Support Groovy destructuring assignment parsing

[MBoegers]

Summary

• Support parsing Groovy multiple/destructuring assignment syntax (def (a, b, c) = expr)
• Add DestructuringVariables marker to track parenthesized variable lists
• Update printer to correctly round-trip destructuring assignments

Problem

The Groovy parser throws UnsupportedOperationException when encountering destructuring assignments like def (major, minor, patch) = tag.tokenize('.'). This syntax is commonly used in Jenkinsfiles and causes GroovyParsingException for customers.

Solution

• Created DestructuringVariables marker that signals the printer to wrap variables in (...) and place the initializer after )
• Replaced the throw UnsupportedOperationException in visitDeclarationExpression with parsing logic that handles TupleExpression on the left side of a DeclarationExpression
• Updated GroovyPrinter.visitVariableDeclarations to handle the new marker

Test plan

• Existing Groovy tests pass

• New tests added:

  • Basic destructuring: def (a, b, c) = [1, 2, 3]
  • Two variables: def (x, y) = [1, 2]
  • Method call RHS: def (major, minor, patch) = tag.tokenize('.')
  • Extra whitespace preservation: def ( a , b , c ) = [1, 2, 3]
  • No spaces: def (a,b,c) = [1,2,3]

• Fixes moderneinc/customer-requests#1478

• Fixes Groovy parser does not support multiple assignments #4756

• Closes Groovy support for multiple assignment/tuple unpacking #5293

[MBoegers]

@knutwannheden added a test to show we also fix the issue you linked. Happy to have a review here.

[greg-at-moderne]

Probably also fixes:

• Groovy parser fails with parentheses on the left-hand side of the assignment #5283
• Groovy parser does not support multiple assignments #4756

Also likely invalidates:

• Groovy support for multiple assignment/tuple unpacking #5293.

[MBoegers]

@greg-at-moderne checked, yes this PR resolves these issues as well and also covers the linked PR.

[timtebeek]

Linking the VariableDeclarator here:

rewrite/rewrite-java/src/main/java/org/openrewrite/java/tree/VariableDeclarator.java

Lines 23 to 31 in f5f5a9a

	* A variable declarator is a variable name(s). As used in {@link NamedVariable} it forms a name and its initializer.
	* In the most common case, a variable declarator is a single name, but in the case of destructuring
	* assignments, it can be multiple names that are each assigned by the single {@link NamedVariable#getInitializer()}.
	* <p>
	* A fun note on the name: the word VariableDeclarator comes from the Typescript compiler's definition
	* of this concept, and it fits the concept well for all languages in the {@link J} grammar island.
	*/
	public interface VariableDeclarator extends TypedTree {
	List<J.Identifier> getNames();

This was suggested as the replacement in

• Groovy support for multiple assignment/tuple unpacking #5293 (review)

[timtebeek]

@knutwannheden any final thoughts here before a merge? The approach had already been signed off on earlier.