Add ParseFileURI and use it when dealing with file URIs (#1088)

* Add ParseFileURI and use it when dealing with file URIs

Fixes #1059

* Missing file

* Linting

internal/sqlutil/uri.go

@@ -0,0 +1,24 @@
+package sqlutil
+
+import (
+	"fmt"
+	"net/url"
+)
+
+// ParseFileURI returns the filepath in the given file: URI. Specifically, this will handle
+// both relative (file:foo.db) and absolute (file:///path/to/foo) paths.
+func ParseFileURI(dataSourceName string) (string, error) {
+	uri, err := url.Parse(dataSourceName)
+	if err != nil {
+		return "", err
+	}
+	var cs string
+	if uri.Opaque != "" { // file:filename.db
+		cs = uri.Opaque
+	} else if uri.Path != "" { // file:///path/to/filename.db
+		cs = uri.Path
+	} else {
+		return "", fmt.Errorf("invalid file uri: %s", dataSourceName)
+	}
+	return cs, nil
+}