Merge pull request #50 from voidspace/maas2-null-filesystem

Handle nils in filesystem

Fixes https://bugs.launchpad.net/juju-core/+bug/1575808

filesystem.go

@@ -39,24 +39,30 @@ func (f *filesystem) UUID() string {
 func filesystem2_0(source map[string]interface{}) (*filesystem, error) {
 	fields := schema.Fields{
 		"fstype":      schema.String(),
-		"mount_point": schema.String(),
-		"label":       schema.String(),
+		"mount_point": schema.OneOf(schema.Nil(""), schema.String()),
+		"label":       schema.OneOf(schema.Nil(""), schema.String()),
 		"uuid":        schema.String(),
-		// TODO: mount_options when we know the type.
+		// TODO: mount_options when we know the type (note it can be
+		// nil).
 	}
-	checker := schema.FieldMap(fields, nil)
+	defaults := schema.Defaults{
+		"mount_point": "",
+		"label":       "",
+	}
+	checker := schema.FieldMap(fields, defaults)
 	coerced, err := checker.Coerce(source, nil)
 	if err != nil {
 		return nil, WrapWithDeserializationError(err, "filesystem 2.0 schema check failed")
 	}
 	valid := coerced.(map[string]interface{})
 	// From here we know that the map returned from the schema coercion
 	// contains fields of the right type.
-
+	mount_point, _ := valid["mount_point"].(string)
+	label, _ := valid["label"].(string)
 	result := &filesystem{
 		fstype:     valid["fstype"].(string),
-		mountPoint: valid["mount_point"].(string),
-		label:      valid["label"].(string),
+		mountPoint: mount_point,
+		label:      label,
 		uuid:       valid["uuid"].(string),
 	}
 	return result, nil

filesystem_test.go

@@ -27,6 +27,21 @@ func (*filesystemSuite) TestParse2_0(c *gc.C) {
 	c.Check(fs.UUID(), gc.Equals, "fake-uuid")
 }
 
+func (*filesystemSuite) TestParse2_Defaults(c *gc.C) {
+	source := map[string]interface{}{
+		"fstype":      "ext4",
+		"mount_point": nil,
+		"label":       nil,
+		"uuid":        "fake-uuid",
+	}
+	fs, err := filesystem2_0(source)
+	c.Assert(err, jc.ErrorIsNil)
+	c.Check(fs.Type(), gc.Equals, "ext4")
+	c.Check(fs.MountPoint(), gc.Equals, "")
+	c.Check(fs.Label(), gc.Equals, "")
+	c.Check(fs.UUID(), gc.Equals, "fake-uuid")
+}
+
 func (*filesystemSuite) TestParse2_0BadSchema(c *gc.C) {
 	source := map[string]interface{}{
 		"mount_point": "/",