podchecker - check pod documents for syntax errors

- NAME
- SYNOPSIS
- OPTIONS/ARGUMENTS

- `podchecker()`

- DESCRIPTION
- DIAGNOSTICS

- Errors
- Warnings
- Hyperlinks

- RETURN VALUE
- EXAMPLES
- INTERFACE
- AUTHOR

# NAME

Pod::Checker, `podchecker()` - check pod documents for syntax errors

# SYNOPSIS

      use Pod::Checker;

      $syntax_okay = podchecker($filepath, $outputpath, %options);

      my $checker = new Pod::Checker %options;
      $checker->parse_from_file($filepath, \*STDERR);

# OPTIONS/ARGUMENTS

`$filepath` is the input POD to read and `$outputpath` is where to write POD syntax error messages. Either argument may be a scalar indicating a file-path, or else a reference to an open filehandle. If unspecified, the input-file it defaults to `\*STDIN`, and the output-file defaults to `\*STDERR`.

## `podchecker()`

This function can take a hash of options:

-warnings => val

  Turn warnings on/off. val is usually 1 for on, but higher values trigger additional warnings. See Warnings.

# DESCRIPTION

podchecker will perform syntax checking of Perl5 POD format documentation.

Curious/ambitious users are welcome to propose additional features they wish to see in Pod::Checker and podchecker and verify that the checks are consistent with the perlpod manpage.

The following checks are currently performed:

- Unknown '=xxxx' commands, unknown 'X<...>' interior-sequences, and unterminated interior sequences.

- Check for proper balancing of `=begin` and `=end`. The contents of such a block are generally ignored, i.e. no syntax checks are performed.

- Check for proper nesting and balancing of `=over`, `=item` and `=back`.

- Check for same nested interior-sequences (e.g. `L<...L<...>...>`).

- Check for malformed or non-existing entities `E<...>`.

- Check for correct syntax of hyperlinks `L<...>`. See the perlpod manpage for details.

- Check for unresolved document-internal links. This check may also reveal misspelled links that seem to be internal links but should be links to something else.

# DIAGNOSTICS

## Errors

- empty =headn

  A heading (`=head1` or `=head2`) without any text? That ain't no heading!

- =over on line N without closing =back

  The `=over` command does not have a corresponding `=back` before the next heading (`=head1` or `=head2`) or the end of the file.

- =item without previous =over
- =back without previous =over

  An `=item` or `=back` command has been found outside a `=over`/`=back` block.

- No argument for =begin

  A `=begin` command was found that is not followed by the formatter specification.

- =end without =begin

  A standalone `=end` command was found.

- Nested =begin's

  There were at least two consecutive `=begin` commands without the corresponding `=end`. Only one `=begin` may be active at a time.

- =for without formatter specification

  There is no specification of the formatter after the `=for` command.

- unresolved internal link NAME

  The given link to NAME does not have a matching node in the current POD. This also happened when a single word node name is not enclosed in `""`.

- Unknown command "CMD"

  An invalid POD command has been found. Valid are `=head1`, `=head2`, `=head3`, `=head4`, `=over`, `=item`, `=back`, `=begin`, `=end`, `=for`, `=pod`, `=cut`

- Unknown interior-sequence "SEQ"

  An invalid markup command has been encountered. Valid are: `B<>`, `C<>`, `E<>`, `F<>`, `I<>`, `L<>`, `S<>`, `X<>`, `Z<>`

- nested commands CMD<...CMD<...>...>

  Two nested identical markup commands have been found. Generally this does not make sense.

- garbled entity STRING

  The STRING found cannot be interpreted as a character entity.

- Entity number out of range

  An entity specified by number (dec, hex, oct) is out of range (1-255).

- malformed link L<>

  The link found cannot be parsed because it does not conform to the syntax described in the perlpod manpage.

- nonempty Z<>

  The `Z<>` sequence is supposed to be empty.

- empty X<>

  The index entry specified contains nothing but whitespace.

- Spurious text after =pod / =cut

  The commands `=pod` and `=cut` do not take any arguments.

- Spurious character(s) after =back

  The `=back` command does not take any arguments.

## Warnings

These may not necessarily cause trouble, but indicate mediocre style.

- multiple occurrence of link target name

  The POD file has some `=item` and/or `=head` commands that have the same text. Potential hyperlinks to such a text cannot be unique then. This warning is printed only with warning level greater than one.

- line containing nothing but whitespace in paragraph

  There is some whitespace on a seemingly empty line. POD is very sensitive to such things, so this is flagged. vi users switch on the list option to avoid this problem.

- previous =item has no contents

  There is a list `=item` right above the flagged line that has no text contents. You probably want to delete empty items.

- preceding non-item paragraph(s)

  A list introduced by `=over` starts with a text or verbatim paragraph, but continues with `=item`s. Move the non-item paragraph out of the `=over`/`=back` block.

