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Devel::Declare::Parser - Higher level interface to Devel-Declare
Contents
Copyright
Copyright (C) 2010 Chad Granum
Devel-Declare-Parser is free software; Standard perl licence.
Devel-Declare-Parser is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the license for
more details.
perl v5.36.0 2023-10-26 Devel::Declare::Parser(3pm)
Description
Devel-Declare-Parser is a higher-level API sitting on top of Devel::Declare. It is used by
Devel::Declare::Exporter to simplify exporting of Devel::Declare magic. Writing custom parsers usually
only requires subclassing this module and overriding a couple methods.
Devel-Declare-Parser Api
INTERNALSWARNINGParserobjectsareblessedarrays,nothashrefs.
If you want to create a new accessor use the add_accessor() class method. It will take care of assigning
an unused array element to the attribute, and will create a read/write accessor sub for you.
__PACKAGE__->add_accessor( 'my_accessor' );
There are many public and private methods on the parser base class. Only the public methods are fully
documented. Be sure to refer often to the list of private methods at the end of this document, accidently
overriding a private method could have devastating consequences.
CLASSMETHODS
$class->new( $name, $declarator, $offset )
The constructor, "DO NOT OVERRIDE THIS!"
$class->DEBUG($bool)
Turn debugging on/off. This will output the line after it has been modified, as well as some context
information.
NOTE: This has a global effect, all parsers will start debugging.
UTILITYMETHODS
bail( @messages )
Like croak, dies providing you context information. Since any death occurs inside the parser, carp
provides useless information.
diag( @message )
Like carp, warns providing you context information. Since the warn occurs inside the parser carp
provides useless information.
end_quote($start_char)
Find the end-character for the provide starting quote character. As in '{' returns '}' and '('
returns ')'. If there is no counter-part the start character is returned: "'" returns "'".
filename()
Filename the rewrite is occurring against.
linenum()
Linenum the rewrite is occurring on.
format_part()
Returns the stringified form of a part datastructure. For variables and operators that is just the
item itself as a string. For barewords or package names it is the item itself with single quotes
wrapped around it. For quoted items it is the string wrapped in its proper quoting characters. If a
second parameter is provided (and true) no single quotes will be added to barewords.
ACCESSORS
These are the read/write accessors used by Parser. Notalloftheseactonanarrayelement,somewilldirectlyalterthecurrentline.line()
This will retrieve the current line from Devel-Declare. If given a value, that value will be set as
the current line using Devel-Declare.
name()
Name of the declarator as provided via the parser.
declarator()
Name of the declarator as provided via the Devel-Declare.
original_offset()
Offset on the line when the parsing was started.
offset()
Current line offset.
parts()
Arrayref of parts (may be undef)
new_parts()
Arrayref of new parts (may be undef)
end_char()
Will be set to the character just after the completely parsed line (usually '{' or ';')
prototype()
Used internally for prototype tracking.
contained()
True if the parser determined this was a contained call. This means your keyword was followed by an
opening paren, and the statement ended with a closing paren and semicolon. By default Parser will not
modify such lines.
OVERRIDABLEMETHODS
These are methods you can, should, or may override in your baseclass.
quote_chars()
Specify the starting characters for quoted strings. (returns a list)
end_chars()
Characters to recognise as end of statement characters (';' and '{') (returns a list)
inject()
Code to inject into functions enhanced by this parser.
pre_parse()
Check if we want to process the line at all.
parse()
Turn the line into 'parts'.
post_parse()
Hook, currently does nothing.
rewrite()
Hook, currently takes all the arguments between the declarator and the codeblock/semicolon (which
have been turned into 'parts' structures in the parts() attribute) and puts them into the new_parts()
attribute.
This is usually the method you want to override.
write_line()
Opens, fills in, and closes the line as a string, then rewrites the actual line using Devel::Declare.
edit_line()
Hook, currently does nothing.
open_line()
Usually returns '('. This is how to start a line following your keyword
close_line()
End the line, this means either re-inserting the opening '{' on the codeblock, along with any
injections, or returning ');'
POSITIONTRACKING
advance( $num_chars )
Advances the offset by $num_chars.
skip_declarator()
Skips the declarator at the start of the line.
skipspace()
Advances the offset past any whitespace.
LINEEXAMINATION(NON-MODIFYING)
These are used by pre_parse() to examine the line prior to any modification.
is_contained()
True if the line is of the format:
keyword( ... );
is_arrow_contained()
True if the line is of the format:
keyword word_or_string => ( ... );
is_defenition()
True if the line matches the regex m/sub[\s\n]+$name/sm
PARTEXAMINATION
These are methods that let you investigate the parts already parsed and placed in the parts() attribute.
has_non_string_or_quote_parts()
Returns a list of parts that are not strings, quotes, or barewords.
has_string_or_quote_parts()
Returns a list of parts that are strings, quotes, or barewords.
has_keyword( $word )
Check for a keyword in the parts
has_comma()has_fat_comma()LINEEXAMINATION(MODIFYING)
This examines the line returning part structures and removing elements from the line each time they are
called.
strip_item()strip_length()strip_remaining_items()LOOKINGAHEAD
These methods help the parser determine what comes next in a line. In most cases these are non-modifying.
peek_is_block()peek_is_end()peek_is_other()peek_is_quote()peek_is_word()peek_item()peek_item_type()peek_num_chars()peek_other()peek_quote()peek_remaining()peek_word()PRIVATEMETHODS
Do not use these, and definitely do not override them in a subclass.
