sj26/mailcatcher · info

Backtrace:

Error message

    Backtrace:

What it means

The backtrace section of log_exception (lib/mail_catcher.rb:63). Each frame of exception.backtrace is printed with gem installation directories rewritten by the regex on line 58 into `gemname (version) relative/path`, so frames read like `mail (2.7.1) lib/mail/message.rb:123` instead of absolute gem paths. It is printed with puts as the label followed by the mapped lines.

Source

Thrown at lib/mail_catcher.rb:63

    windows? or which? "open"
  end

  def browse url
    if windows?
      system "start", "/b", url
    elsif which? "open"
      system "open", url
    end
  end

  def log_exception(message, context, exception)
    gems_paths = (Gem.path | [Gem.default_dir]).map { |path| Regexp.escape(path) }
    gems_regexp = %r{(?:#{gems_paths.join("|")})/gems/([^/]+)-([\w.]+)/(.*)}
    gems_replace = '\1 (\2) \3'

    puts "*** #{message}: #{context.inspect}"
    puts "    Exception: #{exception}"
    puts "    Backtrace:", *exception.backtrace.map { |line| "       #{line.sub(gems_regexp, gems_replace)}" }
    puts "    Please submit this as an issue at https://github.com/sj26/mailcatcher/issues"
  end

  @@defaults = {
    :smtp_ip => "127.0.0.1",
    :smtp_port => "1025",
    :http_ip => "127.0.0.1",
    :http_port => "1080",
    :http_path => "/",
    :messages_limit => nil,
    :verbose => false,
    :daemon => !windows?,
    :browse => false,
    :quit => true,
  }

  def options
    @@options

View on GitHub (pinned to 18a9cb7a79)

Solutions

1. Read the deepest non-gem frame first — it names the code at fault (e.g. `sqlite3 (1.4.x)` frames point at the DB layer, `mail (...)` frames at MIME parsing).
2. Reproduce with `mailcatcher --foreground --verbose` to get the trace directly in your terminal.
3. Pin the guilty gem back to the last working version (common outcome: sqlite3, mail) and restart.
4. If frames point into mailcatcher's own lib/, file the issue with this trace attached.

# Capture the full report (context + exception + rewritten backtrace) yourself when embedding
begin
  MailCatcher::Mail.add_message(msg)
rescue => e
  File.write("mailcatcher-crash.log", [e.message, *e.backtrace].join("\n"))
  raise unless e.is_a?(SQLite3::Exception) # re-raise what you cannot handle
end

When it happens

Trigger: Printed automatically on the same conditions as the `***` header: any exception caught by rescue in MailCatcher::Smtp#receive_message (smtp.rb:62) or in the websocket send callback (application.rb:89). The rewriting itself can raise ArgumentError if Gem.path/Gem.default_dir contain regex-metacharacter characters, but in practice it always renders the cleaned trace.

Common situations: Needing to know whether the fault is inside mailcatcher, the sqlite3 gem, the mail gem, or faye-websocket when only a one-line symptom is visible; debugging in daemon mode where the report scrolls away; comparing traces across gem versions after a bundle update changed behavior.

Related errors

• *** #{message}: #{context.inspect}
• Exception: #{exception}
• Please submit this as an issue at https://github.com/sj2

AI-assisted analysis of sj26/mailcatcher@18a9cb7a79 (2026-08-21). Data as JSON: /api/errors/24c27d5332b463c0. Report an issue: GitHub.