time_until_next_call returns max if timer is canceled.

rclpy/src/rclpy/timer.cpp

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
 
 #include <rcl/context.h>
 #include <rcl/error_handling.h>
@@ -105,11 +106,13 @@ void Timer::change_timer_period(int64_t period_nsec)
   }
 }
 
-int64_t Timer::time_until_next_call()
+std::optional<int64_t> Timer::time_until_next_call()
 {
   int64_t remaining_time;
   rcl_ret_t ret = rcl_timer_get_time_until_next_call(rcl_timer_.get(), &remaining_time);
-  if (ret != RCL_RET_OK) {
+  if (ret == RCL_RET_TIMER_CANCELED) {
+    return std::nullopt;
+  } else if (ret != RCL_RET_OK) {
     throw RCLError("failed to get time until next timer call");
   }
 

rclpy/src/rclpy/timer.hpp

@@ -87,9 +87,10 @@ class Timer : public Destroyable, public std::enable_shared_from_this<Timer>
    *
    * Raises RCLError there is an rcl error
    *
-   * \return the time until next call in nanoseconds
+   * \return the time until next call in nanoseconds.
+   *   std::nullopt if the timer is canceled.
    */
-  int64_t time_until_next_call();
+  std::optional<int64_t> time_until_next_call();
 
   /// Get the time since the timer has been called
   /**

rclpy/test/test_timer.py

@@ -18,6 +18,7 @@
 
 import pytest
 import rclpy
+from rclpy.constants import S_TO_NS
 from rclpy.executors import SingleThreadedExecutor
 
 
@@ -49,7 +50,7 @@ def test_zero_callback(period):
             executor = SingleThreadedExecutor(context=context)
             try:
                 executor.add_node(node)
-                # The first spin_once() takes  long enough for 1ms timer tests to fail
+                # The first spin_once() takes long enough for 1ms timer tests to fail
                 executor.spin_once(timeout_sec=0)
 
                 callbacks = []
@@ -78,7 +79,7 @@ def test_number_callbacks(period):
             executor = SingleThreadedExecutor(context=context)
             try:
                 executor.add_node(node)
-                # The first spin_once() takes  long enough for 1ms timer tests to fail
+                # The first spin_once() takes long enough for 1ms timer tests to fail
                 executor.spin_once(timeout_sec=0)
 
                 callbacks = []
@@ -110,7 +111,7 @@ def test_cancel_reset(period):
             executor = SingleThreadedExecutor(context=context)
             try:
                 executor.add_node(node)
-                # The first spin_once() takes  long enough for 1ms timer tests to fail
+                # The first spin_once() takes long enough for 1ms timer tests to fail
                 executor.spin_once(timeout_sec=0)
 
                 callbacks = []
@@ -148,3 +149,35 @@ def test_cancel_reset(period):
             node.destroy_node()
     finally:
         rclpy.shutdown(context=context)
+
+
+def test_time_until_next_call():
+    context = rclpy.context.Context()
+    rclpy.init(context=context)
+    try:
+        node = rclpy.create_node('test_time_until_next_call', context=context)
+        try:
+            executor = SingleThreadedExecutor(context=context)
+            try:
+                executor.add_node(node)
+                executor.spin_once(timeout_sec=0)
+
+                timer = node.create_timer(1, lambda: None)
+                try:
+                    assert not timer.is_canceled()
+                    executor.spin_once(0.1)
+                    assert timer.time_until_next_call() <= (1 * S_TO_NS)
+                    timer.reset()
+                    assert not timer.is_canceled()
+                    assert timer.time_until_next_call() <= (1 * S_TO_NS)
+                    timer.cancel()
+                    assert timer.is_canceled()
+                    assert timer.time_until_next_call() is None
+                finally:
+                    node.destroy_timer(timer)
+            finally:
+                executor.shutdown()
+        finally:
+            node.destroy_node()
+    finally:
+        rclpy.shutdown(context=context)