# Copyright 2002, 2003 Dave Abrahams
# Copyright 2002, 2005, 2006 Rene Rivera
# Copyright 2002, 2003, 2004, 2005, 2006 Vladimir Prus
# Distributed under the Boost Software License, Version 1.0.
# (See accompanying file LICENSE_1_0.txt or copy at
# http://www.boost.org/LICENSE_1_0.txt)

# Implements project representation and loading. Each project is represented by:
#  - a module where all the Jamfile content lives.
#  - an instance of 'project-attributes' class.
#    (given a module name, can be obtained using the 'attributes' rule)
#  - an instance of 'project-target' class (from targets.jam)
#    (given a module name, can be obtained using the 'target' rule)
#
# Typically, projects are created as result of loading a Jamfile, which is done
# by rules 'load' and 'initialize', below. First, a module is prepared and a new
# project-attributes instance is created. Some rules necessary for all projects
# are added to the module (see the 'project-rules' module). Default project
# attributes are set (inheriting parent project attributes, if it exists). After
# that the Jamfile is read. It can declare its own attributes using the
# 'project' rule which will be combined with any already set.
#
# The 'project' rule can also declare a project id which will be associated with
# the project module.
#
# Besides Jamfile projects, we also support 'standalone' projects created by
# calling 'initialize' in an arbitrary module and not specifying the project's
# location. After the call, the module can call the 'project' rule, declare main
# targets and behave as a regular project except that, since it is not
# associated with any location, it should only declare prebuilt targets.
#
# The list of all loaded Jamfiles is stored in the .project-locations variable.
# It is possible to obtain a module name for a location using the 'module-name'
# rule. Standalone projects are not recorded and can only be referenced using
# their project id.

import "class" : new ;
import modules ;
import path ;
import print ;
import property-set ;
import sequence ;


.debug-loading = [ MATCH ^(--debug-loading)$ : [ modules.peek : ARGV ] ] ;


# Loads the Jamfile at the given location. After loading, project global file
# and Jamfiles needed by the requested one will be loaded recursively. If the
# Jamfile at that location is loaded already, does nothing. Returns the project
# module for the Jamfile.
#
rule load ( jamfile-location : synthesize ? )
{
    local module-name = [ module-name $(jamfile-location) ] ;
    # If Jamfile is already loaded, do not try again.
    if ! $(module-name) in $(.jamfile-modules)
    {
        if $(.debug-loading)
        {
            ECHO Loading Jamfile at '$(jamfile-location)' ;
        }

        load-jamfile $(jamfile-location) : $(module-name) : $(synthesize) ;

        # We want to make sure that child project are loaded only after parent
        # projects. In particular, because parent projects define attributes
        # which are then inherited by children, and we do not want children to
        # be loaded before parent has defined everything.
        #
        # While "build-project" and "use-project" can potentially refer to child
        # projects from parent projects, we do not immediately load child
        # projects when seeing those attributes. Instead, we record the minimal
        # information to be used only later.
        load-used-projects $(module-name) ;
    }
    return $(module-name) ;
}


rule load-used-projects ( module-name )
{
    local used = [ modules.peek $(module-name) : .used-projects ] ;
    local location = [ attribute $(module-name) location ] ;
    while $(used)
    {
        local id = $(used[1]) ;
        local where = [ path.make $(used[2]) ] ;
        register-id $(id) : [ load [ path.root $(where) $(location) ] ] ;
        used = $(used[3-]) ;
    }
}


# Note the use of character groups, as opposed to listing 'Jamroot' and
# 'jamroot'. With the latter, we would get duplicate matches on Windows and
# would have to eliminate duplicates.
JAMROOT ?= [ modules.peek : JAMROOT ] ;
JAMROOT ?= project-root.jam "[Jj]amroot" "[Jj]amroot." "[Jj]amroot.jam" ;


# Loads parent of Jamfile at 'location'. Issues an error if nothing is found.
#
rule load-parent ( location )
{
    local found = [ path.glob-in-parents $(location) : $(JAMROOT) $(JAMFILE) ] ;
    if $(found)
    {
        return [ load $(found[1]:D) ] ;
    }
}


# Returns the project module corresponding to the given project-id or plain
# directory name. Returns nothing if such a project can not be found.
#
rule find ( name : current-location )
{
    local project-module ;

    # Try interpreting name as project id.
    if [ path.is-rooted $(name) ]
    {
        project-module = $($(name).jamfile-module) ;
    }

    if ! $(project-module)
    {
        local location = [ path.root [ path.make $(name) ] $(current-location) ]
            ;

        # If no project is registered for the given location, try to load it.
        # First see if we have a Jamfile. If not, then see if we might have a
        # project root willing to act as a Jamfile. In that case, project root
        # must be placed in the directory referred to by id.

        project-module = [ module-name $(location) ] ;
        if ! $(project-module) in $(.jamfile-modules)
        {
            if [ path.glob $(location) : $(JAMROOT) $(JAMFILE) ]
            {
                project-module = [ load $(location) ] ;
            }
            else
            {
                project-module = ;
            }
        }
    }

    return $(project-module) ;
}


# Returns the name of the module corresponding to 'jamfile-location'. If no
# module corresponds to that location yet, associates the default module name
# with that location.
#
rule module-name ( jamfile-location )
{
    if ! $(.module.$(jamfile-location))
    {
        # Root the path, so that locations are always unambiguous. Without this,
        # we can not decide if '../../exe/program1' and '.' are the same paths.
        local normalized = [ path.root $(jamfile-location) [ path.pwd ] ] ;

