This directory provides a collection of examples for extending Bazel by writing custom rules. The examples are categorized into basic rule features and advanced scenarios to help you understand how to manipulate actions, manage dependencies, and handle outputs.
Basic Rule Features
Use these examples to learn the fundamentals of rule implementation:
- Rule Creation:
empty/ shows the absolute minimum required to define a rule. - Attributes:
attributes/ demonstrates how to define and use rule attributes. - Actions:
actions.run: Using a binary target as an implicit dependency and executing it.actions.write: Generating a file directly.expand_template: Generating files based on a template.shell command: Executing shell commands for text processing.
- Dependency Information:
mandatory provider: Accessing information from a dependency via a mandatory provider.optional provider: Accessing information from a dependency via an optional provider.depsets: Using depset to gather transitive information from dependencies.
Advanced Rule Scenarios
Use these examples for more complex control over rule behavior:
- Execution & Testing:
executable/ for executable rules, test rule/ for test rules, and runfiles/ for rules requiring specific files at runtime. - Dependency Management:
computed dependencies/ where implicit dependencies are determined by rule attributes. - Output Management:
predeclared outputs: Using attr.output_list and outputs.implicit output: Handling outputs that are only available when explicitly requested.
- Aspects:
aspect/ demonstrates how to use an aspect to collect information from other rules in the dependency graph.
