fix: validate that members bound to URI paths are non-null at object construction (#666)

Author: ianbotsf

.changes/ec8ea669-5999-45d9-ad8e-dbb8d35d3c4e.json

@@ -0,0 +1,8 @@
+{
+    "id": "ec8ea669-5999-45d9-ad8e-dbb8d35d3c4e",
+    "type": "bugfix",
+    "description": "Validate that members bound to URI paths are non-null at object construction",
+    "issues": [
+        "awslabs/smithy-kotlin#139"
+    ]
+}

smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/StructureGenerator.kt

@@ -14,6 +14,7 @@ import software.amazon.smithy.model.shapes.MemberShape
 import software.amazon.smithy.model.shapes.ShapeType
 import software.amazon.smithy.model.shapes.StructureShape
 import software.amazon.smithy.model.traits.ErrorTrait
+import software.amazon.smithy.model.traits.HttpLabelTrait
 import software.amazon.smithy.model.traits.RetryableTrait
 import software.amazon.smithy.model.traits.SensitiveTrait
 import software.amazon.smithy.model.traits.StreamingTrait
@@ -69,16 +70,29 @@ class StructureGenerator(
             val (memberName, memberSymbol) = memberNameSymbolIndex[it]!!
             writer.renderMemberDocumentation(model, it)
             writer.renderAnnotations(it)
-            if (shape.isError && "message" == memberName) {
-                val targetShape = model.expectShape(it.target)
+            renderImmutableProperty(it, memberName, memberSymbol)
+        }
+    }
+
+    private fun renderImmutableProperty(memberShape: MemberShape, memberName: String, memberSymbol: Symbol) {
+        when {
+            shape.isError && memberName == "message" -> {
+                val targetShape = model.expectShape(memberShape.target)
                 if (!targetShape.isStringShape) {
                     throw CodegenException("Message is a reserved name for exception types and cannot be used for any other property")
                 }
                 // override Throwable's message property
                 writer.write("override val #1L: #2F = builder.#1L", memberName, memberSymbol)
-            } else {
-                writer.write("val #1L: #2F = builder.#1L", memberName, memberSymbol)
             }
+
+            memberShape.hasTrait<HttpLabelTrait>() ->
+                writer.write(
+                    """val #1L: #2F = requireNotNull(builder.#1L) { "A non-null value must be provided for #1L" }""",
+                    memberName,
+                    memberSymbol,
+                )
+
+            else -> writer.write("val #1L: #2F = builder.#1L", memberName, memberSymbol)
         }
     }
 

smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/protocol/HttpProtocolUnitTestResponseGenerator.kt

@@ -4,12 +4,15 @@
  */
 package software.amazon.smithy.kotlin.codegen.rendering.protocol
 
+import software.amazon.smithy.codegen.core.CodegenException
 import software.amazon.smithy.codegen.core.Symbol
 import software.amazon.smithy.kotlin.codegen.core.*
 import software.amazon.smithy.kotlin.codegen.model.hasStreamingMember
 import software.amazon.smithy.kotlin.codegen.model.hasTrait
+import software.amazon.smithy.kotlin.codegen.model.shape
 import software.amazon.smithy.kotlin.codegen.rendering.ShapeValueGenerator
 import software.amazon.smithy.model.shapes.*
+import software.amazon.smithy.model.traits.HttpLabelTrait
 import software.amazon.smithy.model.traits.StreamingTrait
 import software.amazon.smithy.protocoltests.traits.HttpResponseTestCase
 
@@ -80,8 +83,15 @@ open class HttpProtocolUnitTestResponseGenerator protected constructor(builder:
                     val inputShape = model.expectShape(it)
                     val inputSymbol = symbolProvider.toSymbol(inputShape)
 
+                    val labelMembers = inputShape.members().filter { it.hasTrait<HttpLabelTrait>() }
+
                     // invoke the DSL builder for the input type
-                    writer.write("val input = ${inputSymbol.name}{}")
+                    writer.withBlock("val input = #T {", "}", inputSymbol) {
+                        labelMembers.forEach { memberShape ->
+                            val memberSymbol = symbolProvider.toSymbol(memberShape)
+                            write("#L = #L", memberShape.defaultName(), memberSymbol.defaultUnboxedValue())
+                        }
+                    }
                 }
 
                 val service = symbolProvider.toSymbol(serviceShape)
@@ -178,3 +188,13 @@ open class HttpProtocolUnitTestResponseGenerator protected constructor(builder:
             HttpProtocolUnitTestResponseGenerator(this)
     }
 }
+
+private fun Symbol.defaultUnboxedValue(): String = when (shape) {
+    is LongShape -> "0L"
+    is FloatShape -> "0.0f"
+    is DoubleShape -> "0.0"
+    is NumberShape -> "0"
+    is StringShape -> "\"\""
+    is BooleanShape -> "false"
+    else -> throw CodegenException("Cannot determine default value for unsupported shape $shape")
+}

smithy-kotlin-codegen/src/test/kotlin/software/amazon/smithy/kotlin/codegen/rendering/StructureGeneratorTest.kt

@@ -280,6 +280,44 @@ class StructureGeneratorTest {
         generated.shouldContainOnlyOnceWithDiff(expected)
     }
 
+    @Test
+    fun `it handles HTTP labels in initializers`() {
+        val model = """
+            @http(method: "POST", uri: "/foo/{bar}/{baz}")
+            operation Foo {
+                input: FooRequest
+            }
+            
+            structure FooRequest {
+                @required
+                @httpLabel
+                bar: String,
+                
+                @required
+                @httpLabel
+                baz: Integer,
+                
+                @httpPayload
+                qux: String
+            }
+        """.prependNamespaceAndService(operations = listOf("Foo")).toSmithyModel()
+
+        val provider: SymbolProvider = KotlinCodegenPlugin.createSymbolProvider(model)
+        val writer = KotlinWriter(TestModelDefault.NAMESPACE)
+        val struct = model.expectShape<StructureShape>("com.test#FooRequest")
+        val renderingCtx = RenderingContext(writer, struct, model, provider, model.defaultSettings())
+        StructureGenerator(renderingCtx).render()
+
+        val generated = writer.toString()
+        val expected = """
+            class FooRequest private constructor(builder: Builder) {
+                val bar: kotlin.String? = requireNotNull(builder.bar) { "A non-null value must be provided for bar" }
+                val baz: kotlin.Int? = requireNotNull(builder.baz) { "A non-null value must be provided for baz" }
+                val qux: kotlin.String? = builder.qux
+        """.formatForTest(indent = "")
+        generated.shouldContainOnlyOnceWithDiff(expected)
+    }
+
     @Test
     fun `it handles blob shapes`() {
         // blobs (with and without streaming) require special attention in equals() and hashCode() implementations