Perl::Tidy - Parses and beautifies perl source

    use Perl::Tidy;

    Perl::Tidy::perltidy(
        source      => $source,
        destination => $destination,
        stderr      => $stderr,
        argv        => $argv,
        perltidyrc  => $perltidyrc,
        logfile     => $logfile,
        errorfile   => $errorfile,
        formatter   => $formatter,  # callback object (see below)
    );

This module makes the functionality of the perltidy utility available to perl scripts. Any or all of the input parameters may be omitted, in which case the CW@ARGV array will be used to provide input parameters as described in the perltidy(1) man page.

For example, the perltidy script is basically just this:

    use Perl::Tidy;
    Perl::Tidy::perltidy();

The module accepts input and output streams by a variety of methods. The following list of parameters may be any of a the following: a filename, an ARRAY reference, a SCALAR reference, or an object with either a getline or print method, as appropriate.

        source          - the source of the script to be formatted
        destination     - the destination of the formatted output
        stderr          - standard error output
        perltidyrc      - the .perltidyrc file
        logfile         - the .LOG file stream, if any 
        errorfile       - the .ERR file stream, if any

The following chart illustrates the logic used to decide how to treat a parameter.

   ref($param)  $param is assumed to be:
   -----------  ---------------------
   undef        a filename
   SCALAR       ref to string
   ARRAY        ref to array
   (other)      object with getline (if source) or print method

If the parameter is an object, and the object has a close method, that close method will be called at the end of the stream.

source

If the source parameter is given, it defines the source of the input stream.

destination

If the destination parameter is given, it will be used to define the file or memory location to receive output of perltidy.

stderr

The stderr parameter allows the calling program to capture the output to what would otherwise go to the standard error output device.

perltidyrc

If the perltidyrc file is given, it will be used instead of any .perltidyrc configuration file that would otherwise be used.

argv

If the argv parameter is given, it will be used instead of the @ARGV array. The argv parameter may be a string, a reference to a string, or a reference to an array. If it is a string or reference to a string, it will be parsed into an array of items just as if it were a command line string.

The following example passes perltidy a snippet as a reference to a string and receives the result back in a reference to an array.

 use Perl::Tidy;

 # some messy source code to format
 my $source = <<'EOM';
 use strict;
 my @editors=('Emacs', 'Vi   '); my $rand = rand();
 print "A poll of 10 random programmers gave these results:\n";
 foreach(0..10) {
 my $i=int ($rand+rand());
 print " $editors[$i] users are from Venus" . ", " . 
 "$editors[1-$i] users are from Mars" . 
 "\n";
 }
 EOM

 # We'll pass it as ref to SCALAR and receive it in a ref to ARRAY
 my @dest;
 perltidy( source => \$source, destination => \@dest );
 foreach (@dest) {print}

The formatter parameter is an optional callback object which allows the calling program to receive tokenized lines directly from perltidy for further specialized processing. When this parameter is used, the two formatting options which are built into perltidy (beautification or html) are ignored. The following diagram illustrates the logical flow:

                    |-- (normal route)   -> code beautification
  caller->perltidy->|-- (-html flag )    -> create html 
                    |-- (formatter given)-> callback to write_line

This can be useful for processing perl scripts in some way. The parameter CW$formatter in the perltidy call,

        formatter   => $formatter,

is an object created by the caller with a CWwrite_line method which will accept and process tokenized lines, one line per call. Here is a simple example of a CWwrite_line which merely prints the line number, the line type (as determined by perltidy), and the text of the line:

 sub write_line {

     # This is called from perltidy line-by-line
     my $self              = shift;
     my $line_of_tokens    = shift;
     my $line_type         = $line_of_tokens->{_line_type};
     my $input_line_number = $line_of_tokens->{_line_number};
     my $input_line        = $line_of_tokens->{_line_text};
     print "$input_line_number:$line_type:$input_line";
 }

