Consistently install prerequisites from any scope by default

It is also now possible to adjust this behavior with global
config.install.scope override. Valid values for this variable
are:

  project -- only from project
  strong  -- from strong amalgamation
  weak    -- from weak amalgamation
  global  -- from all projects (default)

5 files changed, 111 insertions, 24 deletions

diff --git a/libbuild2/install/init.cxx b/libbuild2/install/init.cxx
index 677ee07..5b5d1e2 100644
--- a/libbuild2/install/init.cxx
+++ b/libbuild2/install/init.cxx
@@ -392,6 +392,37 @@ namespace build2
 
       // Configuration.
       //
+
+      // config.install.scope
+      //
+      // We do not install prerequisites (for example, shared libraries) of
+      // targets (for example, executables) that belong to projects outside of
+      // this scope. Valid values are:
+      //
+      //   project -- project scope
+      //   strong  -- strong amalgamation
+      //   weak    -- weak amalgamation
+      //   global  -- all projects (default)
+      //
+      // Note: can only be specified as a global override.
+      //
+      {
+        auto& v (vp.insert<string> ("config.install.scope"));
+
+        // If specified, verify it is a global override.
+        //
+        if (lookup l = rs[v])
+        {
+          if (!l.belongs (rs.global_scope ()))
+            fail << "config.install.scope must be a global override" <<
+              info << "specify !config.install.scope=...";
+        }
+
+        config::unsave_variable (rs, v);
+      }
+
+      // Installation directories.
+      //
       // Note that we don't use any defaults for root -- the location
       // must be explicitly specified or the installer will complain
       // if and when we try to install.
diff --git a/libbuild2/install/rule.cxx b/libbuild2/install/rule.cxx
index 388400a..5092d42 100644
--- a/libbuild2/install/rule.cxx
+++ b/libbuild2/install/rule.cxx
@@ -54,16 +54,19 @@ namespace build2
     }
 
     const target* alias_rule::
-    filter (action a, const target& t, prerequisite_iterator& i) const
+    filter (const scope* is,
+            action a, const target& t, prerequisite_iterator& i) const
     {
       assert (i->member == nullptr);
-      return filter (a, t, i->prerequisite);
+      return filter (is, a, t, i->prerequisite);
     }
 
     const target* alias_rule::
-    filter (action, const target& t, const prerequisite& p) const
+    filter (const scope* is,
+            action, const target& t, const prerequisite& p) const
     {
-      return &search (t, p);
+      const target& pt (search (t, p));
+      return is == nullptr || pt.in (*is) ? &pt : nullptr;
     }
 
     recipe alias_rule::
@@ -75,8 +78,9 @@ namespace build2
       //
       // @@ Shouldn't we do match in parallel (here and below)?
       //
-      auto& pts (t.prerequisite_targets[a]);
+      optional<const scope*> is; // Installation scope (resolve lazily).
 
+      auto& pts (t.prerequisite_targets[a]);
       auto pms (group_prerequisite_members (a, t, members_mode::never));
       for (auto i (pms.begin ()), e (pms.end ()); i != e; ++i)
       {
@@ -100,7 +104,10 @@ namespace build2
         // Note: we assume that if the filter enters the group, then it
         // iterates over all its members.
         //
-        const target* pt (filter (a, t, i));
+        if (!is)
+          is = install_scope (t);
+
+        const target* pt (filter (*is, a, t, i));
         if (pt == nullptr)
         {
           l5 ([&]{trace << "ignoring " << p << " (filtered out)";});
@@ -217,7 +224,6 @@ namespace build2
       if (gv.members != nullptr)
       {
         auto& pts (t.prerequisite_targets[a]);
-
         for (size_t i (0); i != gv.count; ++i)
         {
           const target* m (gv.members[i]);
@@ -271,17 +277,19 @@ namespace build2
     }
 
     const target* file_rule::
-    filter (action a, const target& t, prerequisite_iterator& i) const
+    filter (const scope* is,
+            action a, const target& t, prerequisite_iterator& i) const
     {
       assert (i->member == nullptr);
-      return filter (a, t, i->prerequisite);
+      return filter (is, a, t, i->prerequisite);
     }
 
     const target* file_rule::
-    filter (action, const target& t, const prerequisite& p) const
+    filter (const scope* is,
+            action, const target& t, const prerequisite& p) const
     {
       const target& pt (search (t, p));
-      return pt.in (t.root_scope ()) ? &pt : nullptr;
+      return is == nullptr || pt.in (*is) ? &pt : nullptr;
     }
 
     recipe file_rule::
@@ -314,8 +322,9 @@ namespace build2
       if (a.operation () == update_id)
         unchanged = match_inner (a, t, unmatch::unchanged).first;
 
-      auto& pts (t.prerequisite_targets[a]);
+      optional<const scope*> is; // Installation scope (resolve lazily).
 
