Allow specifying multiple objects in YAML source/handler files

Support both single-object and lists when reading handlers and sources
from YAML files in a directory.

config.go

@@ -107,15 +107,22 @@ func (c *Config) parse() (*runtimeAssets, error) {
 	}, merr.OrNil()
 }
 
+// The following functions read YAML files from .d-style directories. To be nice
+// to the user, each file can contain either a single object or a list of
+// multiple objects.
 func readHandlersFromDir(dir string) ([]HandlerSpec, error) {
 	var out []HandlerSpec
 	err := foreachYAMLFile(dir, func(path string) error {
-		var spec HandlerSpec
+		var specs []HandlerSpec
 		log.Printf("reading handler: %s", path)
-		if err := readYAMLFile(path, &spec); err != nil {
-			return err
+		if err := readYAMLFile(path, &specs); err != nil {
+			var spec HandlerSpec
+			if err := readYAMLFile(path, &spec); err != nil {
+				return err
+			}
+			specs = []HandlerSpec{spec}
 		}
-		out = append(out, spec)
+		out = append(out, specs...)
 		return nil
 	})
 	return out, err
@@ -124,12 +131,16 @@ func readHandlersFromDir(dir string) ([]HandlerSpec, error) {
 func readSourcesFromDir(dir string) ([]SourceSpec, error) {
 	var out []SourceSpec
 	err := foreachYAMLFile(dir, func(path string) error {
-		var spec SourceSpec
+		var specs []SourceSpec
 		log.Printf("reading source: %s", path)
-		if err := readYAMLFile(path, &spec); err != nil {
-			return err
+		if err := readYAMLFile(path, &specs); err != nil {
+			var spec SourceSpec
+			if err := readYAMLFile(path, &spec); err != nil {
+				return err
+			}
+			specs = []SourceSpec{spec}
 		}
-		out = append(out, spec)
+		out = append(out, specs...)
 		return nil
 	})
 	return out, err