SCons.Action

Package SCons :: Module Action |
[hide private]
[frames] | no frames]

# Module Action

source code

SCons.Action

This encapsulates information about executing any sort of action that can build one or more target Nodes (typically files) from one or more source Nodes (also typically files) given a specific Environment.

The base class here is ActionBase. The base class supplies just a few OO utility methods and some generic methods for displaying information about an Action in response to the various commands that control printing.

A second-level base class is _ActionAction. This extends ActionBase by providing the methods that can be used to show and perform an action. True Action objects will subclass _ActionAction; Action factory class objects will subclass ActionBase.

The heavy lifting is handled by subclasses for the different types of actions we might execute:

> CommandAction CommandGeneratorAction FunctionAction ListAction

The subclasses supply the following public interface methods used by other modules:

> __call__()
>   THE public interface, "calling" an Action object executes the command or Python function. This also takes care of printing a pre-substitution command for debugging purposes.
> get_contents()
>   Fetches the "contents" of an Action for signature calculation. This is what gets MD5 checksumm'ed to decide if a target needs to be rebuilt because its action changed.
> genstring()
>   Returns a string representation of the Action without command substitution, but allows a CommandGeneratorAction to generate the right action based on the specified target, source and env. This is used by the Signature subsystem (through the Executor) to obtain an (imprecise) representation of the Action operation for informative purposes.

Subclasses also supply the following methods for internal use within this module:

> __str__()
>   Returns a string approximation of the Action; no variable substitution is performed.
> execute()
>   The internal method that really, truly, actually handles the execution of a command or Python function. This is used so that the __call__() methods can take care of displaying any pre-substitution representations, and then execute an action without worrying about the specific Actions involved.
> strfunction()
>   Returns a substituted string representation of the Action. This is used by the _ActionAction.show() command to display the command/function that will be executed to generate the target(s).

There is a related independent ActionCaller class that looks like a regular Action, and which serves as a wrapper for arbitrary functions that we want to let the user specify the arguments to now, but actually execute later (when an out-of-date check determines that it's needed to be executed, for example). Objects of this class are returned by an ActionFactory class that provides a __call__() method as a convenient way for wrapping up the functions.

Classes | [hide private]
| _Null
| _null
| ActionBase Base class for all types of action objects that can be held by other objects (Builders, Executors, etc.) This provides the common methods for manipulating and combining those actions.
| _ActionAction Base class for actions that create output objects.
| CommandAction Class for command-execution actions.
| CommandGeneratorAction Class for command-generator actions.
| LazyAction
| FunctionAction Class for Python function actions.
| ListAction Class for lists of other actions.
| ActionCaller A class for delaying calling an Action function with specific (positional and keyword) arguments until the Action is actually executed.
| ActionFactory A factory class that will wrap up an arbitrary function as an SCons-executable Action object.

Functions | [hide private]
rfile(n) | source code
default_exitstatfunc(s) | source code
remove_set_lineno_codes(x) | source code
_callable_contents(obj) Return the signature contents of a callable Python object. | source code
_object_contents(obj) Return the signature contents of any Python object. | source code
_code_contents(code) Return the signature contents of a code object. | source code
_function_contents(func) Return the signature contents of a function. | source code
_actionAppend(act1, act2) | source code
_do_create_action(act, *args, **kw) This is the actual "implementation" for the Action factory method, below. | source code
Action(act, *args, **kw) A factory for action objects. | source code
_string_from_cmd_list(cmd_list) Takes a list of command line arguments and returns a pretty representation for printing. | source code

Variables | [hide private]
| __revision__ = ``'``src/engine/SCons/Action.py 2725 2008/03/31 12:``...``
| print_actions = `False`
| execute_actions = `False`
| print_actions_presub = `0`
| default_ENV = `False`
| SET_LINENO = `dis.SET_LINENO`
| HAVE_ARGUMENT = `dis.HAVE_ARGUMENT`

Function Details | [hide private]

### _object_contents(obj) | source code
Return the signature contents of any Python object. We have to handle the case where object contains a code object since it can be pickled directly.

### _code_contents(code) | source code
Return the signature contents of a code object. By providing direct access to the code object of the function, Python makes this extremely easy. Hooray! Unfortunately, older versions of Python include line number indications in the compiled byte code. Boo! So we remove the line number byte codes to prevent recompilations from moving a Python function.

### _do_create_action(act, *args, **kw) | source code
This is the actual "implementation" for the Action factory method, below. This handles the fact that passing lists to Action() itself has different semantics than passing lists as elements of lists. The former will create a ListAction, the latter will create a CommandAction by converting the inner list elements to strings.

Variables Details | [hide private]

  ### __revision__ Value:
      'src/engine/SCons/Action.py 2725 2008/03/31 12:52:02 knight'