spin_all with a zero timeout.

rclcpp/include/rclcpp/executor.hpp

@@ -305,7 +305,9 @@ class Executor
    * If the time that waitables take to be executed is longer than the period on which new waitables
    * become ready, this method will execute work repeatedly until `max_duration` has elapsed.
    *
-   * \param[in] max_duration The maximum amount of time to spend executing work. Must be positive.
+   * \param[in] max_duration The maximum amount of time to spend executing work, must be >= 0.
+   *   `0` is potentially block forever until no more work is available.
+   * \throw throw std::invalid_argument if max_duration is less than 0.
    * Note that spin_all() may take longer than this time as it only returns once max_duration has
    * been exceeded.
    */

rclcpp/include/rclcpp/executors/static_single_threaded_executor.hpp

@@ -99,9 +99,10 @@ class StaticSingleThreadedExecutor : public rclcpp::Executor
 
   /// Static executor implementation of spin all
   /**
-   * This non-blocking function will execute entities until
-   * timeout or no more work available. If new entities get ready
-   * while executing work available, they will be executed
+   * This non-blocking function will execute entities until timeout (must be >= 0)
+   * or no more work available.
+   * If timeout is `0`, potentially it blocks forever until no more work is available.
+   * If new entities get ready while executing work available, they will be executed
    * as long as the timeout hasn't expired.
    *
    * Example:

rclcpp/src/rclcpp/executor.cpp

@@ -414,8 +414,8 @@ void Executor::spin_some(std::chrono::nanoseconds max_duration)
 
 void Executor::spin_all(std::chrono::nanoseconds max_duration)
 {
-  if (max_duration <= 0ns) {
-    throw std::invalid_argument("max_duration must be positive");
+  if (max_duration < 0ns) {
+    throw std::invalid_argument("max_duration must be greater than or equal to 0");
   }
   return this->spin_some_impl(max_duration, true);
 }

rclcpp/src/rclcpp/executors/static_single_threaded_executor.cpp

@@ -71,8 +71,8 @@ StaticSingleThreadedExecutor::spin_some(std::chrono::nanoseconds max_duration)
 void
 StaticSingleThreadedExecutor::spin_all(std::chrono::nanoseconds max_duration)
 {
-  if (max_duration <= std::chrono::nanoseconds(0)) {
-    throw std::invalid_argument("max_duration must be positive");
+  if (max_duration < std::chrono::nanoseconds(0)) {
+    throw std::invalid_argument("max_duration must be greater than or equal to 0");
   }
   return this->spin_some_impl(max_duration, true);
 }

rclcpp/test/rclcpp/test_executor.cpp

@@ -248,7 +248,7 @@ TEST_F(TestExecutor, spin_all_invalid_duration) {
 
   RCLCPP_EXPECT_THROW_EQ(
     dummy.spin_all(std::chrono::nanoseconds(-1)),
-    std::invalid_argument("max_duration must be positive"));
+    std::invalid_argument("max_duration must be greater than or equal to 0"));
 }
 
 TEST_F(TestExecutor, spin_some_in_spin_some) {