        # Quick & dirty fix to get the same module name when we supply two
        # equivalent location paths, e.g. 'd:\Foo' & 'D:\fOo\bar\..' on Windows.
        # Note that our current implementation will not work correctly if the
        # given location references an empty folder, but in that case any later
        # attempt to load a Jamfile from this location will fail anyway.
        # FIXME: Implement this cleanly. Support for this type of path
        # normalization already exists internally in Boost Jam and the current
        # fix relies on the GLOB builtin rule using that support. Most likely we
        # just need to add a new builtin rule to do this explicitly.
        normalized = [ NORMALIZE_PATH $(normalized) ] ;
        local glob-result = [ GLOB [ path.native $(normalized) ] : * ] ;
        if $(glob-result)
        {
            normalized = $(glob-result[1]:D) ;
        }
        .module.$(jamfile-location) = Jamfile<$(normalized)> ;
    }
    return $(.module.$(jamfile-location)) ;
}


# Default patterns to search for the Jamfiles to use for build declarations.
#
JAMFILE = [ modules.peek : JAMFILE ] ;
JAMFILE ?= "[Bb]uild.jam" "[Jj]amfile.v2" "[Jj]amfile" "[Jj]amfile." "[Jj]amfile.jam" ;


# Find the Jamfile at the given location. This returns the exact names of all
# the Jamfiles in the given directory. The optional parent-root argument causes
# this to search not the given directory but the ones above it up to the
# parent-root directory.
#
rule find-jamfile (
    dir            # The directory(s) to look for a Jamfile.
    parent-root ?  # Optional flag indicating to search for the parent Jamfile.
    : no-errors ?
    )
{
    # Glob for all the possible Jamfiles according to the match pattern.
    #
    local jamfile-glob = ;
    if $(parent-root)
    {
        if ! $(.parent-jamfile.$(dir))
        {
            .parent-jamfile.$(dir) = [ path.glob-in-parents $(dir) : $(JAMFILE)
                ] ;
        }
        jamfile-glob = $(.parent-jamfile.$(dir)) ;
    }
    else
    {
        if ! $(.jamfile.$(dir))
        {
            .jamfile.$(dir) = [ path.glob $(dir) : $(JAMFILE) ] ;
        }
        jamfile-glob = $(.jamfile.$(dir)) ;

    }

    local jamfile-to-load = $(jamfile-glob) ;
    # Multiple Jamfiles found in the same place. Warn about this and ensure we
    # use only one of them. As a temporary convenience measure, if there is
    # Jamfile.v2 among found files, suppress the warning and use it.
    #
    if $(jamfile-to-load[2-])
    {
        local v2-jamfiles = [ MATCH "^(.*[Jj]amfile\\.v2)|(.*[Bb]uild\\.jam)$" :
            $(jamfile-to-load) ] ;

        if $(v2-jamfiles) && ! $(v2-jamfiles[2])
        {
            jamfile-to-load = $(v2-jamfiles) ;
        }
        else
        {
            local jamfile = [ path.basename $(jamfile-to-load[1]) ] ;
            ECHO "warning: Found multiple Jamfiles at '"$(dir)"'!"
                "Loading the first one: '$(jamfile)'." ;
        }

        jamfile-to-load = $(jamfile-to-load[1]) ;
    }

    # Could not find it, error.
    #
    if ! $(no-errors) && ! $(jamfile-to-load)
    {
        import errors ;
        errors.error Unable to load Jamfile.
            : Could not find a Jamfile in directory '$(dir)'.
            : Attempted to find it with pattern '$(JAMFILE:J=" ")'.
            : Please consult the documentation at "'http://www.boost.org'." ;
    }

    return $(jamfile-to-load) ;
}


# Default patterns to search for auto-include of package manager build declarations.
#
PACKAGE_MANAGER_BUILD_INFO(CONAN) = "conanbuildinfo.jam" ;

# Default to using the package manager build info in this priority order:
# 1. Configuration, user, project, etc.
# 2. Command line argument "--use-package-manager=<name>".
# 3. Environment variable "PACKAGE_MANAGER_BUILD_INFO".
# 4. Conan, others.
#
local .use-package-manager = [ MATCH "^--use-package-manager=(.*)$" : [ modules.peek : ARGV ] ] ;
PACKAGE_MANAGER_BUILD_INFO ?= $(PACKAGE_MANAGER_BUILD_INFO($(.use-package-manager:U))) ;
PACKAGE_MANAGER_BUILD_INFO ?= [ modules.peek : PACKAGE_MANAGER_BUILD_INFO ] ;
PACKAGE_MANAGER_BUILD_INFO ?= $(PACKAGE_MANAGER_BUILD_INFO(CONAN)) ;


