Update empty xml_root_path sanity check case.

Also added tests for it.

Added comment to the *HierarchyPath.AsString() function,
addressing the issue of not being able to retrieve the
element when the root path is equal to the path that
is being processed.

config/configsanity.go

@@ -515,21 +515,24 @@ func (cfg *CGRConfig) checkConfigSanity() error {
 				}
 
 				// The following sanity check prevents a "slice bounds out of range" panic.
-				if rdr.Type == utils.MetaFileXML && !utils.IsSliceMember([]string{utils.META_NONE, utils.META_CONSTANT,
-					utils.META_FILLER, utils.MetaRemoteHost}, field.Type) && len(field.Value) != 0 {
+				if rdr.Type == utils.MetaFileXML && len(field.Value) != 0 &&
+					!utils.IsSliceMember([]string{utils.META_NONE, utils.META_CONSTANT}, field.Type) {
 
-					// Retrieve the number of elements of the parser rule with the fewest elements.
+					// Find the minimum rule length for dynamic RSRParser within the field value.
 					minRuleLength := math.MaxInt
-					for _, rule := range field.Value {
-						if ruleLen := len(strings.Split(rule.AttrName(), utils.NestingSep)); minRuleLength > ruleLen {
-							minRuleLength = ruleLen
+					for _, parser := range field.Value {
+						if !strings.HasPrefix(parser.Rules, utils.DynamicDataPrefix) {
+							continue
 						}
+						ruleLen := len(strings.Split(parser.Rules, utils.NestingSep))
+						minRuleLength = min(minRuleLength, ruleLen)
 					}
 
-					if len(rdr.XmlRootPath) >= minRuleLength {
+					// If a dynamic RSRParser is found, verify xml_root_path length against minRuleLength.
+					if minRuleLength != math.MaxInt && len(rdr.XmlRootPath) >= minRuleLength {
 						return fmt.Errorf("<%s> %s for reader %s at %s",
 							utils.ERs,
-							"len of xml_root_path elements cannot be equal to or exceed the number of value rule elements",
+							"xml_root_path length exceeds value rule elements",
 							rdr.ID, field.Tag)
 					}
 				}

config/configsanity_test.go

@@ -873,3 +873,58 @@ func TestConfigSanityFilterS(t *testing.T) {
 	cfg.filterSCfg.ResourceSConns = []string{}
 
 }
+
+func TestConfigSanityERsXmlRootPath(t *testing.T) {
+	cfg, err := NewCGRConfigFromJsonStringWithDefaults(`{
+"ers": {
+	"enabled": true,
+	"sessions_conns": [],
+	"readers": [
+		{
+			"id": "*default",
+			"type": "*file_xml",
+			"source_path": "/tmp",
+			"processed_path": "/tmp",
+			"flags": ["*dryrun"],
+			"xml_root_path": "A.B",
+			"fields":[
+				{"tag": "VariableFld", "path": "*cgreq.VariableFld", "type": "*variable", "value": "~*req.A.B.Value1", "mandatory": true},
+				{"tag": "ComposedFld", "path": "*cgreq.ComposedFld", "type": "*composed", "value": "~*req.A.B.Value2", "mandatory": true},
+				{"tag": "ComposedFld", "path": "*cgreq.ComposedFld", "type": "*composed", "value": "_", "mandatory": true},
+				{"tag": "ComposedFld", "path": "*cgreq.ComposedFld", "type": "*composed", "value": "~*req.A.B.Value3", "mandatory": true},
+				{"tag": "ConstantFld", "path": "*cgreq.ConstantFld", "type": "*constant", "value": "Value4", "mandatory": true},
+				{"tag": "UsageDiffFld", "path": "*cgreq.UsageDiffFld", "type": "*usage_difference", "value": "~*req.A.B.Value5;~*req.A.B.Value6", "mandatory": true},
+				{"tag": "NoneFld", "path": "*cgreq.NoneFld", "type": "*none", "mandatory": true},
+				{"tag": "FillerFld", "path": "*cgreq.FillerFld", "type": "*filler", "width": 5, "mandatory": true}
+			]
+		}
+	]
+}}`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = cfg.checkConfigSanity()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cfg.ERsCfg().Readers[0].XmlRootPath = utils.ParseHierarchyPath("", utils.EmptyString)
+	err = cfg.checkConfigSanity()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cfg.ERsCfg().Readers[0].XmlRootPath = utils.ParseHierarchyPath("A.B.Value1", utils.EmptyString)
+	err = cfg.checkConfigSanity()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	experr := `<ERs> xml_root_path length exceeds value rule elements for reader *default at VariableFld`
+	cfg.ERsCfg().Readers[0].XmlRootPath = utils.ParseHierarchyPath("A.B.C.D", utils.EmptyString)
+	err = cfg.checkConfigSanity()
+	if err == nil || err.Error() != experr {
+		t.Errorf("expected: %s, received: %s", experr, err)
+	}
+}

utils/coreutils.go

@@ -650,6 +650,12 @@ func (hP HierarchyPath) AsString(sep string, prefix bool) string {
 	if prefix {
 		strHP.WriteString(sep)
 	}
+
+	// TODO: Since this function can convert both the full and the relative HierarchyPath to a string, with
+	// prefix telling us which is which (true -> full path, false -> relative path), we should consider
+	// returning the '.' character when prefix == false. Currently, because we are returning an empty string
+	// if the path we are currently parsing is equal to the root path, when we attempt to retrieve the element
+	// we receive the error "expr expression is nil".
 	if len(hP) == 0 {
 		return strHP.String()
 	}