extend the docs on UTF8 to include recent updates
[catagits/Catalyst-Runtime.git] / lib / Catalyst / UTF8.pod
a09b49d2 1=encoding UTF-8
3=head1 Name
d63cc9c8 5Catalyst::UTF8 - All About UTF8 and Catalyst Encoding
a09b49d2 6
7=head1 Description
b596572b 9Starting in 5.90080 L<Catalyst> will enable UTF8 encoding by default for
a09b49d2 10text like body responses. In addition we've made a ton of fixes around encoding
11and utf8 scattered throughout the codebase. This document attempts to give
12an overview of the assumptions and practices that L<Catalyst> uses when
13dealing with UTF8 and encoding issues. You should also review the
14Changes file, L<Catalyst::Delta> and L<Catalyst::Upgrading> for more.
d63cc9c8 16We attempt to describe all relevant processes, try to give some advice
a09b49d2 17and explain where we may have been exceptional to respect our commitment
18to backwards compatibility.
b596572b 20=head1 UTF8 in Controller Actions
a09b49d2 21
22Using UTF8 characters in your Controller classes and actions.
24=head2 Summary
26In this section we will review changes to how UTF8 characters can be used in
27controller actions, how it looks in the debugging screens (and your logs)
28as well as how you construct L<URL> objects to actions with UTF8 paths
29(or using UTF8 args or captures).
31=head2 Unicode in Controllers and URLs
33 package MyApp::Controller::Root;
473078ff 35 use utf8;
a09b49d2 36 use base 'Catalyst::Controller';
38 sub heart_with_arg :Path('♥') Args(1) {
39 my ($self, $c, $arg) = @_;
40 }
42 sub base :Chained('/') CaptureArgs(0) {
43 my ($self, $c) = @_;
44 }
46 sub capture :Chained('base') PathPart('♥') CaptureArgs(1) {
47 my ($self, $c, $capture) = @_;
48 }
50 sub arg :Chained('capture') PathPart('♥') Args(1) {
51 my ($self, $c, $arg) = @_;
52 }
54=head2 Discussion
56In the example controller above we have constructed two matchable URL routes:
58 http://localhost/root/♥/{arg}
59 http://localhost/base/♥/{capture}/♥/{arg}
61The first one is a classic Path type action and the second uses Chaining, and
62spans three actions in total. As you can see, you can use unicode characters
473078ff 63in your Path and PathPart attributes (remember to use the C<utf8> pragma to allow
a09b49d2 64these multibyte characters in your source). The two constructed matchable routes
65would match the following incoming URLs:
67 (heart_with_arg) -> http://localhost/root/%E2%99%A5/{arg}
68 (base/capture/arg) -> http://localhost/base/%E2%99%A5/{capture}/%E2%99%A5/{arg}
70That path path C<%E2%99%A5> is url encoded unicode (assuming you are hitting this with
71a reasonably modern browser). Its basically what goes over HTTP when your type a
72browser location that has the unicode 'heart' in it. However we will use the unicode
73symbol in your debugging messages:
75 [debug] Loaded Path actions:
76 .-------------------------------------+--------------------------------------.
77 | Path | Private |
78 +-------------------------------------+--------------------------------------+
79 | /root/♥/* | /root/heart_with_arg |
80 '-------------------------------------+--------------------------------------'
82 [debug] Loaded Chained actions:
83 .-------------------------------------+--------------------------------------.
84 | Path Spec | Private |
85 +-------------------------------------+--------------------------------------+
86 | /base/♥/*/♥/* | /root/base (0) |
87 | | -> /root/capture (1) |
88 | | => /root/arg |
89 '-------------------------------------+--------------------------------------'
91And if the requested URL uses unicode characters in your captures or args (such as
92C<http://localhost:/base/♥/♥/♥/♥>) you should see the arguments and captures as their
93unicode characters as well:
95 [debug] Arguments are "♥"
96 [debug] "GET" request for "base/♥/♥/♥/♥" from ""
97 .------------------------------------------------------------+-----------.
