Add full file checker CheckInsertFinalNewLineRule.

editorconfig/full_file_checkers.go

@@ -6,7 +6,10 @@ import (
 )
 
 var fullFileCheckers = map[string]FullFileChecker{
-	"end_of_line": CheckEndOfLineRule,
+	"end_of_line":          CheckEndOfLineRule,
+	"insert_final_newline": CheckInsertFinalNewLineRule,
+	// @todo - add checker for charset.
+	// "charset":              CheckCharsetRule,
 }
 
 type FullFileChecker func(ruleValue string, fileContent string) *FullFileCheckResult
@@ -59,3 +62,36 @@ func CheckEndOfLineRule(ruleValue string, fileContent string) *FullFileCheckResu
 
 	return &FullFileCheckResult{isOk: true}
 }
+
+var endsWithFinalNewLineRegexp = regexp.MustCompile(`(\n|\r|\r\n)$`)
+
+func CheckInsertFinalNewLineRule(ruleValue string, fileContent string) *FullFileCheckResult {
+	// Valid rules values are "true" or "false". The values are case insensitive.
+	ruleValueLowercase := strings.ToLower(ruleValue)
+
+	if ruleValueLowercase != "true" && ruleValueLowercase != "false" {
+		return &FullFileCheckResult{isOk: false, messageIfNotOk: "insert_final_new_line value should be true or false, is: " + ruleValue}
+	}
+
+	if len(fileContent) == 0 {
+		return &FullFileCheckResult{isOk: true}
+	}
+
+	if ruleValueLowercase == "true" {
+		if endsWithFinalNewLineRegexp.MatchString(fileContent) {
+			return &FullFileCheckResult{isOk: true}
+		} else {
+			return &FullFileCheckResult{isOk: false, messageIfNotOk: "should end with an empty line but it does not"}
+		}
+	}
+
+	if ruleValueLowercase == "false" {
+		if !endsWithFinalNewLineRegexp.MatchString(fileContent) {
+			return &FullFileCheckResult{isOk: true}
+		} else {
+			return &FullFileCheckResult{isOk: false, messageIfNotOk: "should not end with an empty line but it does"}
+		}
+	}
+
+	return &FullFileCheckResult{isOk: false, messageIfNotOk: "unexpected condition"}
+}