# Load the configured package manager build information file.
#
rule load-package-manager-build-info ( )
{
    # This first variable is the one from the configuration (user, project, etc).
    local package-manager-build-info = [ modules.peek [ CALLER_MODULE ] : PACKAGE_MANAGER_BUILD_INFO ] ;
    # And this is the rest as it takes it from the settings in the "project" module.
    # I.e. the variable assignments above.
    package-manager-build-info ?= $(PACKAGE_MANAGER_BUILD_INFO) ;
    if $(package-manager-build-info)
    {
        local pm = [ path.glob $(dir) : $(package-manager-build-info) ] ;
        pm = $(pm[1]) ;
        local cm = [ CALLER_MODULE ] ;
        local pm-tag = "$(cm)<$(pm:B)>" ;
        if $(pm) && ! ( $(pm-tag) in $(.package-manager-build-info) )
        {
            .package-manager-build-info += $(pm-tag) ;
            # We found a matching builf info to load, but we have to be careful
            # as the loading can affect the current project since it can define
            # sub-projects. Hence we save and restore the current project.
            local saved-project = $(.current-project) ;
            modules.load $(cm) : $(pm) ;
            .current-project = $(saved-project) ;
        }
    }
}


# Load a Jamfile at the given directory. Returns nothing. Will attempt to load
# the file as indicated by the JAMFILE patterns. Effect of calling this rule
# twice with the same 'dir' is undefined.
#
local rule load-jamfile ( dir : jamfile-module : synthesize ? )
{
    # See if the Jamfile is where it should be.
    #
    local jamfile-to-load = [ path.glob $(dir) : $(JAMROOT) ] ;
    if ! $(jamfile-to-load)
    {
        jamfile-to-load = [ find-jamfile $(dir) : $(synthesize) ] ;
    }

    if $(jamfile-to-load[2])
    {
        import errors ;
        errors.error "Multiple Jamfiles found at '$(dir)'" :
            "Filenames are: " $(jamfile-to-load:D=) ;
    }

    if ! $(jamfile-to-load) && $(synthesize)
    {
        jamfile-to-load = $(dir)/@ ;
    }

    # Now load the Jamfile in its own context.
    # The call to 'initialize' may load the parent Jamfile, which might contain
    # a 'use-project' or a 'project.load' call, causing a second attempt to load
    # the same project we are loading now. Checking inside .jamfile-modules
    # prevents that second attempt from messing things up.
    if ! $(jamfile-module) in $(.jamfile-modules)
    {
        local previous-project = $(.current-project) ;

        # Initialize the Jamfile module before loading.
        initialize $(jamfile-module) : [ path.parent $(jamfile-to-load) ] :
            $(jamfile-to-load:BS) ;

        # Auto-load package manager(s) build information.
        IMPORT project : load-package-manager-build-info
            : $(jamfile-module) : project.load-package-manager-build-info ;
        modules.call-in $(jamfile-module) : project.load-package-manager-build-info ;

        if ! $(jamfile-module) in $(.jamfile-modules)
        {
            .jamfile-modules += $(jamfile-module) ;

            local saved-project = $(.current-project) ;

            mark-as-user $(jamfile-module) ;
            if $(jamfile-to-load:B) = "@"
            {
                # Not a real jamfile to load. Synthsize the load.
                modules.poke $(jamfile-module) : __name__ : $(jamfile-module) ;
                modules.poke $(jamfile-module) : __file__ : [ path.native $(jamfile-to-load) ] ;
                modules.poke $(jamfile-module) : __binding__ : [ path.native $(jamfile-to-load) ] ;
            }
            else
            {
                modules.load $(jamfile-module) : [ path.native $(jamfile-to-load) ]
                    : . ;
                if [ MATCH ^($(JAMROOT))$ : $(jamfile-to-load:BS) ]
                {
                    jamfile = [ find-jamfile $(dir) : no-errors ] ;
                    if $(jamfile)
                    {
                        load-aux $(jamfile-module) : [ path.native $(jamfile) ] ;
                    }
                }
            }

            # Now do some checks.
            if $(.current-project) != $(saved-project)
            {
                import errors ;
                errors.error
                    The value of the .current-project variable has magically
                    : changed after loading a Jamfile. This means some of the
                    : targets might be defined in the wrong project.
                    : after loading $(jamfile-module)
                    : expected value $(saved-project)
                    : actual value $(.current-project) ;
            }

            end-load $(previous-project) ;

            if $(.global-build-dir)
            {
                if [ attribute $(jamfile-module) location ] && ! [ attribute
                    $(jamfile-module) id ]
                {
                    local project-root = [ attribute $(jamfile-module)
                        project-root ] ;
                    if $(project-root) = $(dir)
                    {
                        ECHO "warning: the --build-dir option was specified" ;
                        ECHO "warning: but Jamroot at '$(dir)'" ;
                        ECHO "warning: specified no project id" ;
                        ECHO "warning: the --build-dir option will be ignored" ;
                    }
                }
            }
        }
    }
}


# Called when done loading a project module. Restores the current project to its
# previous value and does some additional checking to make sure our 'currently
# loaded project' identifier does not get left with an invalid value.
#
rule end-load ( previous-project ? )
{
    if ! $(.current-project)
    {
        import errors ;
        errors.error Ending project loading requested when there was no project
            currently being loaded. ;
    }

    if ! $(previous-project) && $(.saved-current-project)
    {
        import errors ;
        errors.error Ending project loading requested with no 'previous project'
            when there were other projects still marked as being loaded
            recursively. ;
    }

