Implement Display for shapes reachable from error shapes

Fahad Zubair · Fahad Zubair · commit 57c93067c5b0 · 2025-04-02T21:17:44.000+01:00
diff --git a/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/ClientCodegenVisitor.kt b/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/ClientCodegenVisitor.kt
@@ -42,6 +42,7 @@ import software.amazon.smithy.rust.codegen.core.smithy.generators.BuilderGenerat
 import software.amazon.smithy.rust.codegen.core.smithy.generators.StructureGenerator
 import software.amazon.smithy.rust.codegen.core.smithy.generators.UnionGenerator
 import software.amazon.smithy.rust.codegen.core.smithy.protocols.ProtocolGeneratorFactory
+import software.amazon.smithy.rust.codegen.core.smithy.transformers.AddSyntheticTraitForImplDisplay
 import software.amazon.smithy.rust.codegen.core.smithy.transformers.EventStreamNormalizer
 import software.amazon.smithy.rust.codegen.core.smithy.transformers.OperationNormalizer
 import software.amazon.smithy.rust.codegen.core.smithy.transformers.RecursiveShapeBoxer
@@ -146,6 +147,9 @@ class ClientCodegenVisitor(
             .let(EventStreamNormalizer::transform)
             // Mark operations incompatible with stalled stream protection as such
             .let(DisableStalledStreamProtection::transformModel)
+            // Add synthetic trait to shapes referenced by error types to ensure they implement `Display`.
+            // This ensures error formatting works correctly for nested structures.
+            .let(AddSyntheticTraitForImplDisplay::transform)
 
     /**
      * Execute code generation
diff --git a/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/generators/protocol/ProtocolParserGenerator.kt b/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/generators/protocol/ProtocolParserGenerator.kt
@@ -14,6 +14,7 @@ import software.amazon.smithy.rust.codegen.client.smithy.generators.OperationCus
 import software.amazon.smithy.rust.codegen.client.smithy.generators.OperationSection
 import software.amazon.smithy.rust.codegen.client.smithy.generators.http.ResponseBindingGenerator
 import software.amazon.smithy.rust.codegen.core.rustlang.Attribute
+import software.amazon.smithy.rust.codegen.core.rustlang.RustType
 import software.amazon.smithy.rust.codegen.core.rustlang.RustWriter
 import software.amazon.smithy.rust.codegen.core.rustlang.Writable
 import software.amazon.smithy.rust.codegen.core.rustlang.assignment
@@ -33,6 +34,7 @@ import software.amazon.smithy.rust.codegen.core.smithy.protocols.HttpLocation
 import software.amazon.smithy.rust.codegen.core.smithy.protocols.Protocol
 import software.amazon.smithy.rust.codegen.core.smithy.protocols.ProtocolFunctions
 import software.amazon.smithy.rust.codegen.core.smithy.protocols.parse.StructuredDataParserGenerator
+import software.amazon.smithy.rust.codegen.core.smithy.rustType
 import software.amazon.smithy.rust.codegen.core.smithy.transformers.operationErrors
 import software.amazon.smithy.rust.codegen.core.util.UNREACHABLE
 import software.amazon.smithy.rust.codegen.core.util.dq
@@ -163,10 +165,11 @@ class ProtocolParserGenerator(
                                     }
                                 }
                                 val errorMessageMember = errorShape.errorMessageMember()
-                                // If the message member is optional and wasn't set, we set a generic error message.
+                                // If the message member is optional, is of `String` Rust type and wasn't set, we set a generic error message.
