parser: Check and prompt for empty patterns and region properties (fix crash) (zyedidia#3256)

* parser: Precise error message for missing `start` & `end` in region

* parser: Check and prompt for empty patterns and region properties

* syntax: Remove empty identifier pattern from log definition

Author: JoeKar

pkg/highlight/parser.go

@@ -355,6 +355,10 @@ func parseRules(input []interface{}, curRegion *region) (ru *rules, err error) {
 
 			switch object := val.(type) {
 			case string:
+				if object == "" {
+					return nil, fmt.Errorf("Empty rule %s", k)
+				}
+
 				if k == "include" {
 					ru.includes = append(ru.includes, object)
 				} else {
@@ -408,30 +412,56 @@ func parseRegion(group string, regionInfo map[interface{}]interface{}, prevRegio
 	r.group = groupNum
 	r.parent = prevRegion
 
-	r.start, err = regexp.Compile(regionInfo["start"].(string))
+	// start is mandatory
+	if start, ok := regionInfo["start"]; ok {
+		start := start.(string)
+		if start == "" {
+			return nil, fmt.Errorf("Empty start in %s", group)
+		}
 
-	if err != nil {
-		return nil, err
+		r.start, err = regexp.Compile(start)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		return nil, fmt.Errorf("Missing start in %s", group)
 	}
 
-	r.end, err = regexp.Compile(regionInfo["end"].(string))
+	// end is mandatory
+	if end, ok := regionInfo["end"]; ok {
+		end := end.(string)
+		if end == "" {
+			return nil, fmt.Errorf("Empty end in %s", group)
+		}
 
-	if err != nil {
-		return nil, err
+		r.end, err = regexp.Compile(end)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		return nil, fmt.Errorf("Missing end in %s", group)
 	}
 
 	// skip is optional
-	if _, ok := regionInfo["skip"]; ok {
-		r.skip, err = regexp.Compile(regionInfo["skip"].(string))
+	if skip, ok := regionInfo["skip"]; ok {
+		skip := skip.(string)
+		if skip == "" {
+			return nil, fmt.Errorf("Empty skip in %s", group)
+		}
 
+		r.skip, err = regexp.Compile(skip)
 		if err != nil {
 			return nil, err
 		}
 	}
 
 	// limit-color is optional
-	if _, ok := regionInfo["limit-group"]; ok {
-		groupStr := regionInfo["limit-group"].(string)
+	if groupStr, ok := regionInfo["limit-group"]; ok {
+		groupStr := groupStr.(string)
+		if groupStr == "" {
+			return nil, fmt.Errorf("Empty limit-group in %s", group)
+		}
+
 		if _, ok := Groups[groupStr]; !ok {
 			numGroups++
 			Groups[groupStr] = numGroups

runtime/syntax/log.yaml

@@ -62,8 +62,6 @@ rules:
 # - identifier: "^([0-2][0-9][0-2][0-9][-/]?[0-9][0-9][-/]?[0-9][0-9]\\s[0-9][0-9]:[0-9][0-9](:[0-9][0-9])?(\\.?[0-9][0-9][0-9])?)"
 - identifier: "^(\\d{4}[-/]?\\d{2}[-/]?\\d{2}\\s\\d{2}:\\d{2}(:\\d{2})?(\\.?\\d{2,8})?)"
 - identifier: "^([0-2][0-9]|[0-2]-?[0-9][0-9]-?[0-9][0-9])\\-([0-1][0-9])\\-([0-3][0-9]) ([0-2][0-9])\\:([0-5][0-9])\\:([0-5][0-9]),([0-9][0-9][0-9])"
-# ISO 8601:2004(E)
-- identifier: ""
 # Complete precision:
 - identifier: "^(\\d{4}-[01]\\d-[0-3]\\dT[0-2]\\d:[0-5]\\d:[0-5]\\d\\.\\d+([+-][0-2]\\d:[0-5]\\d|Z))"
 # No milliseconds: