Support recursive shapes (#32) (a6ce8395) · Commits · Public Repositories / Smithy Rust

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/CodegenVisitor.kt

+6 −2

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		@@ -31,6 +31,7 @@ import software.amazon.smithy.rust.codegen.smithy.generators.ServiceGenerator
		import software.amazon.smithy.rust.codegen.smithy.generators.StructureGenerator
		import software.amazon.smithy.rust.codegen.smithy.generators.UnionGenerator
		import software.amazon.smithy.rust.codegen.smithy.protocols.ProtocolLoader
		import software.amazon.smithy.rust.codegen.smithy.transformers.RecursiveShapeBoxer
		import software.amazon.smithy.rust.codegen.util.CommandFailed
		import software.amazon.smithy.rust.codegen.util.runCommand
		import java.util.logging.Logger
		@@ -57,10 +58,11 @@ class CodegenVisitor(context: PluginContext) : ShapeVisitor.Default<Unit>() {

		init {
		val symbolVisitorConfig = SymbolVisitorConfig(runtimeConfig = settings.runtimeConfig)
		val service = settings.getService(context.model)
		val baseModel = baselineTransform(context.model)
		val service = settings.getService(baseModel)
		val (protocol, generator) = ProtocolLoader.Default.protocolFor(context.model, service)
		protocolGenerator = generator
		model = generator.transformModel(context.model)
		model = generator.transformModel(baseModel)
		val baseProvider = RustCodegenPlugin.BaseSymbolProvider(model, symbolVisitorConfig)
		symbolProvider = generator.symbolProvider(model, baseProvider)

		@@ -74,6 +76,8 @@ class CodegenVisitor(context: PluginContext) : ShapeVisitor.Default<Unit>() {
		httpGenerator = protocolGenerator.buildProtocolGenerator(protocolConfig)
		}

		private fun baselineTransform(model: Model) = RecursiveShapeBoxer.transform(model)

		private fun CodegenWriterDelegator<RustWriter>.includedModules(): List<String> = this.writers.values.mapNotNull { it.module() }

		fun execute() {

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/RustBox.kt→codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/RustBoxTrait.kt

+1 −1

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		@@ -9,7 +9,7 @@ import software.amazon.smithy.model.node.Node
		import software.amazon.smithy.model.shapes.ShapeId
		import software.amazon.smithy.model.traits.Trait

		class RustBox : Trait {
		class RustBoxTrait : Trait {
		val ID = ShapeId.from("software.amazon.smithy.rust.codegen.smithy.rust.synthetic#box")
		override fun toNode(): Node = Node.objectNode()

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/SymbolVisitor.kt

+1 −1

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		@@ -132,7 +132,7 @@ class SymbolVisitor(
		}

		private fun handleRustBoxing(symbol: Symbol, shape: Shape): Symbol {
		return if (shape.hasTrait(RustBox::class.java)) {
		return if (shape.hasTrait(RustBoxTrait::class.java)) {
		val rustType = RustType.Box(symbol.rustType())
		with(Symbol.builder()) {
		rustType(rustType)

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/transformers/RecursiveShapeBoxer.kt

0 → 100644

+87 −0

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		package software.amazon.smithy.rust.codegen.smithy.transformers

		import software.amazon.smithy.codegen.core.TopologicalIndex
		import software.amazon.smithy.model.Model
		import software.amazon.smithy.model.shapes.ListShape
		import software.amazon.smithy.model.shapes.MapShape
		import software.amazon.smithy.model.shapes.MemberShape
		import software.amazon.smithy.model.shapes.SetShape
		import software.amazon.smithy.model.shapes.Shape
		import software.amazon.smithy.model.transform.ModelTransformer
		import software.amazon.smithy.rust.codegen.smithy.RustBoxTrait

		object RecursiveShapeBoxer {
		/**
		* Transform a model which may contain recursive shapes into a model annotated with [RustBoxTrait]
		*
		* When recursive shapes do NOT go through a List, Map, or Set, they must be boxed in Rust. This function will
		* iteratively find loops & add the `RustBox` trait in a deterministic way until it reaches a fixed point.
		*
		* This function MUST be deterministic (always choose the same shapes to `Box`). If it is not, that is a bug. Even so
		* this function may cause backward compatibility issues in certain pathological cases where a changes to recursive
		* structures cause different members to be boxed. We may need to address these via customizations.
		*/
		fun transform(model: Model): Model {
		val next = transformInner(model)
		return if (next == null) {
		model
		} else {
		transform(next)
		}
		}

