Groovy for Domain-specific Languages - Second Edition

Chapter 12

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// X O X

// O X O

// Expect next X play to win

when:

engine = new GameEngineClient()

engine.play_round([player: 'X'], savedSession)

then:

engine.page == 'game_over'

We now have a Groovy class-based pattern, which implements our game engine.
The DSL will be implemented with an AST transform, which generates classes in
that pattern. So we can now focus on building the AST transform. We know we have
successfully built the AST transformation when the DSL version works with the
preceding test.

Implementing the AST transform

As with all the previous AST transforms, our work begins with writing an
ASTTransformation class:

@GroovyASTTransformation (phase = CompilePhase.SEMANTIC_ANALYSIS)

class GameEngineASTTransformation implements ASTTransformation,

CompilationUnitAware {

def parser

def builder

def compilationUnit

void visit(ASTNode[] nodes, SourceUnit source) {

if (!nodes) return

if (!(nodes[0] instanceof ModuleNode)) return

if (!source?.name?.endsWith('Engine.groovy')) {

return

}

def gameEngineModel = new GameEngineModel()

parser = new EnginePatternParser(gameEngineModel, source)

builder = new EnginePatternBuilder(nodes,

gameEngineModel, source, compilationUnit)

for (ClassNode classNode : nodes[0].classes) {

classNode.visitContents(parser)

}

builder.buildEnginePattern()

}

@Override