    .current-project = $(previous-project) ;
}


rule mark-as-user ( module-name )
{
    if USER_MODULE in [ RULENAMES ]
    {
        USER_MODULE $(module-name) ;
    }
}


rule load-aux ( module-name : file )
{
    mark-as-user $(module-name) ;

    module $(module-name)
    {
        include $(2) ;
        local rules = [ RULENAMES $(1) ] ;
        IMPORT $(1) : $(rules) : $(1) : $(1).$(rules) ;
    }
}


.global-build-dir = [ MATCH ^--build-dir=(.*)$ : [ modules.peek : ARGV ] ] ;
if $(.global-build-dir)
{
    # If the option is specified several times, take the last value.
    .global-build-dir = [ path.make $(.global-build-dir[-1]) ] ;
}


# Initialize the module for a project.
#
rule initialize (
    module-name   # The name of the project module.
    : location ?  # The location (directory) of the project to initialize. If
                  # not specified, a standalone project will be initialized.
    : basename ?
    )
{
    if $(.debug-loading)
    {
        ECHO "Initializing project '$(module-name)'" ;
    }

    local jamroot ;

    local parent-module ;
    if $(module-name) in test-config all-config
    {
        # No parent.
    }
    else if $(module-name) = site-config
    {
        parent-module = test-config ;
    }
    else if $(module-name) = user-config
    {
        parent-module = site-config ;
    }
    else if $(module-name) = project-config
    {
        parent-module = user-config ;
    }
    else if $(location)
    {
        if ! [ MATCH ^($(JAMROOT))$ : $(basename) ]
        {
            # We search for parent/jamroot only if this is a jamfile project, i.e.
            # if is not a standalone or a jamroot project.
            parent-module = [ load-parent $(location) ] ;
        }
        if ! $(parent-module)
        {
            # We have a jamroot project, or a jamfile project
            # without a parent that becomes a jamroot. Inherit from
            # user-config (or project-config
            # if it exists).
            if $(project-config.attributes)
            {
                parent-module = project-config ;
            }
            else
            {
                parent-module = user-config ;
            }
            jamroot = true ;
        }
    }

    # TODO: need to consider if standalone projects can do anything but define
    # prebuilt targets. If so, we need to give them a more sensible "location",
    # so that source paths are correct.
    location ?= "" ;
    # Create the module for the Jamfile first.
    module $(module-name)
    {
    }

    # load-parent can end up loading this module again. Make sure this is not
    # duplicated.
    if ! $($(module-name).attributes)
    {
        $(module-name).attributes = [ new project-attributes $(location)
            $(module-name) ] ;
        local attributes = $($(module-name).attributes) ;

        if $(location)
        {
            $(attributes).set source-location : [ path.make $(location) ] :
                exact ;
        }
        else
        {
            local cfgs = project site test user all ;
            if ! $(module-name) in $(cfgs)-config
            {
                # This is a standalone project with known location. Set its
                # source location so it can declare targets. This is needed so
                # you can put a .jam file with your sources and use it via
                # 'using'. Standard modules (in the 'tools' subdir) may not
                # assume source dir is set.
                local s = [ modules.binding $(module-name) ] ;
                if ! $(s)
                {
                    import errors ;
                    errors.error Could not determine project location
                        $(module-name) ;
                }
                $(attributes).set source-location : $(s:D) : exact ;
            }
        }

        $(attributes).set requirements       : [ property-set.empty ] : exact ;
        $(attributes).set usage-requirements : [ property-set.empty ] : exact ;

        # Import rules common to all project modules from project-rules module,
        # defined at the end of this file.
        local rules = [ RULENAMES project-rules ] ;
        IMPORT project-rules : $(rules) : $(module-name) : $(rules) ;

        if $(parent-module)
        {
            inherit-attributes $(module-name) : $(parent-module) ;
            $(attributes).set parent-module : $(parent-module) : exact ;
        }

        if $(jamroot)
        {
            $(attributes).set project-root : $(location) : exact ;
            if ! $(.first-project-root)
            {
                .first-project-root = $(module-name) ;
            }
        }

        local parent ;
        if $(parent-module)
        {
            parent = [ target $(parent-module) ] ;
        }

        if ! $(.target.$(module-name))
        {
            local requirements = [ attribute $(module-name) requirements ] ;
            .target.$(module-name) = [ new project-target $(module-name) :
                $(module-name) $(parent) : $(requirements) ] ;

            if $(.debug-loading)
            {
                ECHO Assigned project target $(.target.$(module-name)) to
                    '$(module-name)' ;
            }
        }
    }

    .current-project = [ target $(module-name) ] ;
}


# Make 'project-module' inherit attributes of project root and parent module.
#
rule inherit-attributes ( project-module : parent-module )
{
    local attributes = $($(project-module).attributes) ;
    local pattributes = [ attributes $(parent-module) ] ;
    # Parent module might be locationless configuration module.
    if [ modules.binding $(parent-module) ]
    {
        $(attributes).set parent :
            [ path.parent [ path.make [ modules.binding $(parent-module) ] ] ] ;
    }
    $(attributes).set project-root :
        [ $(pattributes).get project-root ] : exact ;
    $(attributes).set default-build :
        [ $(pattributes).get default-build ] ;
    $(attributes).set requirements :
        [ $(pattributes).get requirements ] : exact ;
    $(attributes).set usage-requirements :
        [ $(pattributes).get usage-requirements ] : exact ;

    local parent-build-dir = [ $(pattributes).get build-dir ] ;
    if $(parent-build-dir)
    {
        # Have to compute relative path from parent dir to our dir. Convert both
        # paths to absolute, since we cannot find relative path from ".." to
        # ".".

