NAME

Dancer2::Plugin::DoFile - A file based MVC style plugin for Dancer2

SYNOPSYS

In your config.yml

    plugins:
      DoFile:
        page_loc: "dofiles/pages"
        default_file: "index"
        extension_list: ['.do','.view']

Make sure you have created the directory used for page_loc

Within a route in dancer2:

    my $result = dofile 'path/to/file'

You must not include the extension of the file as part of the path, as this will be added per the settings.

Or a default route, with example handling of some return values:

    prefix '/';
    any qr{.*} => sub {
      my $self = shift;
      my $result = dofile undef;
      if ($result && ref $result eq "HASH") {
        if (defined $result->{status}) {
          status $result->{status};
        }
        if (defined $result->{url}) {
          if (defined $result->{redirect} && $result->{redirect} eq "forward") {
            return forward $result->{url};
          } else {
            return redirect $result->{url};
          }
        } elsif (defined $result->{content}) {
          return $result->{content};
        }
      }
    };

When the 1st parameter to 'dofile' is undef it'll use the request URI to work out what the file(s) to execute are.

DESCRIPTION

DoFile is a way of automatically pulling multiple perl files to execute as a way to simplify routing complexity in Dancer2 for very large applications. In particular it was designed to offload "as many as possible" URIs that related to some standard functionality through a default route, just by having files existing for the specific URI.

The magic will look through your filesystem for files to 'do' (execute), and there may be several. The intent is to split out controller files and view files, and these may individually be rolled out or split out. In the default configuration the controller files are suffixed .do, and the view files .view

File Search Ordering

When presented with the URI path/to/file DoFile will begin searching for files that can be executed for this request, until it finds one that returns something that looks like content, a URL or is told you're done, when it stops.

Files are searched:

• By extension

  The default extensions .do and .view are checked, unless defined in your config.yml. The intention here is that .do files contain controller code and don't typically return content, but may return redirects. After .do files have been executed, .view files are executed. These are expected to return content.

  You can define as many extensions as you like. You could, for example have: ['.init','.do','.view','.final']

• Root/HTTP request method

  For each extension, first the "root" file file.ext is tested, then a file that matches file-METHOD.ext is tested (where METHOD is the HTTP request method for this request, .ext is the extension).

• Iterating up the directory tree

  If your call to path/to/file results in a miss for path/to/file.do, DoFile will then test for path/to.do and finally path.do before moving on to path/to/file-METHOD.do

  Once DoFile has found one it will not transcend the directory tree any further. Therefore defining path/to/file.do and path/to.do will not result in both being executed for the URI path/to/file - only the first will be executed.

If you define files like so:

    path.do
    path/
      to.view
      to/
        file-POST.do

A POST to the URI path/to/file will execute path.do, then path/to/file-POST.do and finally path/to.view.

Arguments to the executed files

During execution of the file a hashref called $args is available that contains some important things.

If the executed file returns a coderef, the coderef is executed with this same hashref as the only argument.

• path (arrayref)

  Anything that appears after the currently executing file on the URI. For example if I request /path/to/file and DoFile is executing path-POST.do, the path element will contain ['to','file']

• this_url (string)

  The currently executing file without any extension. In the above example this would be path.

• stash (hashref)

  The stash can be initially passed from the router:

      dofile 'path/to/file', stash => { option => 1 }

  The stash can be read/written to from each file that executes:

      if ($args->{stash}->{option} == 1) {
        $args->{stash}->{anotheroption} = 2;
      }

  Or if the file being executed returns a hashref that does not contain any of the elements contents, url or done (see below), it's merged into the stash automatically for passing on to the next file to be executed

  The stash is used to pass internal state down the file chain.

• dofile_plugin (object)

  Just in case the file being executed wants to mess about with Dancer2 or the plugin's internals.

How DoFile interprets individual executed files response

The result (returned value) of each file is checked; if something is returned DoFile will inspect the value to determine what to do next.

Coderef (anonymous sub)

You can return a coderef; this will be cached within the plugin and the file will not be checked again, but the coderef will be executed each time that "file" is requested. Generally whether the file should be checked or not is left up to the application (e.g. plackup -R ./ -r ...).

In the case a coderef is used, when the code is executed it is passed one argument, a hashref, which is the stash. This saves needing to import the stash from within the code of the file.

The return of the coderef will be evaluated exactly as below.

Internal Redirects

If a hashref is returned it's checked for a url element but NO done element. In this case, the DoFile restarts from the begining using the new URL. This is a method for internally redirecting. For example, returning:

    {
      url => "account/login"
    }

Will cause DoFile to start over with the new URI account/login, without processing any more files from the old URI. The stash is preserved.

Content

If a scalar or arrayref is returned, it's wrapped into a hashref into the contents element and sent back to the router.

If a hashref is returned and contains a contents element, no more files will be processed. The entire hashref is returned to the router. NB: the contents element must contain something that evals to true, else it's considered not there.

Done

If a hashref is returned and there is a done element that evals to a true value, DoFile will stop processing files and return the returned hashref to the router.

Continue

If a hashref is returned and there is no url, content or done element then the contents of the hasref is combined with the stash and DoFile will look for the next file.

If nothing is returned at all, DoFile will continue with the next file.

What the router gets back

DoFile will always return a hashref, even if the files being executed do not return a hashref. This hashref may have anything, but the recommended design is to return one of the following:

• A contents element

  The implication is that you've had the web page to be served back. Note that DoFile doesn't care if this is a scalar string or an arrayref. This Plugin was designed to work with Obj2HTML, so in the case of an arrayref the implication is that Obj2HTML should be asked to convert that to HTML.

• A url element

  In this case the router should probably send a 30x response redirecting the client, or perform an internal forward... implementors choice.

• A status element

  This could be used to set the status code for returning to the client

DoFile may however return pretty much whatever you want to handle in your final router code.

EXAMPLES

As noted, what's returned from a DoFile can contain anything. That gives you the opportunity to do pretty much whatever you want with what's returned.

AUTHOR

Pero Moretti

COPYRIGHT AND LICENSE

This software is copyright (c) 2022 by Pero Moretti.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

cpanm Dancer2::Plugin::DoFile

perl -MCPAN -e shell
install Dancer2::Plugin::DoFile