From 8fa6559d0f70e10f28fa28faa3beea4d2a65618b Mon Sep 17 00:00:00 2001
From: Colin Alworth <colin@colinalworth.com>
Date: Mon, 20 Apr 2026 14:29:36 -0500
Subject: [PATCH] Add feature flag

---
 .../deephaven/web/client/api/CoreClient.java  | 11 ++++++++
 .../io/deephaven/web/client/api/Features.java | 28 +++++++++++++++++++
 .../web/client/api/tree/JsTreeTable.java      |  7 +++--
 3 files changed, 43 insertions(+), 3 deletions(-)
 create mode 100644 web/client-api/src/main/java/io/deephaven/web/client/api/Features.java

diff --git a/web/client-api/src/main/java/io/deephaven/web/client/api/CoreClient.java b/web/client-api/src/main/java/io/deephaven/web/client/api/CoreClient.java
index 0abbdd30efe..62184029d2d 100644
--- a/web/client-api/src/main/java/io/deephaven/web/client/api/CoreClient.java
+++ b/web/client-api/src/main/java/io/deephaven/web/client/api/CoreClient.java
@@ -22,6 +22,7 @@
 import io.deephaven.web.shared.data.ConnectToken;
 import io.deephaven.web.shared.fu.JsBiConsumer;
 import io.deephaven.web.shared.fu.JsFunction;
+import jsinterop.annotations.JsNullable;
 import jsinterop.annotations.JsOptional;
 import jsinterop.annotations.JsType;
 import jsinterop.base.Js;
@@ -32,6 +33,16 @@
 
 @JsType(namespace = "dh")
 public class CoreClient extends HasEventHandling {
+    /**
+     * A collection of feature flags that the JS API advertises. All must be nullable booleans, and if listed, the value
+     * is true.
+     * <p>
+     * Marked as nullable as past releases will not have this property, be sure to test for null if an older release
+     * might be in use.
+     */
+    @JsNullable
+    public static final Features FEATURES = new Features();
+
     public static final String EVENT_CONNECT = "connect",
             EVENT_DISCONNECT = "disconnect",
             EVENT_RECONNECT = "reconnect",
diff --git a/web/client-api/src/main/java/io/deephaven/web/client/api/Features.java b/web/client-api/src/main/java/io/deephaven/web/client/api/Features.java
new file mode 100644
index 00000000000..35582debe3c
--- /dev/null
+++ b/web/client-api/src/main/java/io/deephaven/web/client/api/Features.java
@@ -0,0 +1,28 @@
+//
+// Copyright (c) 2016-2026 Deephaven Data Labs and Patent Pending
+//
+package io.deephaven.web.client.api;
+
+import io.deephaven.web.client.api.tree.JsTreeTable;
+import jsinterop.annotations.JsNullable;
+import jsinterop.annotations.JsType;
+
+/**
+ * Collection of feature flags that the JS API advertises. All must be nullable booleans, and if listed, the value is
+ * true.
+ * <p>
+ * Preferred format is to first list the type or category of feature, then the feature name. Docs should link
+ * bidirectionally with the feature in question.
+ *
+ * Exposed as {@link CoreClient#FEATURES}, which may be null in older releases.
+ */
+@JsType(namespace = "dh")
+public class Features {
+    /**
+     * {@link io.deephaven.web.client.api.tree.JsTreeTable} support for providing a number rather than a boolean when
+     * {@link io.deephaven.web.client.api.tree.JsTreeTable#expand(JsTreeTable.RowReferenceUnion, JsTreeTable.ExpandDescendantsUnion)
+     * expanding} to signify expanding to a depth relative to the given element.
+     */
+    @JsNullable
+    public final Boolean treeTableExpandToDepth = true;
+}
diff --git a/web/client-api/src/main/java/io/deephaven/web/client/api/tree/JsTreeTable.java b/web/client-api/src/main/java/io/deephaven/web/client/api/tree/JsTreeTable.java
index 23d423ee487..156e477afda 100644
--- a/web/client-api/src/main/java/io/deephaven/web/client/api/tree/JsTreeTable.java
+++ b/web/client-api/src/main/java/io/deephaven/web/client/api/tree/JsTreeTable.java
@@ -926,13 +926,14 @@ private void setRowAction(RowReferenceUnion row, double action) {
      * {@code true} to expand the row and all descendants, a {@code number} to expand to a specified depth relative to
      * the target node, or omit / pass {@code false} to expand only the row itself. A depth of 1 is equivalent to a
      * regular expand (one level). A depth of 2 expands the node and its children, etc. Equivalent to
-     * {@code setExpanded(row, true)} with an optional third parameter.
+     * {@code setExpanded(row, true)} with an optional third parameter. Numeric value is only supported if
+     * {@link Features#treeTableExpandToDepth} is true.
      *
      * @param row The row to expand - either the absolute row index or the row object.
      * @param expandDescendants Controls descendant expansion: {@code true} for all descendants, a {@code number} for
      *        depth-limited expansion (relative to the target node), or {@code false}/omitted for a single level.
      */
-    public void expand(RowReferenceUnion row, @JsOptional ExpandDescendantsUnion expandDescendants) {
+    public void expand(RowReferenceUnion row, @JsOptional @JsNullable ExpandDescendantsUnion expandDescendants) {
         setExpanded(row, true, expandDescendants);
     }
 
@@ -1037,7 +1038,7 @@ default int asInt() {
      *        Defaults to {@code false}.
      */
     public void setExpanded(RowReferenceUnion row, boolean isExpanded,
-            @JsOptional ExpandDescendantsUnion expandDescendants) {
+            @JsOptional @JsNullable ExpandDescendantsUnion expandDescendants) {
         // TODO check row number is within bounds
         final double action;
         if (!isExpanded) {