Fix generation of constrained shapes reaching @sensitive shapes (#2585

)

Constrained shapes should always be able to `#[derive(Debug)]`.

Fixes #2582.

## Testing

The modified integration test fails without this patch applied.

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._

Co-authored-by: Matteo Bigoi <1781140+crisidev@users.noreply.github.com>

CHANGELOG.next.toml

@@ -116,3 +116,9 @@ message = "`aws_smithy_types::date_time::Format` has been re-exported in service
 references = ["smithy-rs#2534"]
 meta = { "breaking" = false, "tada" = false, "bug" = false, "target" = "client" }
 author = "ysaito1001"
+
+[[smithy-rs]]
+message = "Fix generation of constrained shapes reaching `@sensitive` shapes"
+references = ["smithy-rs#2582", "smithy-rs#2585"]
+meta = { "breaking" = false, "tada" = false, "bug" = true, "target" = "server" }
+author = "david-perez"

codegen-core/common-test-models/constraints.smithy

@@ -454,6 +454,7 @@ structure ConA {
 
     conBList: ConBList,
     lengthList: LengthList,
+    sensitiveLengthList: SensitiveLengthList,
 
     conBSet: ConBSet,
 
@@ -866,6 +867,14 @@ list LengthList {
     member: String
 }
 
+@length(max: 69)
+list SensitiveLengthList {
+    member: SensitiveStructure
+}
+
+@sensitive
+structure SensitiveStructure { }
+
 set ConBSet {
     member: ConBSetInner
 }

codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ConstrainedShapeSymbolMetadataProvider.kt

@@ -16,6 +16,7 @@ import software.amazon.smithy.model.shapes.StructureShape
 import software.amazon.smithy.model.shapes.UnionShape
 import software.amazon.smithy.rust.codegen.core.rustlang.RustMetadata
 import software.amazon.smithy.rust.codegen.core.rustlang.Visibility
+import software.amazon.smithy.rust.codegen.core.smithy.RuntimeType
 import software.amazon.smithy.rust.codegen.core.smithy.RustSymbolProvider
 import software.amazon.smithy.rust.codegen.core.smithy.SymbolMetadataProvider
 import software.amazon.smithy.rust.codegen.core.smithy.containerDefaultMetadata
@@ -47,6 +48,11 @@ class ConstrainedShapeSymbolMetadataProvider(
             derives += containerDefaultMetadata(shape, model).derives
         }
 
+        // We should _always_ be able to `#[derive(Debug)]`: all constrained shapes' types are simply tuple newtypes
+        // wrapping a single type which always implements `Debug`.
+        // The wrapped type may not _derive_ `Debug` though, hence why this line is required; see https://github.com/awslabs/smithy-rs/issues/2582.
+        derives += RuntimeType.Debug
+
         val visibility = Visibility.publicIf(constrainedTypes, Visibility.PUBCRATE)
         return RustMetadata(derives, additionalAttributes, visibility)
     }