "4ae310f8ad2bc728934e3509b6102ca658e828b9cd668f79990e95c6663f9633"
...
}

If --includeTargetType is specified, the JSON schema will include the target type (SourceFile/Rule/GeneratedFile)
Example:
{
"//cli:src/test/resources/fixture/integration-test-1.zip": "SourceFile#c259eba8539f4c14e4536c61975457c2990e090067893f4a2981e7bb5f4ef4cf",
"//external:android_gmaven_r8": "Rule#795f583449a40814c05e1cc5d833002afed8d12bce5b835579c7f139c2462d61",
"//cli:bazel-diff_deploy.jar": "GeneratedFile#4ae310f8ad2bc728934e3509b6102ca658e828b9cd668f79990e95c6663f9633",
...
}
----[no-]includeTargetType
Whether include target type in the generated JSON or not.
If false, the generate JSON schema is: {"": ""}
If true, the generate JSON schema is: {"": "#"
-tt, --targetType=
The type of targets to filter, available options are SourceFile/Rule/GeneratedFile
Only works if the JSON was generated with `--includeTargetType` enabled.
If not specified, all types of impacted targets will be returned.
-b, --bazelPath=
Path to Bazel binary. If not specified, the Bazel
binary available in PATH will be used.
-co, --bazelCommandOptions=
Additional space separated Bazel command options used
when invoking `bazel query`
--contentHashPath=
Path to content hash json file. It's a map which maps
relative file path from workspace path to its
content hash. Files in this map will skip content
hashing and use provided value
--cqueryCommandOptions=
Additional space separated Bazel command options used
when invoking `bazel cquery`. This flag is has no
effect if `--useCquery`is false.
--fineGrainedHashExternalRepos=
Comma separate list of external repos in which
fine-grained hashes are computed for the targets.
By default, external repos are treated as an opaque
blob. If an external repo is specified here,
bazel-diff instead computes the hash for individual
targets. For example, one wants to specify `maven`
here if they user rules_jvm_external so that
individual third party dependency change won't
invalidate all targets in the mono repo.
-h, --help Show this help message and exit.
--ignoredRuleHashingAttributes=
Attributes that should be ignored when hashing rule
targets.
-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=
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=
Additional space separated Bazel client startup
options used when invoking Bazel
--[no-]useCquery If true, use cquery instead of query when generating
dependency graphs. Using cquery would yield more
accurate build graph at the cost of slower query
execution. When this is set, one usually also wants
to set `--cqueryCommandOptions` to specify a
targeting platform. Note that this flag only works
with Bazel 6.2.0 or above because lower versions
does not support `--query_file` flag.
-v, --verbose Display query string, missing files and elapsed time
-V, --version Print version information and exit.
-w, --workspacePath=
Path to Bazel workspace directory.
```

**Note**: `--useCquery` flag may not work with very large repos due to limitation
of Bazel. You may want to fallback to use normal query mode in that case.
See for more details.

### What does the SHA256 value of `generate-hashes` represent?

`generate-hashes` is a canonical SHA256 value representing all attributes and inputs into a target. These inputs
are the summation of the rule implementation hash, the SHA256 value
for every attribute of the rule and then the summation of the SHA256 value for
all `rule_inputs` using the same exact algorithm. For source_file inputs the
content of the file are converted into a SHA256 value.

### `get-impacted-targets` command

```terminal
Usage: bazel-diff get-impacted-targets [-v] -fh=
-o=
-tt=
-sh=
Command-line utility to analyze the state of the bazel build graph
-fh, --finalHashes=
The path to the JSON file of target hashes for the final
revision. Run 'generate-hashes' to get this value.
-o, --output=
Filepath to write the impacted Bazel targets to, newline
separated
-sh, --startingHashes=
The path to the JSON file of target hashes for the initial
revision. Run 'generate-hashes' to get this value.
-tt, --targetType=
The type of targets to filter, available options are SourceFile/Rule/GeneratedFile
Only works if the JSON was generated with `--includeTargetType` enabled.
If not specified, all types of impacted targets will be returned.
-v, --verbose
Display query string, missing files and elapsed time
```

## Installing

### Integrate into your project (recommended)

First, add the following snippet to your project:

#### WORKSPACE Snippet

```bazel
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/6.1.0/bazel-diff_deploy.jar",
],
sha256 = "5d90de4561afd1e711bc62956560a9dfcbb4454bd6b209d6e68272b65c3cb50a",
)
```

#### MODULE.bazel Snippet (if you are using Bzlmod)

```bazel
http_jar = use_repo_rule("@bazel_tools//tools/build_defs/repo:http.bzl", "http_jar")
http_jar(
name = "bazel_diff",
urls = [
"https://github.com/Tinder/bazel-diff/releases/download/7.0.0/bazel-diff_deploy.jar"
],
sha256 = "0b9e32f9c20e570846b083743fe967ae54d13e2a1f7364983e0a7792979442be",
)
```

#### WORKSPACE snippet

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

bazel_diff_dependencies()
```

Second, add in your root `BUILD.bazel` file:

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

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

That's it! You can now run the tool with:

```terminal
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

```terminal
curl -Lo bazel-diff.jar https://github.com/Tinder/bazel-diff/releases/latest/download/bazel-diff_deploy.jar
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

```terminal
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:

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

### Build your own deployable JAR

```terminal
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:

```bazel
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:

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

## Running the tests

To run the tests simply run

```terminal
bazel test //...
```

## Versioning

We use [SemVer](http://semver.org/) for versioning. For the versions available,
see the [tags on this repository](https://github.com/Tinder/bazel-diff/tags).

## License

---

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.
```