SCons Builder objects can create an action "on the fly"
by using a function called a generator.
(Note: this is not the same thing as a Python generator function
described in PEP 255)
This provides a great deal of flexibility to
construct just the right list of commands
to build your target.
A generator looks like:
def generate_actions(source, target, env, for_signature):
return 'foobuild < %s > %s' % (target[0], source[0])
The arguments of a generator are:
A list of Node objects representing
the sources to be built
by the command or other action
generated by this function.
The file names of these source(s)
may be extracted using the Python str function.
A list of Node objects representing
the target or targets to be built
by the command or other action
generated by this function.
The file names of these target(s)
may be extracted using the Python str function.
The construction environment used for building the target(s). The generator may use any of the environment's construction variables in any way to determine what command or other action to return.
A flag that specifies whether the generator is being called to contribute to a build signature, as opposed to actually executing the command.
The generator must return a
command string or other action that will be used to
build the specified target(s) from the specified source(s).
Once you've defined a generator,
you create a Builder to use it
by specifying the generator keyword argument
instead of action.
def generate_actions(source, target, env, for_signature):
return 'foobuild < %s > %s' % (source[0], target[0])
bld = Builder(generator = generate_actions,
suffix = '.foo',
src_suffix = '.input')
env = Environment(BUILDERS = {'Foo' : bld})
env.Foo('file')
% scons -Q
foobuild < file.input > file.foo
Note that it's illegal to specify both an
action
and a
generator
for a Builder.