Bindings¶

Chainsaw has a concept of bindings which can be seen as an execution context.

Bindings are used in assertion trees and resource templating, as well as when using the --values flag when invoking chainsaw.

While some bindings are built-in and provided by chainsaw, it's possible to define custom bindings at the test, step, or individual operation level. Those bindings can in turn be used to create custom environment variables in command and script operations.

Immutability¶

It's important to note that bindings are immutable, it's not possible to overwrite a binding and two bindings with the same name can exist without overwriting each other.

When a binding value is resolved, chainsaw will walk the binding chain upwards until it finds a binding with the expected name. Effectively, the last one registered in the chain will be used.

Templating¶

A binding name supports templating.

The name of a binding can therefore be dynamic and depend on values or other bindings.

Usage¶

The example below defines custom bindings at the test level.

Test level bindings

apiVersion: chainsaw.kyverno.io/v1alpha1
kind: Test
metadata:
  name: example
spec:
  # bindings defined at the test level are available to all steps and operations
  bindings:
  - name: hello
    value: hello
  - name: chainsaw
    value: chainsaw
  # `greetings` depends on `$hello` and `$chainsaw` bindings defined above
  - name: greetings
    value: (join(' ', [$hello, $chainsaw]))
  steps:
  - try:
    - script:
        # custom environment variables, defined using custom bindings
        env:
        - name: GREETINGS
          value: ($greetings)
        content: echo $GREETINGS
        check:
          ($error): ~
          ($stdout): hello chainsaw

The example below is similar to the previous one but also defines custom bindings at the step level.

Step level bindings

apiVersion: chainsaw.kyverno.io/v1alpha1
kind: Test
metadata:
  name: example
spec:
  # bindings defined at the test level are available to all steps and operations
  bindings:
  - name: hello
    value: hello
  - name: chainsaw
    value: chainsaw
  steps:
  - bindings:
    # `greetings` depends on `$hello` and `$chainsaw` bindings defined at higher levels
    - name: greetings
      value: (join(' ', [$hello, $chainsaw]))
    try:
    - script:
        # custom environment variables, defined using custom bindings
        env:
        - name: GREETINGS
          value: ($greetings)
        content: echo $GREETINGS
        check:
          ($error): ~
          ($stdout): hello chainsaw

Finally, custom bindings can also be defined at the operation level.

Operation level bindings

apiVersion: chainsaw.kyverno.io/v1alpha1
kind: Test
metadata:
  name: example
spec:
  # bindings defined at the test level are available to all steps and operations
  bindings:
  - name: hello
    value: hello
  steps:
  - bindings:
    - name: chainsaw
      value: chainsaw
    try:
    - script:
        bindings:
        # `greetings` depends on `$hello` and `$chainsaw` bindings defined at the higher levels
        - name: greetings
          value: (join(' ', [$hello, $chainsaw]))
        # custom environment variables, defined using custom bindings
        env:
        - name: GREETINGS
          value: ($greetings)
        content: echo $GREETINGS
        check:
          ($error): ~
          ($stdout): hello chainsaw

Outputs¶

Under certain conditions, bindings can also be used to add computed results to the context.

See Outputs for details.