98 | Action | Time |
99 +------------------------------------------------------------+-----------+
100 | /root/base | 0.000080s |
101 | /root/capture | 0.000075s |
102 | /root/arg | 0.000755s |
103 '------------------------------------------------------------+-----------'
105Again, remember that we are display the unicode character and using it to match actions
106containing such multibyte characters BUT over HTTP you are getting these as URL encoded
b596572b 107bytes. For example if you looked at the L<PSGI> C<$env> value for C<REQUEST_URI> you
108would see (for the above request)
a09b49d2 109
110 REQUEST_URI => "/base/%E2%99%A5/%E2%99%A5/%E2%99%A5/%E2%99%A5"
112So on the incoming request we decode so that we can match and display unicode characters
113(after decoding the URL encoding). This makes it straightforward to use these types of
114multibyte characters in your actions and see them incoming in captures and arguments. Please
115keep this in might if you are doing for example regular expression matching, length determination
116or other string comparisons, you will need to try these incoming variables as though UTF8
117strings. For example in the following action:
119 sub arg :Chained('capture') PathPart('♥') Args(1) {
120 my ($self, $c, $arg) = @_;
121 }
123when $arg is "♥" you should expect C<length($arg)> to be C<1> since it is indeed one character
124although it will take more than one byte to store.
126=head2 UTF8 in constructing URLs via $c->uri_for
128For the reverse (constructing meaningful URLs to actions that contain multibyte characters
129in their paths or path parts, or when you want to include such characters in your captures
130or arguments) L<Catalyst> will do the right thing (again just remember to use the C<utf8>
133 use utf8;
134 my $url = $c->uri_for( $c->controller('Root')->action_for('arg'), ['♥','♥']);
473078ff 136When you stringify this object (for use in a template, for example) it will automatically
a09b49d2 137do the right thing regarding utf8 encoding and url encoding.
139 http://localhost/base/%E2%99%A5/%E2%99%A5/%E2%99%A5/%E2%99%A5
141Since again what you want is a properly url encoded version of this. In this case your string
142length will reflect URL encoded bytes, not the character length. Ultimately what you want
143to send over the wire via HTTP needs to be bytes.
145=head1 UTF8 in GET Query and Form POST
147What Catalyst does with UTF8 in your GET and classic HTML Form POST
149=head2 UTF8 in URL query and keywords
473078ff 151The same rules that we find in URL paths also cover URL query parts. That is
152if one types a URL like this into the browser
a09b49d2 153
154 http://localhost/example?♥=♥♥
156When this goes 'over the wire' to your application server its going to be as
157percent encoded bytes:
160 http://localhost/example?%E2%99%A5=%E2%99%A5%E2%99%A5
162When L<Catalyst> encounters this we decode the percent encoding and the utf8
163so that we can properly display this information (such as in the debugging
164logs or in a response.)
166 [debug] Query Parameters are:
167 .-------------------------------------+--------------------------------------.
168 | Parameter | Value |
169 +-------------------------------------+--------------------------------------+
170 | ♥ | ♥♥ |
171 '-------------------------------------+--------------------------------------'
173All the values and keys that are part of $c->req->query_parameters will be
174utf8 decoded. So you should not need to do anything special to take those
175values/keys and send them to the body response (since as we will see later
176L<Catalyst> will do all the necessary encoding for you).
178Again, remember that values of your parameters are now decode into Unicode strings. so
179for example you'd expect the result of length to reflect the character length not
b596572b 180the byte length.
a09b49d2 181
182Just like with arguments and captures, you can use utf8 literals (or utf8
183strings) in $c->uri_for:
185 use utf8;
186 my $url = $c->uri_for( $c->controller('Root')->action_for('example'), {'♥' => '♥♥'});
473078ff 188When you stringify this object (for use in a template, for example) it will automatically
a09b49d2 189do the right thing regarding utf8 encoding and url encoding.
191 http://localhost/example?%E2%99%A5=%E2%99%A5%E2%99%A5
193Since again what you want is a properly url encoded version of this. Ultimately what you want
b596572b 194to send over the wire via HTTP needs to be bytes (not unicode characters).
a09b49d2 195
196Remember if you use any utf8 literals in your source code, you should use the
197C<use utf8> pragma.
199=head2 UTF8 in Form POST
201In general most modern browsers will follow the specification, which says that POSTed
202form fields should be encoded in the same way that the document was served with. That means
203that if you are using modern Catalyst and serving UTF8 encoded responses, a browser is
204supposed to notice that and encode the form POSTs accordingly.
