namedref() method and function fail if the fallback is NULL, and add

tests for failure if the name parameter is NULL or empty

src/tests/backref_fail.vtc

@@ -163,6 +163,15 @@ varnish v1 -vcl+backend {
 		if (barbaz.match(resp.http.foo)) {
 			set resp.http.foo1 = barbaz.namedref("bar", "error1");
 			set resp.http.foo2 = barbaz.namedref("baz", "error2");
+			set resp.http.undeffallback
+				= barbaz.namedref("bar", resp.http.undef);
+
+			# Fail if the name is empty or undefined
+			set resp.http.emptyname
+				= barbaz.namedref("", "name empty");
+			set resp.http.undefname
+				= barbaz.namedref(req.http.undef,
+				                  "name undefined");
 		}
 
 		if (barbaz.match(resp.http.barf)) {
@@ -184,12 +193,16 @@ varnish v1 -vcl+backend {
 		}
 		set resp.http.never1 = never.namedref("bar", "fallback1");
 		set resp.http.never2 = never.namedref("baz", "fallback2");
+		set resp.http.nofallback = never.namedref("bar");
 	}
 }
 
 logexpect l2 -v v1 -d 0 -g vxid -q "VCL_Error" {
 	expect 0 * Begin req
 	expect * = VCL_Error "^vmod re2 error: backref 1, fallback .fallback.: backref called without prior match$"
+	expect * = VCL_Error "^vmod re2 error: barbaz.namedref..: fallback is undefined$"
+	expect * = VCL_Error "^vmod re2 error: barbaz.namedref.name=.., fallback=.name empty..: name is empty$"
+	expect * = VCL_Error "^vmod re2 error: barbaz.namedref.name=.., fallback=.name undefined..: name is empty$"
 	expect * = VCL_Error "^vmod re2 error: never.namedref.name=.bar., fallback=.fallback1..: never_capture is true for object never$"
 	expect * = VCL_Error "^vmod re2 error: never.namedref.name=.baz., fallback=.fallback2..: never_capture is true for object never$"
 
@@ -206,6 +219,9 @@ client c2 {
 	expect resp.http.frob2 == "fallback2"
 	expect resp.http.foo1 == "bar"
 	expect resp.http.foo2 == "baz"
+	expect resp.http.undeffallback ~ "^..NAMEDREF (METHOD|FUNCTION) FAILED..$"
+	expect resp.http.emptyname == "name empty"
+	expect resp.http.undefname == "name undefined"
 	expect resp.http.puke == <undef>
 	expect resp.http.barf1 == "fallback1"
 	expect resp.http.barf2 == "fallback2"
@@ -216,6 +232,7 @@ client c2 {
 	expect resp.http.never == "match"
 	expect resp.http.never1 == "fallback1"
 	expect resp.http.never2 == "fallback2"
+	expect resp.http.nofallback ~ "^..NAMEDREF (METHOD|FUNCTION) FAILED..$"
 } -run
 
 logexpect l2 -wait
@@ -316,6 +333,13 @@ varnish v1 -vcl+backend {
 		if (re2.match("(?P<bar>bar)(?P<baz>baz)", resp.http.foo)) {
 			set resp.http.foo1 = re2.namedref("bar", "error1");
 			set resp.http.foo2 = re2.namedref("baz", "error2");
+			set resp.http.undeffallback
+				= re2.namedref("bar", resp.http.undef);
+			set resp.http.emptyname
+				= re2.namedref("", "name empty");
+			set resp.http.undefname
+				= re2.namedref(req.http.undef,
+				               "name undefined");
 		}
 
 		if (re2.match("(?P<bar>bar)(?P<baz>baz)", resp.http.barf)) {
@@ -338,12 +362,16 @@ varnish v1 -vcl+backend {
 		}
 		set resp.http.never1 = re2.namedref("bar", "fallback1");
 		set resp.http.never2 = re2.namedref("baz", "fallback2");
+		set resp.http.nofallback = re2.namedref("bar");
 	}
 }
 
 logexpect l4 -v v1 -d 0 -g vxid -q "VCL_Error" {
 	expect 0 * Begin req
 	expect * = VCL_Error "^vmod re2 error: re2.namedref.name=.bar., fallback=.fallback..: called without previous match$"
+	expect * = VCL_Error "^vmod re2 error: re2.namedref..: fallback is undefined$"
+	expect * = VCL_Error "^vmod re2 error: re2.namedref.name=.., fallback=.name empty..: name is empty$"
+	expect * = VCL_Error "^vmod re2 error: re2.namedref.name=.., fallback=.name undefined..: name is empty$"
 	expect * = VCL_Error "^vmod re2 error: re2.namedref.name=.bar., fallback=.fallback1..: never_capture was true in previous match$"
 	expect * = VCL_Error "^vmod re2 error: re2.namedref.name=.baz., fallback=.fallback2..: never_capture was true in previous match$"
 

src/vmod_re2.c

@@ -43,6 +43,9 @@
 #include "vre2/vre2.h"
 #include "vre2/vre2set.h"
 
+#define ERR(ctx, msg) \
+        errmsg((ctx), "vmod re2 error: " msg)
+
 #define VERR(ctx, fmt, ...) \
         errmsg((ctx), "vmod re2 error: " fmt, __VA_ARGS__)
 
@@ -394,8 +397,10 @@ vmod_regex_namedref(VRT_CTX, struct vmod_re2_regex *re, VCL_STRING name,
 
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(re, VMOD_RE2_REGEX_MAGIC);
-	if (fallback == NULL)
-		fallback = "";
+	if (fallback == NULL) {
+		VERR(ctx, "%s.namedref(): fallback is undefined", re->vcl_name);
+		return "**NAMEDREF METHOD FAILED**";
+	}
 	if (name == NULL || name[0] == '\0') {
 		VERR(ctx, ERR_PREFIX "name is empty", re->vcl_name, "",
 		     fallback);
@@ -690,8 +695,10 @@ vmod_namedref(VRT_CTX, struct vmod_priv *priv, VCL_STRING name,
 
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	AN(priv);
-	if (fallback == NULL)
-		fallback = "";
+	if (fallback == NULL) {
+		ERR(ctx, "re2.namedref(): fallback is undefined");
+		return "**NAMEDREF FUNCTION FAILED**";
+	}
 	if (name == NULL || name[0] == '\0') {
 		VERR(ctx, ERR_PREFIX "name is empty", "", fallback);
 		return fallback;