        local location = [ attribute $(project-module) location ] ;
        local parent-location = [ attribute $(parent-module) location ] ;

        local pwd = [ path.pwd ] ;
        local parent-dir = [ path.root $(parent-location) $(pwd) ] ;
        local our-dir = [ path.root $(location) $(pwd) ] ;
        $(attributes).set build-dir : [ path.join $(parent-build-dir)
            [ path.relative $(our-dir) $(parent-dir) ] ] : exact ;
    }
}


# Returns whether the given string is a valid registered project id.
#
rule is-registered-id ( id )
{
    return $($(id).jamfile-module) ;
}


# Associate the given id with the given project module. Returns the possibly
# corrected project id.
#
rule register-id ( id : module )
{
    id = [ path.root $(id) / ] ;

    if [ MATCH (//) : $(id) ]
    {
        import errors ;
        errors.user-error Project id may not contain two consecutive slash
            characters (project "id:" '$(id)'). ;
    }

    local orig-module = $($(id).jamfile-module) ;
    if $(orig-module) && $(orig-module) != $(module)
    {
        local new-file = [ modules.peek $(module) : __file__ ] ;
        local new-location = [ project.attribute $(module) location ] ;

        local orig-file = [ modules.peek $(orig-module) : __file__ ] ;
        local orig-main-id = [ project.attribute $(orig-module) id ] ;
        local orig-location = [ project.attribute $(orig-module) location ] ;
        local orig-project = [ target $(orig-module) ] ;
        local orig-name = [ $(orig-project).name ] ;

        import errors ;
        errors.user-error Attempt to redeclare already registered project id
            '$(id)'.
            : Original "project:"
            : "   " "Name:" $(orig-name:E=---)
            : "   " "Module:" $(orig-module)
            : "   " "Main id: "$(orig-main-id:E=---)
            : "   " "File:" $(orig-file:E=---)
            : "   " "Location:" $(orig-location:E=---)
            : New "project:"
            : "   " "Module:" $(module)
            : "   " "File:" $(new-file:E=---)
            : "   " "Location:" $(new-location:E=---) ;
    }

    $(id).jamfile-module = $(module) ;
    return $(id) ;
}


# Class keeping all the attributes of a project.
#
# The standard attributes are "id", "location", "project-root", "parent"
# "requirements", "default-build", "source-location" and "projects-to-build".
#
class project-attributes
{
    import path ;
    import print ;
    import project ;
    import property ;
    import property-set ;
    import sequence ;

    rule __init__ ( location project-module )
    {
        self.location = $(location) ;
        self.project-module = $(project-module) ;
    }

    # Set the named attribute from the specification given by the user. The
    # value actually set may be different.
    #
    rule set ( attribute : specification *
        : exact ?  # Sets value from 'specification' without any processing.
        )
    {
        if $(exact)
        {
            self.$(attribute) = $(specification) ;
        }
        else if $(attribute) = "requirements"
        {
            local result = [ property-set.refine-from-user-input
                $(self.requirements) : $(specification)
                : $(self.project-module) : $(self.location) ] ;

            if $(result[1]) = "@error"
            {
                import errors : error : errors.error ;
                errors.error Requirements for project at '$(self.location)'
                    conflict with parent's. : "Explanation:" $(result[2-]) ;
            }

            self.requirements = $(result) ;
        }
        else if $(attribute) = "usage-requirements"
        {
            local unconditional ;
            for local p in $(specification)
            {
                local split = [ property.split-conditional $(p) ] ;
                split ?= nothing $(p) ;
                unconditional += $(split[2]) ;
            }

            local non-free = [ property.remove free : $(unconditional) ] ;
            if $(non-free)
            {
                import errors : error : errors.error ;
                errors.error usage-requirements $(specification) have non-free
                    properties $(non-free) ;
            }
            local t = [ property.translate-paths $(specification) :
                $(self.location) ] ;
            if $(self.usage-requirements)
            {
                self.usage-requirements = [ property-set.create
                    [ $(self.usage-requirements).raw ] $(t) ] ;
            }
            else
            {
                self.usage-requirements = [ property-set.create $(t) ] ;
            }
        }
        else if $(attribute) = "default-build"
        {
            self.default-build = [ property.make $(specification) ] ;
        }
        else if $(attribute) = "source-location"
        {
            self.source-location = ;
            for local src-path in $(specification)
            {
                self.source-location += [ path.root [ path.make $(src-path) ]
                    $(self.location) ] ;
            }
        }
        else if $(attribute) = "build-dir"
        {
            self.build-dir = [ path.root [ path.make $(specification) ]
                $(self.location) ] ;
        }
        else if $(attribute) = "id"
        {
            self.id = [ project.register-id $(specification) :
                $(self.project-module) ] ;
        }
        else if ! $(attribute) in "default-build" "location" "parent"
            "projects-to-build" "project-root" "source-location"
        {
            import errors : error : errors.error ;
            errors.error Invalid project attribute '$(attribute)' specified for
                project at '$(self.location)' ;
        }
        else
        {
            self.$(attribute) = $(specification) ;
        }
    }