206As a result since L<Catalyst> now serves UTF8 encoded responses by default, this means that
207you can mostly rely on incoming form POSTs to be so encoded. L<Catalyst> will make this
208assumption and decode accordingly (unless you explicitly turn off encoding...) If you are
b596572b 209running Catalyst in developer debug, then you will see the correct unicode characters in
a09b49d2 210the debug output. For example if you generate a POST request:
212 use Catalyst::Test 'MyApp';
213 use utf8;
215 my $res = request POST "/example/posted", ['♥'=>'♥', '♥♥'=>'♥'];
217Running in CATALYST_DEBUG=1 mode you should see output like this:
219 [debug] Body Parameters are:
220 .-------------------------------------+--------------------------------------.
221 | Parameter | Value |
222 +-------------------------------------+--------------------------------------+
223 | ♥ | ♥ |
224 | ♥♥ | ♥ |
225 '-------------------------------------+--------------------------------------'
227And if you had a controller like this:
229 package MyApp::Controller::Example;
b596572b 230
a09b49d2 231 use base 'Catalyst::Controller';
233 sub posted :POST Local {
234 my ($self, $c) = @_;
235 $c->res->content_type('text/plain');
236 $c->res->body("hearts => ${\$c->req->post_parameters->{♥}}");
237 }
239The following test case would be true:
241 use Encode 2.21 'decode_utf8';
242 is decode_utf8($req->content), 'hearts => ♥';
b596572b 244In this case we decode so that we can print and compare strings with multibyte characters.
a09b49d2 245
246B<NOTE> In some cases some browsers may not follow the specification and set the form POST
247encoding based on the server response. Catalyst itself doesn't attempt any workarounds, but one
248common approach is to use a hidden form field with a UTF8 value (You might be familiar with
249this from how Ruby on Rails has HTML form helpers that do that automatically). In that case
250some browsers will send UTF8 encoded if it notices the hidden input field contains such a
251character. Also, you can add an HTML attribute to your form tag which many modern browsers
252will respect to set the encoding (accept-charset="utf-8"). And lastly there are some javascript
253based tricks and workarounds for even more odd cases (just search the web for this will return
254a number of approaches. Hopefully as more compliant browsers become popular these edge cases
255will fade.
b16a64af 257B<NOTE> It is possible for a form POST multipart response (normally a file upload) to contain
258inline content with mixed content character sets and encoding. For example one might create
259a POST like this:
261 use utf8;
262 use HTTP::Request::Common;
264 my $utf8 = 'test ♥';
265 my $shiftjs = 'test テスト';
266 my $req = POST '/root/echo_arg',
267 Content_Type => 'form-data',
268 Content => [
269 arg0 => 'helloworld',
270 Encode::encode('UTF-8','♥') => Encode::encode('UTF-8','♥♥'),
271 arg1 => [
272 undef, '',
273 'Content-Type' =>'text/plain; charset=UTF-8',
274 'Content' => Encode::encode('UTF-8', $utf8)],
275 arg2 => [
276 undef, '',
277 'Content-Type' =>'text/plain; charset=SHIFT_JIS',
278 'Content' => Encode::encode('SHIFT_JIS', $shiftjs)],
279 arg2 => [
280 undef, '',
281 'Content-Type' =>'text/plain; charset=SHIFT_JIS',
282 'Content' => Encode::encode('SHIFT_JIS', $shiftjs)],
283 ];
285In this case we've created a POST request but each part specifies its own content
286character set (and setting a content encoding would also be possible). Generally one
287would not run into this situation in a web browser context but for completeness sake
288Catalyst will notice if a multipart POST contains parts with complex or extended
289header information and in those cases it will not attempt to apply decoding to the
290form values. Instead the part will be represented as an instance of an object
291L<Catalyst::Request::PartData> which will contain all the header information needed
292for you to perform custom parser of the data.
a09b49d2 294=head1 UTF8 Encoding in Body Response
296When does L<Catalyst> encode your response body and what rules does it use to
297determine when that is needed.
