fix: remove Volume#server= to attach volumes

new fog-core model#reload resets the model the current remote state.
The previous implementation of volume relied upon initializing with a
device, reloading the model several times, and then attaching with a
server instance is set.  IMO, the new fog-core is doing the correct
thing.

To support this behavior, make #attach and #detach public methods and
require a device argument in #attach.  #server= does exist but only as
an attr_writer.  This may cause some confusion in the future release
and must be included in the CHANGELOG.

lib/fog/aws/models/compute/volume.rb

@@ -59,25 +59,19 @@ def save
             requires :availability_zone
             requires_one :size, :snapshot_id
 
-            if type == 'io1'
-              requires :iops
-            end
+            requires :iops if type == 'io1'
 
             data = service.create_volume(availability_zone, size, create_params).body
             merge_attributes(data)
 
             if tags = self.tags
               # expect eventual consistency
-              Fog.wait_for { self.reload rescue nil }
-              service.create_tags(
-                self.identity,
-                tags
-              )
+              Fog.wait_for { service.volumes.get(identity) }
+              service.create_tags(identity, tags)
             end
 
-            if @server
-              self.server = @server
-            end
+            attach(@service, device) if @server
+
             true
           end
         end
@@ -87,13 +81,7 @@ def server
           service.servers.get(server_id)
         end
 
-        def server=(new_server)
-          if new_server
-            attach(new_server)
-          else
-            detach
-          end
-        end
+        attr_writer :server
 
         def snapshots
           requires :id
@@ -109,22 +97,15 @@ def force_detach
           detach(true)
         end
 
-        private
-
-        def attachmentSet=(new_attachment_set)
-          merge_attributes(new_attachment_set.first || {})
-        end
-
-        def attach(new_server)
+        def attach(new_server, new_device)
           if !persisted?
             @server = new_server
             self.availability_zone = new_server.availability_zone
           elsif new_server
-            requires :device
             wait_for { ready? }
             @server = nil
             self.server_id = new_server.id
-            service.attach_volume(server_id, id, device)
+            service.attach_volume(server_id, id, new_device)
             reload
           end
         end
@@ -138,6 +119,12 @@ def detach(force = false)
           end
         end
 
+        private
+
+        def attachmentSet=(new_attachment_set)
+          merge_attributes(new_attachment_set.first || {})
+        end
+
         def create_params
           {
             'Encrypted'  => encrypted,

tests/models/compute/volume_tests.rb

@@ -1,14 +1,22 @@
-Shindo.tests("Fog::Compute[:aws] | volume", ['aws']) do
-
+Shindo.tests('Fog::Compute[:aws] | volume', ['aws']) do
   @server = Fog::Compute[:aws].servers.create
   @server.wait_for { ready? }
 
-  model_tests(Fog::Compute[:aws].volumes, {:availability_zone => @server.availability_zone, :size => 1, :device => '/dev/sdz1', :tags => {"key" => "value"}, :type => 'gp2'}, true) do
+  model_tests(
+    Fog::Compute[:aws].volumes,
+    {
+      availability_zone: @server.availability_zone,
+      size: 1,
+      tags: { 'key' => 'value' },
+      type: 'gp2'
+    },
+    true
+  ) do
 
     @instance.wait_for { ready? }
 
-    tests('#server = @server').succeeds do
-      @instance.server = @server
+    tests('#attach(server, device)').succeeds do
+      @instance.attach(@server, '/dev/sdz1')
     end
 
     @instance.wait_for { state == 'in-use' }
@@ -17,13 +25,14 @@
       @instance.server.id == @server.id
     end
 
-    tests('#server = nil').succeeds do
-      (@instance.server = nil).nil?
+    tests('#detach').succeeds do
+      @instance.detach
+      @instance.server.nil?
     end
 
     @instance.wait_for { ready? }
 
-    @instance.server = @server
+    @instance.attach(@server, '/dev/sdz1')
     @instance.wait_for { state == 'in-use' }
 
     tests('#force_detach').succeeds do