+      auto& pts (t.prerequisite_targets[a]);
       auto pms (group_prerequisite_members (a, t, members_mode::never));
       for (auto i (pms.begin ()), e (pms.end ()); i != e; ++i)
       {
@@ -339,7 +348,11 @@ namespace build2
         // Note: we assume that if the filter enters the group, then it
         // iterates over all its members.
         //
-        const target* pt (filter (a, t, i));
+        if (!is)
+          is = install_scope (t);
+
+        const target* pt (filter (*is, a, t, i));
+
         if (pt == nullptr)
         {
           l5 ([&]{trace << "ignoring " << p << " (filtered out)";});
@@ -541,7 +554,9 @@ namespace build2
         {
           if (fail_unknown)
             fail << "unknown installation directory name '" << sn << "'" <<
-              info << "did you forget to specify config." << var << "?";
+              info << "did you forget to specify config." << var << "?" <<
+              info << "specify !config." << var << "=... if installing "
+                   << "from multiple projects";
 
           return rs; // Empty.
         }
diff --git a/libbuild2/install/rule.hxx b/libbuild2/install/rule.hxx
index 73f2486..ce60bb9 100644
--- a/libbuild2/install/rule.hxx
+++ b/libbuild2/install/rule.hxx
@@ -25,7 +25,9 @@ namespace build2
       match (action, target&, const string&) const override;
 
       // Return NULL if this prerequisite should be ignored and pointer to its
-      // target otherwise. The default implementation allows all prerequsites.
+      // target otherwise. The default implementation ignores prerequsites
+      // that are outside of the installation scope (see install_scope() for
+      // details).
       //
       // The prerequisite is passed as an iterator allowing the filter to
       // "see" inside groups.
@@ -34,10 +36,11 @@ namespace build2
         prerequisite_members_range<group_prerequisites>::iterator;
 
       virtual const target*
-      filter (action, const target&, prerequisite_iterator&) const;
+      filter (const scope*,
+              action, const target&, prerequisite_iterator&) const;
 
       virtual const target*
-      filter (action, const target&, const prerequisite&) const;
+      filter (const scope*, action, const target&, const prerequisite&) const;
 
       virtual recipe
       apply (action, target&) const override;
@@ -103,11 +106,8 @@ namespace build2
 
       // Return NULL if this prerequisite should be ignored and pointer to its
       // target otherwise. The default implementation ignores prerequsites
-      // that are outside of this target's project.
-      //
-      // @@ I wonder why we do weak amalgamation for alias but project for
-      //    file? And then override this for prerequisite libraries/modules
-      //    in cc::install_rule and bash::install_rule...
+      // that are outside of the installation scope (see install_scope() for
+      // details).
       //
       // The prerequisite is passed as an iterator allowing the filter to
       // "see" inside groups.
@@ -116,10 +116,11 @@ namespace build2
         prerequisite_members_range<group_prerequisites>::iterator;
 
       virtual const target*
-      filter (action, const target&, prerequisite_iterator&) const;
+      filter (const scope*,
+              action, const target&, prerequisite_iterator&) const;
 
       virtual const target*
-      filter (action, const target&, const prerequisite&) const;
+      filter (const scope*, action, const target&, const prerequisite&) const;
 
       virtual recipe
       apply (action, target&) const override;
diff --git a/libbuild2/install/utility.cxx b/libbuild2/install/utility.cxx
new file mode 100644
index 0000000..12215f8
--- /dev/null
+++ b/libbuild2/install/utility.cxx
@@ -0,0 +1,32 @@
+// file      : libbuild2/install/utility.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/install/utility.hxx>
+
+namespace build2
+{
+  namespace install
+  {
+    const scope*
+    install_scope (const target& t)
+    {
+      context& ctx (t.ctx);
+
+      const variable& var (*ctx.var_pool.find ("config.install.scope"));
+
+      if (const string* s = cast_null<string> (ctx.global_scope[var]))
+      {
+        if (*s == "project")
+          return &t.root_scope ();
+        else if (*s == "strong")
+          return &t.strong_scope ();
+        else if (*s == "weak")
+          return &t.weak_scope ();
+        else if (*s != "global")
+          fail << "invalid " << var << " value '" << *s << "'";
+      }
+
+      return nullptr;
+    }
+  }
+}
diff --git a/libbuild2/install/utility.hxx b/libbuild2/install/utility.hxx
index 2c0ca56..cc5cd53 100644
--- a/libbuild2/install/utility.hxx
+++ b/libbuild2/install/utility.hxx
@@ -56,6 +56,14 @@ namespace build2
       return install_mode (s, T::static_type, move (m));
     }
 
+    // Return the "installation scope". We do not install prerequisites (for
+    // example, shared libraries) of targets (for example, executables) that
+    // belong to projects outside of this scope. If it's NULL, install
+    // prerequisites from all projects. See also config.install.scope.
+    //
+    LIBBUILD2_SYMEXPORT const scope*
+    install_scope (const target&);
+
     // Resolve relative installation directory path (e.g., include/libfoo) to
     // its absolute directory path (e.g., /usr/include/libfoo). If the
     // resolution encountered an unknown directory, issue diagnostics and fail