Handle missing export directive in export stub

If none were executed, then we assume the requested target is not exported.

2 files changed, 14 insertions, 2 deletions

diff --git a/build2/file.cxx b/build2/file.cxx
index 728de64..05527f3 100644
--- a/build2/file.cxx
+++ b/build2/file.cxx
@@ -1370,7 +1370,7 @@ namespace build2
       value& v (ts.assign (var_import_target));
 
       if (!target.empty ()) // Otherwise leave NULL.
-        v = move (target);
+        v = target; // Can't move (need for diagnostics below).
     }
 
     // Load the export stub. Note that it is loaded in the context
@@ -1391,7 +1391,16 @@ namespace build2
       // name?
       //
       parser p;
-      return p.parse_export_stub (ifs, es, iroot, ts);
+      names v (p.parse_export_stub (ifs, es, iroot, ts));
+
+      // If there were no export directive executed in an export stub, assume
+      // the target is not exported.
+      //
+      if (v.empty () && !target.empty ())
+        fail (loc) << "target " << target << " is not exported by project "
+                   << proj;
+
+      return v;
     }
     catch (const io_error& e)
     {
diff --git a/build2/parser.cxx b/build2/parser.cxx
index 6d025a6..1dd49b6 100644
--- a/build2/parser.cxx
+++ b/build2/parser.cxx
@@ -1509,6 +1509,9 @@ namespace build2
 
     export_value_ = move (rhs).as<names> ();
 
+    if (export_value_.empty ())
+      fail (l) << "empty value in export";
+
     if (tt == type::newline)
       next (t, tt);
     else if (tt != type::eos)