Yaml `new DeleteKey("$.*")` leads to two cycles if followed by `new MergeYaml`

[timtebeek]

This test fails with the Expected recipe to complete in 1 cycle, but took 2 cycles. Each individual recipe would pass its own equivalent test, so this is a minimal subset required to fail the test.

Also this test no longer fails if the JSON matcher passed to DeleteKey is $.x rather than $.*. So there is clearly something different about how DeleteKey operates when asked to remove all root entries rather than the only root entry.

import org.junit.jupiter.api.Test;
import org.openrewrite.config.CompositeRecipe;
import org.openrewrite.test.RewriteTest;

import java.util.List;

import static org.openrewrite.yaml.Assertions.yaml;

class CycleTest implements RewriteTest {
    @Test
    void testCycles() {
        rewriteRun(
          spec -> spec.recipe(
            new CompositeRecipe(
              List.of(
                new DeleteKey("$.*", null),
                new MergeYaml("$", "foo: bar", null, "test.yml", null, null, null, null)
              )
            )
          ),
          yaml(
            """
              x: y
              """,
            """
              foo: bar
              """,
            spec -> spec.path("test.yml")
          )
        );
    }
}

Slack Message

[knutwannheden]

I think I remember having to allow this recipe to use two cycles in many tests. As this is a pretty frequently used recipe, it would be great if we could fix this.

[greg-at-moderne]

Isn't it the case that the LST nodes get re-generated with different UUIDs?

After the first cycle, the YAML should be:

foo: bar

And when you apply DeleteKey() + Merge(foo:bar), the resulting text is the same, but the LST is different because of changed UUID?

Also this test no longer fails if the JSON matcher passed to DeleteKey is $.x rather than $.*

Yeah, because after the first cycle, there's no $.x to delete.

[knutwannheden]

I took another look at this. The problem appears to be that the DeleteKey has no "idempotence protection". So both recipes do the right thing in the first cycle and then in the second cycle the DeleteKey recipe just deletes what the MergeYaml recipe inserted.