Metadata

ID: ruby-best-practices/no-end-blocks

Language: Ruby

Severity: Notice

Category: Best Practices

Description

The rule of avoiding END blocks in Ruby is important due to the nature of how such blocks are executed. Unlike at_exit blocks, END blocks are run whenever the program exits, regardless of whether it’s a normal termination or due to an unhandled exception. This can lead to unpredictable behavior and makes debugging more difficult.

The use of END blocks also makes your code less readable and harder to maintain. It’s not immediately clear when or why these blocks are executed, and they can easily be overlooked when reading through the code. This can lead to unexpected side effects and bugs.

To adhere to this rule, use at_exit blocks instead of END blocks. This ensures that the block is only executed when the program exits normally, making your code more predictable and easier to debug. Also, consider structuring your code in a way that avoids the need for such blocks in the first place. This will make your code cleaner and easier to understand. For instance, instead of using END to perform cleanup tasks, you can use a begin/rescue/ensure block or make sure that resources are released as soon as they are no longer needed.

Non-Compliant Code Examples

END { puts("end") }
END {puts("end")}
END {
  puts("end")
}
END
{
  puts("end")
}
END {}

puts("begin")
my_str = begin
  a = "more "
  b = "things"
  a + b
end
puts(my_str)

Compliant Code Examples

at_exit { puts("end") }
at_exit {puts("end")}
at_exit {
  puts("end")
}
at_exit
{
  puts("end")
}
at_exit {}

puts("begin")
my_str = begin
  a = "more "
  b = "things"
  a + b
end
puts(my_str)

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