feat: Add support for list-namespaces

.gitignore

@@ -8,3 +8,4 @@ target
 .devbox
 /.envrc
 *.credentials
+.DS_Store

ice-rest-catalog/src/test/resources/scenarios/basic-operations/run.sh.tmpl

@@ -17,6 +17,15 @@ INPUT_PATH="${SCENARIO_DIR}/${INPUT_FILE}"
 {{ICE_CLI}} --config {{CLI_CONFIG}} create-namespace ${NAMESPACE_NAME}
 echo "OK Created namespace: ${NAMESPACE_NAME}"
 
+# List namespaces via list-namespaces command (top-level)
+{{ICE_CLI}} --config {{CLI_CONFIG}} list-namespaces > /tmp/basic_ops_list_namespace.txt
+if ! grep -q "${NAMESPACE_NAME}" /tmp/basic_ops_list_namespace.txt; then
+  echo "FAIL: list-namespaces output missing namespace ${NAMESPACE_NAME}"
+  cat /tmp/basic_ops_list_namespace.txt
+  exit 1
+fi
+echo "OK list-namespaces listed ${NAMESPACE_NAME}"
+
 # List namespaces (ice describe) - no output when no tables yet
 {{ICE_CLI}} --config {{CLI_CONFIG}} describe
 echo "OK Listed namespaces"

ice-rest-catalog/src/test/resources/scenarios/basic-operations/verify.sh.tmpl

@@ -3,12 +3,13 @@ set -e
 
 # Verification script - checks that the test completed successfully
 # Exit code 0 = success, non-zero = failure
-# Expects run.sh to have written: basic_ops_describe.txt, basic_ops_scan_iris.txt,
-# basic_ops_scan_partitioned.txt, basic_ops_scan_sorted.txt, basic_ops_files.txt under /tmp
+# Expects run.sh to have written: basic_ops_list_namespace.txt, basic_ops_describe.txt,
+# basic_ops_scan_iris.txt, basic_ops_scan_partitioned.txt, basic_ops_scan_sorted.txt,
+# basic_ops_files.txt under /tmp
 
 echo "Verifying basic operations test..."
 
-for f in /tmp/basic_ops_describe.txt /tmp/basic_ops_scan_iris.txt /tmp/basic_ops_scan_partitioned.txt /tmp/basic_ops_scan_sorted.txt; do
+for f in /tmp/basic_ops_list_namespace.txt /tmp/basic_ops_describe.txt /tmp/basic_ops_scan_iris.txt /tmp/basic_ops_scan_partitioned.txt /tmp/basic_ops_scan_sorted.txt; do
   if [ ! -f "$f" ]; then
     echo "FAIL Output file not found: $f"
     exit 1
@@ -65,8 +66,14 @@ if ! grep -qE "s3a://test-bucket/warehouse/test_ns/.*/data/.*\.parquet" "$F"; th
   echo "FAIL $F does not contain expected datafile path pattern"
   exit 1
 fi
+# Verify list-namespaces output contains the test namespace
+if ! grep -q "test_ns" /tmp/basic_ops_list_namespace.txt; then
+  echo "FAIL basic_ops_list_namespace.txt does not contain expected namespace 'test_ns'"
+  exit 1
+fi
+
 # Cleanup temp files
-rm -f /tmp/basic_ops_describe.txt /tmp/basic_ops_scan_iris.txt /tmp/basic_ops_scan_partitioned.txt /tmp/basic_ops_scan_sorted.txt /tmp/basic_ops_files.txt
+rm -f /tmp/basic_ops_list_namespace.txt /tmp/basic_ops_describe.txt /tmp/basic_ops_scan_iris.txt /tmp/basic_ops_scan_partitioned.txt /tmp/basic_ops_scan_sorted.txt /tmp/basic_ops_files.txt
 
 echo "OK Verification passed"
 exit 0

ice/src/main/java/com/altinity/ice/cli/Main.java

@@ -22,6 +22,7 @@
 import com.altinity.ice.cli.internal.cmd.Files;
 import com.altinity.ice.cli.internal.cmd.Insert;
 import com.altinity.ice.cli.internal.cmd.InsertWatch;
+import com.altinity.ice.cli.internal.cmd.ListNamespaces;
 import com.altinity.ice.cli.internal.cmd.ListPartitions;
 import com.altinity.ice.cli.internal.cmd.Scan;
 import com.altinity.ice.cli.internal.config.Config;
@@ -708,6 +709,28 @@ void deleteNamespace(
     }
   }
 
+  @CommandLine.Command(name = "list-namespaces", description = "List namespaces.")
+  void listNamespaces(
+      @CommandLine.Parameters(
+              arity = "0..1",
+              paramLabel = "<parent>",
+              description =
+                  "Parent namespace to list children of (e.g. parent_ns). Omit for top-level.")
+          String parent,
+      @CommandLine.Option(
+              names = {"--json"},
+              description = "Output JSON instead of YAML")
+          boolean json)
+      throws IOException {
+    try (RESTCatalog catalog = loadCatalog()) {
+      Namespace namespace =
+          (parent == null || parent.isEmpty())
+              ? Namespace.empty()
+              : Namespace.of(parent.split("[.]"));
+      ListNamespaces.run(catalog, namespace, json);
+    }
+  }
+
   @CommandLine.Command(name = "delete", description = "Delete data from catalog.")
   void delete(
       @CommandLine.Parameters(

ice/src/main/java/com/altinity/ice/cli/internal/cmd/ListNamespaces.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2025 Altinity Inc and/or its affiliates. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ */
+package com.altinity.ice.cli.internal.cmd;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
+import com.fasterxml.jackson.dataformat.yaml.YAMLGenerator;
+import java.io.IOException;
+import java.util.List;
+import java.util.stream.Collectors;
+import org.apache.iceberg.catalog.Namespace;
+import org.apache.iceberg.rest.RESTCatalog;
+
+public final class ListNamespaces {
+
+  private ListNamespaces() {}
+
+  public static void run(RESTCatalog catalog, Namespace parent, boolean json) throws IOException {
+    List<Namespace> namespaces = catalog.listNamespaces(parent);
+    List<String> names =
+        namespaces.stream().map(Namespace::toString).sorted().collect(Collectors.toList());
+    var result = new Result(names);
+    output(result, json);
+  }
+
+  private static void output(Result result, boolean json) throws IOException {
+    ObjectMapper mapper =
+        json
+            ? new ObjectMapper()
+            : new ObjectMapper(new YAMLFactory().enable(YAMLGenerator.Feature.MINIMIZE_QUOTES));
+    mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
+    System.out.println(mapper.writeValueAsString(result));
+  }
+
+  @JsonInclude(JsonInclude.Include.NON_NULL)
+  record Result(List<String> namespaces) {}
+}