    # Returns the value of the given attribute.
    #
    rule get ( attribute )
    {
        return $(self.$(attribute)) ;
    }

    # Returns whether these attributes belong to a Jamroot project module.
    #
    rule is-jamroot ( )
    {
        if $(self.location) && $(self.project-root) = $(self.location)
        {
            return true ;
        }
    }

    # Prints the project attributes.
    #
    rule print ( )
    {
        local id = '$(self.id)' ;
        print.section $(id:E=(none)) ;
        print.list-start ;
        print.list-item "Parent project:" $(self.parent:E=(none)) ;
        print.list-item "Requirements:" [ $(self.requirements).raw ] ;
        print.list-item "Default build:" $(self.default-build) ;
        print.list-item "Source location:" $(self.source-location) ;
        print.list-item "Projects to build:" [ sequence.insertion-sort
            $(self.projects-to-build) ] ;
        print.list-end ;
    }
}


# Returns the build directory for standalone projects
#
rule standalone-build-dir ( )
{
    project = [ target $(.first-project-root) ] ;
    return [ path.join [ $(project).build-dir ] standalone ] ;
}

# Returns the project which is currently being loaded.
#
rule current ( )
{
    if ! $(.current-project)
    {
        import errors ;
        errors.error Reference to the project currently being loaded requested
            when there was no project module being loaded. ;
    }
    return $(.current-project) ;
}


# Temporarily changes the current project to 'project'. Should be followed by
# 'pop-current'.
#
rule push-current ( project ? )
{
    .saved-current-project += $(.current-project) ;
    .current-project = $(project) ;
}


rule pop-current ( )
{
    .current-project = $(.saved-current-project[-1]) ;
    .saved-current-project = $(.saved-current-project[1--2]) ;
}


# Returns the project-attribute instance for the specified Jamfile module.
#
rule attributes ( project )
{
    return $($(project).attributes) ;
}


# Returns the value of the specified attribute in the specified Jamfile module.
#
rule attribute ( project attribute )
{
    return [ $($(project).attributes).get $(attribute) ] ;
}


# Returns whether a project module is one of Boost Build's configuration
# modules.
#
rule is-config-module ( project )
{
    local cfgs = project site test user ;
    if $(project) in $(cfgs)-config
    {
        return true ;
    }
}


# Returns whether a project module is a Jamroot project module.
#
rule is-jamroot-module ( project )
{
    return [ $($(project).attributes).is-jamroot ] ;
}


# Returns a project's parent jamroot module. Returns nothing if there is no such
# module, i.e. if this is a standalone project or one of the internal Boost
# Build configuration projects.
#
rule get-jamroot-module ( project )
{
    local jamroot-location = [ attribute $(project) project-root ] ;
    if $(jamroot-location)
    {
        return [ module-name $(jamroot-location) ] ;
    }
}


# Returns the project target corresponding to the 'project-module'.
#
rule target ( project-module : allow-missing ? )
{
    if ! $(.target.$(project-module)) && ! $(allow-missing)
    {
        import errors ;
        errors.user-error Project target requested but not yet assigned for
            module '$(project-module)'. ;
    }
    return $(.target.$(project-module)) ;
}


# Defines a B2 extension project. Such extensions usually contain
# library targets and features that can be used by many people. Even though
# extensions are really projects, they can be initialized as a module would be
# with the "using" (project.project-rules.using) mechanism.
#
rule extension ( id space ? : options * : * )
{
    # The caller is a standalone module for the extension.
    local mod = [ CALLER_MODULE ] ;

    # We need to do the rest within the extension module.
    module $(mod)
    {
        import path ;

        # Find the root project.
        local root-project = [ project.current ] ;
        root-project = [ $(root-project).project-module ] ;
        while
            [ project.attribute $(root-project) parent-module ] &&
            [ project.attribute $(root-project) parent-module ] != user-config
        {
            root-project = [ project.attribute $(root-project) parent-module ] ;
        }

        # Default to creating extensions in /ext/.. project space.
        local id = $(1[1]) ;
        local space = $(1[2]) ;
        space ?= ext ;

        # Create the project data, and bring in the project rules into the
        # module.
        project.initialize $(__name__) : [ path.join [ project.attribute
            $(root-project) location ] $(space:L) $(id:L) ] ;

        # Create the project itself, i.e. the attributes.
        project /$(space:L)/$(id:L) : $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) :
            $(9) : $(10) : $(11) : $(12) : $(13) : $(14) : $(15) : $(16) : $(17)
            : $(18) : $(19) ;
        local attributes = [ project.attributes $(__name__) ] ;