299=head2 Summary
301 use utf8;
302 use warnings;
303 use strict;
305 package MyApp::Controller::Root;
307 use base 'Catalyst::Controller';
308 use File::Spec;
310 sub scalar_body :Local {
311 my ($self, $c) = @_;
312 $c->response->content_type('text/html');
313 $c->response->body("<p>This is scalar_body action ♥</p>");
314 }
316 sub stream_write :Local {
317 my ($self, $c) = @_;
318 $c->response->content_type('text/html');
319 $c->response->write("<p>This is stream_write action ♥</p>");
b596572b 320 }
a09b49d2 321
322 sub stream_write_fh :Local {
323 my ($self, $c) = @_;
324 $c->response->content_type('text/html');
326 my $writer = $c->res->write_fh;
327 $writer->write_encoded('<p>This is stream_write_fh action ♥</p>');
328 $writer->close;
329 }
331 sub stream_body_fh :Local {
332 my ($self, $c) = @_;
333 my $path = File::Spec->catfile('t', 'utf8.txt');
334 open(my $fh, '<', $path) || die "trouble: $!";
335 $c->response->content_type('text/html');
336 $c->response->body($fh);
337 }
339=head2 Discussion
341Beginning with L<Catalyst> version 5.90080 You no longer need to set the encoding
342configuration (although doing so won't hurt anything).
344Currently we only encode if the content type is one of the types which generally expects a
345UTF8 encoding. This is determined by the following regular expression:
347 our $DEFAULT_ENCODE_CONTENT_TYPE_MATCH = qr{text|xml$|javascript$};
348 $c->response->content_type =~ /$DEFAULT_ENCODE_CONTENT_TYPE_MATCH/
350This is a global variable in L<Catalyst::Response> which is stored in the C<encodable_content_type>
351attribute of $c->response. You may currently alter this directly on the response or globally. In
352the future we may offer a configuration setting for this.
354This would match content-types like the following (examples)
356 text/plain
357 text/html
358 text/xml
359 application/javascript
360 application/xml
361 application/vnd.user+xml
b596572b 363You should set your content type prior to header finalization if you want L<Catalyst> to
a09b49d2 364encode.
366B<NOTE> We do not attempt to encode C<application/json> since the two most commonly used
367approaches (L<Catalyst::View::JSON> and L<Catalyst::Action::REST>) have already configured
368their JSON encoders to produce properly encoding UTF8 responses. If you are rolling your
369own JSON encoding, you may need to set the encoder to do the right thing (or override
370the global regular expression to include the JSON media type).
372=head2 Encoding with Scalar Body
374L<Catalyst> supports several methods of supplying your response with body content. The first
375and currently most common is to set the L<Catalyst::Response> ->body with a scalar string (
376as in the example):
378 use utf8;
380 sub scalar_body :Local {
381 my ($self, $c) = @_;
382 $c->response->content_type('text/html');
383 $c->response->body("<p>This is scalar_body action ♥</p>");
384 }
386In general you should need to do nothing else since L<Catalyst> will automatically encode
387this string during body finalization. The only matter to watch out for is to make sure
388the string has not already been encoded, as this will result in double encoding errors.
390B<NOTE> pay attention to the content-type setting in the example. L<Catalyst> inspects that
391content type carefully to determine if the body needs encoding).
393B<NOTE> If you set the character set of the response L<Catalyst> will skip encoding IF the
473078ff 394character set is set to something that doesn't match $c->encoding->mime_name. We will assume
a09b49d2 395if you are setting an alternative character set, that means you want to handle the encoding
396yourself. However it might be easier to set $c->encoding for a given response cycle since
397you can override this for a given response. For example here's how to override the default
398encoding and set the correct character set in the response:
400 sub override_encoding :Local {
401 my ($self, $c) = @_;
402 $c->res->content_type('text/plain');
403 $c->encoding(Encode::find_encoding('Shift_JIS'));
404 $c->response->body("テスト");
405 }
407This will use the alternative encoding for a single response.
409B<NOTE> If you manually set the content-type character set to whatever $c->encoding->mime_name
410is set to, we STILL encode, rather than assume your manual setting is a flag to override. This
aca337aa 411is done to support backward compatible assumptions (in particular L<Catalyst::View::TT> has set
412a utf-8 character set in its default content-type for ages, even though it does not itself do any
413encoding on the body response). If you are going to handle encoding manually you may set
414$c->clear_encoding for a single request response cycle, or as in the above example set an alternative
a09b49d2 416
417=head2 Encoding with streaming type responses
419L<Catalyst> offers two approaches to streaming your body response. Again, you must remember
420to set your content type prior to streaming, since invoking a streaming response will automatically
421finalize and send your HTTP headers (and your content type MUST be one that matches the regular
422expression given above.)
