From 0fb73d07d24154b8a3b14c54faf164a5e5e92a2f Mon Sep 17 00:00:00 2001
From: Patrick McDermott <patrick.mcdermott@libiquity.com>
Date: Tue, 12 Mar 2019 11:47:04 -0400
Subject: ob_set_substvar(): Make validation more immediately clear

The original version in 000a27ff used a "${parameter:-word}" default
value expansion to detect an empty string.  Instead, let the case
construct match empty strings directly.
---
diff --git a/lib/control.sh b/lib/control.sh
index a20ea3c..439f52a 100644
--- a/lib/control.sh
+++ b/lib/control.sh
@@ -208,10 +208,8 @@ ob_set_substvar()
 
 	# Convert variable name to uppercase and validate.
 	name="$(echo "${name}" | tr 'a-z-' 'A-Z_')"
-	case "${name:- }" in
-		*[!A-Z0-9_]*)
-			return 125
-			;;
+	case "${name}" in *[!A-Z0-9_]* | '')
+		return 125
 	esac
 
 	# Trim leading and trailing whitespace from value.
--
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