Fix several serde issues with HTTP headers

This commit fixes casing comparison issues related to fetch for HTTP
bindings of headers and prefix headers for both request and response.
It also includes a fix to more robustly validate headers before
serialization.

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/HttpBindingProtocolGenerator.java

@@ -19,6 +19,7 @@
 
 import java.util.Comparator;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
@@ -146,6 +147,7 @@ public void generateSharedComponents(GenerationContext context) {
         HttpProtocolGeneratorUtils.generateMetadataDeserializer(context, getApplicationProtocol().getResponseType());
         HttpProtocolGeneratorUtils.generateCollectBody(context);
         HttpProtocolGeneratorUtils.generateCollectBodyString(context);
+        HttpProtocolGeneratorUtils.generateHttpBindingUtils(context);
     }
 
     /**
@@ -355,26 +357,26 @@ private void writeHeaders(
         operation.getInput().ifPresent(outputId -> {
             Model model = context.getModel();
             for (HttpBinding binding : bindingIndex.getRequestBindings(operation, Location.HEADER)) {
-                String memberName = symbolProvider.toMemberName(binding.getMember());
-                writer.openBlock("if (input.$L !== undefined) {", "}", memberName, () -> {
+                String memberLocation = "input." + symbolProvider.toMemberName(binding.getMember());
+                writer.openBlock("if (isSerializableHeaderValue($1L)) {", "}", memberLocation, () -> {
                     Shape target = model.expectShape(binding.getMember().getTarget());
-                    String headerValue = getInputValue(context, binding.getLocation(), "input." + memberName,
+                    String headerValue = getInputValue(context, binding.getLocation(), memberLocation + "!",
                             binding.getMember(), target);
                     writer.write("headers[$S] = $L;", binding.getLocationName(), headerValue);
                 });
             }
 
             // Handle assembling prefix headers.
             for (HttpBinding binding : bindingIndex.getRequestBindings(operation, Location.PREFIX_HEADERS)) {
-                String memberName = symbolProvider.toMemberName(binding.getMember());
-                writer.openBlock("if (input.$L !== undefined) {", "}", memberName, () -> {
+                String memberLocation = "input." + symbolProvider.toMemberName(binding.getMember());
+                writer.openBlock("if ($L !== undefined) {", "}", memberLocation, () -> {
                     MapShape prefixMap = model.expectShape(binding.getMember().getTarget()).asMapShape().get();
                     Shape target = model.expectShape(prefixMap.getValue().getTarget());
                     // Iterate through each entry in the member.
-                    writer.openBlock("Object.keys(input.$L).forEach(suffix => {", "});", memberName, () -> {
+                    writer.openBlock("Object.keys($L).forEach(suffix => {", "});", memberLocation, () -> {
                         // Use a ! since we already validated the input member is defined above.
                         String headerValue = getInputValue(context, binding.getLocation(),
-                                "input." + memberName + "![suffix]", binding.getMember(), target);
+                                memberLocation + "![suffix]", binding.getMember(), target);
                         // Append the suffix to the defined prefix and serialize the value in to that key.
                         writer.write("headers[$S + suffix] = $L;", binding.getLocationName(), headerValue);
                     });
@@ -951,7 +953,7 @@ private void readHeaders(
         Model model = context.getModel();
         for (HttpBinding binding : bindingIndex.getResponseBindings(operationOrError, Location.HEADER)) {
             String memberName = symbolProvider.toMemberName(binding.getMember());
-            String headerName = binding.getLocationName().toLowerCase();
+            String headerName = binding.getLocationName().toLowerCase(Locale.US);
             writer.openBlock("if ($L.headers[$S] !== undefined) {", "}", outputName, headerName, () -> {
                 Shape target = model.expectShape(binding.getMember().getTarget());
                 String headerValue = getOutputValue(context, binding.getLocation(),
@@ -973,16 +975,17 @@ private void readHeaders(
                         writer.write("contents.$L = {};", memberName);
                     });
 
-                    // Generate a single block for each group of prefix headers.
-                    writer.openBlock("if (header.startsWith($S)) {", "}", binding.getLocationName(), () -> {
+                    // Generate a single block for each group of lower-cased prefix headers.
+                    String headerLocation = binding.getLocationName().toLowerCase(Locale.US);
+                    writer.openBlock("if (header.startsWith($S)) {", "}", headerLocation, () -> {
                         MapShape prefixMap = model.expectShape(binding.getMember().getTarget()).asMapShape().get();
                         Shape target = model.expectShape(prefixMap.getValue().getTarget());
                         String headerValue = getOutputValue(context, binding.getLocation(),
                                 outputName + ".headers[header]", binding.getMember(), target);
 
                         // Extract the non-prefix portion as the key.
                         writer.write("contents.$L[header.substring($L)] = $L;",
-                                memberName, binding.getLocationName().length(), headerValue);
+                                memberName, headerLocation.length(), headerValue);
                     });
                 }
             });

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/HttpProtocolGeneratorUtils.java

@@ -40,6 +40,7 @@
 import software.amazon.smithy.typescript.codegen.TypeScriptDependency;
 import software.amazon.smithy.typescript.codegen.TypeScriptWriter;
 import software.amazon.smithy.typescript.codegen.integration.ProtocolGenerator.GenerationContext;
+import software.amazon.smithy.utils.IoUtils;
 
 /**
  * Utility methods for generating HTTP protocols.
@@ -233,6 +234,16 @@ static void generateCollectBodyString(GenerationContext context) {
         writer.write("");
     }
 
+    /**
+     * Writes any additional utils needed for HTTP protocols with bindings.
+     *
+     * @param context The generation context.
+     */
+    static void generateHttpBindingUtils(GenerationContext context) {
+        TypeScriptWriter writer = context.getWriter();
+        writer.write(IoUtils.readUtf8Resource(HttpProtocolGeneratorUtils.class, "http-binding-utils.ts"));
+    }
+
     /**
      * Writes a function used to dispatch to the proper error deserializer
      * for each error that the operation can return. The generated function

smithy-typescript-codegen/src/main/resources/software/amazon/smithy/typescript/codegen/integration/http-binding-utils.ts

@@ -0,0 +1,6 @@
+function isSerializableHeaderValue(value: any): boolean {
+  return value !== undefined
+      && value !== ""
+      && (!Object.getOwnPropertyNames(value).includes("length") || value.length != 0)
+      && (!Object.getOwnPropertyNames(value).includes("size") || value.size != 0);
+}