feat: Preserve OpenAPI extensions on Spec

Author: thced

src/main/java/com/retailsvc/http/spec/Spec.java

@@ -19,12 +19,23 @@ public record Spec(
     Map<String, Parameter> componentParameters,
     String basePath,
     Map<String, Schema> schemaRefIndex,
-    Map<String, Parameter> parameterRefIndex) {
+    Map<String, Parameter> parameterRefIndex,
+    Map<String, Object> extensions) {
 
   private static final String SCHEMA_KEY = "schema";
   private static final String SCHEMA_REF_PREFIX = "#/components/schemas/";
   private static final String PARAMETER_REF_PREFIX = "#/components/parameters/";
 
+  static Map<String, Object> extractExtensions(Map<String, Object> raw) {
+    Map<String, Object> out = new LinkedHashMap<>();
+    for (var e : raw.entrySet()) {
+      if (e.getKey().startsWith("x-")) {
+        out.put(e.getKey(), e.getValue());
+      }
+    }
+    return Map.copyOf(out);
+  }
+
   @SuppressWarnings("unchecked")
   public static Spec from(Map<String, Object> raw) {
     String openapi = (String) raw.get("openapi");
@@ -46,7 +57,8 @@ public static Spec from(Map<String, Object> raw) {
         componentParameters,
         computeBasePath(servers),
         indexByRef(componentSchemas, SCHEMA_REF_PREFIX),
-        indexByRef(componentParameters, PARAMETER_REF_PREFIX));
+        indexByRef(componentParameters, PARAMETER_REF_PREFIX),
+        extractExtensions(raw));
   }
 
   private static String computeBasePath(List<Server> servers) {

src/test/java/com/retailsvc/http/internal/RequestPreparationFilterTest.java

@@ -52,6 +52,7 @@ private Spec specWith(Operation... ops) {
         Map.of(),
         "",
         Map.of(),
+        Map.of(),
         Map.of());
   }
 

src/test/java/com/retailsvc/http/spec/ExtensionsTest.java

@@ -0,0 +1,44 @@
+package com.retailsvc.http.spec;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class ExtensionsTest {
+
+  @Test
+  void specExtensionsExposeTopLevelXKeys() {
+    Map<String, Object> raw =
+        Map.of(
+            "openapi",
+            "3.1.0",
+            "info",
+            Map.of("title", "t", "version", "1"),
+            "servers",
+            List.of(Map.of("url", "https://example.com")),
+            "paths",
+            Map.of(),
+            "x-vendor-build",
+            "abc");
+    Spec spec = Spec.from(raw);
+    assertThat(spec.extensions()).containsEntry("x-vendor-build", "abc");
+  }
+
+  @Test
+  void specExtensionsEmptyWhenNoXKeys() {
+    Map<String, Object> raw =
+        Map.of(
+            "openapi",
+            "3.1.0",
+            "info",
+            Map.of("title", "t", "version", "1"),
+            "servers",
+            List.of(Map.of("url", "https://example.com")),
+            "paths",
+            Map.of());
+    Spec spec = Spec.from(raw);
+    assertThat(spec.extensions()).isEmpty();
+  }
+}