		/**
		* If [model] contains a recursive loop that must be boxed, apply one instance of [RustBoxTrait] return the new model.
		* If [model] contains no loops, return null.
		*/
		private fun transformInner(model: Model): Model? {
		// Execute 1-step of the boxing algorithm in the path to reaching a fixed point
		// 1. Find all the shapes that are part of a cycle
		// 2. Find all the loops that those shapes are part of
		// 3. Filter out the loops that go through a layer of indirection
		// 3. Pick _just one_ of the remaining loops to fix
		// 4. Select the member shape in that loop with the earliest shape id
		// 5. Box it.
		// (External to this function) Go back to 1.
		val index = TopologicalIndex(model)
		val recursiveShapes = index.recursiveShapes
		val loops = recursiveShapes.map {
		// Get all the shapes in the closure (represented as Paths
		shapeId ->
		index.getRecursiveClosure(shapeId)
		}.flatMap {
		// flatten the connections into shapes
		loops ->
		loops.map { it.shapes }
		}
		val loopToFix = loops.firstOrNull { !containsIndirection(it) }

		return loopToFix?.let { loop: List<Shape> ->
		check(loop.isNotEmpty())
		// pick the shape to box in a deterministic way
		val shapeToBox = loop.filterIsInstance<MemberShape>().minBy { it.id }!!
		ModelTransformer.create().mapShapes(model) { shape ->
		if (shape == shapeToBox) {
		shape.asMemberShape().get().toBuilder().addTrait(RustBoxTrait()).build()
		} else {
		shape
		}
		}
		}
		}

		/**
		* Check if a List<Shape> contains a shape which will use a pointer when represented in Rust, avoiding the
		* need to add more Boxes
		*/
		private fun containsIndirection(loop: List<Shape>): Boolean {
		return loop.find {
		when (it) {
		is ListShape,
		is MapShape,
		is SetShape -> true
		else -> it.hasTrait(RustBoxTrait::class.java)
		}
		} != null
		}
		}

codegen/src/test/kotlin/software/amazon/smithy/rust/codegen/smithy/transformers/RecursiveShapeBoxerTest.kt

0 → 100644

+75 −0

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		package software.amazon.smithy.rust.codegen.smithy.transformers

		import io.kotest.matchers.shouldBe
		import org.junit.jupiter.api.Test
		import software.amazon.smithy.model.shapes.MemberShape
		import software.amazon.smithy.rust.codegen.smithy.RustBoxTrait
		import software.amazon.smithy.rust.codegen.util.lookup
		import software.amazon.smithy.rust.testutil.asSmithy
		import kotlin.streams.toList

		internal class RecursiveShapeBoxerTest {
		@Test
		fun `leave non-recursive models unchanged`() {
		val model = """
		namespace com.example
		list BarList {
		member: Bar
		}
		structure Hello {
		bars: BarList
		}

		structure Bar {
		hello: Hello
		}
		""".asSmithy()
		RecursiveShapeBoxer.transform(model) shouldBe model
		}

		@Test
		fun `add the box trait to simple recursive shapes`() {
		val model = """
		namespace com.example
		structure Recursive {
		RecursiveStruct: Recursive,
		anotherField: Boolean
		}
		""".asSmithy()
		val transformed = RecursiveShapeBoxer.transform(model)
		val member: MemberShape = transformed.lookup("com.example#Recursive\$RecursiveStruct")
		member.expectTrait(RustBoxTrait::class.java)
		}

		@Test
		fun `add the box trait to complex structures`() {
		val model = """
		namespace com.example
		structure Expr {
		left: Atom,
		right: Atom
		}

		union Atom {
		add: Expr,
		sub: Expr,
		literal: Integer,
		more: SecondTree
		}

		structure SecondTree {
		member: Expr,
		otherMember: Atom,
		third: SecondTree
		}
		""".asSmithy()
		val transformed = RecursiveShapeBoxer.transform(model)
		val boxed = transformed.shapes().filter { it.hasTrait(RustBoxTrait::class.java) }.toList()
		boxed.map { it.id.toString().removePrefix("com.example#") }.toSet() shouldBe setOf(
		"Atom\$add",
		"Atom\$sub",
		"SecondTree\$third",
		"Atom\$more"
		)
		}
		}