Config from code (fclairamb#714) (fclairamb#749)

Allow Config to be created without a file.

It's sometimes desirable to create a server that is configured by logic
that creates the `Content`. Prior to this commit, such content needed
to be written to a temporary file and then loaded into memory again in
order to get a complete `Config`.

This commit adds a `FromContent` method, allowing the `Config` to be
created directly from a `Content`.

Authored-by: Thomas Hallgren <[email protected]>

config/config.go

@@ -40,6 +40,22 @@ func NewConfig(fileName string, logger log.Logger) (*Config, error) {
 	return config, nil
 }
 
+// FromContent creates a new config instance from a pre-created Content and logger. The
+// fileName should indicate origin of the given Content, but the file will never be opened.
+func FromContent(content *confpar.Content, fileName string, logger log.Logger) (*Config, error) {
+	c := &Config{
+		fileName: fileName,
+		logger:   logger,
+		Content:  content,
+	}
+
+	if err := c.Prepare(); err != nil {
+		return nil, err
+	}
+
+	return c, nil
+}
+
 // Load the config
 func (c *Config) Load() error {
 	file, errOpen := os.Open(c.fileName)