import serde on rust files.

Author: thomas-k-cameron

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/rustlang/RustType.kt

@@ -471,6 +471,10 @@ class Attribute(val inner: Writable) {
         return Attribute(serde("skip"))
     }
 
+    public fun SerdeSerializeOrDeserialize(): Attribute {
+        return Attribute(cfgAttr(all(writable("aws_sdk_unstable"), any(feature("serde-serialize"), feature("serde-deserialize")))))
+    }
+
     companion object {
         val AllowClippyBoxedLocal = Attribute(allow("clippy::boxed_local"))
         val AllowClippyLetAndReturn = Attribute(allow("clippy::let_and_return"))

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/rustlang/RustWriter.kt

@@ -8,6 +8,7 @@ package software.amazon.smithy.rust.codegen.core.rustlang
 import org.intellij.lang.annotations.Language
 import org.jsoup.Jsoup
 import org.jsoup.nodes.Element
+import software.amazon.smithy.rust.codegen.core.smithy.generators.RenderSerdeAttribute
 import software.amazon.smithy.codegen.core.CodegenException
 import software.amazon.smithy.codegen.core.Symbol
 import software.amazon.smithy.codegen.core.SymbolDependencyContainer
@@ -453,7 +454,9 @@ class RustWriter private constructor(
         fun forModule(module: String?): RustWriter = if (module == null) {
             RustWriter("lib.rs", "crate")
         } else {
-            RustWriter("$module.rs", "crate::$module")
+            var writer = RustWriter("$module.rs", "crate::$module")
+            RenderSerdeAttribute.importSerde(writer)
+            writer
         }
 
         fun factory(debugMode: Boolean): Factory<RustWriter> = Factory { fileName: String, namespace: String ->

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/RenderSerdeAttribute.kt

@@ -10,6 +10,7 @@ import software.amazon.smithy.model.shapes.MemberShape
 import software.amazon.smithy.model.shapes.StructureShape
 import software.amazon.smithy.rust.codegen.core.rustlang.Attribute
 import software.amazon.smithy.rust.codegen.core.rustlang.RustWriter
+import software.amazon.smithy.rust.codegen.core.rustlang.raw
 import software.amazon.smithy.rust.codegen.core.util.isEventStream
 import software.amazon.smithy.rust.codegen.core.util.isStreaming
 
@@ -30,6 +31,13 @@ public object RenderSerdeAttribute {
         }
     }
 
+    public fun importSerde(writer: RustWriter) {
+        // we need this for skip serde to work
+        Attribute.AllowUnusedImports.render(writer)
+        Attribute("").SerdeSerializeOrDeserialize().render(writer)
+        writer.raw("use serde;")
+    }
+
     public fun writeAttributes(writer: RustWriter) {
         Attribute("").SerdeSerialize().render(writer)
         Attribute("").SerdeDeserialize().render(writer)