Implement optional module loading

The syntax is:

using? cli

Now each module use results in two bool variables: <module>.loaded and
<module>.configured.

Also implement variable visibility (the above two variables are limited
to project).

3 files changed, 20 insertions, 15 deletions

diff --git a/build/dist/module b/build/dist/module
index 9fad86f..20082ec 100644
--- a/build/dist/module
+++ b/build/dist/module
@@ -6,15 +6,17 @@
 #define BUILD_DIST_MODULE
 
 #include <build/types>
+#include <build/utility>
+
 #include <build/module>
 
 namespace build
 {
   namespace dist
   {
-    extern "C" void
+    extern "C" bool
     dist_init (
-      scope&, scope&, const location&, std::unique_ptr<module>&, bool);
+      scope&, scope&, const location&, unique_ptr<module>&, bool, bool);
   }
 }
 
diff --git a/build/dist/module.cxx b/build/dist/module.cxx
index 9bd058a..a624c20 100644
--- a/build/dist/module.cxx
+++ b/build/dist/module.cxx
@@ -22,12 +22,13 @@ namespace build
   {
     static rule rule_;
 
-    extern "C" void
+    extern "C" bool
     dist_init (scope& r,
                scope& b,
                const location& l,
-               std::unique_ptr<module>&,
-               bool first)
+               unique_ptr<module>&,
+               bool first,
+               bool)
     {
       tracer trace ("dist::init");
 
@@ -37,7 +38,7 @@ namespace build
       if (!first)
       {
         warn (l) << "multiple dist module initializations";
-        return;
+        return true;
       }
 
       const dir_path& out_root (r.out_path ());
@@ -58,20 +59,20 @@ namespace build
       //
       if (first)
       {
-        variable_pool.find ("dist", bool_type);
+        var_pool.find ("dist", bool_type);
 
-        variable_pool.find ("dist.package", string_type);
+        var_pool.find ("dist.package", string_type);
 
-        variable_pool.find ("dist.root", dir_path_type);
-        variable_pool.find ("config.dist.root", dir_path_type);
+        var_pool.find ("dist.root", dir_path_type);
+        var_pool.find ("config.dist.root", dir_path_type);
 
         //@@ VAR type
         //
-        variable_pool.find ("dist.cmd", string_type);
-        variable_pool.find ("config.dist.cmd", string_type);
+        var_pool.find ("dist.cmd", string_type);
+        var_pool.find ("config.dist.cmd", string_type);
 
-        variable_pool.find ("dist.archives", strings_type);
-        variable_pool.find ("config.dist.archives", strings_type);
+        var_pool.find ("dist.archives", strings_type);
+        var_pool.find ("config.dist.archives", strings_type);
       }
 
       // Configuration.
@@ -127,6 +128,8 @@ namespace build
             v = cv;
         }
       }
+
+      return true;
     }
   }
 }
diff --git a/build/dist/operation.cxx b/build/dist/operation.cxx
index 2a84894..0069432 100644
--- a/build/dist/operation.cxx
+++ b/build/dist/operation.cxx
@@ -199,7 +199,7 @@ namespace build
       // entered.
       //
       action_targets files;
-      const variable& dist_var (variable_pool.find ("dist"));
+      const variable& dist_var (var_pool.find ("dist"));
 
       for (const auto& pt: targets)
       {