Refactor commit-lint.csx to improve message validation

Author: JaCraig

.husky/csxScripts/commit-lint.csx

@@ -1,16 +1,41 @@
 using System.Text.RegularExpressions;
 
-private var pattern = @"^(?=.{1,90}$)(?:build|feat|ci|chore|docs|fix|perf|refactor|revert|style|test)(?:\(.+\))*(?::).{4,}(?:#\d+)*(?<![\.\s])$";
-private var msg = File.ReadAllLines(Args[0])[0];
+var pattern = @"^(?=.{1,90}$)(?:build|feat|ci|chore|docs|fix|perf|refactor|revert|style|test)(?:\(.+\))*(?::).{4,}(?:#\d+)*(?<![\.\s])$";
+var lines = File.ReadAllLines(Args[0]);
+var header = lines.Length > 0 ? lines[0] : string.Empty;
 
-if (Regex.IsMatch(msg, pattern))
+if (Regex.IsMatch(header, pattern))
    return 0;
 
+var reason = GetFailureReason(header);
+
 Console.ForegroundColor = ConsoleColor.Red;
 Console.WriteLine("Invalid commit message");
 Console.ResetColor();
+Console.WriteLine($"Reason: {reason}");
 Console.WriteLine("e.g: 'feat(scope): subject' or 'fix: subject'");
 Console.ForegroundColor = ConsoleColor.Gray;
 Console.WriteLine("more info: https://www.conventionalcommits.org/en/v1.0.0/");
 
-return 1;
+return 1;
+
+static string GetFailureReason(string header)
+{
+   if (string.IsNullOrWhiteSpace(header))
+      return "The first line of the commit message is empty.";
+
+   if (header.Length > 90)
+      return $"The first line is {header.Length} characters; max allowed is 90.";
+
+   if (Regex.IsMatch(header, @"[\.\s]$"))
+      return "The subject must not end with a period or trailing whitespace.";
+
+   if (!Regex.IsMatch(header, @"^(?:build|feat|ci|chore|docs|fix|perf|refactor|revert|style|test)(?:\(.+\))*:"))
+      return "Header must start with a valid type, optional scope, and colon (for example: feat(scope):).";
+
+   var colonIndex = header.IndexOf(':');
+   if (colonIndex < 0 || header.Length - colonIndex - 1 < 4)
+      return "Header must include at least 4 characters of subject text after the colon.";
+
+   return "Header does not match the conventional commit format expected by this repository.";
+}