Perl::Critic::Policy::InputOutput::ProhibitJoinedReadline3pm

Affiliation

This Policy is part of the core Perl::Critic distribution.

Overview

It's really easy to slurp a whole filehandle in at once with "join q{}, <$fh">, but that's inefficient -- Perl goes to the trouble of splitting the file into lines only to have that work thrown away.

To save performance, either slurp the filehandle without splitting like so:

  do { local $/ = undef; <$fh> }

or use Path::Tiny, which is even faster.

Note that if the "ProhibitPunctuationVars" policy is also in effect, it will complain about the use of $/ in the line above. In that case, write this instead:

  use English '-no_match_vars';
  do { local $INPUT_RECORD_SEPARATOR = undef; <$fh> };

Configuration

This Policy is not configurable except for the standard options.

Caveats

Due to a bug in the current version of PPI (v1.119_03) and earlier, the readline operator is often misinterpreted as less-than and greater-than operators after a comma. Therefore, this policy only works well on the empty filehandle, "<>". When PPI is fixed, this should just start working.

Credits

Initial development of this policy was supported by a grant from the Perl Foundation.