1PPI::Token::HereDoc(3)User Contributed Perl DocumentationPPI::Token::HereDoc(3)
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NAME

6       PPI::Token::HereDoc - Token class for the here-doc
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INHERITANCE

9         PPI::Token::HereDoc
10         isa PPI::Token
11             isa PPI::Element
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DESCRIPTION

14       Here-docs are incredibly handy when writing Perl, but incredibly tricky
15       when parsing it, primarily because they don't follow the general flow
16       of input.
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18       They jump ahead and nab lines directly off the input buffer. Whitespace
19       and newlines may not matter in most Perl code, but they matter in here-
20       docs.
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22       They are also tricky to store as an object. They look sort of like an
23       operator and a string, but they don't act like it. And they have a
24       second section that should be something like a separate token, but
25       isn't because a string can span from above the here-doc content to
26       below it.
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28       So when parsing, this is what we do.
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30       Firstly, the PPI::Token::HereDoc object, does not represent the "<<"
31       operator, or the "END_FLAG", or the content, or even the terminator.
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33       It represents all of them at once.
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35       The token itself has only the declaration part as its "content".
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37         # This is what the content of a HereDoc token is
38         <<FOO
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40         # Or this
41         <<"FOO"
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43         # Or even this
44         <<      'FOO'
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46       That is, the "operator", any whitespace separator, and the quoted or
47       bare terminator. So when you call the "content" method on a HereDoc
48       token, you get '<< "FOO"'.
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50       As for the content and the terminator, when treated purely in "content"
51       terms they do not exist.
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53       The content is made available with the "heredoc" method, and the name
54       of the terminator with the "terminator" method.
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56       To make things work in the way you expect, PPI has to play some games
57       when doing line/column location calculation for tokens, and also during
58       the content parsing and generation processes.
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60       Documents cannot simply by recreated by stitching together the token
61       contents, and involve a somewhat more expensive procedure, but the
62       extra expense should be relatively negligible unless you are doing huge
63       quantities of them.
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65       Please note that due to the immature nature of PPI in general, we
66       expect "HereDocs" to be a rich (bad) source of corner-case bugs for
67       quite a while, but for the most part they should more or less DWYM.
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69   Comparison to other string types
70       Although technically it can be considered a quote, for the time being
71       "HereDocs" are being treated as a completely separate "Token" subclass,
72       and will not be found in a search for PPI::Token::Quote or
73       PPI::Token::QuoteLike objects.
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75       This may change in the future, with it most likely to end up under
76       QuoteLike.
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METHODS

79       Although it has the standard set of "Token" methods, "HereDoc" objects
80       have a relatively large number of unique methods all of their own.
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82   heredoc
83       The "heredoc" method is the authoritative method for accessing the
84       contents of the "HereDoc" object.
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86       It returns the contents of the here-doc as a list of newline-terminated
87       strings. If called in scalar context, it returns the number of lines in
88       the here-doc, excluding the terminator line.
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90   indentation
91       The "indentation" method returns the indentation string of an indented
92       here-doc if that can be determined. If the indented here-doc is damaged
93       (say, missing terminator) or the here-doc was not indented, it returns
94       "undef".
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96   terminator
97       The "terminator" method returns the name of the terminating string for
98       the here-doc.
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100       Returns the terminating string as an unescaped string (in the rare case
101       the terminator has an escaped quote in it).
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TO DO

104       - Implement PPI::Token::Quote interface compatibility
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106       - Check CPAN for any use of the null here-doc or here-doc-in-s///e
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108       - Add support for the null here-doc
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110       - Add support for here-doc in s///e
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SUPPORT

113       See the support section in the main module.
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AUTHOR

116       Adam Kennedy <adamk@cpan.org>
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119       Copyright 2001 - 2011 Adam Kennedy.
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121       This program is free software; you can redistribute it and/or modify it
122       under the same terms as Perl itself.
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124       The full text of the license can be found in the LICENSE file included
125       with this module.
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129perl v5.36.0                      2023-01-20            PPI::Token::HereDoc(3)
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