Add timestampFormat trait support

Author: JordonPhillips

smithy-docgen-core/src/main/java/software/amazon/smithy/docgen/core/integrations/BuiltinsIntegration.java

@@ -31,6 +31,7 @@
 import software.amazon.smithy.docgen.core.interceptors.SensitiveInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.SinceInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.SparseInterceptor;
+import software.amazon.smithy.docgen.core.interceptors.TimestampFormatInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.UniqueItemsInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.UnstableInterceptor;
 import software.amazon.smithy.docgen.core.interceptors.XmlNameInterceptor;
@@ -77,6 +78,7 @@ public List<? extends CodeInterceptor<? extends CodeSection, DocWriter>> interce
         return List.of(
                 new OperationAuthInterceptor(),
                 new ApiKeyAuthInterceptor(),
+                new TimestampFormatInterceptor(),
                 new JsonNameInterceptor(),
                 new XmlNameInterceptor(),
                 new PaginationInterceptor(),

smithy-docgen-core/src/main/java/software/amazon/smithy/docgen/core/interceptors/TimestampFormatInterceptor.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.docgen.core.interceptors;
+
+import software.amazon.smithy.docgen.core.sections.ProtocolSection;
+import software.amazon.smithy.docgen.core.writers.DocWriter;
+import software.amazon.smithy.model.shapes.ShapeId;
+import software.amazon.smithy.model.traits.TimestampFormatTrait;
+import software.amazon.smithy.utils.Pair;
+import software.amazon.smithy.utils.SmithyInternalApi;
+
+/**
+ * Adds a member's <a href="https://smithy.io/2.0/spec/protocol-traits.html#timestampformat-trait">
+ * timestamp format</a> to the {@link ProtocolSection} if the protocol supports it.
+ */
+@SmithyInternalApi
+public final class TimestampFormatInterceptor extends ProtocolTraitInterceptor<TimestampFormatTrait> {
+    private static final Pair<String, String> DATE_TIME_REF = Pair.of(
+            "RFC3339 date-time", "https://datatracker.ietf.org/doc/html/rfc3339.html#section-5.6"
+    );
+    private static final Pair<String, String> HTTP_DATE_REF = Pair.of(
+            "RFC7231 IMF-fixdate", "https://tools.ietf.org/html/rfc7231.html#section-7.1.1.1"
+    );
+
+    @Override
+    protected Class<TimestampFormatTrait> getTraitClass() {
+        return TimestampFormatTrait.class;
+    }
+
+    @Override
+    protected ShapeId getTraitId() {
+        return TimestampFormatTrait.ID;
+    }
+
+    @Override
+    void write(DocWriter writer, String previousText, ProtocolSection section, TimestampFormatTrait trait) {
+        writer.writeInline("$B ", "TimestampFormat:");
+        switch (trait.getFormat()) {
+            case DATE_TIME -> writer.write("$R", DATE_TIME_REF);
+            case HTTP_DATE -> writer.write("$R", HTTP_DATE_REF);
+            case EPOCH_SECONDS -> writer.write("epoch seconds");
+            default -> {
+                return;
+            }
+        }
+        writer.writeWithNoFormatting("\n" + previousText);
+    }
+}

smithy-docgen-test/model/main.smithy

@@ -128,6 +128,9 @@ structure DocumentedStructure {
     @deprecated
     integer: Integer
 
+    /// This is a timestamp with a custom format
+    timestamp: DateTime
+
     // This doesn't have a doc string (this is just a normal comment), so it should
     // pull the docs from the target shape.
     @deprecated(message: "Please use intEnum instead")
@@ -146,6 +149,10 @@ structure DocumentedStructure {
     union: DocumentedUnion
 }
 
+/// Timestamp in RFC3339 format
+@timestampFormat("date-time")
+timestamp DateTime
+
 /// This in an enum that can have one of the following values:
 ///
 /// - `FOO`