cache xlat can succeed if it returns no data.

i.e. "no data in cache" isn't an xlat failure, it's an xlat
success with no data.

Author: alandekok

src/modules/rlm_cache/rlm_cache.c

@@ -937,6 +937,11 @@ xlat_action_t cache_xlat(TALLOC_CTX *ctx, fr_dcursor_t *out,
 	case RLM_MODULE_OK:		/* found */
 		break;
 
+	case RLM_MODULE_NOTFOUND:      	/* !found is "no data" */
+		talloc_free(target);
+		cache_release(inst, request, &handle);
+		return XLAT_ACTION_DONE;
+
 	default:
 		talloc_free(target);
 		cache_release(inst, request, &handle);
@@ -966,9 +971,9 @@ xlat_action_t cache_xlat(TALLOC_CTX *ctx, fr_dcursor_t *out,
 	cache_release(inst, request, &handle);
 
 	/*
-	 *	Check if we found a matching map
+	 *	If we found a value, then the output has been updated.
+	 *	Otherwise, there is no output.  Either way, the xlat succeeded.
 	 */
-	if (!map) return XLAT_ACTION_FAIL;
 
 	return XLAT_ACTION_DONE;
 }

src/tests/modules/cache_rbtree/cache-xlat.unlang

@@ -29,9 +29,31 @@ if (Login-LAT-Node) {
 # Regression test for deadlock on notfound
 Filter-Id := 'testkey0'
 
+#
+#  There is no request.Login-LAT-Port, so the input is empty.
+#
 Login-LAT-Node := %cache(request.Login-LAT-Port)
 
 # Would previously deadlock
 Login-LAT-Port := %cache(request.Login-LAT-Port)
 
+#
+#  Get the value for a key which doesn't exist.  The xlat should succeed, but return no data.
+#
+Filter-Id := 'nosuchkey'
+request.Login-LAT-Service := %cache('request.Callback-Id')
+if request.Login-LAT-Service {
+	test_fail
+}
+
+#
+#  And then verify that the previous cache entry hasn't been deleted
+#
+Filter-Id := 'testkey'
+request.Login-LAT-Service := %cache('request.Callback-Id')
+
+if (Login-LAT-Service != control.Callback-Id) {
+        test_fail
+}
+
 test_pass