The complete program, perllinetype, is contained in the examples section of the source distribution. As this example shows, the callback method receives a parameter $line_of_tokens, which is a reference to a hash of other useful information. This example uses these hash entries:

 $line_of_tokens->{_line_number} - the line number (1,2,...)
 $line_of_tokens->{_line_text}   - the text of the line
 $line_of_tokens->{_line_type}   - the type of the line, one of:

    SYSTEM         - system-specific code before hash-bang line
    CODE           - line of perl code (including comments)
    POD_START      - line starting pod, such as '=head'
    POD            - pod documentation text
    POD_END        - last line of pod section, '=cut'
    HERE           - text of here-document
    HERE_END       - last line of here-doc (target word)
    FORMAT         - format section
    FORMAT_END     - last line of format section, '.'
    DATA_START     - __DATA__ line
    DATA           - unidentified text following __DATA__
    END_START      - __END__ line
    END            - unidentified text following __END__
    ERROR          - we are in big trouble, probably not a perl script

Most applications will be only interested in lines of type CODE. For another example, let's write a program which checks for one of the so-called naughty matching variables CW&`, CW$&, and CW$', which can slow down processing. Here is a write_line, from the example program find_naughty.pl, which does that:

 sub write_line {

     # This is called back from perltidy line-by-line
     # We're looking for $`, $&, and $'
     my ( $self, $line_of_tokens ) = @_;

     # pull out some stuff we might need
     my $line_type         = $line_of_tokens->{_line_type};
     my $input_line_number = $line_of_tokens->{_line_number};
     my $input_line        = $line_of_tokens->{_line_text};
     my $rtoken_type       = $line_of_tokens->{_rtoken_type};
     my $rtokens           = $line_of_tokens->{_rtokens};
     chomp $input_line;

     # skip comments, pod, etc
     return if ( $line_type ne 'CODE' );

     # loop over tokens looking for $`, $&, and $'
     for ( my $j = 0 ; $j < @$rtoken_type ; $j++ ) {

         # we only want to examine token types 'i' (identifier)
         next unless $$rtoken_type[$j] eq 'i';

         # pull out the actual token text
         my $token = $$rtokens[$j];

         # and check it
         if ( $token =~ /^\$[\`\&\']$/ ) {
             print STDERR
               "$input_line_number: $token\n";
         }
     }
 }

This example pulls out these tokenization variables from the CW$line_of_tokens hash reference:

     $rtoken_type = $line_of_tokens->{_rtoken_type};
     $rtokens     = $line_of_tokens->{_rtokens};

The variable CW$rtoken_type is a reference to an array of token type codes, and CW$rtokens is a reference to a corresponding array of token text. These are obviously only defined for lines of type CODE. Perltidy classifies tokens into types, and has a brief code for each type. You can get a complete list at any time by running perltidy from the command line with

     perltidy --dump-token-types

In the present example, we are only looking for tokens of type i (identifiers), so the for loop skips past all other types. When an identifier is found, its actual text is checked to see if it is one being sought. If so, the above write_line prints the token and its line number.

The formatter feature is relatively new in perltidy, and further documentation needs to be written to complete its description. However, several example programs have been written and can be found in the examples section of the source distribution. Probably the best way to get started is to find one of the examples which most closely matches your application and start modifying it.

For help with perltidy's pecular way of breaking lines into tokens, you might run, from the command line,

 perltidy -D filename

where filename is a short script of interest. This will produce filename.DEBUG with interleaved lines of text and their token types. The -D flag has been in perltidy from the beginning for this purpose. If you want to see the code which creates this file, it is CWwrite_debug_entry in Tidy.pm.

  &perltidy

Thanks to Hugh Myers who developed the initial modular interface to perltidy.

This man page documents Perl::Tidy version 20031021.

 Steve Hancock
 perltidy at users.sourceforge.net

The perltidy(1) man page describes all of the features of perltidy. It can be found at http://perltidy.sourceforge.net.