Unable to add to array using MergeYaml

[seachicken]

Hi. I'm trying to add values ​​to an array using org.openrewrite.yaml.MergeYaml , but it's not merging into the target YAML as expected. Am I using it incorrectly?

versions:

• id("org.openrewrite.rewrite") version "7.26.0"
• rewrite(platform("org.openrewrite:rewrite-bom:8.75.2"))

./gradlew rewriteRun -Drewrite.activeRecipe=test

# rewrite.yml
---
type: specs.openrewrite.org/v1beta/recipe
name: test
recipeList:
- org.openrewrite.yaml.MergeYaml:
    key: $
    yaml: |
      fruit:
      - name: blueberry
    filePattern: config/hoge.yml
    objectIdentifyingProperty: fruit

# config/hoge.yml
---
fruit:
- name: apple
  specs:
  - id: 1

expected:

---
fruit:
- name: apple
  specs:
  - id: 1
- name: blueberry

actual:

---
fruit:
- name: apple
  specs:
  - id: 1
  - name: blueberry

[timtebeek]

Hi @seachicken, thanks for reporting this.

The issue is with the objectIdentifyingProperty value. This parameter specifies the property name within each sequence entry that uniquely identifies it — it's used to determine whether an incoming entry should be merged with an existing one or appended as new.

In your case, the sequence entries under fruit have properties like name and specs. So the correct value is name (not fruit):

---
type: specs.openrewrite.org/v1beta/recipe
name: test
recipeList:
- org.openrewrite.yaml.MergeYaml:
    key: $
    yaml: |
      fruit:
      - name: blueberry
    filePattern: config/hoge.yml
    objectIdentifyingProperty: name

With objectIdentifyingProperty: name, MergeYaml will:

1. Compare name: blueberry (incoming) against name: apple (existing)
2. See they don't match → append blueberry as a new entry in the fruit array

This should give you the expected output:

---
fruit:
- name: apple
  specs:
  - id: 1
- name: blueberry

Let us know if this resolves the issue!

[seachicken]

Thank you for the quick reply. I tried objectIdentifyingProperty: name, but the result was the same.
It works when I modify the target YAML as shown below, so it seems like it's not correctly recognizing the structure.

# config/hoge.yml
---
fruit:
  - name: apple
    specs:
    - id: 1

[seachicken]

Ah, no, I don't want to change the existing format, so I'm looking for a way to add the target YAML to the array without changing its indentation.

The previous information is just for reference, as it showed that it was possible to add to the array when applied to YAML.
I want it to work even in case 1.

case1: ❌ incorrect

# config/hoge.yml
---
fruit:
- name: apple
  specs:
  - id: 1
  ↓
---
fruit:
- name: apple
  specs:
  - id: 1
  - name: blueberry

case2: ✅ correct

# config/hoge.yml
---
fruit:
  - name: apple
    specs:
    - id: 1
  ↓
---
fruit:
  - name: apple
    specs:
    - id: 1
  - name: blueberry

[timtebeek]

Hmm; Would it be possible to fork the project and add a unit test to explain what's not working?

rewrite/rewrite-yaml/src/test/java/org/openrewrite/yaml/MergeYamlTest.java

Lines 32 to 73 in 40ac304

	@DocumentExample
	@Test
	void nonExistentBlock() {
	rewriteRun(
	spec -> spec.recipe(new MergeYaml(
	"$.spec",
	//language=yaml
	"""
	lifecycleRule:
	- action:
	type: Delete
	condition:
	age: 7
	""",
	false,
	null,
	null,
	null,
	null,
	null
	)),
	yaml(
	"""
	apiVersion: storage.cnrm.cloud.google.com/v1beta1
	kind: StorageBucket
	spec:
	bucketPolicyOnly: true
	""",
	"""
	apiVersion: storage.cnrm.cloud.google.com/v1beta1
	kind: StorageBucket
	spec:
	bucketPolicyOnly: true
	lifecycleRule:
	- action:
	type: Delete
	condition:
	age: 7
	"""
	)
	);
	}

[seachicken]

This is the test to reproduce.
seachicken@c690cc1#diff-208ae7e16cd121aa54cf1ca2984631854abae12551307acbcec0a79fba812ca2

[timtebeek]

Thanks so much! We'll see if we can get that sorted

[timtebeek]

Exploring a possible fix in

• Fix MergeYaml sequence entry indentation with objectIdentifyingProperty #7113

[timtebeek]

This has been fixed on main and will be available in the next release. With objectIdentifyingProperty: name, MergeYaml correctly appends a new entry as a sibling in the sequence, even with compact YAML indentation (dash at the same level as the parent key).

Added regression tests to confirm both with and without explicit --- document separator:

@Issue("https://github.com/openrewrite/rewrite/discussions/7107")
@Test
void mergeSequenceWithCompactIndentationAndNestedSequence() {
    rewriteRun(
      spec -> spec
        .recipe(new MergeYaml(
          "$",
          //language=yaml
          """
            fruit:
            - name: blueberry
            """,
          false,
          "name",
          null, null, null, null
        )),
      yaml(
        """
          fruit:
          - name: apple
            specs:
            - id: 1
          """,
        """
          fruit:
          - name: apple
            specs:
            - id: 1
          - name: blueberry
          """
      )
    );
}