1PPIx::QuoteLike(3) User Contributed Perl Documentation PPIx::QuoteLike(3)
2
6 PPIx::QuoteLike - Parse Perl string literals and string-literal-like
7 things.
8
10 use PPIx::QuoteLike;
11 my $str = PPIx::QuoteLike->new( q<"fu$bar"> );
13 say $str->interpolates() ?
14 'interpolates' :
15 'does not interpolate';
16
18 This Perl class parses Perl string literals and things that are
19 reasonably like string literals. Its real reason for being is to find
20 interpolated variables for Perl::Critic policies and similar code.
21 The parse is fairly straightforward, and a little poking around with
23 eg/pqldump should show how it normally goes.
24 But there is at least one quote-like thing that probably needs some
26 explanation.
27 Indented Here Documents
29 These were introduced in Perl 5.25.7 (November 2016) but not recognized
30 by this module until its version 0.015 (February 2021). The indentation
31 is parsed as PPIx::QuoteLike::Token::Whitespace objects, provided it is
32 at least one character wide, otherwise it is not represented in the
33 parse. That is to say,
34 <<~EOD
36 How doth the little crocodile
37 Improve his shining tail
38 EOD
39 will have the three indentations represented by whitespace objects and
41 each line of the literal represented by its own string object, but
42 <<~EOD
44 How doth the little crocodile
45 Improve his shining tail
46 EOD
47 will parse the same as the non-indented version, except for the
49 addition of the token representing the '~'.
50 PPI is ahead of this module, and recognized indented here documents as
52 of its version 1.246 (May 2019). Unfortunately, as of version 1.270 the
53 indent gets lost in the parse, so a "PPIx::QuoteLike" object
54 initialized from such a PPI::Token::HereDoc will be seen as having an
55 indentation of '' regardless of the actual indentation in the source.
56 I believe this restriction will go away when
57 <https://github.com/Perl-Critic/PPI/issues/251> is resolved.
58
60 The "postderef" argument to new() is being put through a deprecation
61 cycle and retracted. After the retraction, postfix dereferences will
62 always be recognized.
63 Starting with version 0.012_01, the first use of this argument warned.
65 With version 0.016_01, all uses warn. With version 0.017_01 all uses
66 are fatal. With 0.0.021_01, all mention of this argument is removed,
67 except of course for this notice.
68
70 "PPIx::QuoteLike" is not descended from any other class.
71 "PPIx::QuoteLike" has no descendants.
73
75 This class supports the following public methods:
76 new
78 my $str = PPIx::QuoteLike->new( $source, %arg );
79 This static method parses the argument, and returns a new object
81 containing the parse. The $source argument can be either a scalar or an
82 appropriate PPI::Element object.
83 If the $source argument is a scalar, it is presumed to represent a
85 quote-like literal of some sort, provided it begins like one. Otherwise
86 this method will return nothing. The scalar representation of a here
87 document is a multi-line string whose first line consists of the
88 leading " << " and the start delimiter, and whose subsequent lines
89 consist of the content of the here document and the end delimiter.
90 Indented here documents were not supported by this class until version
91 0.015.
92 "PPI" classes that can be handled are PPI::Token::Quote,
94 PPI::Token::QuoteLike::Backtick, PPI::Token::QuoteLike::Command,
95 PPI::Token::QuoteLike::Readline, and PPI::Token::HereDoc. Any other
96 object will cause "new()" to return nothing.
97 Additional optional arguments can be passed as name/value pairs.
99 Supported arguments are:
100 encoding
102 This is the encoding of the $source. If this is specified as
103 something other than "undef", the $source will be decoded before
104 processing.
105 If the $source is a "PPI::Element", this encoding is used only if
107 the document that contains the element has neither a byte order
108 mark nor 'use utf8'.
109 index_locations
111 This Boolean argument determines whether the locations of the
112 tokens should be computed. It defaults to true if the $source
113 argument is a PPI::Element or if the "location" argument was
114 provided, and false otherwise.
115 location
117 This argument is a reference to an array compatible with that
118 returned by the PPI::Element location() method. It defaults to the
119 location of the $source argument if that was a PPI::Element,
120 otherwise no locations will be available.
121 trace
123 This Boolean argument causes a trace of the parse to be written to
124 standard out. Setting this to a true value is unsupported in the
125 sense that the author makes no representation as to what will
126 happen if you do it, and reserves the right to make changes to the
127 functionality, or retract it completely, without notice.
128 All other arguments are unsupported and reserved to the author.
130 child
132 my $kid = $str->child( 0 );
133 This method returns the child element whose index is given as the
135 argument. Children do not include the type(), or the start() or
136 finish() delimiters. Negative indices are valid, and given the usual
137 Perl interpretation.
138 children
140 my @kids = $str->children();
141 This method returns all child elements. Children do not include the
143 type(), or the start() or finish() delimiters.
