Fix review comments: getRpc() IllegalStateException, UnknownSessionEvent wire type, anyOf heuristic, remove unused var

Agent-Logs-Url: https://github.com/github/copilot-sdk-java/sessions/9b8b782c-22ad-450f-885d-2b11d5808a0c

Co-authored-by: edburns <75821+edburns@users.noreply.github.com>

Author: Copilot

scripts/codegen/java.ts

@@ -115,10 +115,12 @@ function schemaTypeToJava(
         }
         // When exactly two non-null types and one of them is string, prefer String
         // over Object to avoid unnecessary type erasure on common wire-level unions
-        // (e.g., string | null, string | boolean).  For wider unions keep Object.
+        // (e.g., string | null, string | boolean).  For string | object keep Object
+        // so downstream code is not forced to cast.  For wider unions keep Object.
         if (nonNull.length === 2) {
             const hasString = nonNull.some((s) => typeof s === "object" && (s as JSONSchema7).type === "string");
-            if (hasString) {
+            const hasObject = nonNull.some((s) => typeof s === "object" && (s as JSONSchema7).type === "object");
+            if (hasString && !hasObject) {
                 return { javaType: "String", imports };
             }
         }
@@ -308,7 +310,7 @@ async function generateSessionEventBaseClass(
     lines.push(` */`);
     lines.push(`@JsonIgnoreProperties(ignoreUnknown = true)`);
     lines.push(`@JsonInclude(JsonInclude.Include.NON_NULL)`);
-    lines.push(`@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type", defaultImpl = UnknownSessionEvent.class)`);
+    lines.push(`@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type", visible = true, defaultImpl = UnknownSessionEvent.class)`);
     lines.push(`@JsonSubTypes({`);
     for (let i = 0; i < variants.length; i++) {
         const v = variants[i];
@@ -378,20 +380,46 @@ async function generateUnknownEventClass(packageName: string, packageDir: string
     lines.push("");
     lines.push(`package ${packageName};`);
     lines.push("");
+    lines.push(`import com.fasterxml.jackson.annotation.JsonIgnore;`);
     lines.push(`import com.fasterxml.jackson.annotation.JsonIgnoreProperties;`);
+    lines.push(`import com.fasterxml.jackson.annotation.JsonProperty;`);
     lines.push(`import javax.annotation.processing.Generated;`);
     lines.push("");
     lines.push(`/**`);
     lines.push(` * Fallback for event types not yet known to this SDK version.`);
     lines.push(` *`);
+    lines.push(` * <p>The {@link #getOriginalType()} method returns the raw event-type discriminator`);
+    lines.push(` * value received on the wire, which can be used for forward-compatibility`);
+    lines.push(` * telemetry and handling.`);
+    lines.push(` *`);
     lines.push(` * @since 1.0.0`);
     lines.push(` */`);
     lines.push(`@JsonIgnoreProperties(ignoreUnknown = true)`);
     lines.push(GENERATED_ANNOTATION);
     lines.push(`public final class UnknownSessionEvent extends SessionEvent {`);
     lines.push("");
+    lines.push(`    @JsonProperty("type")`);
+    lines.push(`    private String originalType;`);
+    lines.push("");
+    lines.push(`    /**`);
+    lines.push(`     * Returns the raw event-type discriminator string received on the wire,`);
+    lines.push(`     * or {@code "unknown"} if the value was not present in the JSON payload.`);
+    lines.push(`     *`);
+    lines.push(`     * @return the original wire type string, or {@code "unknown"}`);
+    lines.push(`     */`);
     lines.push(`    @Override`);
-    lines.push(`    public String getType() { return "unknown"; }`);
+    lines.push(`    @JsonProperty("type")`);
+    lines.push(`    public String getType() { return originalType != null ? originalType : "unknown"; }`);
+    lines.push("");
+    lines.push(`    /**`);
+    lines.push(`     * Returns the raw event-type discriminator string received on the wire.`);
+    lines.push(`     *`);
+    lines.push(`     * @return the original wire type string, or {@code null} if not present`);
+    lines.push(`     */`);
+    lines.push(`    @JsonIgnore`);
+    lines.push(`    public String getOriginalType() { return originalType; }`);
+    lines.push("");
+    lines.push(`    public void setOriginalType(String originalType) { this.originalType = originalType; }`);
     lines.push(`}`);
     lines.push("");
 
@@ -430,7 +458,6 @@ function renderNestedType(nested: JavaClassDef, indentLevel: number, nestedTypes
         lines.push(`${ind}}`);
     } else if (nested.kind === "class" && nested.schema?.properties) {
         const localNestedTypes = new Map<string, JavaClassDef>();
-        const requiredSet = new Set(nested.schema.required || []);
         const fields: { jsonName: string; javaName: string; javaType: string; description?: string }[] = [];
 
         for (const [propName, propSchema] of Object.entries(nested.schema.properties)) {

src/generated/java/com/github/copilot/sdk/generated/SessionEvent.java

@@ -299,7 +299,8 @@ public SessionUiApi getUi() {
      */
     public SessionRpc getRpc() {
         if (rpc == null) {
-            return null;
+            throw new IllegalStateException(
+                    "Session is not connected or initialized: getRpc() requires an active session.");
         }
         SessionRpc current = sessionRpc;
         if (current == null) {

src/generated/java/com/github/copilot/sdk/generated/UnknownSessionEvent.java

@@ -53,7 +53,7 @@ void parse_unknownEventType_returnsUnknownSessionEvent() throws Exception {
         SessionEvent result = MAPPER.readValue(json, SessionEvent.class);
 
         assertInstanceOf(UnknownSessionEvent.class, result);
-        assertEquals("unknown", result.getType());
+        assertEquals("future.feature_from_server", result.getType());
     }
 
     @Test
@@ -69,7 +69,8 @@ void parse_unknownEventType_preservesOriginalType() throws Exception {
         SessionEvent result = MAPPER.readValue(json, SessionEvent.class);
 
         assertInstanceOf(UnknownSessionEvent.class, result);
-        assertEquals("unknown", result.getType());
+        assertEquals("future.feature_from_server", result.getType());
+        assertEquals("future.feature_from_server", ((UnknownSessionEvent) result).getOriginalType());
     }
 
     @Test

src/main/java/com/github/copilot/sdk/CopilotSession.java

@@ -844,7 +844,7 @@ void testParseUnknownEventType() throws Exception {
         assertNotNull(event, "Unknown event types should return an UnknownSessionEvent");
         assertInstanceOf(com.github.copilot.sdk.generated.UnknownSessionEvent.class, event,
                 "Unknown event types should return UnknownSessionEvent for forward compatibility");
-        assertEquals("unknown", event.getType());
+        assertEquals("unknown.event.type", event.getType());
     }
 
     @Test