NAME

OO::Plugin::Manager - the conductor for a plugin orchestra.

SYNOPSIS

my $mgr = OO::Plugin::Manager.new( base => 'MyApp' )
            .load-plugins
            .initialize( plugin-parameter => $param-value );

my $plugged-object = $mgr.create( MyClass, class-param => "a value" );

DESCRIPTION

Most of the description for the functionality of this module can be found in OO::Plugin::Manual. Here we just cover the technical details and attributes/methods.

TYPES

enum `PlugPriority`

Constants defining where the user whants to have a particular plugin:

plugFirst – in the beginning of the plugin list
plugNormal – in the middle of the list
plugLast – in the end of the list

Read about sorting in OO::Plugin::Manual.

ATTRIBUTES

has Bool $.debug

When True will print debug info to the console.

has Str $.base

The base namespace where to look for plugin modules. See @.namespaces below.

has Positional @.namespaces

Defines a list of namespaces within $.base attribute where to look from plugin modules. I.e. if set to the default then the manager will load modules from ::($.base)::Plugin or ::($.base)::Plugins.

has Callable[] &.validator

Callback to validate plugin. Allows the user code to check for plugin compatibility, for example. (Not implemented yet)

has Bool $.strict

In strict mode non-pluggable classes/methods cannot be overriden.

has Positional @.load-errors

Errors collected while loading plugin modules. List of hashes of form 'Module::Name' => "Error String".

has Bool $.initialized

Indicates that the manager object has been initialized; i.e. method initialize() has been run.

has $.event-workers

Number of simulatenous event handlers running. Default is 3

has Real:D $.ev-dispatcher-timeout

Number of seconds for the dispatcher to wait for another event after processing one. Default 1 sec.

METHODS

method normalize-name

normalize-name( Str:D $plugin, Bool :$strict = True )

Normalize plugin name, i.e. makes a name in any form and returns FQN. With :strict fails if no plugin found by the name in $plugin. With :!strict fails with a text error. Always fails if more than one variant for the given name found what would happen when two or more plugins register common short name for themselves.
normalize-name( Str:D :$plugin, Bool :$strict = True )

Similar to the above variant except that it takes named argument :plugin.

Note would always return the $plugin parameter before the plugin manager is initialized.

method short-name

Takes a plugin name and returns its corresponding short name.

short-name( Str:D $name )
short-name( Str:D :$fqn )

A faster variant of the method because it doesn't attempt to normalize the name and performs fast lookup by FQN.
short-name( Plugin:U \plugin-type )

Gives short name by using plugin's class itself. This is a faster version too because it also uses FQN lookup.
```
my $sname = $plugin-manager.short-name( $plugin-obj.WHAT );
```

method meta

Returns plugin's META Hash.

meta( Str:D $plugin )
meta( Str:D :$fqn )

Faster version, avoids name normalization.

method info

info( Str:D $plugin )

Returns a copy of information hash on a plugin. The hash contains the following keys:

priority

Priority (see PlugPriority)
shortname

Plugin's short name
type

Type (class) object of the plugin
version

Version (Version object)

method set-priority

Set plugins priority in the plugin order.

set-priority( @plugins, PlugPriority:D :$priority, :$with-order? )

set-priority( *@plugins, PlugPriority:D :$priority, :$with-order? )

The most comprehensive version of the method. Allow not only setting of the priority for a bulk of the plugins but also to define their order within the specified priority when :with-order is used.

Note that each new call of this method with :with-order adverb will override previously set order for the specified priority.
set-priority( $plugin, PlugPriority:D :$priority )

See PlugPriority

method get-priority

Returns priority value for a given plugin.

get-priority( Str:D $plugin )
get-priority( Str:D :$fqn )

Faster version, avoids name normalization.

See PlugPriority

method load-plugins

Initiates automatic loading of plugin modules by traversing modules in repositories and search paths. Only the modules with names begining in prefix defined by base attribute and followed by any of namespaces will be loaded. For example:

my $mgr = OO::Plugin::Manager.new( base => 'MyApp' ).load-plugins;

would auto-load all modules starting with MyApp::Plugin:: or MyApp::Plugins::; whereas:

my $mgr = OO::Plugin::Manager.new( base => 'MyApp', namespaces => <Ext Extensions> ).load-plugins;

would autoload MyApp::Ext:: or MyApp::Extensions::.