144 column_number
146 This method returns the column number of the first character in the
147 element, or "undef" if that can not be determined.
148 content
150 say $str->content();
151 This method returns the content of the object. If the original argument
153 was a valid Perl string, this should be the same as the originally-
154 parsed string.
155 delimiters
157 say $str->delimiters();
158 This method returns the delimiters of the object, as a string. This
160 will be two characters unless the argument to new() was a here
161 document, missing its end delimiter, or an invalid string. In the
162 latter case the return might be anything.
163 elements
165 my @elem = $str->elements();
166 This method returns all elements of the object. This includes type(),
168 start(), children(), and finish(), in that order.
169 failures
171 say $str->failures();
172 This method returns the number of parse failures found. These are
174 instances where the parser could not figure out what was going on, and
175 should be the same as the number of PPIx::QuoteLike::Token::Unknown
176 objects returned by elements().
177 find
179 for ( @{[ $str->find( $criteria ) || [] } ) {
180 ...
181 }
182 This method finds and returns a reference to an array of all elements
184 that meet the given criteria. If nothing is found, a false value is
185 returned.
186 The $criteria can be either the name of a PPIx::QuoteLike::Token class,
188 or a code reference. In the latter case, the code is called for each
189 element in elements(), with the element as the only argument. The
190 element is included in the output if the code returns a true value.
191 finish
193 say map { $_->content() } $str->finish();
194 This method returns the finishing elements of the parse. It is actually
196 an array, with the first element being a
197 PPIx::QuoteLike::Token::Delimiter. If the parse is of a here document
198 there will be a second element, which will be a
199 PPIx::QuoteLike::Token::Whitespace containing the trailing new line
200 character.
201 If called in list context you get the whole array. If called in scalar
203 context you get the element whose index is given in the argument, or
204 element zero if no argument is specified.
205 handles
207 say PPIx::QuoteLike->handles( $string ) ?
208 "We can handle $string" :
209 "We can not handle $string";
210 This convenience static method returns a true value if this package can
212 be expected to handle the content of $string (be it scalar or object),
213 and a false value otherwise.
214 indentation
216 This method returns the indentation string if the object represents an
217 indented here document, or "undef" if it represents anything else,
218 including an unindented here document.
219 Note that if indented syntax is used but the here document is not in
221 fact indented, this will return '', which evaluates to false.
222 interpolates
224 say $str->interpolates() ?
225 'The string interpolates' :
226 'The string does not interpolate';
227 This method returns a true value if the parsed string interpolates, and
229 a false value if it does not. This does not indicate whether any
230 interpolation actually takes place, only whether the string is double-
231 quotish or single-quotish.
232 line_number
234 This method returns the line number of the first character in the
235 element, or "undef" if that can not be determined.
236 location
238 This method returns a reference to an array describing the position of
239 the string, or "undef" if the location is unavailable.
240 The array is compatible with the corresponding PPI::Element method.
242 logical_filename
244 This method returns the logical file name (taking "#line" directives
245 into account) of the file containing first character in the element, or
246 "undef" if that can not be determined.
247 logical_line_number
249 This method returns the logical line number (taking "#line" directives
250 into account) of the first character in the element, or "undef" if that
251 can not be determined.
252 parent
254 This method returns nothing, since the invocant is only used at the top
255 of the object hierarchy.
256 perl_version_introduced
258 This method returns the maximum value of "perl_version_introduced"
259 returned by any of its elements. In other words, it returns the minimum
260 version of Perl under which this quote-like object is valid. If there
261 are no elements, 5.000 is returned, since that is the minimum value of
262 Perl supported by this package.
263 perl_version_removed
265 This method returns the minimum defined value of "perl_version_removed"
266 returned by any of the quote-like object's elements. In other words, it
267 returns the lowest version of Perl in which this object is "not" valid.
268 If there are no elements, or if no element has a defined
269 "perl_version_removed", "undef" is returned.
270 schild
272 my $skid = $str->schild( 0 );
273 This method returns the significant child elements whose index is given
275 by the argument. Negative indices are interpreted in the usual way.
276 schildren
278 my @skids = $str->schildren();
279 This method returns the significant children.
281 source
283 my $source = $str->source();
284 This method returns the $source argument to new(), whatever it was.
286 start
288 say map { $_->content() } $str->start();
289 This method returns the starting elements of the parse. It is actually
291 an array, with the first element being a
292 PPIx::QuoteLike::Token::Delimiter. If the parse is of a here document
293 there will be a second element, which will be a
294 PPIx::QuoteLike::Token::Whitespace containing the trailing new line
295 character.
