Declarative YAML format

OpenRewrite allows you to create recipes and styles in YAML. While doing so potentially reduces customizability, it makes up for that with development speed and portability.

To help you confidently define recipes and styles in YAML, this guide will walk you through all of the ways you can configure an OpenRewrite YAML file.

Where OpenRewrite YAML files can exist

There are two places where you can define an OpenRewrite YAML file:

1. Within the rewrite.yml file of a project that applies rewrite recipes via the rewrite-gradle-plugin or rewrite-maven-plugin

2. Inside the META-INF/rewrite folder of a JAR (such as in the rewrite-testing-frameworks)

If you define a recipe or style in the rewrite.yml file, they will not be included in the JARs published from your project.

If you want to distribute a recipe or a style and apply them to other projects, you'll need to create them inside of the META-INF/rewrite folder of a JAR.

Best practices

Please keep these conventions in mind when you're creating OpenRewrite YAML files:

• A file may contain any number of recipes and styles, separated by ---.

• Within a file, recipe and style names must be fully qualified.

• Custom recipes should not be placed into the org.openrewrite namespace. Instead, they should follow the same reverse domain name notation used in Java packages.

Recipes

Format

You can find the full recipe schema here.

Key	Type	Description
type	const	A constant: specs.openrewrite.org/v1beta/recipe
name	string	A fully qualified, unique name for this recipe
displayName	string	A human-readable name for this recipe (does not end with a period)
description	string	A human-readable description for this recipe (ends with a period)
tags	array of strings	A list of strings that help categorize this recipe
estimatedEffortPerOccurrence	duration	The expected amount of time saved each time this recipe fixes something
causesAnotherCycle	boolean	Whether or not this recipe can cause another cycle (defaults to false)
recipeList	array of recipes	The list of recipes which comprise this recipe

Preconditions

Preconditions are used to limit which source files a recipe is run on. This is commonly used to target specific files or directories, but any recipe which is not a ScanningRecipe can be used as a precondition.

Preconditions are a per-file check. If a file passes the precondition check, all recipes will be run on it.

If you need to check if your repository meets certain criteria, instead (e.g., ensuring that a test source set exists), then you will need to write a custom ScanningRecipe.

When a recipe is used as a precondition, any file it would make a change to is considered to meet the precondition. When more than one recipe are used as preconditions, all of them must make a change to the file for it to be considered to meet the precondition.

Only when all preconditions are met will the recipes in the recipe list be run. When applying preconditions to ScanningRecipes they limit both the scanning phase and the edit phase.

Changes made by preconditions are not included in the final result of the recipe. Changes made by preconditions are used only to determine if the recipe should be run.

To create these top-level preconditions, you'll need to add the preconditions map to your declarative recipe's YAML. This object is a list of one or more recipes (formatted the same way as the recipeList).

---
type: specs.openrewrite.org/v1beta/recipe
name: org.openrewrite.PreconditionExample
preconditions:
  - org.openrewrite.text.Find:
      find: 1
recipeList:
  - org.openrewrite.text.ChangeText:
     toText: 2

On its own ChangeText would change the contents of all text files in the project to 2. But because Find is used as a precondition, ChangeText will only be run on files that contain a 1.

Recipes commonly used as preconditions include:

• org.openrewrite.FindSourceFiles - limits the recipe to only run on files whose path matches a glob pattern

• org.openrewrite.text.Find - limits the recipe to only run on files that contain a given string

• org.openrewrite.java.search.FindTypes - limits the recipe to run only on source code which contain a given type

• org.openrewrite.java.search.HasJavaVersion - limits the recipe to run only on Java source code with the specified source or target compatibility versions. Allowing a recipe to be targeted only at Java 8, 11, 17, etc., code.

• org.openrewrite.java.search.IsLikelyTest - limits the recipe to run only on source code which is likely to be test code.

• org.openrewrite.java.search.IsLikelyNotTest - limits the recipe to run only on source code which is likely to be production code.

Recipe list

A declarative recipe can be made up of one or more recipes. The recipes in the list could be other declarative recipes defined in the same file or they can be imperative recipes created elsewhere. Like imperative recipes, each recipe in this list can potentially have configuration options that need to be specified.

Recipes in the recipeList will run in the order they are listed. That being said, a declarative recipe may include another declarative recipe declared later in the same rewrite.yml file.

Recipe example

Consider this example declarative recipe:

---
type: specs.openrewrite.org/v1beta/recipe
name: com.yourorg.RecipeA
displayName: Recipe A
description: Applies Recipe B.
tags:
  - tag1
  - tag2
estimatedEffortPerOccurrence: PT15M
causesAnotherCycle: true
recipeList:
  - com.yourorg.RecipeB:
      exampleConfig1: foo
      exampleConfig2: bar
  - com.yourorg.RecipeC

If you wanted to run this recipe (but not distribute it to others), you would:

1. Copy the above YAML into a rewrite.yml file at the root of your project

2. Configure the Gradle plugin or Maven plugin to have an active recipe of com.yourorg.RecipeA

3. Run the mvn rewrite:run or the gradle rewriteRun command

Styles

Format

You can find the full style schema here.

Key	Type	Description
type	const	A constant: specs.openrewrite.org/v1beta/style
name	string	A fully qualified, unique name for this style
displayName	string	A human-readable name for this style (does not end with a period)
description	string	A human-readable description for this style (ends with a period)
tags	array of strings	A list of strings that help categorize this style
styleConfigs	array of styles	The list of styles which comprise this style

Style example

Consider this example declarative style, which specifies that tabs should be used for indentation and that at least 9999 imports from a given package should be required before collapsing them into a single star import:

---
type: specs.openrewrite.org/v1beta/style
name: com.yourorg.YesTabsNoStarImports
styleConfigs:
  - org.openrewrite.java.style.TabsAndIndentsStyle:
      useTabCharacter: true
  - org.openrewrite.java.style.ImportLayoutStyle:
      classCountToUseStarImport: 9999

To put this style in effect for any formatting performed by OpenRewrite within the current project:

1. Put the above into a rewrite.yml file at the project root

2. Configure the gradle plugin or maven plugin with com.yourorg.YesTabsNoStarImports listed as the active style

The next time any OpenRewrite recipe is run in that project, any formatting it performs will take these styles into account.