                                 if (errorMessageMember != null) {
                                     val symbol = symbolProvider.toSymbol(errorMessageMember)
-                                    if (symbol.isOptional()) {
+                                    val currentRustType = symbol.rustType()
+                                    if (symbol.isOptional() && currentRustType == RustType.String) {
                                         rust(
                                             """
                                             if tmp.message.is_none() {
diff --git a/codegen-client/src/test/kotlin/software/amazon/smithy/rust/codegen/client/smithy/generators/ClientErrorReachableShapesDisplayTest.kt b/codegen-client/src/test/kotlin/software/amazon/smithy/rust/codegen/client/smithy/generators/ClientErrorReachableShapesDisplayTest.kt
@@ -0,0 +1,16 @@
+package software.amazon.smithy.rust.codegen.client.smithy.generators
+
+import org.junit.jupiter.api.Test
+import software.amazon.smithy.rust.codegen.client.testutil.clientIntegrationTest
+import software.amazon.smithy.rust.codegen.core.testutil.asSmithyModel
+import java.io.File
+
+class ClientErrorReachableShapesDisplayTest {
+    @Test
+    fun correctMissingFields() {
+        var sampleModel = File("../codegen-core/common-test-models/nested-error.smithy").readText().asSmithyModel()
+        clientIntegrationTest(sampleModel) { _, _ ->
+            // It should compile.
+        }
+    }
+}
diff --git a/codegen-core/common-test-models/nested-error.smithy b/codegen-core/common-test-models/nested-error.smithy
@@ -0,0 +1,70 @@
+$version: "2"
+
+namespace sample
+
+use smithy.framework#ValidationException
+use aws.protocols#restJson1
+
+@restJson1
+service SampleService {
+    operations: [SampleOperation]
+}
+
+@http(uri: "/anOperation", method: "POST")
+operation SampleOperation {
+    output:= {}
+    input:= {}
+    errors: [
+        SimpleError,
+        ErrorWithCompositeShape,
+        ErrorWithDeepCompositeShape,
+        ComposedSensitiveError
+    ]
+}
+
+@error("client")
+structure ErrorWithCompositeShape {
+    message: ErrorMessage
+}
+
+@error("client")
+structure SimpleError {
+    message: String
+}
+
+structure ErrorMessage {
+    @required
+    statusCode: String
+    @required
+    errorMessage: String
+    requestId: String
+    @required
+    toolName: String
+}
+
+structure WrappedErrorMessage {
+    someValue: Integer
+    contained: ErrorMessage
+}
+
+@error("client")
+structure ErrorWithDeepCompositeShape {
+    message: WrappedErrorMessage
+}
+
+@sensitive
+structure SensitiveMessage {
+    nothing: String
+    should: String
+    bePrinted: String
+}
+
+@error("server")
+structure ComposedSensitiveError {
+    message: SensitiveMessage
+}
+
+@error("server")
+structure ErrorWithNestedError {
+    message: ErrorWithDeepCompositeShape
+}
diff --git a/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/StructureGenerator.kt b/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/StructureGenerator.kt
@@ -24,15 +24,20 @@ import software.amazon.smithy.rust.codegen.core.rustlang.isDeref
 import software.amazon.smithy.rust.codegen.core.rustlang.render
 import software.amazon.smithy.rust.codegen.core.rustlang.rust
 import software.amazon.smithy.rust.codegen.core.rustlang.rustBlock
+import software.amazon.smithy.rust.codegen.core.rustlang.rustBlockTemplate
 import software.amazon.smithy.rust.codegen.core.rustlang.stripOuter
 import software.amazon.smithy.rust.codegen.core.smithy.RuntimeType
+import software.amazon.smithy.rust.codegen.core.smithy.RuntimeType.Companion.preludeScope
 import software.amazon.smithy.rust.codegen.core.smithy.RustSymbolProvider
 import software.amazon.smithy.rust.codegen.core.smithy.customize.NamedCustomization
 import software.amazon.smithy.rust.codegen.core.smithy.customize.Section
 import software.amazon.smithy.rust.codegen.core.smithy.customize.writeCustomizations
 import software.amazon.smithy.rust.codegen.core.smithy.expectRustMetadata
+import software.amazon.smithy.rust.codegen.core.smithy.isOptional
+import software.amazon.smithy.rust.codegen.core.smithy.protocols.serialize.ValueExpression
 import software.amazon.smithy.rust.codegen.core.smithy.renamedFrom
 import software.amazon.smithy.rust.codegen.core.smithy.rustType
+import software.amazon.smithy.rust.codegen.core.smithy.traits.SyntheticImplDisplayTrait
 import software.amazon.smithy.rust.codegen.core.util.REDACTION
 import software.amazon.smithy.rust.codegen.core.util.dq
 import software.amazon.smithy.rust.codegen.core.util.getTrait
@@ -104,20 +109,9 @@ open class StructureGenerator(
         ) {
             writer.rustBlock("fn fmt(&self, f: &mut #1T::Formatter<'_>) -> #1T::Result", RuntimeType.stdFmt) {
                 rust("""let mut formatter = f.debug_struct(${name.dq()});""")
-
                 members.forEach { member ->
                     val memberName = symbolProvider.toMemberName(member)
-                    // If the struct is marked sensitive all fields get redacted, otherwise each field is determined on its own
-                    val fieldValue =
-                        if (shape.shouldRedact(model)) {
-                            REDACTION
-                        } else {
-                            member.redactIfNecessary(
-                                model,
-                                "self.$memberName",
-                            )
-                        }
-
+                    val fieldValue = getFieldValue(member, memberName)
                     rust(
                         "formatter.field(${memberName.dq()}, &$fieldValue);",
                     )
@@ -128,6 +122,66 @@ open class StructureGenerator(
         }
     }
 
+    // If the struct is marked sensitive all fields get redacted, otherwise each field is determined on its own.
