AST Refactoring

AST_refactoring.md

Refactoring with AST transforms

Problem

• We want to change the k8s.Client interface to match the client.Client interface.
• The two interfaces are identical except for the fact that client.Client methods all take a context.Context as the first parameter.
• k8s.Client is used everywhere in the codebase and manually changing all occurrences would be very tedious and error-prone.
• In most places, when we modify the method call we need to add an import for context as well.

Possible solutions

• Search and replace script
  • Requires very complicated regex to be written
  • Lots of false positives because it's not aware of the context. (E.g. It will update all Get methods regardless of whether those methods actually belong to the k8s.Client interface.
• Go's example-based refactoring tool eg
  • Unfortunately it doesn't work on my machine and always gets stuck. I suspect it is because it doesn't understand Go modules and tries to refactor ALL the Go code it finds in my machine.
• Custom AST transform
  • What could go wrong?

Go AST Transform

• Convert k8s.Client to match client.Client: https://github.com/charith-elastic/go-ast-refactoring/blob/k8s-client/refactor/main.go

  • Scan the codebase looking for method calls.
  • Check whether the method call is done on a receiver that implements the k8s.Client interface.
  • Prepend context.Background() to the arg list of identified method calls.
  • Import context if required.

• Redirect all log calls to go through the utils/log package instead of the controller-runtime log package: https://github.com/charith-elastic/go-ast-refactoring/blob/log-pkg/refactor/main.go