424Also, if you are going to override $c->encoding (or invoke $c->clear_encoding), you should do
425that before anything else!
427The first streaming method is to use the C<write> method on the response object. This method
428allows 'inlined' streaming and is generally used with blocking style servers.
430 sub stream_write :Local {
431 my ($self, $c) = @_;
432 $c->response->content_type('text/html');
433 $c->response->write("<p>This is stream_write action ♥</p>");
434 }
436You may call the C<write> method as often as you need to finish streaming all your content.
437L<Catalyst> will encode each line in turn as long as the content-type meets the 'encodable types'
438requirement and $c->encoding is set (which it is, as long as you did not change it).
440B<NOTE> If you try to change the encoding after you start the stream, this will invoke an error
473078ff 441response. However since you've already started streaming this will not show up as an HTTP error
a09b49d2 442status code, but rather error information in your body response and an error in your logs.
444The second way to stream a response is to get the response writer object and invoke methods
445on that directly:
447 sub stream_write_fh :Local {
448 my ($self, $c) = @_;
449 $c->response->content_type('text/html');
451 my $writer = $c->res->write_fh;
452 $writer->write_encoded('<p>This is stream_write_fh action ♥</p>');
453 $writer->close;
454 }
473078ff 456This can be used just like the C<write> method, but typically you request this object when
a09b49d2 457you want to do a nonblocking style response since the writer object can be closed over or
458sent to a model that will invoke it in a non blocking manner. For more on using the writer
459object for non blocking responses you should review the C<Catalyst> documentation and also
460you can look at several articles from last years advent, in particular:
462L<http://www.catalystframework.org/calendar/2013/10>, L<http://www.catalystframework.org/calendar/2013/11>,
463L<http://www.catalystframework.org/calendar/2013/12>, L<http://www.catalystframework.org/calendar/2013/13>,
466The main difference this year is that previously calling ->write_fh would return the actual
467L<Plack> writer object that was supplied by your plack application handler, whereas now we wrap
468that object in a lightweight decorator object that proxies the C<write> and C<close> methods
469and supplies an additional C<write_encoded> method. C<write_encoded> does the exact same thing
470as C<write> except that it will first encode the string when necessary. In general if you are
471streaming encodable content such as HTML this is the method to use. If you are streaming
472binary content, you should just use the C<write> method (although if the content type is set
473correctly we would skip encoding anyway, but you may as well avoid the extra noop overhead).
475The last style of content response that L<Catalyst> supports is setting the body to a filehandle
476like object. In this case the object is passed down to the Plack application handler directly
477and currently we do nothing to set encoding.
479 sub stream_body_fh :Local {
480 my ($self, $c) = @_;
481 my $path = File::Spec->catfile('t', 'utf8.txt');
482 open(my $fh, '<', $path) || die "trouble: $!";
483 $c->response->content_type('text/html');
484 $c->response->body($fh);
485 }
487In this example we create a filehandle to a text file that contains UTF8 encoded characters. We
488pass this down without modification, which I think is correct since we don't want to double
489encode. However this may change in a future development release so please be sure to double
490check the current docs and changelog. Its possible a future release will require you to to set
491a encoding on the IO layer level so that we can be sure to properly encode at body finalization.
492So this is still an edge case we are writing test examples for. But for now if you are returning
493a filehandle like response, you are expected to make sure you are following the L<PSGI> specification
473078ff 494and return raw bytes.
a09b49d2 495
496=head2 Override the Encoding on Context
498As already noted you may change the current encoding (or remove it) by setting an alternative
499encoding on the context;
501 $c->encoding(Encode::find_encoding('Shift_JIS'));
503Please note that you can continue to change encoding UNTIL the headers have been finalized. The
504last setting always wins. Trying to change encoding after header finalization is an error.