_block_end_injection()_debug()_edit_block_end()_item_via_()_linestr_offset_from_dd()_move_via_()_peek_is_package()_peek_is_word()_quoted_from_dd()_scope_end()_stash()_unstash()Documentation
Devel::Declare::Interface
This is the primary interface for those who want to use Devel-Declare-Parser magic, and don't want to
use Exporter-Declare.
Devel::Declare::Parser
This Document covers the API for Devel::Declare::Parser. This API is a useful reference when writing
or modifying a custom parser.
Fennec Project
This module is part of the Fennec project. See Fennec for more details. Fennec is a project to develop
an extendable and powerful testing framework. Together the tools that make up the Fennec framework
provide a potent testing environment.
The tools provided by Fennec are also useful on their own. Sometimes a tool created for Fennec is useful
outside the greator framework. Such tools are turned into their own projects. This is one such project.
Fennec - The core framework
The primary Fennec project that ties them all together.
Name
Devel::Declare::Parser - Higher level interface to Devel-Declare
Overview
This is a brief overview of how a parser is used.
WORKFLOW
Parser is constructed
Name, Declarator, and Offset are provided by Devel::Declare.
The process() method is called
The process method calls all of the following in sequence, if any returns false, process() will
return.
pre_parse()
Check if we want to process the line at all.
parse() Turn the line into 'parts' (see below).
post_parse()
Hook, currently does nothing.
rewrite()
Hook, currently takes all the arguments between the declarator and the codeblock/semicolon
(which have been turned into 'parts' structures in the parts() attribute) and puts them into
the new_parts() attribute.
This is usually the method you want to override.
write_line()
Opens, fills in, and closes the line as a string, then rewrites the actual line using
Devel::Declare.
edit_line()
Hook, currently does nothing.
"PARTS"
'Parts' are datastructures created by the parse() method. Every argument on the line (space separated) up
until an opening curly brace ({) or a semicolon (;) will be turned into a part. Here are the parts to
expect:
Parts will either be a plain string, or an arrayref containing a string and the quote character used to
define the string. "String" or [ "String", '"' ]. Variables and operators (excluding those containing
only string characters) are typically the only parts left in a plain string form.
See the format_parts() method for an easy way to get what you need from a 'part' datastructure.
Bareword or Package Name
A bareword name is anything that starts with [a-zA-z] and contains only alpha-numerics plus
underscore. It is also not quoted. Examples include my_name, something5, etc.
The structure will be an arrayref, the first element will be the string form of the bareword name,
the second element will be undef.
Example:
# my_keyword My::Package;
$part = [
'My::Package',
undef,
];
# my_keyword some_name;
$part = [
"some_name",
undef,
];
Quoted or Enclosed Element
A quoted or enclosed element includes strings quoted with single or double quotes, and text contained
within opening and closing brackets, braces or parens (excluding the curly brace '{').
Example Structures:
# my_keyword "double quoted string";
$part = [
'double quoted string',
'"',
];
# my_keyword 'single quoted string';
$part = [
'double quoted string',
'"',
];
# my_keyword ... ( a => 'b', c => 'd' );
$part = [
" a => 'b', c => 'd' ",
"(",
];
Variable or Operator
Anything starting with a non-alphanumeric, non-quoting character will be placed as-is (not
interpolated) into a string. This catches most variables and operators, the exception are alpha-
numeric operators such as 'eq', 'gt', 'cmp', etc. Eventually I plan to add logic to catch all
operators, but it appears I will have to hard-code them.
# my_keyword $variable
$part = '$variable';
# my_keyword <=>
$part = '<=>';
EVENTUALOUTPUT
Parser is designed such that it will transform any and all uses of your keyword into proper function
calls.
That is this:
function x { ... }
Will become this:
function( 'x', sub { ... });
Note Parser does not read in the entire codeblock, rather it injects a statement into the start of the
block that uses a callback to attach the ');' to the end of the statement. This is per the documentation
of Devel::Declare. Reading in the entire sub is not a desirable scenario.
Synopsis
package Devel::Declare::Parser::MyParser;
use strict;
use warnings;
use base 'Devel::Declare::Parser';
use Devel::Declare::Interface;
# Create an accessor (See INTERNALS WARNING below)
__PACKAGE__->add_accessor( 'my_accessor' );
# Register the parser for use.
Devel::Declare::Interface::register_parser( 'myparser' );
# Override the rewrite() method to take the parsed bits (parts) and put the
# ones you want into new_parts.
sub rewrite {
my $self = shift;
my $parts = $self->parts;
$new_parts = $self->process_parts( $parts );
$self->new_parts( $new_parts );
1;
}
1;
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