Add "network exists" command (#632)

Podman has support for a "network exists" command which checks if a
network exists. This adds support for that command, although it does so
by way of network inspect for compatibility with Docker, which does not
have a standalone `network exists` command.

Closes #618

---------

Co-authored-by: Gabriel de Marmiesse <[email protected]>

python_on_whales/components/network/cli_wrapper.py

@@ -15,6 +15,7 @@
     NetworkInspectResult,
     NetworkIPAM,
 )
+from python_on_whales.exceptions import NoSuchNetwork
 from python_on_whales.utils import format_mapping_for_cli, run, to_list
 
 
@@ -104,6 +105,13 @@ def config_only(self) -> bool:
     def __repr__(self):
         return f"python_on_whales.Network(id='{self.id[:12]}', name={self.name})"
 
+    def exists(self) -> bool:
+        """Returns `True` if the network exists and `False` if it doesn't exist.
+
+        If it doesn't exist, that most likely means it was removed.
+        """
+        return NetworkCLI(self.client_config).exists(self.id)
+
     def remove(self) -> None:
         """Removes this Docker network.
 
@@ -209,6 +217,22 @@ def disconnect(
         full_cmd += [network, container]
         run(full_cmd)
 
+    def exists(
+        self,
+        network: ValidNetwork,
+    ) -> bool:
+        """Check if a network exists
+
+        Parameters:
+            network: The name of the network.
+        """
+        try:
+            self.inspect(str(network))
+        except NoSuchNetwork:
+            return False
+        else:
+            return True
+
     @overload
     def inspect(self, x: str) -> Network: ...
 

python_on_whales/exceptions.py

@@ -49,6 +49,10 @@ class NoSuchImage(DockerException):
     pass
 
 
+class NoSuchNetwork(DockerException):
+    pass
+
+
 class NoSuchPod(DockerException):
     pass
 

python_on_whales/utils.py

@@ -28,6 +28,7 @@
     DockerException,
     NoSuchContainer,
     NoSuchImage,
+    NoSuchNetwork,
     NoSuchPod,
     NoSuchService,
     NoSuchVolume,
@@ -218,6 +219,13 @@ def run(
                     completed_process.stdout,
                     completed_process.stderr,
                 )
+            if "network" in decoded_stderr and "not found" in decoded_stderr:
+                raise NoSuchNetwork(
+                    args,
+                    completed_process.returncode,
+                    completed_process.stdout,
+                    completed_process.stderr,
+                )
 
         raise DockerException(
             args,

tests/python_on_whales/components/test_network.py

@@ -78,3 +78,17 @@ def test_swarm_service_create(docker_client: DockerClient):
             "busybox", ["sleep", "infinity"], network=my_net.name
         ):
             assert len(my_net.containers) == 2  # 1 container + 1 endpoint
+
+
+@pytest.mark.parametrize("ctr_client", ["docker", "podman"], indirect=True)
+def test_network_exists(ctr_client: DockerClient):
+    network_name = random_name()
+    assert not ctr_client.network.exists(network_name)
+    with ctr_client.network.create(network_name) as network:
+        assert ctr_client.network.exists(network_name)
+        assert ctr_client.network.exists(network)
+        assert network.exists()
+
+    # Outside with clause, network should be removed and no longer exist
+    assert not ctr_client.network.exists(network)
+    assert not network.exists()