TaskGen

Task generators

The class waflib.TaskGen.task_gen encapsulates the creation of task objects (low-level code) The instances can have various parameters, but the creation of task nodes (Task.py) is always postponed. To achieve this, various methods are called from the method “apply”

waflib.TaskGen.feats

remember the methods declaring features

class waflib.TaskGen.task_gen(*k, **kw)[source]

Bases: object

Instances of this class create waflib.Task.TaskBase when calling the method waflib.TaskGen.task_gen.post() from the main thread. A few notes:

  • The methods to call (self.meths) can be specified dynamically (removing, adding, ..)
  • The ‘features’ are used to add methods to self.meths and then execute them
  • The attribute ‘path’ is a node representing the location of the task generator
  • The tasks created are added to the attribute tasks
  • The attribute ‘idx’ is a counter of task generators in the same path
__init__(*k, **kw)[source]

The task generator objects predefine various attributes (source, target) for possible processing by process_rule (make-like rules) or process_source (extensions, misc methods)

The tasks are stored on the attribute ‘tasks’. They are created by calling methods listed in self.meths or referenced in the attribute features A topological sort is performed to ease the method re-use.

The extra key/value elements passed in kw are set as attributes

meths

List of method names to execute (it is usually a good idea to avoid touching this)

prec

Precedence table for sorting the methods in self.meths

mappings

List of mappings {extension -> function} for processing files by extension

features

List of feature names for bringing new methods in

tasks

List of tasks created.

__str__()[source]

for debugging purposes

__repr__()[source]

for debugging purposes

get_name()[source]

If not set, the name is computed from the target name:

def build(bld):
        x = bld(name='foo')
        x.get_name() # foo
        y = bld(target='bar')
        y.get_name() # bar
Return type:string
Returns:name of this task generator
name

If not set, the name is computed from the target name:

def build(bld):
        x = bld(name='foo')
        x.get_name() # foo
        y = bld(target='bar')
        y.get_name() # bar
Return type:string
Returns:name of this task generator
to_list(val)[source]

Ensure that a parameter is a list

Parameters:val (string or list of string) – input to return as a list
Return type:list
post()[source]

Create task objects. The following operations are performed:

  1. The body of this method is called only once and sets the attribute posted
  2. The attribute features is used to add more methods in self.meths
  3. The methods are sorted by the precedence table self.prec or :waflib:attr:waflib.TaskGen.task_gen.prec
  4. The methods are then executed in order
  5. The tasks created are added to waflib.TaskGen.task_gen.tasks
get_hook(node)[source]
Parameters:node (waflib.Tools.Node.Node) – Input file to process
Returns:A method able to process the input node by looking at the extension
Return type:function
create_task(name, src=None, tgt=None)[source]

Wrapper for creating task objects easily

Parameters:
  • name (string) – task class name
  • src (list of waflib.Tools.Node.Node) – input nodes
  • tgt (list of waflib.Tools.Node.Node) – output nodes
Returns:

A task object

Return type:

waflib.Task.TaskBase

clone(env)[source]

Make a copy of a task generator. Once the copy is made, it is necessary to ensure that the task generator does not create the same output files as the original, or the same files may be compiled twice.

Parameters:env (waflib.ConfigSet.ConfigSet) – A configuration set
Returns:A copy
Return type:waflib.TaskGen.task_gen
process_dbus()

Process the dbus files stored in the attribute dbus_lst to create waflib.Tools.dbus.dbus_binding_tool instances.

process_enums()

Process the enum files stored in the attribute enum_list to create waflib.Tools.glib2.glib_mkenums instances.

process_marshal()

Process the marshal files stored in the attribute marshal_list to create waflib.Tools.glib2.glib_genmarshal instances. Add the c file created to the list of source to process.

waflib.TaskGen.declare_chain(name='', rule=None, reentrant=None, color='BLUE', ext_in=[], ext_out=[], before=[], after=[], decider=None, scan=None, install_path=None, shell=False)[source]

Create a new mapping and a task class for processing files by extension. See Tools/flex.py for an example.

Parameters:
  • name (string) – name for the task class
  • rule (string or function) – function to execute or string to be compiled in a function
  • reentrant (int) – re-inject the output file in the process (done automatically, set to 0 to disable)
  • color (string) – color for the task output
  • ext_in (list of string) – execute the task only after the files of such extensions are created
  • ext_out (list of string) – execute the task only before files of such extensions are processed
  • before (list of string) – execute instances of this task before classes of the given names
  • after (list of string) – execute instances of this task after classes of the given names
  • decider (function) – if present, use it to create the output nodes for the task
  • scan (function) – scanner function for the task
  • install_path (string) – installation path for the output nodes
waflib.TaskGen.taskgen_method(func)[source]

Decorator: register a method as a task generator method. The function must accept a task generator as first parameter:

from waflib.TaskGen import taskgen_method
@taskgen_method
def mymethod(self):
        pass
Parameters:func (function) – task generator method to add
Return type:function
waflib.TaskGen.feature(*k)[source]

