[PATCH 3/9] ktest: Treat undefined self-reference as empty

[Ricardo B. Marlière]

Config variables are expanded when they are assigned. A first-time append
such as:

  VAR := ${VAR} foo

leaves the literal ${VAR} in the stored value because VAR has not been
defined yet. Later expansions then carry the self-reference forward instead
of behaving like an empty prefix.

Drop an unescaped self-reference when the variable has no current value,
and trim the outer whitespace left behind. Keep escaped \${VAR} references
unchanged so literal text still works.

Signed-off-by: Ricardo B. Marlière <rbm@xxxxxxxx>
---
 tools/testing/ktest/ktest.pl | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/testing/ktest/ktest.pl b/tools/testing/ktest/ktest.pl
index b7a1c8c617e0..b8fcdabffffe 100755
--- a/tools/testing/ktest/ktest.pl
+++ b/tools/testing/ktest/ktest.pl
@@ -910,6 +910,14 @@ sub set_variable {
     if (defined($command_tmp_vars{$lvalue})) {
 	return;
     }
+
+    # If a variable is undefined, treat an unescaped self-reference as empty.
+    if (!defined($variable{$lvalue})) {
+	$rvalue =~ s/(?<!\\)\$\{\Q$lvalue\E\}//g;
+	$rvalue =~ s/^\s+//;
+	$rvalue =~ s/\s+$//;
+    }
+
     if ($rvalue =~ /^\s*$/) {
 	delete $variable{$lvalue};
     } else {

-- 
2.53.0