api/types/container: make ContainerState a concrete type

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

api/types/container/state.go

@@ -6,9 +6,7 @@ import (
 )
 
 // ContainerState is a string representation of the container's current state.
-//
-// It currently is an alias for string, but may become a distinct type in the future.
-type ContainerState = string
+type ContainerState string
 
 const (
 	StateCreated    ContainerState = "created"    // StateCreated indicates the container is created, but not (yet) started.
@@ -20,8 +18,14 @@ const (
 	StateDead       ContainerState = "dead"       // StateDead indicates that the container failed to be deleted. Containers in this state are attempted to be cleaned up when the daemon restarts.
 )
 
-var validStates = []ContainerState{
-	StateCreated, StateRunning, StatePaused, StateRestarting, StateRemoving, StateExited, StateDead,
+var validStates = []string{
+	string(StateCreated),
+	string(StateRunning),
+	string(StatePaused),
+	string(StateRestarting),
+	string(StateRemoving),
+	string(StateExited),
+	string(StateDead),
 }
 
 // ValidateContainerState checks if the provided string is a valid

api/types/container/state_test.go

@@ -21,7 +21,7 @@ func TestValidateContainerState(t *testing.T) {
 		{state: "invalid-state-string", expectedErr: `invalid value for state (invalid-state-string): must be one of created, running, paused, restarting, removing, exited, dead`},
 	}
 	for _, tc := range tests {
-		t.Run(tc.state, func(t *testing.T) {
+		t.Run(string(tc.state), func(t *testing.T) {
 			err := ValidateContainerState(tc.state)
 			if tc.expectedErr == "" {
 				assert.NilError(t, err)