mstate: state package replacement using mgo.

mstate/state.go

 // The state package enables reading, observing, and changing
 // the state stored in MongoDB of a whole environment
 // managed by juju.
 package mstate
 
 import (
         "fmt"
         "launchpad.net/mgo"
         "launchpad.net/mgo/bson"
 )
@@ skipping 26 matching lines @@
                 return fmt.Errorf("can't remove machine %d", id)
         }
         return nil
 }
 
 // AllMachines returns all machines in the environment.
 func (s *State) AllMachines() (machines []*Machine, err error) {
         mdocs := []machineDoc{}
         err = s.machines.Find(nil).Select(bson.D{{"_id", 1}}).All(&mdocs)
         if err != nil {
-                return

[niemeyer, 2012/06/20 19:31:55]

fmt.Errorf(<sensible message>, err)

[aram, 2012/06/21 08:28:41]

Done.

+                return nil, fmt.Errorf("can't get all machines: %v", err)
         }
         for _, v := range mdocs {
                 machines = append(machines, &Machine{st: s, id: v.Id})
         }
         return
 }
 
 // Machine returns the machine with the given id.
 func (s *State) Machine(id int) (*Machine, error) {
         mdoc := &machineDoc{}
         err := s.machines.Find(bson.D{{"_id", id}}).One(mdoc)
+        if err == mgo.NotFound {
+                return nil, fmt.Errorf("machine %d not found", id)
+        }
         if err != nil {

[niemeyer, 2012/06/20 19:31:55]

if err == mgo.NotFound {

We'll need another branch for actual errors.

[aram, 2012/06/21 08:28:41]

Done.

-                return nil, fmt.Errorf("machine %d not found", id)
+                return nil, fmt.Errorf("can't get machine %d: %v", id, err)
         }
         return &Machine{st: s, id: mdoc.Id}, nil
 }