salesforce / bazel-mystery

An interactive way to learn bazel.

Bazel Mystery

Can you solve the mystery of the missing Basil? 🌱

This project aims to help with learning how to use the Bazel build tool.

Prerequisites

• Bazelisk installed. Bazelisk will dynamically use the required version of bazel defined in the .bazelversion file.

The Case of the Missing Basil 🌱

Overview

John is a basil farmer. Some of his basil mysteriously went missing. Relevant authorities were informed and a crime scene report was written.

Rules

• Try not to look into the BUILD files at all.
• Try to solve the case by only using bazel queries and this README file.

Crime Scene Report

The crime scene report for this case is kept in a secret location. You can uncover it once. However, after that first time of seeing it, you'll need to use some workarounds to see it again. This is because bazel is very good at caching artifacts that have already been built, so they only need to be built once (until they change or the cache is invalidated).

To see the crime scene report for this case, build the following target:

bazel build crime_scene_reports:missing_basil_089324

If you need to see it again, look at the README.md file in crime_scene_reports for details of how to do that.

Packages

Each package in this repository (e.g. crime_scene_reports and people) contains a README.md file which explains how to interract with the targets contained in the package.

Having an entity relationship diagram for bazel packages seems strange, but for this case it helps to describe the environment and the relationships between targets:

Hints

Discovering the dependencies and reverse dependencies of targets is an important part of solving the case. For example:

Dependencies

bazel query 'deps(//people:john)' --noimplicit_deps
# Returns all of the things that John depends on.
# e.g. his car.

//cars:74383

Reverse Dependencies

bazel query 'rdeps(//..., //people:amy)'
# Returns all of the things that depend on Amy.
# e.g. an interview.

//interviews:454235

Tags

Bazel targets can be tagged with different identifiers. This can be useful if you only want some targets to run in certain environments (e.g. only run a set of tests locally). You can query for the targets that have specific tags:

bazel query 'attr(tags, "blue", cars/...)'
# Returns all of the targets in the car package that have a tag of "blue"

//cars:74383

Checking Your Answer

You can test your answer in the following way:

bazel test solution --test_env guess=John
# Use test_env guess=your_guess to make a guess.
# If the test passes, your guess is correct.

//solution:solution  FAILED in 0.1s

In the above case, we're checking whether John took the missing basil. He didn't, he has plenty of basil already.

Full Solution Walkthrough

If you'd like a walkthrough of how to solve the case, see solution_walkthrough.md.