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.

NOTE THAT THIS MODULE IS CURRENTLY IN THE BETA STAGE!

It is hoped that curious/ambitious user will help flesh out and add the 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 preformed:

- 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 nonexisting 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 happend when a single word node name is not enclosed in `""`.

- Unknown command ``CMD''
  An invalid POD command has been found. Valid are `=head1`, `=head2`, `=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 occurence 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.

- 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 bulletted `=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.

## Hyperlinks

There are some warnings wrt. 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

[T.B.D.]

# 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.

`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->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 occurence. 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 an 2-item array: line number and `Pod::Hyperlink` object.

# AUTHOR

Brad Appleton <bradapp@enteract.com> (initial version), Marek Rouchal <marek@saftsack.fs.uni-bayreuth.de>

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

podchecker - check pod documents for syntax errors