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.\" ========================================================================
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.IX Title "Plack::Middleware::Lint 3pm"
.TH Plack::Middleware::Lint 3pm 2024-01-20 "perl v5.38.2" "User Contributed Perl Documentation"
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.SH NAME
Plack::Middleware::Lint \- Validate request and response
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\&  use Plack::Middleware::Lint;
\&
\&  my $app = sub { ... }; # your app or middleware
\&  $app = Plack::Middleware::Lint\->wrap($app);
\&
\&  # Or from plackup
\&  plackup \-e \*(Aqenable "Lint"\*(Aq myapp.psgi
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Plack::Middleware::Lint is a middleware component to validate request
and response environment formats. You are strongly suggested to use
this middleware when you develop a new framework adapter or a new PSGI
web server that implements the PSGI interface.
.PP
This middleware is enabled by default when you run plackup or other
launcher tools with the default environment \fIdevelopment\fR value.
.SH DEBUGGING
.IX Header "DEBUGGING"
Because of how this middleware works, it may not be easy to debug Lint
errors when you encounter one, unless you're writing a PSGI web server
or a framework.
.PP
For example, when you're an application developer (user of some
framework) and see errors like:
.PP
.Vb 1
\&  Body should be an array ref or filehandle at lib/Plack/Middleware/Lint.pm line XXXX
.Ve
.PP
there's no clue about which line of \fIyour application\fR produces that
error.
.PP
We're aware of the issue, and have a plan to spit out more helpful
errors to diagnose the issue. But until then, currently there are some
workarounds to make this easier. For now, the easiest one would be to
enable Plack::Middleware::REPL outside of the Lint middleware,
like:
.PP
.Vb 1
\&  plackup \-e \*(Aqenable "REPL"; enable "Lint"\*(Aq app.psgi
.Ve
.PP
so that the Lint errors are caught by the REPL shell, where you can
inspect all the variables in the response.
.SH AUTHOR
.IX Header "AUTHOR"
Tatsuhiko Miyagawa
.PP
Tokuhiro Matsuno
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Plack