        # Inherit from the root project of whomever is defining us.
        project.inherit-attributes $(__name__) : $(root-project) ;
        $(attributes).set parent-module : $(root-project) : exact ;
    }
}


rule glob-internal ( project : wildcards + : excludes * : rule-name )
{
    local location = [ $(project).get source-location ] ;

    local result ;
    local paths = [ path.$(rule-name) $(location) :
        [ sequence.transform path.make : $(wildcards) ] :
        [ sequence.transform path.make : $(excludes) ] ] ;
    if $(wildcards:D) || $(rule-name) != glob
    {
        # The paths we have found are relative to the current directory, but the
        # names specified in the sources list are assumed to be relative to the
        # source directory of the corresponding project. So, just make the names
        # absolute.
        for local p in $(paths)
        {
            # If the path is below source location, use relative path.
            # Otherwise, use full path just to avoid any ambiguities.
            local rel = [ path.relative $(p) $(location) : no-error ] ;
            if $(rel) = not-a-child
            {
                result += [ path.root $(p) [ path.pwd ] ] ;
            }
            else
            {
                result += $(rel) ;
            }
        }
    }
    else
    {
        # There were no wildcards in the directory path, so the files are all in
        # the source directory of the project. Just drop the directory, instead
        # of making paths absolute.
        result = $(paths:D="") ;
    }

    return $(result) ;
}


rule glob-path-root ( root path )
{
    return [ path.root $(path) $(root) ] ;
}

rule glob-internal-ex ( project : paths + : wildcards + : excludes * : rule-name )
{
    # Make the paths we search in absolute, if they aren't already absolute.
    # If the given paths are relative, they will be relative to the source
    # directory. So that's what we root against.
    local source-location
        = [ path.root [ $(project).get source-location ] [ path.pwd ] ] ;
    local search-paths
        = [ sequence.transform project.glob-path-root $(source-location) : $(paths) ] ;
    paths
        = [ path.$(rule-name) $(search-paths) : $(wildcards) : $(excludes) ] ;
    # The paths we have found are absolute, but the names specified in the
    # sources list are assumed to be relative to the source directory of the
    # corresponding project. Make the results relative to the source again.
    local result
        = [ sequence.transform path.relative-to $(source-location) : $(paths) ] ;

    return $(result) ;
}


# This module defines rules common to all projects.
#
module project-rules
{
    import modules ;

    rule using ( toolset-module : * )
    {
        import toolset ;

        local saved-project = [ modules.peek project : .current-project ] ;

        # Temporarily change the search path so the module referred to by
        # 'using' can be placed in the same directory as Jamfile. User will
        # expect the module to be found even though the directory is not in
        # BOOST_BUILD_PATH.
        local x = [ modules.peek : BOOST_BUILD_PATH ] ;
        local caller = [ CALLER_MODULE ] ;
        local caller-location = [ modules.binding $(caller) ] ;
        modules.poke : BOOST_BUILD_PATH : $(caller-location:D) $(x) ;
        toolset.using $(1) : $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) :
            $(9) : $(10) : $(11) : $(12) : $(13) : $(14) : $(15) : $(16) : $(17)
            : $(18) : $(19) ;
        modules.poke : BOOST_BUILD_PATH : $(x) ;

        # The above might have clobbered .current-project in case it caused a
        # new project instance to be created (which would then automatically
        # get set as the 'current' project). Restore the correct value so any
        # main targets declared after this do not get mapped to the loaded
        # module's project.
        modules.poke project : .current-project : $(saved-project) ;
    }

    rule import ( * : * : * )
    {
        local caller = [ CALLER_MODULE ] ;
        local saved-project = [ modules.peek project : .current-project ] ;
        module $(caller)
        {
            modules.import $(1) : $(2) : $(3) ;
        }

        # The above might have clobbered .current-project in case it caused a
        # new project instance to be created (which would then automatically
        # get set as the 'current' project). Restore the correct value so any
        # main targets declared after this do not get mapped to the loaded
        # module's project.
        modules.poke project : .current-project : $(saved-project) ;
    }

    rule project ( id ? : options * : * )
    {
        import path ;
        import project ;

        local caller = [ CALLER_MODULE ] ;
        local attributes = [ project.attributes $(caller) ] ;
        if $(id)
        {
            $(attributes).set id : $(id) ;
        }

        local explicit-build-dir ;

        for n in 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
        {
            local option = $($(n)) ;
            if $(option)
            {
                $(attributes).set $(option[1]) : $(option[2-]) ;
            }
            if $(option[1]) = "build-dir"
            {
                explicit-build-dir = [ path.make $(option[2-]) ] ;
            }
        }

        # If '--build-dir' is specified, change the build dir for the project.
        local global-build-dir = [ modules.peek project : .global-build-dir ] ;

        if $(global-build-dir)
        {
            local location = [ $(attributes).get location ] ;
            # Project with an empty location is a 'standalone' project such as
            # user-config or qt. It has no build dir. If we try to set build dir
            # for user-config, we shall then try to inherit it, with either
            # weird or wrong consequences.
            if $(location) && $(location) = [ $(attributes).get project-root ]
            {
                # Re-read the project id, since it might have been modified a
                # bit when setting the project's id attribute, e.g. might have
                # been prefixed by a slash if it was not already.
                id = [ $(attributes).get id ] ;
                # This is Jamroot.
                if $(id)
                {
                    if $(explicit-build-dir) &&
                        [ path.is-rooted $(explicit-build-dir) ]
                    {
                        import errors ;
                        errors.user-error Absolute directory specified via
                            'build-dir' project attribute : Do not know how to
                            combine that with the --build-dir option. ;
                    }
                    # Strip the leading slash from id.
                    local rid = [ MATCH ^/(.*) : $(id) ] ;
                    local p = [ path.join $(global-build-dir) $(rid)
                        $(explicit-build-dir) ] ;

