Test expansion of empty patterns with MSI

This was subject to a regression in 3.15.6. See lp:1810946.

src/ioc/dbtemplate/test/msi.plt

@@ -11,7 +11,7 @@
 use strict;
 use Test;
 
-BEGIN {plan tests => 9}
+BEGIN {plan tests => 11}
 
 # Check include/substitute command model
 ok(msi('-I .. ../t1-template.txt'),             slurp('../t1-result.txt'));
@@ -50,6 +50,12 @@ ok(msi('-I.. -D -o t8.txt ../t1-template.txt'), slurp('../t8-result.txt'));
 # Dependency generation, dbLoadTemplate format
 ok(msi('-I.. -D -ot9.txt -S ../t2-substitution.txt'), slurp('../t9-result.txt'));
 
+# Substitution file, variable format, with 0 variable definitions
+ok(msi('-I. -I.. -S ../t10-substitute.txt'), slurp('../t10-result.txt'));
+
+# Substitution file, pattern format, with 0 pattern definitions
+ok(msi('-I. -I.. -S ../t11-substitute.txt'), slurp('../t11-result.txt'));
+
 
 # Test support routines
 

src/ioc/dbtemplate/test/t10-result.txt

@@ -0,0 +1,4 @@
+# comment line
+a=$(a)
+# comment line
+a=gbl

src/ioc/dbtemplate/test/t10-substitute.txt

@@ -0,0 +1,8 @@
+file t10-template.txt {
+    {}
+}
+
+global { a=gbl }
+file t10-template.txt {
+    {}
+}

src/ioc/dbtemplate/test/t10-template.txt

@@ -0,0 +1,2 @@
+# comment line
+a=$(a)

src/ioc/dbtemplate/test/t11-result.txt

@@ -0,0 +1,4 @@
+# comment line
+a=$(a)
+# comment line
+a=gbl

src/ioc/dbtemplate/test/t11-substitute.txt

@@ -0,0 +1,10 @@
+file t11-template.txt {
+    pattern {}
+    {}
+}
+
+global { a=gbl }
+file t11-template.txt {
+    pattern {}
+    {}
+}

src/ioc/dbtemplate/test/t11-template.txt

@@ -0,0 +1,2 @@
+# comment line
+a=$(a)