charm: Add config.Convert()

charm/config.go

 package charm
 
 import (
         "errors"
         "fmt"
         "io"
         "io/ioutil"
         "launchpad.net/goyaml"
         "launchpad.net/juju-core/schema"
         "reflect"
@@ skipping 99 matching lines @@
                 }
         }
         for k, opt := range c.Options {
                 if _, ok := out[k]; !ok && opt.Default != nil {
                         out[k] = opt.Default
                 }
         }
         return out, nil
 }
 
+// Convert converts the given config values such that they match the
+// existing schema. Unknown values are silently ignored.
+func (c *Config) Convert(values map[string]interface{}) (converted map[string]interface{}, err error) {

[rog, 2013/02/26 18:15:10]

no need to name the return params, i think.

[dimitern, 2013/02/26 18:24:57]

Done.

+        converted = make(map[string]interface{})
+        for k, v := range values {
+                opt, ok := c.Options[k]
+                if !ok {
+                        continue
+                }
+                if reflect.TypeOf(v).Kind() != validTypes[opt.Type] {
+                        return nil, fmt.Errorf("cannot convert: type of %q has changed", k)

[rog, 2013/02/26 18:15:10]

It might be nice to include a bit more information here to help the user.

return nil, fmt.Errorf("unexpected type in service configuration %q=%#v;
expected %s", k, v, opt.Type)

perhaps?

[dimitern, 2013/02/26 18:24:57]

Done.

+                }
+                converted[k] = v
+        }
+        return converted, nil
+}
+
 var validTypes = map[string]reflect.Kind{
         "string":  reflect.String,
         "int":     reflect.Int64,
         "boolean": reflect.Bool,
         "float":   reflect.Float64,
 }
 
 var optionSchema = schema.FieldMap(
         schema.Fields{
                 "type":        schema.OneOf(schema.Const("string"), schema.Const("int"), schema.Const("float"), schema.Const("boolean")),
                 "default":     schema.OneOf(schema.String(), schema.Int(), schema.Float(), schema.Bool()),
                 "description": schema.String(),
         },
         schema.Defaults{
                 "default":     schema.Omit,
                 "description": schema.Omit,
         },
 )
 
 var configSchema = schema.FieldMap(
         schema.Fields{
                 "options": schema.StringMap(optionSchema),
         },
         nil,
 )