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----
# bad
=begin
comment line
another comment line
=end
# good
# comment line
# another comment line
----
.From Perl's POD to RD
****
This is not really a block comment syntax, but more of
an attempt to emulate Perl's https://perldoc.perl.org/perlpod.html[POD] documentation system.
There's an https://github.com/uwabami/rdtool[rdtool] for Ruby that's pretty similar to POD.
Basically `rdtool` scans a file for `=begin` and `=end` pairs, and extracts
the text between them all. This text is assumed to be documentation in
https://github.com/uwabami/rdtool/blob/master/doc/rd-draft.rd[RD format].
You can read more about it
https://ruby-doc.com/docs/ProgrammingRuby/html/rdtool.html[here].
RD predated the rise of RDoc and YARD and was effectively obsoleted by them.footnote:[According to this https://en.wikipedia.org/wiki/Ruby_Document_format[Wikipedia article] the format used to be popular until the early 2000s when it was superseded by RDoc.]
****
== Gemfile and Gemspec
=== No `RUBY_VERSION` in the gemspec [[no-ruby-version-in-the-gemspec]]
The gemspec should not contain `RUBY_VERSION` as a condition to switch dependencies.
`RUBY_VERSION` is determined by `rake release`, so users may end up with wrong dependency.
[source,ruby]
----
# bad
Gem::Specification.new do |s|
if RUBY_VERSION >= '2.5'
s.add_runtime_dependency 'gem_a'
else
s.add_runtime_dependency 'gem_b'
end
end
----
Fix by either:
* Post-install messages.
* Add both gems as dependency (if permissible).
* If development dependencies, move to Gemfile.
== Misc
=== No Flip-flops [[no-flip-flops]]
Avoid the use of flip-flops.
=== No non-`nil` Checks [[no-non-nil-checks]]
Don't do explicit non-`nil` checks unless you're dealing with boolean values.
[source,ruby]
----
# bad
do_something if !something.nil?
do_something if something != nil
# good
do_something if something
# good - dealing with a boolean
def value_set?
!@some_boolean.nil?
end
----
=== Global Input/Output Streams [[global-stdout]]
Use `$stdout/$stderr/$stdin` instead of `STDOUT/STDERR/STDIN`.
`STDOUT/STDERR/STDIN` are constants, and while you can actually reassign (possibly to redirect some stream) constants in Ruby, you'll get an interpreter warning if you do so.
[source,ruby]
----
# bad
STDOUT.puts('hello')
hash = { out: STDOUT, key: value }
def m(out = STDOUT)
out.puts('hello')
end
# good
$stdout.puts('hello')
hash = { out: $stdout, key: value }
def m(out = $stdout)
out.puts('hello')