I broke discarding old objects when they have been replaced

in c709e110.

Spotted by:	Martin
Test-case by:	Martin

bin/varnishd/cache/cache_fetch.c

@@ -186,7 +186,8 @@ vbf_stp_mkbereq(const struct worker *wrk, struct busyobj *bo)
 	} else
 		AZ(bo->stale_oc);
 
-	if (bo->stale_oc != NULL) {
+	if (bo->stale_oc != NULL &&
+	    ObjCheckFlag(bo->wrk, bo->stale_oc, OF_IMSCAND)) {
 		q = HTTP_GetHdrPack(bo->wrk, bo->stale_oc, H_Last_Modified);
 		if (q != NULL)
 			http_PrintfHeader(bo->bereq0,
@@ -393,7 +394,8 @@ vbf_stp_startfetch(struct worker *wrk, struct busyobj *bo)
 	AZ(bo->was_304);
 
 	if (http_IsStatus(bo->beresp, 304)) {
-		if (bo->stale_oc != NULL) {
+		if (bo->stale_oc != NULL &&
+		    ObjCheckFlag(bo->wrk, bo->stale_oc, OF_IMSCAND)) {
 			if (ObjCheckFlag(bo->wrk, bo->stale_oc, OF_CHGGZIP)) {
 				/*
 				 * If we changed the gzip status of the object
@@ -904,12 +906,14 @@ vbf_fetch_thread(struct worker *wrk, void *priv)
 	bo->wrk = wrk;
 	wrk->vsl = bo->vsl;
 
+#if 0
 	if (bo->stale_oc != NULL) {
 		CHECK_OBJ_NOTNULL(bo->stale_oc, OBJCORE_MAGIC);
 		/* We don't want the oc/stevedore ops in fetching thread */
 		if (!ObjCheckFlag(wrk, bo->stale_oc, OF_IMSCAND))
 			(void)HSH_DerefObjCore(wrk, &bo->stale_oc);
 	}
+#endif
 
 	while (stp != F_STP_DONE) {
 		CHECK_OBJ_NOTNULL(bo, BUSYOBJ_MAGIC);

bin/varnishtest/tests/c00072.vtc

+varnishtest "purge stale on refresh with and without IMS"
+
+server s1 {
+	rxreq
+	txresp -hdr "foo: bar"
+	rxreq
+	txresp -hdr "foo: bar" -hdr {ETag: "asdf"}
+
+	rxreq
+	txresp -hdr "foo: baz"
+	rxreq
+	expect req.http.if-none-match == {"asdf"}
+	txresp -status 304 -nolen -hdr "foo: baz"
+} -start
+
+varnish v1 -vcl+backend {
+	sub vcl_backend_response {
+		set beresp.ttl = 0.1s;
+		set beresp.grace = 0s;
+		set beresp.keep = 60s;
+	}
+} -start
+
+client c1 {
+	txreq -url /no-ims
+	rxresp
+	expect resp.http.foo == "bar"
+	txreq -url /ims
+	rxresp
+	expect resp.http.foo == "bar"
+} -run
+
+# Wait for ttl to expire on both objects
+delay 0.2
+varnish v1 -expect n_object == 2
+
+client c1 {
+	txreq -url /no-ims
+	rxresp
+	expect resp.http.foo == "baz"
+	txreq -url /ims
+	rxresp
+	expect resp.http.foo == "baz"
+} -run
+
+# Make sure expiry is done
+delay 1
+
+# Only one of each of /no-ims and /ims should be left
+varnish v1 -expect n_object == 2