Returns the invocing OO::Plugin::Manager object, making chained method calls possible.

If a module cannot be loaded due to a error the method appends a Pair of $module-name => $error-text to @.load-errors. When $.debug is True the error text will include error's stack backtrace too.

Note that modules are just loaded and no other work is done by this method.

method initialize

initialize( |create-params )

Performs final initialization of the plugin manager object. This includes:

iterating over all plugin classes and collecting their meta information and technical info
rebuilding internal caches and structures to reflect the collected information
order the plugins corresponding based on priorities, user-defined order, and dependencies
create plugin objects

After completion the plugin manager object is marked as initialized effictevly disabling some of its functionality which only makes sense until the initialization.

The create-params parameter is passed to plugin object constructors at the creation stage. For example:

class MyApp {
    has $.mgr;
    submethod TWEAK {
        $.mgr = OO::Plugin::Manager.new
                    .load-plugins
                    .initialize( app => self );
    }
}

would pass the application object to all loaded plugins. This would simplify the communication between a plugin and the user code.

NOTE The second initialization stage includes building of mapping of short plugin names to FQN. Before this is done

method disable

Disables plugins.

disable( Str:D $plugin, Str:D $reason )
disable( Plugin:U \type, Str:D $reason )
disable( @plugins, Str:D $reason )
disable( *@plugins, Str:D $reason )

A disabled plugin won't have its object created and will be excluded from any interaction with application code. For any disabled plugin there is a text reason explaining why it was disabled. For example, if a plugin has been found to participate in a demain cyclic dependecy then it will be disabled with "Participated in a demand circle" reason. The applicatiob code can later collect the reasons to display them back to the end-user.

Implementation note. The method allows both short plugin names and FQN, as most other methods do. But the name normalization is not possible before the initialization is complete. To make it all even more fun, disabling is not possible after the initialization! To resolve this collision, all calls to disable from the user code are only getting recorded by the framework. The recorded calls are then replayed at the initialization time. Because of this trick it is not possible to read disable reasons at early stages of the plugin manager life cycle.

method disabled

If plugin is disabled, a reason text is returned. Undefined value is returned otherwise.

disabled( Str:D $plugin )
disabled( Str:D :$fqn )

Faster version, not using name normalization
disabled( Plugin:U \type )

There is a parameter-less variant of the method:

disabled()

which would return a hash where keys are plugin FQNs and values are reasons.

method enabled

Opposite to disabled method. Returns True if plugin is enabled. Supports all the same signatures as disabled does.

method order

Returns list of plugin names as they were ordered at the initialization time.

method plugin-objects

Returns a ordered Seq plugin objects.

See order

method callback

callback( Str:D $callback-name, |callback-params )

Initiate a callback named $callback-name. Passes callback-params to plugins' callback handlers.

Method returns what callback handler requested to return.

method cb

Shortcut for callback.

method event

event( Str:D $event-name, |event-params )

Initiates an event named $event-name and passes event-params to all event handlers.

Returns a Promise which will be kept upon this particular event is completely handled; i.e. when all event handlers are completed. The promise is resolved to an array of Promises, one per each event handler been called.

method has-plugin

has-plugin( Str:D $plugin )

Returns true if plugin is registered with this manager

method plugin-object

plugin-object( Str:D $plugin )
plugin-object( Str:D :$fqn )

Retruns the requested plugin object if it exists. As always, the :$fqn version is slightly faster.

method all-enabled

Returns unordered Seq of all enabled plugin FQNs.

method class

class( MyClass )

One of the two key methods of this class. For a given class it creates a newly generated one with all plug-classes and method handlers applied. All the magic this framework provides with regard to extending application classes functionality through delegating to the plugins is only possible after calling this method. Read more in OO::Plugin::Manual.

method create

create( MyClass, |constructor-params )

Creates a new instance for class MyClass with all the magic applied, as described for method class and in OO::Plugin::Manual. This method is what must be used in place of the standard new.

method finish

This is the plugin manager finalization method. It must always be called before application shutdown to ensure proper completion of all event handers possibly still running in the background.

AUTHOR

Vadim Belman vrurg@cpan.org

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