Add support for modular build structure. (#274)

* Make the library modular usable.

* Switch to library requirements instead of source. As source puts extra source in install targets.

* Add missing import-search for cconfig/predef checks.

* Add requires-b2 check to top-level build file.

* Bump B2 require to 5.2

* Change all <source> references to <library>.

* Update copyright dates.

* Move inter-lib dependencies to a project variable and into the build targets.

* Update build deps.

build.jam

@@ -0,0 +1,34 @@
+# Copyright René Ferdinand Rivera Morell 2023-2024
+# 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)
+
+require-b2 5.2 ;
+
+constant boost_dependencies :
+    /boost/config//boost_config
+    /boost/container_hash//boost_container_hash
+    /boost/core//boost_core
+    /boost/function_types//boost_function_types
+    /boost/functional//boost_functional
+    /boost/mpl//boost_mpl
+    /boost/preprocessor//boost_preprocessor
+    /boost/static_assert//boost_static_assert
+    /boost/tuple//boost_tuple
+    /boost/type_traits//boost_type_traits
+    /boost/typeof//boost_typeof
+    /boost/utility//boost_utility ;
+
+project /boost/fusion
+    : common-requirements
+        <include>include
+    ;
+
+explicit
+    [ alias boost_fusion : : : : <library>$(boost_dependencies) ]
+    [ alias all : boost_fusion test ]
+    ;
+
+call-if : boost-library fusion
+    ;
+

test/Jamfile

@@ -10,7 +10,8 @@
 # bring in rules for testing
 import testing ;
 import os ;
-import ../../config/checks/config : requires ;
+import-search /boost/config/checks ;
+import config : requires ;
 
 if [ os.environ CI ]
 {
@@ -19,14 +20,15 @@ if [ os.environ CI ]
 
 project
     : requirements
+        <library>/boost/fusion//boost_fusion
         $(CI_DEFINES)
     ;
 
 {
     test-suite fusion :
 
-    [ run algorithm/all.cpp ]
-    [ run algorithm/any.cpp ]
+    [ run algorithm/all.cpp : : : <library>/boost/lambda//boost_lambda ]
+    [ run algorithm/any.cpp : : : <library>/boost/lambda//boost_lambda ]
     [ run algorithm/clear.cpp ]
     [ run algorithm/copy.cpp ]
     [ run algorithm/count.cpp ]
@@ -44,8 +46,8 @@ project
     [ run algorithm/iter_fold.cpp ]
     [ run algorithm/move.cpp : :
         : [ requires cxx11_rvalue_references ] ]
-    [ run algorithm/none.cpp ]
-    [ run algorithm/pop_back.cpp ]
+    [ run algorithm/none.cpp : : : <library>/boost/lambda//boost_lambda ]
+    [ run algorithm/pop_back.cpp : : : <library>/boost/array//boost_array ]
     [ run algorithm/pop_front.cpp ]
     [ run algorithm/push_back.cpp ]
     [ run algorithm/push_front.cpp ]
@@ -76,7 +78,7 @@ project
     [ run sequence/as_vector.cpp ]
     [ run sequence/boost_tuple.cpp ]
     [ run sequence/boost_tuple_iterator.cpp ]
-    [ run sequence/cons.cpp ]
+    [ run sequence/cons.cpp : : : <library>/boost/lambda//boost_lambda ]
     [ run sequence/convert_boost_tuple.cpp ]
     [ run sequence/convert_deque.cpp ]
     [ run sequence/convert_list.cpp ]
@@ -134,7 +136,7 @@ project
     [ run sequence/set.cpp ]
     [ run sequence/single_view.cpp ]
     [ run sequence/std_pair.cpp ]
-    [ run sequence/boost_array.cpp ]
+    [ run sequence/boost_array.cpp : : : <library>/boost/array//boost_array ]
     [ run sequence/array.cpp ]
     [ run sequence/std_array.cpp : :
         : [ requires cxx11_hdr_array ] ]
@@ -241,7 +243,7 @@ project
     [ compile sequence/github-159.cpp ]
     [ run sequence/github-176.cpp ]
 
-    [ compile sequence/size.cpp ]
+    [ compile sequence/size.cpp : <library>/boost/array//boost_array ]
 
     [ run functional/fused.cpp ]
     [ run functional/fused_function_object.cpp ]