Decorator: register a task generator method that will be executed when the object attribute ‘feature’ contains the corresponding key(s):

from waflib.Task import feature
@feature('myfeature')
def myfunction(self):
        print('that is my feature!')
def build(bld):
        bld(features='myfeature')
Parameters:k (list of string) – feature names
waflib.TaskGen.before_method(*k)[source]

Decorator: register a task generator method which will be executed before the functions of given name(s):

from waflib.TaskGen import feature, before
@feature('myfeature')
@before_method('fun2')
def fun1(self):
        print('feature 1!')
@feature('myfeature')
def fun2(self):
        print('feature 2!')
def build(bld):
        bld(features='myfeature')
Parameters:k (list of string) – method names
waflib.TaskGen.before(*k)

Decorator: register a task generator method which will be executed before the functions of given name(s):

from waflib.TaskGen import feature, before
@feature('myfeature')
@before_method('fun2')
def fun1(self):
        print('feature 1!')
@feature('myfeature')
def fun2(self):
        print('feature 2!')
def build(bld):
        bld(features='myfeature')
Parameters:k (list of string) – method names
waflib.TaskGen.after_method(*k)[source]

Decorator: register a task generator method which will be executed after the functions of given name(s):

from waflib.TaskGen import feature, after
@feature('myfeature')
@after_method('fun2')
def fun1(self):
        print('feature 1!')
@feature('myfeature')
def fun2(self):
        print('feature 2!')
def build(bld):
        bld(features='myfeature')
Parameters:k (list of string) – method names
waflib.TaskGen.after(*k)

Decorator: register a task generator method which will be executed after the functions of given name(s):

from waflib.TaskGen import feature, after
@feature('myfeature')
@after_method('fun2')
def fun1(self):
        print('feature 1!')
@feature('myfeature')
def fun2(self):
        print('feature 2!')
def build(bld):
        bld(features='myfeature')
Parameters:k (list of string) – method names
waflib.TaskGen.extension(*k)[source]

Decorator: register a task generator method which will be invoked during the processing of source files for the extension given:

from waflib import Task
class mytask(Task):
        run_str = 'cp ${SRC} ${TGT}'
@extension('.moo')
def create_maa_file(self, node):
        self.create_task('mytask', node, node.change_ext('.maa'))
def build(bld):
        bld(source='foo.moo')
waflib.TaskGen.to_nodes(self, lst, path=None)[source]

Task generator method

Convert the input list into a list of nodes. It is used by waflib.TaskGen.process_source() and waflib.TaskGen.process_rule(). It is designed for source files, for folders, see waflib.Tools.ccroot.to_incnodes():

Parameters:
  • lst (list of string and nodes) – input list
  • path (waflib.Tools.Node.Node) – path from which to search the nodes (by default, waflib.TaskGen.task_gen.path)
Return type:

list of waflib.Tools.Node.Node

waflib.TaskGen.process_source(self)[source]

Task generator method

Process each element in the attribute source by extension.

  1. The source list is converted through waflib.TaskGen.to_nodes() to a list of waflib.Node.Node first.
  2. File extensions are mapped to methods having the signature: def meth(self, node) by waflib.TaskGen.extension()
  3. The method is retrieved through waflib.TaskGen.task_gen.get_hook()
  4. When called, the methods may modify self.source to append more source to process
  5. The mappings can map an extension or a filename (see the code below)
Feature :all
waflib.TaskGen.process_rule(self)[source]

Task generator method

Process the attribute rule. When present, waflib.TaskGen.process_source() is disabled:

def build(bld):
        bld(rule='cp ${SRC} ${TGT}', source='wscript', target='bar.txt')
Feature :all
Before :waflib.TaskGen.process_source()
waflib.TaskGen.sequence_order(self)[source]

Task generator method

Add a strict sequential constraint between the tasks generated by task generators. It works because task generators are posted in order. It will not post objects which belong to other folders.

Example:

bld(features='javac seq')
bld(features='jar seq')

To start a new sequence, set the attribute seq_start, for example:

obj = bld(features='seq')
obj.seq_start = True

Note that the method is executed in last position. This is more an example than a widely-used solution.

Feature :seq
class waflib.TaskGen.subst_pc(*k, **kw)[source]

Bases: waflib.Task.Task

Create .pc files from .pc.in. The task is executed whenever an input variable used in the substitution changes.

sig_vars()[source]

Compute a hash (signature) of the variables used in the substitution

waflib.TaskGen.add_pcfile(self, node)[source]

Process .pc.in files to .pc. Install the results to ${PREFIX}/lib/pkgconfig/

def build(bld):
bld(source=’foo.pc.in’, install_path=’${LIBDIR}/pkgconfig/’)
waflib.TaskGen.process_subst(self)[source]

Task generator method

Define a transformation that substitutes the contents of source files to target files:

def build(bld):
        bld(
                features='subst',
                source='foo.c.in',
                target='foo.c',
                install_path='${LIBDIR}/pkgconfig',
                VAR = 'val'
        )

The input files are supposed to contain macros of the form @VAR@, where VAR is an argument of the task generator object.

This method overrides the processing by waflib.TaskGen.process_source().

Feature :subst
Before :waflib.TaskGen.process_source(), waflib.TaskGen.process_rule()

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