bazel-differ

README

bazel-differ

bazel-differ is a command line interface for Bazel that helps you do incremental builds across different Git versions. bazel-differ is a mostly a pure Go port of the excellent bazel-diff and should be able to function as a drop-in replacement for most use cases.

CLI

bazel-differ is a CLI tool to assist with doing differential Bazel builds

Usage:
  bazel-differ [command]

Available Commands:
  completion      Generate the autocompletion script for the specified shell
  diff            Writes to a file the impacted targets between two Bazel graph JSON files
  generate-hashes Writes to a file the SHA256 hashes for each Bazel Target in the provided workspace.
  get-targets     Collects a set of a targets between the specified commit ranges
  help            Help about any command

Flags:
  -z, --bazelCommandOptions string   Additional space separated Bazel command options used when invoking Bazel
  -b, --bazelPath string             Path to Bazel binary
  -y, --bazelStartupOptions string   Additional space separated Bazel client startup options used when invoking Bazel
  -h, --help                         help for bazel-differ
  -k, --keep_going bazel query       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` (default true)
  -v, --verbose                      enables verbose output
  -w, --workspacePath string         Path to Bazel workspace directory.

Use "bazel-differ [command] --help" for more information about a command.

If you are using as a replacement for bazel-diff, then you will probably use the generate-hashes and diff commands. Alternatively, you can make use of the get-targets command to eliminate the need for an external shell script:

Collects a set of a targets between the specified commit ranges. By default,
the final set of targets is run through a Bazel query "set({{.Targets}})" which can be customized by the -q parameter.
If you want to query all tests impacted for the given commit range, you can do:

$ bazel-differ get-targets -w path/to/workspace -b $(which bazel) -s START_HASH -f FINAL_HASH -q 'kind(".*_test",set({{.Targets}}))' -o test_targets.txt

Usage:
  bazel-differ get-targets [flags]

Flags:
      --cache-dir string          Directory to cache hashes associated with commits
  -f, --finalRevision string      The Git revision to use to generate the ending hashes
  -h, --help                      help for get-targets
      --nocache                   Disables hash caching (default false)
  -o, --output string             Filepath to write the impacted Bazel targets to, newline separated
  -q, --query string              The query template to use when querying for changed targets
  -s, --startingRevision string   The Git revision to generate the ending hashes

Global Flags:
  -z, --bazelCommandOptions string   Additional space separated Bazel command options used when invoking Bazel
  -b, --bazelPath string             Path to Bazel binary
  -y, --bazelStartupOptions string   Additional space separated Bazel client startup options used when invoking Bazel
  -k, --keep_going bazel query       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` (default true)
  -v, --verbose                      enables verbose output
  -w, --workspacePath string         Path to Bazel workspace directory.

Running the example above, then allows you to run:

$ bazel test --target_pattern_file=test_targets.txt

By default, the hashes for a given Git revision are cached to disk so you can run multiple invocations of get-target without paying a penalty for recalculating the hashes every time.

FAQ

1. Why did you port bazel-diff?

A couple reasons:

• The projects I work with don't have any JVM dependencies so using bazel-diff was adding some additional build time we wanted to eliminate
• We wanted to add a fair amount of functionality on top of bazel-diff and porting it to Go wasn't a huge lift. Most tooling in the Bazel ecosystem is written in Go (with the exception of the Bazel server)

1. What are the differences from bazel-diff?

• Some of the short codes for the CLI are different (only supporting one character instead of two)
• Due to some minor implementation differences, the actual hashes generated by the two programs are different

1. What target types has this been tested against?

• bazel-differ runs compatibility tests to validate it's target outputs vs. bazel-diff. Additional test cases can be added via tools/test_compatibility.sh.