                    $(attributes).set build-dir : $(p) : exact ;
                }
            }
            else
            {
                # Not Jamroot.
                if $(explicit-build-dir)
                {
                    import errors ;
                    errors.user-error When --build-dir is specified, the
                        'build-dir' project : attribute is allowed only for
                        top-level 'project' invocations ;
                }
            }
        }
    }

    # Declare and set a project global constant. Project global constants are
    # normal variables but should not be changed. They are applied to every
    # child Jamfile.
    #
    rule constant ( name : value + )
    {
        import project ;
        local caller = [ CALLER_MODULE ] ;
        local p = [ project.target $(caller) ] ;
        $(p).add-constant $(name) : $(value) ;
    }

    # Declare and set a project global constant, whose value is a path. The path
    # is adjusted to be relative to the invocation directory. The given value
    # path is taken to be either absolute, or relative to this project root.
    #
    rule path-constant ( name : value + )
    {
        import project ;
        local caller = [ CALLER_MODULE ] ;
        local p = [ project.target $(caller) ] ;
        $(p).add-constant $(name) : $(value) : path ;
    }

    rule use-project ( id : where )
    {
        # See comment in 'load' for explanation.
        local caller = [ CALLER_MODULE ] ;
        modules.poke $(caller) : .used-projects : [ modules.peek $(caller) :
            .used-projects ] $(id) $(where) ;
    }

    rule build-project ( dir )
    {
        import project ;
        local caller = [ CALLER_MODULE ] ;
        local attributes = [ project.attributes $(caller) ] ;
        local now = [ $(attributes).get projects-to-build ] ;
        $(attributes).set projects-to-build : $(now) $(dir) ;
    }

    rule explicit ( target-names * )
    {
        import project ;
        # If 'explicit' is used in a helper rule defined in Jamroot and
        # inherited by children, then most of the time we want 'explicit' to
        # operate on the Jamfile where the helper rule is invoked.
        local t = [ project.current ] ;
        for local n in $(target-names)
        {
            $(t).mark-target-as-explicit $(n) ;
        }
    }

    rule always ( target-names * )
    {
        import project ;
        local t = [ project.current ] ;
        for local n in $(target-names)
        {
            $(t).mark-target-as-always $(n) ;
        }
    }

    rule glob ( wildcards + : excludes * )
    {
        import project ;
        return [ project.glob-internal [ project.current ] : $(wildcards) :
            $(excludes) : glob ] ;
    }

    rule glob-tree ( wildcards + : excludes * )
    {
        import project ;
        if $(wildcards:D) || $(excludes:D)
        {
            import errors ;
            errors.user-error The patterns to 'glob-tree' may not include
                directory ;
        }
        return [ project.glob-internal [ project.current ] : $(wildcards) :
            $(excludes) : glob-tree ] ;
    }

    rule glob-ex ( paths + : wildcards + : excludes * )
    {
        import project ;
        return [ project.glob-internal-ex [ project.current ]
            : $(paths) : $(wildcards) : $(excludes) : glob ] ;
    }

    rule glob-tree-ex ( paths + : wildcards + : excludes * )
    {
        import project ;
        return [ project.glob-internal-ex [ project.current ]
            : $(paths) : $(wildcards) : $(excludes) : glob-tree ] ;
    }

    # Calculates conditional requirements for multiple requirements at once.
    # This is a shorthand to reduce duplication and to keep an inline
    # declarative syntax. For example:
    #
    #   lib x : x.cpp : [ conditional <toolset>gcc <variant>debug :
    #       <define>DEBUG_EXCEPTION <define>DEBUG_TRACE ] ;
    #
    rule conditional ( condition + : requirements * )
    {
        local condition = $(condition:J=,) ;
        if [ MATCH "(:)" : $(condition) ]
        {
            return $(condition)$(requirements) ;
        }
        else
        {
            return "$(condition):$(requirements)" ;
        }
    }

    rule option ( name : value )
    {
        local m = [ CALLER_MODULE ] ;
        local cfgs = project site test user ;
        if ! $(m) in $(cfgs)-config
        {
            import errors ;
            errors.error The 'option' rule may only be used "in" Boost Build
                configuration files. ;
        }
        import option ;
        option.set $(name) : $(value) ;
    }

    # This allows one to manually import a package manager build information file.
    # The argument can be either a symbolic name of a supported package manager or
    # the a glob pattern to load a b2 jam file.
    #
    rule use-packages ( name-or-glob-pattern ? )
    {
        local m = [ CALLER_MODULE ] ;
        local glob-pattern = $(name-or-glob-pattern) ;
        local glob-for-name = [ modules.peek project : PACKAGE_MANAGER_BUILD_INFO($(name-or-glob-pattern:U)) ] ;
        if $(glob-for-name)
        {
            glob-pattern = $(glob-for-name) ;
        }
        modules.call-in $(m) : constant PACKAGE_MANAGER_BUILD_INFO : $(glob-pattern) ;
        IMPORT project : load-package-manager-build-info : $(m) : project.load-package-manager-build-info ;
        modules.call-in $(m) : project.load-package-manager-build-info ;
    }
}
