.\" Automatically generated by Pod::Man 4.14 (Pod::Simple 3.40) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. Capital omega is used to do unbreakable dashes and .\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff, .\" nothing in troff, for use with C<>. .tr \(*W- .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' .ie n \{\ . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} .el\{\ . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\} .\" .\" Escape single quotes in literal strings from groff's Unicode transform. .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" .\" If the F register is >0, we'll generate index entries on stderr for .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index .\" entries marked with X<> in POD. Of course, you'll have to process the .\" output yourself in some meaningful fashion. .\" .\" Avoid warning from groff about undefined register 'F'. .de IX .. .nr rF 0 .if \n(.g .if rF .nr rF 1 .if (\n(rF:(\n(.g==0)) \{\ . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF .\" ======================================================================== .\" .IX Title "Perl::Critic::Policy::ValuesAndExpressions::ProhibitNullStatements 3pm" .TH Perl::Critic::Policy::ValuesAndExpressions::ProhibitNullStatements 3pm "2021-02-28" "perl v5.32.1" "User Contributed Perl Documentation" .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" Perl::Critic::Policy::ValuesAndExpressions::ProhibitNullStatements \- disallow empty statements (stray semicolons) .SH "DESCRIPTION" .IX Header "DESCRIPTION" This policy is part of the \f(CW\*(C`Perl::Critic::Pulp\*(C'\fR add-on. It prohibits empty statements, ie. bare \f(CW\*(C`;\*(C'\fR semicolons. This can be a typo doubling up a semi like .PP .Vb 1 \& use Foo;; # bad .Ve .PP Or a stray left at the end of a control structure like .PP .Vb 4 \& if ($foo) { \& print "foo\en"; \& return; \& }; # bad .Ve .PP An empty statement is harmless, so this policy is under the \*(L"cosmetic\*(R" theme (see \*(L"\s-1POLICY THEMES\*(R"\s0 in Perl::Critic) and medium severity. It's surprisingly easy to leave a semi behind when chopping code around, especially when changing a statement to a loop or conditional. .SS "Allowed forms" .IX Subsection "Allowed forms" A C style \f(CW\*(C`for (;;) { ...}\*(C'\fR loop is ok. Those semicolons are expression separators and empties there are quite usual. .PP .Vb 3 \& for (;;) { # ok \& print "infinite loop\en"; \& } .Ve .PP A semicolon at the start of a \f(CW\*(C`map\*(C'\fR or \f(CW\*(C`grep\*(C'\fR block is allowed. It's commonly used to ensure Perl parses it as a block, not an anonymous hash. (Perl decides at the point it parses the \f(CW\*(C`{\*(C'\fR. A \f(CW\*(C`;\*(C'\fR there forces a block when it might otherwise guess wrongly. See \*(L"map\*(R" in perlfunc for more on this.) .PP .Vb 1 \& map {; $_, 123} @some_list; # ok \& \& grep {# this is a block \& ; # ok \& length $_ and $something } @some_list; .Ve .PP The \f(CW\*(C`map\*(C'\fR form is much more common than the \f(CW\*(C`grep\*(C'\fR, but both suffer the same ambiguity. \f(CW\*(C`grep\*(C'\fR doesn't normally inspire people to quite such convoluted forms as \f(CW\*(C`map\*(C'\fR does. .SS "Try/Catch Blocks" .IX Subsection "Try/Catch Blocks" The \f(CW\*(C`Try\*(C'\fR, \f(CW\*(C`TryCatch\*(C'\fR and \f(CW\*(C`Syntax::Feature::Try\*(C'\fR modules all add new \&\f(CW\*(C`try\*(C'\fR block statement forms. These statements don't require a terminating semicolon (the same as an \f(CW\*(C`if\*(C'\fR doesn't require one). Any semicolon there is reckoned as a null statement. .PP .Vb 5 \& use TryCatch; \& sub foo { \& try { attempt_something() } \& catch { error_recovery() }; # bad \& } .Ve .PP This doesn't apply to other try modules such as \f(CW\*(C`Try::Tiny\*(C'\fR and friends. They're implemented as ordinary function calls (with prototypes), so a terminating semicolon is normal for them. .PP .Vb 5 \& use Try::Tiny; \& sub foo { \& try { attempt_something() } \& catch { error_recovery() }; # ok \& } .Ve .SH "CONFIGURATION" .IX Header "CONFIGURATION" .ie n .IP """allow_perl4_semihash"" (boolean, default false)" 4 .el .IP "\f(CWallow_perl4_semihash\fR (boolean, default false)" 4 .IX Item "allow_perl4_semihash (boolean, default false)" If true then Perl 4 style documentation comments like the following are allowed. .Sp .Vb 3 \& ;# Usage: \& ;# require \*(Aqmypkg.pl\*(Aq; \& ;# ... .Ve .Sp The \f(CW\*(C`;\*(C'\fR must be at the start of the line. This is fairly outdated, so it's disabled by default. If you're crunching through some old code you can enable it by adding to your \fI.perlcriticrc\fR file .Sp .Vb 2 \& [ValuesAndExpressions::ProhibitNullStatements] \& allow_perl4_semihash=1 .Ve .SH "SEE ALSO" .IX Header "SEE ALSO" Perl::Critic::Pulp, Perl::Critic, Perl::Critic::Policy::CodeLayout::RequireFinalSemicolon .SH "HOME PAGE" .IX Header "HOME PAGE" http://user42.tuxfamily.org/perl\-critic\-pulp/index.html .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2019, 2021 Kevin Ryde .PP Perl-Critic-Pulp is free software; you can redistribute it and/or modify it under the terms of the \s-1GNU\s0 General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. .PP Perl-Critic-Pulp is distributed in the hope that it will be useful, but \&\s-1WITHOUT ANY WARRANTY\s0; without even the implied warranty of \s-1MERCHANTABILITY\s0 or \s-1FITNESS FOR A PARTICULAR PURPOSE.\s0 See the \s-1GNU\s0 General Public License for more details. .PP You should have received a copy of the \s-1GNU\s0 General Public License along with Perl-Critic-Pulp. If not, see .