296 If called in list context you get the whole array. If called in scalar
298 context you get the element whose index is given in the argument, or
299 element zero if no argument is specified.
300 statement
302 This method returns the PPI::Statement that contains this string, or
303 nothing if the statement can not be determined.
304 In general this method will return something only under the following
306 conditions:
307 • The string is contained in a PPIx::QuoteLike object;
309 • That object was initialized from a PPI::Element;
311 • The PPI::Element is contained in a statement.
313 top
315 This method returns the top of the hierarchy -- in this case, the
316 invocant.
317 type
319 my $type = $str->type();
320 This method returns the type object. This will be a
322 PPIx::QuoteLike::Token::Structure if the parse was successful;
323 otherwise it might be "undef". Its contents will be everything up to
324 the start delimiter, and will typically be 'q', 'qq', 'qx', '<<' (for
325 here documents), or '' (for quoted strings).
326 The type data are actually an array. If the second element is present
328 it will be the white space (if any) separating the actual type from the
329 value. If called in list context you get the whole array. If called in
330 scalar context you get the element whose index is given in the
331 argument, or element zero if no argument is specified.
332 variables
334 say "Interpolates $_" for $str->variables();
335 NOTE that this method is discouraged, and may well be deprecated and
337 removed. I have two problems with it. The first is that it returns
338 variable names rather than PPI::Element objects, leaving you no idea
339 how the variables are used. The second is that it does not properly
340 handle things like "${^CAPTURE[0]}", and it seems infeasible to make it
341 do so. It was originally written for the benefit of
342 Perl::Critic::Policy::Variables::ProhibitUnusedVarsStricter, but has
343 proven inadequate to that policy's needs.
344 This convenience method returns all interpolated variables. Each is
346 returned only once, and they are returned in no particular order. If
347 the object does not represent a string that interpolates, nothing is
348 returned.
349 visual_column_number
351 This method returns the visual column number (taking tabs into account)
352 of the first character in the element, or "undef" if that can not be
353 determined.
354
356 By the nature of this module, it is never going to get everything
357 right. Many of the known problem areas involve interpolations one way
358 or another.
359 Changes in Syntax
361 Sometimes the introduction of new syntax changes the way a string is
362 parsed. For example, the "\F" (fold case) case control was introduced
363 in Perl 5.15.8. But it did not represent a syntax error prior to that
364 version of Perl, it was simply parsed as "F". So
365 $ perl -le 'print "Foo\FBar"'
367 prints "FooFBar" under Perl 5.14.4, but "Foobar" under 5.16.0.
369 "PPIx::QuoteLike" generally assumes the more modern parse in cases like
370 this.
371 Static Parsing
373 It is well known that Perl can not be statically parsed. That is, you
374 can not completely parse a piece of Perl code without executing that
375 same code.
376 Nevertheless, this class is trying to statically parse quote-like
378 things. I do not have any examples of where the parse of a quote-like
379 thing would change based on what is interpolated, but neither can I
380 rule it out. Caveat user.
381 PPI Restrictions
383 As of version 0.015 of this module, the only known instance of this is
384 the handling of indented here documents, as discussed above under
385 Indented Here Documents.
386 Non-Standard Syntax
388 There are modules out there that alter the syntax of Perl. If the
389 syntax of a quote-like string is altered, this module has no way to
390 understand that it has been altered, much less to adapt to the
391 alteration. The following modules are known to cause problems:
392 Acme::PerlML, which renders Perl as XML.
394 "Data::PostfixDeref", which causes Perl to interpret suffixed empty
396 brackets as dereferencing the thing they suffix. This module by Ben
397 Morrow ("BMORROW") appears to have been retracted.
398 Filter::Trigraph, which recognizes ANSI C trigraphs, allowing Perl to
400 be written in the ISO 646 character set.
401 Perl6::Pugs. Enough said.
403
405 Support is by the author. Please file bug reports at
406 <https://rt.cpan.org/Public/Dist/Display.html?Name=PPIx-QuoteLike>,
407 <https://github.com/trwyant/perl-PPIx-QuoteLike/issues>, or in
408 electronic mail to the author.
409
411 Thomas R. Wyant, III wyant at cpan dot org
412
414 Copyright (C) 2016-2022 by Thomas R. Wyant, III
415 This program is free software; you can redistribute it and/or modify it
417 under the same terms as Perl 5.10.0. For more details, see the full
418 text of the licenses in the directory LICENSES.
419 This program is distributed in the hope that it will be useful, but
421 without any warranty; without even the implied warranty of
422 merchantability or fitness for a particular purpose.
423perl v5.36.0 2022-09-17 PPIx::QuoteLike(3)