build/modules.jam

#  (C) Copyright David Abrahams 2001. Permission to copy, use, modify, sell and
#  distribute this software is granted provided this copyright notice appears in
#  all copies. This software is provided "as is" without express or implied
#  warranty, and with no claim as to its suitability for any purpose.

# Keep a record so that no module is included multiple times
module local loaded-modules ;

# meant to be invoked from import when no __test__ rule is defined in a given
# module
local rule no_test_defined
{
    ECHO warning: no __test__ rule defined in module [ CALLER_MODULE ] ;
}

# return the binding of the given module
rule binding ( module )
{
    return $($(module).__binding__) ;
}

# load the indicated module. Any members of rules-opt will be available without
# qualification in the caller's module. Any members of rename-opt will be taken
# as the names of the rules in the caller's module, in place of the names they
# have in the imported module. If rules-opt = '*', all rules from the indicated
# module are imported into the caller's module.
rule import ( module-name : rules-opt * : rename-opt * )
{
    # First see if the module needs to be loaded
    if ! ( $(module-name) in $(loaded-modules) )
    {
        loaded-modules += $(module-name) ;
        
        module $(module-name)
        {
            module local __name__ = $(module-name) ;
            
            # Prepare a default behavior, in case no __test__ is defined.
            IMPORT $(module-name) : modules : no_test_defined : __test__ ;

            # Add some grist so that the module will have a unique target name
            local module-target = $(module-name:G=module@:S=.jam) ;
            
            SEARCH on $(module-target) = $(BOOST_BUILD_PATH) ;
            BINDRULE on $(module-target) = modules.record-binding ;
            include $(module-name:G=module@:S=.jam) ;

            # run the module's test, if any.
            if nonempty$(BOOST_BUILD_TEST)
            {
                ECHO testing module $(module-name)... ;
                local ignored = [ __test__ ] ;
            }
        }
    }

    # If any rules are to be imported, do so now.
    if $(rules-opt)
    {
        if $(rules-opt) = *
        {
            rules-opt = ;
        }
        IMPORT [ CALLER_MODULE ]
           : $(module-name) : $(rules-opt) : $(rename-opt) ;
    }
}

# This helper is used by import (above) to record the binding (path) of
# each loaded module.
rule record-binding ( module-target : binding )
{
    module local $(module-target:G=:S=).__binding__ = $(binding) ;
}

# Returns the module-local value of a variable.
rule peek ( module-name variable )
{
    module $(module-name)
    {
        return $($(variable)) ;
    }
}

rule __test__ ( )
{
    import assert ;
    module modules.__test__
    {
        module local foo = bar ;
    }
    assert.result bar :  peek modules.__test__ foo ;
}