+    private fun getFieldValue(
+        member: MemberShape,
+        memberName: String?,
+    ): String {
+        val fieldValue =
+            if (shape.shouldRedact(model)) {
+                REDACTION
+            } else {
+                member.redactIfNecessary(
+                    model,
+                    "self.$memberName",
+                )
+            }
+        return fieldValue
+    }
+
+    private fun renderImplDisplayIfSyntheticImplDisplayTraitApplied() {
+        if (shape.getTrait<SyntheticImplDisplayTrait>() == null) {
+            return
+        }
+
+        val lifetime = shape.lifetimeDeclaration(symbolProvider)
+        writer.rustBlock(
+            "impl ${shape.lifetimeDeclaration(symbolProvider)} #T for $name $lifetime",
+            RuntimeType.Display,
+        ) {
+            writer.rustBlock("fn fmt(&self, f: &mut #1T::Formatter<'_>) -> #1T::Result", RuntimeType.stdFmt) {
+                write("""::std::write!(f, "$name {{")?;""")
+
+                members.forEachIndexed { index, member ->
+                    val separator = if (index > 0) ", " else ""
+                    val memberName = symbolProvider.toMemberName(member)
+                    val shouldRedact = shape.shouldRedact(model) || member.shouldRedact(model)
+
+                    // If the shape is redacted then each member shape will be redacted.
+                    if (shouldRedact) {
+                        write("""::std::write!(f, "$separator$memberName={}", $REDACTION)?;""")
+                    } else {
+                        val variable = ValueExpression.Reference("&self.$memberName")
+                        val memberSymbol = symbolProvider.toSymbol(member)
+
+                        if (memberSymbol.isOptional()) {
+                            rustBlockTemplate("if let #{Some}(inner) = ${variable.asRef()}", *preludeScope) {
+                                write("""::std::write!(f, "$separator$memberName=Some({})", inner)?;""")
+                            }
+                            rustBlock("else") {
+                                write("""::std::write!(f, "$separator$memberName=None")?;""")
+                            }
+                        } else {
+                            write("""::std::write!(f, "$separator$memberName={}", ${variable.asRef()})?;""")
+                        }
+                    }
+                }
+
+                write("""::std::write!(f, "}}")""")
+            }
+        }
+    }
+
     private fun renderStructureImpl() {
         if (accessorMembers.isEmpty()) {
             return
@@ -209,6 +263,7 @@ open class StructureGenerator(
         if (!containerMeta.hasDebugDerive()) {
             renderDebugImpl()
         }
+        renderImplDisplayIfSyntheticImplDisplayTraitApplied()
 
         writer.writeCustomizations(customizations, StructureSection.AdditionalTraitImpls(shape, name))
     }
diff --git a/codegen-core/src/test/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/error/NestedErrorStructureTest.kt b/codegen-core/src/test/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/error/NestedErrorStructureTest.kt
diff --git a/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ServerCodegenVisitor.kt b/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ServerCodegenVisitor.kt
