From 1ffb4abd427722e850989d6ea28ea6fee7bba310 Mon Sep 17 00:00:00 2001
From: Ken Gaillot <kgaillot@redhat.com>
Date: Feb 24 2021 16:08:51 +0000
Subject: Low: scheduler: treat NULL and empty string the same in literal attribute comparisons


Previously, expand_value_source() returned NULL if the value was the empty
string ("") only when value-source was "param" or "meta". If value-source was
literal, it would return the empty string.

This behavior shouldn't depend on value-source, so it now returns NULL when a
literal value is the empty string.

This could change the behavior for "defined"/"not_defined" checks, and
comparisons against another NULL or empty string value (NULL compares less than
empty strings). But the consistency seems worth it.

(Another question not addressed here is whether NULL and empty string should
compare as equal.)

---

diff --git a/lib/pengine/rules.c b/lib/pengine/rules.c
index aa5d6ab..d69f449 100644
--- a/lib/pengine/rules.c
+++ b/lib/pengine/rules.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 2004-2020 the Pacemaker project contributors
+ * Copyright 2004-2021 the Pacemaker project contributors
  *
  * The version control history for this file may have further details.
  *
@@ -1039,7 +1039,10 @@ expand_value_source(const char *value, const char *value_source,
 {
     GHashTable *table = NULL;
 
-    if (pcmk__str_eq(value_source, "param", pcmk__str_casei)) {
+    if (pcmk__str_empty(value)) {
+        return NULL; // value_source is irrelevant
+
+    } else if (pcmk__str_eq(value_source, "param", pcmk__str_casei)) {
         table = match_data->params;
 
     } else if (pcmk__str_eq(value_source, "meta", pcmk__str_casei)) {
@@ -1049,7 +1052,7 @@ expand_value_source(const char *value, const char *value_source,
         return value;
     }
 
-    if ((table == NULL) || pcmk__str_empty(value)) {
+    if (table == NULL) {
         return NULL;
     }
     return (const char *) g_hash_table_lookup(table, value);