environs: add NewEnviron(kind, config)

environs/open.go

Index: environs/open.go
=== modified file 'environs/open.go'
--- environs/open.go	2012-05-14 23:40:28 +0000
+++ environs/open.go	2012-05-17 01:43:20 +0000
@@ -2,9 +2,8 @@
 
 import "fmt"
 
-// New creates a new Environ using the
-// environment configuration with the given name.
-// If name is empty, the default environment will be used.
+// Open creates a new Environ using the environment configuration with the 
+// given name. If name is empty, the default environment will be used.
 func (envs *Environs) Open(name string) (Environ, error) {
 	if name == "" {
 		name = envs.Default
@@ -26,3 +25,20 @@
 
 	return env, nil
 }
+
+// NewEnviron creates a new Environ of the registered kind using the configuration
+// supplied.
+func NewEnviron(kind string, config map[string]interface{}) (Environ, error) {
+	p, ok := providers[kind]
+	if !ok {
+		return nil, fmt.Errorf("no registered provider for kind: %q", kind)
+	}
+	cfg, err := p.ConfigChecker().Coerce(config, nil)
+	if err != nil {
+		return nil, fmt.Errorf("error validating environment: %v", err)
+	}
+
+	// TODO(dfc) the name of the environment needs to be injected when it is 
+	// created from environments.yaml
+	return p.Open("default", cfg)
+}