conf: fix title and description for virDomainSetMetadata API

If we pass XML to virDomainDefineXML API with these two elements:

    ...
    <title></title>
    <description></description>
    ...

libvirt correctly ignores these two elements and they will not appear
in the parsed XML.

However, if we use virDomainSetMetadata API and with "" as value for
title or description we will end up with the parsed XML that contains
these empty elements.

Let's fix the behavior of this API to behave the same as
virDomainDefineXML.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1518042Reviewed-by: NJohn Ferlan <jferlan@redhat.com>
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

src/conf/domain_conf.c

@@ -29678,7 +29678,7 @@ virDomainDefSetMetadata(virDomainDefPtr def,
     xmlDocPtr doc = NULL;
     xmlNodePtr old;
     xmlNodePtr new = NULL;
-    char *tmp;
+    char *tmp = NULL;
     int ret = -1;
 
     if (type >= VIR_DOMAIN_METADATA_LAST) {
@@ -29689,7 +29689,7 @@ virDomainDefSetMetadata(virDomainDefPtr def,
 
     switch ((virDomainMetadataType) type) {
     case VIR_DOMAIN_METADATA_DESCRIPTION:
-        if (VIR_STRDUP(tmp, metadata) < 0)
+        if (STRNEQ_NULLABLE(metadata, "") && VIR_STRDUP(tmp, metadata) < 0)
             goto cleanup;
 
         VIR_FREE(def->description);
@@ -29697,7 +29697,7 @@ virDomainDefSetMetadata(virDomainDefPtr def,
         break;
 
     case VIR_DOMAIN_METADATA_TITLE:
-        if (VIR_STRDUP(tmp, metadata) < 0)
+        if (STRNEQ_NULLABLE(metadata, "") && VIR_STRDUP(tmp, metadata) < 0)
             goto cleanup;
 
         VIR_FREE(def->title);

tests/metadatatest.c

@@ -167,6 +167,7 @@ struct metadataTest {
     virDomainPtr dom;
 
     const char *data;
+    const char *expect;
     int type;
     bool fail;
 };
@@ -232,7 +233,7 @@ testTextMetadata(const void *data)
 
     actual = virDomainGetMetadata(test->dom, test->type, NULL, 0);
 
-    if (STRNEQ_NULLABLE(test->data, actual)) {
+    if (STRNEQ_NULLABLE(test->expect, actual)) {
         virReportError(VIR_ERR_INTERNAL_ERROR,
                        "expected metadata doesn't match actual: "
                        "expected:'%s'\ngot: '%s'",
@@ -248,10 +249,11 @@ testTextMetadata(const void *data)
     return ret;
 }
 
-#define TEST_TEXT_METADATA(INDEX, TYPE, DATA, FAIL) \
+#define TEST_TEXT_METADATA(INDEX, TYPE, DATA, EXPECT, FAIL) \
     do { \
         test.type = VIR_DOMAIN_METADATA_ ## TYPE; \
         test.data = DATA; \
+        test.expect = EXPECT; \
         test.fail = FAIL; \
  \
         if (virTestRun("text metadata: " #TYPE " " INDEX " ", \
@@ -259,9 +261,16 @@ testTextMetadata(const void *data)
             ret = EXIT_FAILURE; \
     } while (0)
 
-#define TEST_TITLE(INDEX, DATA) TEST_TEXT_METADATA(INDEX, TITLE, DATA, false)
-#define TEST_TITLE_FAIL(INDEX, DATA) TEST_TEXT_METADATA(INDEX, TITLE, DATA, true)
-#define TEST_DESCR(INDEX, DATA) TEST_TEXT_METADATA(INDEX, DESCRIPTION, DATA, false)
+#define TEST_TITLE(INDEX, DATA) \
+    TEST_TEXT_METADATA(INDEX, TITLE, DATA, DATA, false)
+#define TEST_TITLE_EXPECT(INDEX, DATA, EXPECT) \
+    TEST_TEXT_METADATA(INDEX, TITLE, DATA, EXPECT, false)
+#define TEST_TITLE_FAIL(INDEX, DATA) \
+    TEST_TEXT_METADATA(INDEX, TITLE, DATA, DATA, true)
+#define TEST_DESCR(INDEX, DATA) \
+    TEST_TEXT_METADATA(INDEX, DESCRIPTION, DATA, DATA, false)
+#define TEST_DESCR_EXPECT(INDEX, DATA, EXPECT) \
+    TEST_TEXT_METADATA(INDEX, DESCRIPTION, DATA, EXPECT, false)
 
 static int
 mymain(void)
@@ -290,7 +299,7 @@ mymain(void)
     TEST_TITLE("2", NULL);
     TEST_TITLE("3", "blah");
     TEST_TITLE_FAIL("4", "qwe\nrt");
-    TEST_TITLE("5", "");
+    TEST_TITLE_EXPECT("5", "", NULL);
     TEST_TITLE_FAIL("6", "qwert\n");
     TEST_TITLE_FAIL("7", "\n");
 
@@ -298,7 +307,7 @@ mymain(void)
     TEST_DESCR("2", NULL);
     TEST_DESCR("3", "qwert");
     TEST_DESCR("4", "\n");
-    TEST_DESCR("5", "");
+    TEST_DESCR_EXPECT("5", "", NULL);
 
     virDomainFree(test.dom);
     virConnectClose(test.conn);