Changing structure¶ ↑

First and foremost, changing the structure of the tree in any way is a major breaking change. It forces the consumers to update their visitors, pattern matches, and method calls. It should not be taking lightly, and can only happen on a major version change. So keep that in mind.

That said, if you do want to change the structure of the tree, there are a few steps that you have to take. They are enumerated below.

1. Change the structure in the required node classes. This could mean adding/removing classes or adding/removing fields. Be sure to also update the copy and === methods to be sure that they are correct.

2. Update the parser to correctly create the new structure.

3. Update any visitor methods that are affected by the change. For example, if adding a new node make sure to create the new visit method alias in the Visitor class.

4. Update the FieldVisitor class to be sure that the various serializers, pretty printers, and matchers all get updated accordingly.

5. Update the DSL module to be sure that folks can correctly create nodes with the new structure.

6. Ensure the formatting of the code hasn’t changed. This can mostly be done by running the tests, but if there’s a corner case that we don’t cover that is now exposed by your change be sure to add test cases.

7. Update the translation visitors to ensure we’re still translating into other ASTs correctly.

8. Update the YARV compiler visitor to ensure we’re still compiling correctly.

9. Make sure we aren’t referencing the previous structure in any documentation or tests.

10. Be sure to update CHANGELOG.md with a description of the change that you made.