docker: improve validation of runtime constraints

builtin/providers/docker/resource_docker_container.go

@@ -182,18 +182,39 @@ func resourceDockerContainer() *schema.Resource {
 				Type:     schema.TypeInt,
 				Optional: true,
 				ForceNew: true,
+				ValidateFunc: func(v interface{}, k string) (ws []string, es []error) {
+					value := v.(int)
+					if value < 0 {
+						es = append(es, fmt.Errorf("%q must be greater than or equal to 0", k))
+					}
+					return
+				},
 			},
 
 			"memory_swap": &schema.Schema{
 				Type:     schema.TypeInt,
 				Optional: true,
 				ForceNew: true,
+				ValidateFunc: func(v interface{}, k string) (ws []string, es []error) {
+					value := v.(int)
+					if value < -1 {
+						es = append(es, fmt.Errorf("%q must be greater than or equal to -1", k))
+					}
+					return
+				},
 			},
 
 			"cpu_shares": &schema.Schema{
 				Type:     schema.TypeInt,
 				Optional: true,
 				ForceNew: true,
+				ValidateFunc: func(v interface{}, k string) (ws []string, es []error) {
+					value := v.(int)
+					if value < 0 {
+						es = append(es, fmt.Errorf("%q must be greater than or equal to 0", k))
+					}
+					return
+				},
 			},
 
 			"log_driver": &schema.Schema{

builtin/providers/docker/resource_docker_container_funcs.go

@@ -118,27 +118,19 @@ func resourceDockerContainerCreate(d *schema.ResourceData, meta interface{}) err
 	}
 
 	if v, ok := d.GetOk("memory"); ok {
-		memory := int64(v.(int))
-		if memory > 0 {
-			hostConfig.Memory = memory * 1024 * 1024
-		}
+		hostConfig.Memory = int64(v.(int)) * 1024 * 1024
 	}
 
 	if v, ok := d.GetOk("memory_swap"); ok {
 		swap := int64(v.(int))
-		if swap != 0 {
-			if swap > 0 { // only convert positive #s to bytes
+		if swap > 0 {
 			swap = swap * 1024 * 1024
 		}
 		hostConfig.MemorySwap = swap
 	}
-	}
 
 	if v, ok := d.GetOk("cpu_shares"); ok {
-		shares := int64(v.(int))
-		if shares > 0 {
-			hostConfig.CPUShares = shares
-		}
+		hostConfig.CPUShares = int64(v.(int))
 	}
 
 	if v, ok := d.GetOk("log_opts"); ok {