- =item type mismatch (one vs. two)

  A list started with e.g. a bullet-like `=item` and continued with a numbered one. This is obviously inconsistent. For most translators the type of the first `=item` determines the type of the list.

- N unescaped `<>` in paragraph

  Angle brackets not written as `<lt>` and `<gt>` can potentially cause errors as they could be misinterpreted as markup commands. This is only printed when the -warnings level is greater than 1.

- Unknown entity

  A character entity was found that does not belong to the standard ISO set or the POD specials `verbar` and `sol`.

- No items in =over

  The list opened with `=over` does not contain any items.

- No argument for =item

  `=item` without any parameters is deprecated. It should either be followed by `*` to indicate an unordered list, by a number (optionally followed by a dot) to indicate an ordered (numbered) list or simple text for a definition list.

- empty section in previous paragraph

  The previous section (introduced by a `=head` command) does not contain any text. This usually indicates that something is missing. Note: A `=head1` followed immediately by `=head2` does not trigger this warning.

- Verbatim paragraph in NAME section

  The NAME section (`=head1 NAME`) should consist of a single paragraph with the script/module name, followed by a dash `-' and a very short description of what the thing is good for.

- =headn without preceding higher level

  For example if there is a `=head2` in the POD file prior to a `=head1`.

## Hyperlinks

There are some warnings with respect to malformed hyperlinks:

- ignoring leading/trailing whitespace in link

  There is whitespace at the beginning or the end of the contents of L<...>.

- (section) in '$page' deprecated

  There is a section detected in the page name of L<...>, e.g. `L<passwd(2)>`. POD hyperlinks may point to POD documents only. Please write `C<passwd(2)>` instead. Some formatters are able to expand this to appropriate code. For links to (builtin) functions, please say `L<perlfunc/mkdir>`, without ().

- alternative text/node '%s' contains non-escaped | or /

  The characters `|` and `/` are special in the L<...> context. Although the hyperlink parser does its best to determine which "/" is text and which is a delimiter in case of doubt, one ought to escape these literal characters like this:

        /     E<sol>
        |     E<verbar>

# RETURN VALUE

podchecker returns the number of POD syntax errors found or -1 if there were no POD commands at all found in the file.

# EXAMPLES

See SYNOPSIS

# INTERFACE

While checking, this module collects document properties, e.g. the nodes for hyperlinks (`=headX`, `=item`) and index entries (`X<>`). POD translators can use this feature to syntax-check and get the nodes in a first pass before actually starting to convert. This is expensive in terms of execution time, but allows for very robust conversions.

Since PodParser-1.24 the Pod::Checker module uses only the poderror method to print errors and warnings. The summary output (e.g. "Pod syntax OK") has been dropped from the module and has been included in podchecker (the script). This allows users of Pod::Checker to control completely the output behavior. Users of podchecker (the script) get the well-known behavior.

`Pod::Checker->new( %options )`

  Return a reference to a new Pod::Checker object that inherits from Pod::Parser and is used for calling the required methods later. The following options are recognized:

  `-warnings => num` Print warnings if `num` is true. The higher the value of `num`, the more warnings are printed. Currently there are only levels 1 and 2.

  `-quiet => num` If `num` is true, do not print any errors/warnings. This is useful when Pod::Checker is used to munge POD code into plain text from within POD formatters.

`$checker->poderror( @args )`
`$checker->poderror( {%opts}, @args )`

  Internal method for printing errors and warnings. If no options are given, simply prints "@_". The following options are recognized and used to form the output:

        -msg

  A message to print prior to `@args`.

        -line

  The line number the error occurred in.

        -file

  The file (name) the error occurred in.

        -severity

  The error level, should be 'WARNING' or 'ERROR'.

`$checker->num_errors()`

  Set (if argument specified) and retrieve the number of errors found.

`$checker->num_warnings()`

  Set (if argument specified) and retrieve the number of warnings found.

`$checker->name()`

  Set (if argument specified) and retrieve the canonical name of POD as found in the `=head1 NAME` section.

`$checker->node()`

  Add (if argument specified) and retrieve the nodes (as defined by `=headX` and `=item`) of the current POD. The nodes are returned in the order of their occurrence. They consist of plain text, each piece of whitespace is collapsed to a single blank.

`$checker->idx()`

  Add (if argument specified) and retrieve the index entries (as defined by `X<>`) of the current POD. They consist of plain text, each piece of whitespace is collapsed to a single blank.

`$checker->hyperlink()`

  Add (if argument specified) and retrieve the hyperlinks (as defined by `L<>`) of the current POD. They consist of a 2-item array: line number and `Pod::Hyperlink` object.

# AUTHOR

Please report bugs using http://rt.cpan.org.

Brad Appleton <bradapp@enteract.com> (initial version), Marek Rouchal <marekr@cpan.org>

Based on code for Pod::Text::pod2text() written by Tom Christiansen <tchrist@mox.perl.com>

podchecker - check pod documents for syntax errors