Module: Vagrant::CapabilityHost

Included in:
Guest, Host, Plugin::V2::Provider, Plugin::V2::SyncedFolder
Defined in:
lib/vagrant/capability_host.rb

Overview

This module enables a class to host capabilities. Prior to being able to use any capabilities, the initialize_capabilities! method must be called.

Capabilities allow small pieces of functionality to be plugged in using the Vagrant plugin model. Capabilities even allow for a certain amount of inheritance, where only a subset of capabilities may be implemented but a parent implements the rest.

Capabilities are used heavily in Vagrant for host/guest interactions. For example, "mount_nfs_folder" is a guest-OS specific operation, so capabilities defer these operations to the guest.

Instance Method Summary collapse

Instance Method Details

#capability(cap_name, *args) ⇒ Object

Executes the capability with the given name, optionally passing more arguments onwards to the capability. If the capability returns a value, it will be returned.

Parameters:

  • cap_name (Symbol)

    Name of the capability


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# File 'lib/vagrant/capability_host.rb', line 91

def capability(cap_name, *args)
  cap_mod = capability_module(cap_name.to_sym)
  if !cap_mod
    raise Errors::CapabilityNotFound,
      cap:  cap_name.to_s,
      host: @cap_host_chain[0][0].to_s
  end

  cap_method = nil
  begin
    cap_method = cap_mod.method(cap_name)
  rescue NameError
    raise Errors::CapabilityInvalid,
      cap: cap_name.to_s,
      host: @cap_host_chain[0][0].to_s
  end

  args = @cap_args + args
  @cap_logger.info(
    "Execute capability: #{cap_name} #{args.inspect} (#{@cap_host_chain[0][0]})")
  cap_method.call(*args)
end

#capability?(cap_name) ⇒ Boolean

Tests whether the given capability is possible.

Parameters:

  • cap_name (Symbol)

    Capability name

Returns:

  • (Boolean)

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# File 'lib/vagrant/capability_host.rb', line 82

def capability?(cap_name)
  !capability_module(cap_name.to_sym).nil?
end

#capability_host_chainArray<Array<Symbol, Class>>

Returns the chain of hosts that will be checked for capabilities.

Returns:

  • (Array<Array<Symbol, Class>>)

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# File 'lib/vagrant/capability_host.rb', line 74

def capability_host_chain
  @cap_host_chain
end

#initialize_capabilities!(host, hosts, capabilities, *args) ⇒ Object

Initializes the capability system by detecting the proper capability host to execute on and building the chain of capabilities to execute.

Parameters:

  • host (Symbol)

    The host to use for the capabilities, or nil if we should auto-detect it.

  • hosts (Hash<Symbol, Array<Class, Symbol>>)

    Potential capability hosts. The key is the name of the host, value[0] is a class that implements #detect? and value[1] is a parent host (if any).

  • capabilities (Hash<Symbol, Hash<Symbol, Class>>)

    The capabilities that are supported. The key is the host of the capability. Within that is a hash where the key is the name of the capability and the value is the class/module implementing it.


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# File 'lib/vagrant/capability_host.rb', line 27

def initialize_capabilities!(host, hosts, capabilities, *args)
  @cap_logger = Log4r::Logger.new(
    "vagrant::capability_host::#{self.class.to_s.downcase}")

  if host && !hosts[host]
    raise Errors::CapabilityHostExplicitNotDetected, value: host.to_s
  end

  if !host
    host = autodetect_capability_host(hosts, *args) if !host
    raise Errors::CapabilityHostNotDetected if !host
  end

  if !hosts[host]
    # This should never happen because the autodetect above uses the
    # hosts hash to look up hosts. And if an explicit host is specified,
    # we do another check higher up.
    raise "Internal error. Host not found: #{host}"
  end

  name      = host
  host_info = hosts[name]
  host      = host_info[0].new
  chain     = []
  chain << [name, host]

  # Build the proper chain of parents if there are any.
  # This allows us to do "inheritance" of capabilities later
  if host_info[1]
    parent_name = host_info[1]
    parent_info = hosts[parent_name]
    while parent_info
      chain << [parent_name, parent_info[0].new]
      parent_name = parent_info[1]
      parent_info = hosts[parent_name]
    end
  end

  @cap_host_chain = chain
  @cap_args       = args
  @cap_caps       = capabilities
  true
end