Emanuele Zeppieri

NAME

HTML::PodCodeReformat - Reformats HTML code blocks coming from Pod verbatim paragraphs

VERSION

version 0.20000

SYNOPSIS

    use HTML::PodCodeReformat;
    
    my $f = HTML::PodCodeReformat->new;
    my $fixed_html = $f->reformat_pre( *DATA );
    
    print $fixed_html; # It prints:
    
    #<!-- HTML produced by a Pod transformer -->
    #<html>
    #<h1>SYNOPSIS</h1>
    #<pre>
    #while (<>) {
    #    chomp;
    #    print;
    #}
    #</pre>
    #<h1>DESCRIPTION</h1>
    #<p>Remove trailing newline from every line.</p>
    #</html>
    
    __DATA__
    <!-- HTML produced by a Pod transformer -->
    <html>
    <h1>SYNOPSIS</h1>
    <pre>
        while (<>) {
            chomp;
            print;
        }
    </pre>
    <h1>DESCRIPTION</h1>
    <p>Remove trailing newline from every line.</p>
    </html>

DESCRIPTION

This module is mainly intended to strip the extra leading spaces which appear in text lines inside <pre>...</pre> blocks (corresponding to Pod verbatim paragraphs) in an HTML-transformed pod (then it can optionally apply other transformations as well on such blocks).

perlpodspec states that (leading) whitespace is significant in verbatim paragraphs, that is, they must be preserved in the final output (e.g. HTML).

This is an unfortunate mixture between syntax and semantics (which is really unavoidable, given the freedom perlpodspec leaves in choosing the verbatim paragraphs indentation width), which leads to (at least) a couple of annoying consequences:

  • the code blocks are awful to see (at least in HTML, where those leading spaces have no meaning);

  • the extra leading spaces can break the code (for example with non-free form code such as YAML, but it can even happen with plain Perl code - think of heredocs), so that, in the general case, the code cannot be taken verbatim from the document (for example by copying and pasting it into a text editor) and run without modifications.

This module takes any document created by a Pod to HTML transformer and eliminates the extra leading spaces in code blocks (rendered in HTML as <pre>...</pre> blocks).

Really, Pod::Simple already offers a sane solution to this problem (through its strip_verbatim_indent method), which has the advantage that it works with any final format.

However it requires you to pass the leading string to strip, which, to work across different pods, of course requires the indentation of verbatim paragraphs to be consistent (which is very unlikely, if said pods come from many different authors). Alternatively, an heuristic to remove the extra indentation can be provided (through a code reference).

Though much more limited in scope, since it works only on HTML, this module offers instead a ready-made simple but effective heuristic, which has proved to work on 100% of the HTML-rendered pods tested so far (including a large CPAN Search subset). For the details, please look at the "ALGORITHM" section below.

Furthermore, since it works only on the final HTML (produced by any Pod transformer), it can more easily be integrated into existing workflows.

METHODS

new

  • HTML::PodCodeReformat->new( %options )

  • HTML::PodCodeReformat->new( \%options )

It creates and returns a new HTML::PodCodeReformat object. It accepts its options either as a hash or a hashref.

It can take the following options:

  • squash_blank_lines

    Boolean option which, when set to true, causes every line composed solely of spaces (\s) in a pre block, to be squashed to an empty string (the newline is left untouched).

    When set to false (which is the default) the blank lines in a pre block will be treated as normal lines, that is, they will be stripped only of the extra leading whitespaces, as any other line.

  • line_numbers

    Boolean option which, when set to true, causes every line in a pre text to be wrapped in <li>...</li> tags, and the whole text to be wrapped in <ol>...</ol> tags (so that a line number is prepended to every line in the pre text, when the HTML document is viewed in a browser).

    In this case the original newlines in the pre text are removed, to not add extra empty lines when the HTML document is rendered.

    It defaults to false.

The above options can be read/set after the object construnction through their corresponding methods as well.

reformat_pre

  • reformat_pre( $filename )

  • reformat_pre( $filehandle )

  • reformat_pre( \$string )

Instance method which removes the extra leading spaces from the lines contained in every <pre>...</pre> block in the given HTML document (of course preserving any real indentation inside code, as showed in the "SYNOPSIS" above), and returns a string containing the HTML code modified that way.

It can take the name of the HTML file, an already opened filehandle or a reference to a string containing the HTML code.

It would work even on nested pre blocks, though this situation has never been encountered in real pods.

If the options squash_blank_lines and line_numbers are set, the corresponding transformations (described above) are applied as well (after the extra leading spaces removal).

ALGORITHM

The adopted algorithm to remove the extra leading whitespaces is extremely simple.

Skipping some minor details, it basically works this way: given an HTML document, for each text block inside <pre>...</pre> tags, first the length of the shortest leading whitespace string across all the lines in the block is calculated (ignoring empty lines), then every line in the block is shifted to the left by such amount.

LIMITATIONS

With the exception explained below in the "Non-limitations" section, any <pre>...</pre> block which has extra leading spaces will be reformatted. This will happen also if a given verbatim paragraph (most probably composed of text, not code) is intended to stay indented (no pun intended) that way, such as in, for example:

        This text
        should really stay
        8-spaces indented
        (but it will be shifted to the first column :-(

Currently there is no way to protect a pre block, but such requirement should be really rare.

Non-limitations

  • Really, perlpodspec says that indenting only the first line it is sufficient to qualify a verbatim paragraph. But this seems not to be used by any author (at least not for real code), and it's even not fully honoured by some Pod parsers.

    Furthermore, the only time I've found such a situation, it was text (not code) meant to really remain indented that way. Since you asked, it was the following block:

                               columns
    <------------------------------------------------------------>
    <----------><------><---------------------------><----------->
     leftMargin  indent  text is formatted into here  rightMargin

    from Text::Format.

    That's why such blocks will be left unaltered, and that's why it's more an advantage than a limitation (hopefully).

  • Working only on pre tags may seem a limitation, but this is the way any Pod to HTML transformer I'm aware of renders a Pod verbatim paragraph in HTML.

AUTHOR

Emanuele Zeppieri, <emazep@cpan.org>

BUGS

No known bugs.

Please report any bugs or feature requests to bug-html-PodCodeReformat at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=HTML-PodCodeReformat. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command:

    perldoc HTML::PodCodeReformat

You can also look for information at:

SEE ALSO

LICENSE AND COPYRIGHT

Copyright 2011 Emanuele Zeppieri.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation, or the Artistic License.

See http://dev.perl.org/licenses/ for more information.