506=head2 Setting the Content Encoding HTTP Header
508In some cases you may set a content encoding on your response. For example if you are encoding
509your response with gzip. In this case you are again on your own. If we notice that the
510content encoding header is set when we hit finalization, we skip automatic encoding:
512 use Encode;
513 use Compress::Zlib;
514 use utf8;
516 sub gzipped :Local {
517 my ($self, $c) = @_;
519 $c->res->content_type('text/plain');
520 $c->res->content_type_charset('UTF-8');
521 $c->res->content_encoding('gzip');
523 $c->response->body(
524 Compress::Zlib::memGzip(
525 Encode::encode_utf8("manual_1 ♥")));
526 }
529If you are using L<Catalyst::Plugin::Compress> you need to upgrade to the most recent version
530in order to be compatible with changes introduced in L<Catalyst> 5.90080. Other plugins may
531require updates (please open bugs if you find them).
533B<NOTE> Content encoding may be set to 'identify' and we will still perform automatic encoding
534if the content type is encodable and an encoding is present for the context.
536=head2 Using Common Views
538The following common views have been updated so that their tests pass with default UTF8
539encoding for L<Catalyst>:
541L<Catalyst::View::TT>, L<Catalyst::View::Mason>, L<Catalyst::View::HTML::Mason>,
544See L<Catalyst::Upgrading> for additional information on L<Catalyst> extensions that require
547In generally for the common views you should not need to do anything special. If your actual
548template files contain UTF8 literals you should set configuration on your View to enable that.
549For example in TT, if your template has actual UTF8 character in it you should do the following:
551 MyApp::View::TT->config(ENCODING => 'utf-8');
553However L<Catalyst::View::Xslate> wants to do the UTF8 encoding for you (We assume that the
554authors of that view did this as a workaround to the fact that until now encoding was not core
555to L<Catalyst>. So if you use that view, you either need to tell it to not encode, or you need
556to turn off encoding for Catalyst.
558 MyApp::View::Xslate->config(encode_body => 0);
562 MyApp->config(encoding=>undef);
564Preference is to disable it in the View.
566Other views may be similar. You should review View documentation and test during upgrading.
567We tried to make sure most common views worked properly and noted all workaround but if we
568missed something please alert the development team (instead of introducing a local hack into
569your application that will mean nobody will ever upgrade it...).
aca337aa 571=head2 Setting the response from an external PSGI application.
573L<Catalyst::Response> allows one to set the response from an external L<PSGI> application.
574If you do this, and that external application sets a character set on the content-type, we
575C<clear_encoding> for the rest of the response. This is done to prevent double encoding.
577B<NOTE> Even if the character set of the content type is the same as the encoding set in
578$c->encoding, we still skip encoding. This is a regrettable difference from the general rule
579outlined above, where if the current character set is the same as the current encoding, we
580encode anyway. Nevertheless I think this is the correct behavior since the earlier rule exists
581only to support backward compatibility with L<Catalyst::View::TT>.
583In general if you want L<Catalyst> to handle encoding, you should avoid setting the content
584type character set since Catalyst will do so automatically based on the requested response
585encoding. Its best to request alternative encodings by setting $c->encoding and if you really
586want manual control of encoding you should always $c->clear_encoding so that programmers that
587come after you are very clear as to your intentions.
a09b49d2 589=head2 Disabling default UTF8 encoding
591You may encounter issues with your legacy code running under default UTF8 body encoding. If
592so you can disable this with the following configurations setting:
594 MyApp->config(encoding=>undef);
596Where C<MyApp> is your L<Catalyst> subclass.
b16a64af 598If you do not wish to disable all the Catalyst encoding features, you may disable specific
599features via two additional configuration options: 'skip_body_param_unicode_decoding'
600and 'skip_complex_post_part_handling'. The first will skip any attempt to decode POST
601parameters in the creating of body parameters and the second will skip creation of instances
602of L<Catalyst::Request::PartData> in the case that the multipart form upload contains parts
603with a mix of content character sets.
a09b49d2 605If you believe you have discovered a bug in UTF8 body encoding, I strongly encourage you to
606report it (and not try to hack a workaround in your local code). We also recommend that you
607regard such a workaround as a temporary solution. It is ideal if L<Catalyst> extension
b16a64af 608authors can start to count on L<Catalyst> doing the write thing for encoding.
a09b49d2 609
610=head1 Conclusion
612This document has attempted to be a complete review of how UTF8 and encoding works in the
613current version of L<Catalyst> and also to document known issues, gotchas and backward
614compatible hacks. Please report issues to the development team.
616=head1 Author
618John Napiorkowski L<jjnapiork@cpan.org|email:jjnapiork@cpan.org>