NAME¶
Perl::Critic::Policy::Freenode::DeprecatedFeatures - Avoid features that have
been deprecated or removed from Perl
DESCRIPTION¶
While Perl::Critic::Policy::Freenode::StrictWarnings will expose usage of
deprecated or removed features when a modern perl is used, this policy will
detect such features in use regardless of perl version, to assist in keeping
your code modern and forward-compatible.
FEATURES¶
Because the whitespace between an attribute list and assignment operator is not
significant, it was possible to specify assignment to a variable with an empty
attribute list with a construction like "my $foo :=
'bar'". This is deprecated in perl v5.12.0 to allow the
possibility of a future ":=" operator. Avoid
the issue by either putting whitespace between the
":" and
"=" characters or simply omitting the empty
attribute list.
The magic "$[" in perlvar variable was used in very old perls to
determine the index of the first element of arrays or the first character in
substrings, and also allow modifying this value. It was discouraged from the
start of Perl 5, its functionality changed in v5.10.0, deprecated in v5.12.0,
re-implemented as arybase.pm in v5.16.0, and it is essentially a synonym for
0 under "use v5.16"
or "no feature "array_base"".
While it is probably a bad idea in general, the modules Array::Base and
String::Base can now be used to replace this functionality.
/\C/¶
The "\C" regular expression character class
would match a single byte of the internal representation of the string, which
was dangerous because it violated the logical character abstraction of Perl
strings, and substitutions using it could result in malformed UTF-8 sequences.
It was deprecated in perl v5.20.0 and removed in perl v5.24.0. Instead,
explicitly encode the string to UTF-8 using Encode to examine its
UTF-8-encoded byte representation.
?PATTERN?¶
The "?PATTERN?" regex match syntax is
deprecated in perl v5.14.0 and removed in perl v5.22.0. Use
"m?PATTERN?" instead.
autoderef¶
An experimental feature was introduced in perl v5.14.0 to allow calling various
builtin functions (which operate on arrays or hashes) on a reference, which
would automatically dereference the operand. This led to ambiguity when passed
objects that overload both array and hash dereferencing, and so was removed in
perl v5.24.0. Instead, explicitly dereference the reference when calling these
functions. The functions affected are
"each",
"keys",
"pop",
"push",
"shift",
"splice",
"unshift", and
"values".
Bare here-doc¶
Using " << " to initiate a here-doc
would create it with an empty terminator, similar to "
<<'' ", so the here-doc would terminate on the next empty
line. Omitting the quoted empty string has been deprecated since perl 5, and
is a fatal error in perl v5.28.0.
chdir('')¶
Passing an empty string or "undef" to
"chdir()" would change to the home
directory, but this usage is deprecated in perl v5.8.0 and throws an error in
perl v5.24.0. Instead, call "chdir()" with
no arguments for this behavior.
defined on array/hash¶
Using the function "defined()" on an array or
hash probably does not do what you expected, and is deprecated in perl v5.6.2
and throws a fatal error in perl v5.22.0. To check if an array or hash is
non-empty, test if it has elements.
if (@foo) { ... }
if (keys %bar) { ... }
do SUBROUTINE(LIST)¶
This form of "do" to call a subroutine has
been deprecated since perl 5, and is removed in perl v5.20.0.
NBSP in \N{...}¶
Use of the "no-break space" character in character names is deprecated
in perl v5.22.0 and an error in perl v5.26.0.
POSIX character functions¶
Several character matching functions in POSIX.pm are deprecated in perl v5.20.0.
See the POSIX documentation for more details. Most uses of these functions can
be replaced with appropriate regex matches.
isalnum, isalpha, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, issuper, isxdigit
POSIX::tmpnam()¶
The "tmpnam()" function from POSIX.pm is
deprecated in perl v5.22.0 and removed in perl v5.26.0. Use File::Temp
instead.
qw(...) as parentheses¶
Literal parentheses are required for certain statements such as a
"for my $foo (...) { ... }" construct. Using
a "qw(...)" list literal without surrounding
parentheses in this syntax is deprecated in perl v5.14.0 and a syntax error in
perl v5.18.0. Wrap the literal in parentheses: "for my
$foo (qw(...)) { ... }".
require ::Foo::Bar¶
A bareword "require" (or
"use") starting with a double colon would
inadvertently translate to a path starting with
"/". Starting in perl v5.26.0, this is a
fatal error.
UNIVERSAL->import()¶
The method "UNIVERSAL->import()" and
similarly passing import arguments to "use
UNIVERSAL" is deprecated in perl v5.12.0 and throws a fatal error
in perl v5.22.0. Calling "use UNIVERSAL"
with no arguments is not an error, but serves no purpose.
AFFILIATION¶
This policy is part of Perl::Critic::Freenode.
CONFIGURATION¶
This policy is not configurable except for the standard options.
CAVEATS¶
This policy is incomplete, as many deprecations are difficult to test for
statically. It is recommended to use perlbrew or perl-build to test your code
under newer versions of Perl, with
"warnings" enabled.
AUTHOR¶
Dan Book, "dbook@cpan.org"
COPYRIGHT AND LICENSE¶
Copyright 2015, Dan Book.
This library is free software; you may redistribute it and/or
modify it under the terms of the Artistic License version 2.0.