From 04be612dead00c36c8c6ff748c252e8e5d3b1e5c Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 24 Oct 2019 11:49:44 +0200
Subject: Allow multiple forwarded configurations

The new constraint is that such configurations should not have any common
packages (a package cannot be forwarded to multiple configurations).
---
 bdep/config.cli |  7 +++++--
 bdep/config.cxx | 38 ++++++++++++++++++++++++--------------
 bdep/init.cxx   | 27 +++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 16 deletions(-)

diff --git a/bdep/config.cli b/bdep/config.cli
index 3ad2bb9..818f600 100644
--- a/bdep/config.cli
+++ b/bdep/config.cli
@@ -90,8 +90,11 @@ namespace bdep
          configuration is already designated as forwarded. When a project is
          initialized in a forwarded build configuration, its source directory
          is configured to forward to this configuration (see \l{b(1)} for
-         details on forwarded configurations). To forward to a non-default
-         configuration use the \cb{--forward} option.
+         details on forwarded configurations). To designate a non-default
+         configuration as forwarded use the \cb{--forward} option. Note also
+         that it is possible to have multiple forwarded configurations,
+         however, any given package within a project can only be initialized
+         in one such configuration.
 
          Unless the \cb{--no-auto-sync} option is specified, an added or
          created build configuration will be automatically synchronized on
diff --git a/bdep/config.cxx b/bdep/config.cxx
index d8cf33a..f08bd41 100644
--- a/bdep/config.cxx
+++ b/bdep/config.cxx
@@ -187,20 +187,14 @@ namespace bdep
             info << "use 'bdep config set --no-default' to clear";
       }
 
-      // By default the default configuration is forwarded unless another
-      // is already forwarded.
+      // By default the default configuration is forwarded unless another is
+      // already forwarded.
       //
       if (ao.forward () || ao.no_forward ())
         fwd = ao.forward ()  && !ao.no_forward ();
 
       if (!fwd)
         fwd = *def && db.query_one<configuration> (query::forward) == nullptr;
-      else if (*fwd)
-      {
-        if (auto p = db.query_one<configuration> (query::forward))
-          fail << "configuration " << *p << " is already forwarded" <<
-            info << "use 'bdep config set --no-forward' to clear";
-      }
     }
 
     shared_ptr<configuration> r (
@@ -701,23 +695,39 @@ namespace bdep
               info << "while updating configuration " << *c;
         }
 
-        c->default_   = *d;
+        c->default_ = *d;
       }
 
       if (f)
       {
         if (*f && !c->forward)
         {
-          if (auto p = db.query_one<configuration> (query::forward))
-            fail << "configuration " << *p << " is already forwarded" <<
-              info << "while updating configuration " << *c;
+          // Make sure there are no other forwarded configurations with the
+          // same package as us.
+          //
+          for (const shared_ptr<configuration>& o:
+                 pointer_result (db.query<configuration> (query::forward)))
+          {
+            auto i (find_first_of (
+                      o->packages.begin (), o->packages.end (),
+                      c->packages.begin (), c->packages.end (),
+                      [] (const package_state& x, const package_state& y)
+                      {
+                        return x.name == y.name;
+                      }));
+
+            if (i != o->packages.end ())
+              fail << "configuration " << *o << " is also forwarded and "
+                   << "also has package " << i->name << " initialized" <<
+                info << "while updating configuration " << *c;
+          }
         }
 
-        c->forward    = *f;
+        c->forward = *f;
       }
 
       if (s)
-        c->auto_sync  = *s;
+        c->auto_sync = *s;
 
       db.update (c);
     }
diff --git a/bdep/init.cxx b/bdep/init.cxx
index 04afd3c..1e794f8 100644
--- a/bdep/init.cxx
+++ b/bdep/init.cxx
@@ -94,6 +94,33 @@ namespace bdep
           continue;
         }
 
+        // If this configuration is forwarded, verify there is no other
+        // forwarded configuration that also has this package.
+        //
+        if (c->forward)
+        {
+          using query = bdep::query<configuration>;
+
+          for (const shared_ptr<configuration>& o:
+                 pointer_result (db.query<configuration> (query::forward)))
+          {
+            if (o == c)
+              continue;
+
+            if (find_if (o->packages.begin (),
+                         o->packages.end (),
+                         [&p] (const package_state& s)
+                         {
+                           return p.name == s.name;
+                         }) != o->packages.end ())
+            {
+              fail << "forwarded configuration " << *o << " also has package "
+                   << p.name << " initialized" <<
+                info << "while initializing in forwarded configuration " << *c;
+            }
+          }
+        }
+
         // If we are initializing multiple packages, print their names.
         //
         if (verb && pkgs.size () > 1)
-- 
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