Add AtMostOneDepSpec

17 files changed, 198 insertions, 0 deletions

diff --git a/paludis/dep_spec-fwd.hh b/paludis/dep_spec-fwd.hh
index 51128b675..7b1bfeaaf 100644
--- a/paludis/dep_spec-fwd.hh
+++ b/paludis/dep_spec-fwd.hh
@@ -41,6 +41,7 @@ namespace paludis
     class AllDepSpec;
     class ExactlyOneDepSpec;
     class AnyDepSpec;
+    class AtMostOneDepSpec;
     class ConditionalDepSpec;
     class BlockDepSpec;
     class StringDepSpec;
diff --git a/paludis/dep_spec.cc b/paludis/dep_spec.cc
index f6acb350b..29a31422b 100644
--- a/paludis/dep_spec.cc
+++ b/paludis/dep_spec.cc
@@ -110,6 +110,18 @@ ExactlyOneDepSpec::clone() const
     return result;
 }
 
+AtMostOneDepSpec::AtMostOneDepSpec()
+{
+}
+
+std::shared_ptr<DepSpec>
+AtMostOneDepSpec::clone() const
+{
+    std::shared_ptr<AtMostOneDepSpec> result(std::make_shared<AtMostOneDepSpec>());
+    result->set_annotations(maybe_annotations());
+    return result;
+}
+
 namespace paludis
 {
     template <>
diff --git a/paludis/dep_spec.hh b/paludis/dep_spec.hh
index 9f8254345..3fc076af1 100644
--- a/paludis/dep_spec.hh
+++ b/paludis/dep_spec.hh
@@ -170,6 +170,27 @@ namespace paludis
     };
 
     /**
+     * Represents a ?? ( first second third ) group of requirements.
+     *
+     * \ingroup g_dep_spec
+     * \nosubgrouping
+     * \since 0.56
+     */
+    class PALUDIS_VISIBLE AtMostOneDepSpec :
+        public DepSpec
+    {
+        public:
+            ///\name Basic operations
+            ///\{
+
+            AtMostOneDepSpec();
+
+            ///\}
+
+            virtual std::shared_ptr<DepSpec> clone() const PALUDIS_ATTRIBUTE((warn_unused_result));
+    };
+
+    /**
      * Represents a dependency spec whose children should only be considered
      * upon a certain condition (for example, a use dependency block).
      *
diff --git a/paludis/repositories/e/required_use_verifier.cc b/paludis/repositories/e/required_use_verifier.cc
index 593881cd3..6c55c742d 100644
--- a/paludis/repositories/e/required_use_verifier.cc
+++ b/paludis/repositories/e/required_use_verifier.cc
@@ -176,6 +176,25 @@ RequiredUseVerifier::visit(const RequiredUseSpecTree::NodeType<ExactlyOneDepSpec
 }
 
 void
+RequiredUseVerifier::visit(const RequiredUseSpecTree::NodeType<AtMostOneDepSpec>::Type & node)
+{
+    _imp->stack.push_front(Met{0, false});
+    std::for_each(indirect_iterator(node.begin()), indirect_iterator(node.end()), accept_visitor(*this));
+
+    Met met(*_imp->stack.begin());
+    _imp->stack.pop_front();
+
+    if (met.number_met <= 1)
+        ++_imp->stack.begin()->number_met;
+    else if (met.number_met > 1)
+        _imp->stack.begin()->any_unmet = true;
+    else if (met.any_unmet)
+        _imp->stack.begin()->any_unmet = true;
+    else
+        ++_imp->stack.begin()->number_met;
+}
+
+void
 RequiredUseVerifier::visit(const RequiredUseSpecTree::NodeType<ConditionalDepSpec>::Type & node)
 {
     if (! node.spec()->condition_met(_imp->env, _imp->id))
diff --git a/paludis/repositories/e/required_use_verifier.hh b/paludis/repositories/e/required_use_verifier.hh
index a193c38d1..7b6689635 100644
--- a/paludis/repositories/e/required_use_verifier.hh
+++ b/paludis/repositories/e/required_use_verifier.hh
@@ -51,6 +51,7 @@ namespace paludis
                 void visit(const RequiredUseSpecTree::NodeType<AllDepSpec>::Type & node);
                 void visit(const RequiredUseSpecTree::NodeType<AnyDepSpec>::Type & node);
                 void visit(const RequiredUseSpecTree::NodeType<ExactlyOneDepSpec>::Type & node);
+                void visit(const RequiredUseSpecTree::NodeType<AtMostOneDepSpec>::Type & node);
                 void visit(const RequiredUseSpecTree::NodeType<ConditionalDepSpec>::Type & node);
         };
     }
diff --git a/paludis/repositories/e/spec_tree_pretty_printer.cc b/paludis/repositories/e/spec_tree_pretty_printer.cc
index da9996a59..d0437c270 100644
--- a/paludis/repositories/e/spec_tree_pretty_printer.cc
+++ b/paludis/repositories/e/spec_tree_pretty_printer.cc
@@ -139,6 +139,10 @@ namespace
         {
         }
 
+        void visit(const GenericSpecTree::NodeType<AtMostOneDepSpec>::Type &)
+        {
+        }
+
         void visit(const GenericSpecTree::NodeType<AnyDepSpec>::Type &)
         {
         }
@@ -275,6 +279,42 @@ SpecTreePrettyPrinter::visit(const GenericSpecTree::NodeType<ExactlyOneDepSpec>:
 }
 
 void
+SpecTreePrettyPrinter::visit(const GenericSpecTree::NodeType<AtMostOneDepSpec>::Type & node)
+{
+    Save<bool> old_outer(&_imp->outer_block, false);
+    Save<bool> old_needs_parens(&_imp->all_needs_parens, true);
+
+    if (_imp->use_newlines)
+        _imp->s << _imp->pretty_printer.indentify(_imp->indent);
+    else if (_imp->need_space)
+        _imp->s << " ";
+    _imp->s << "?? (";
+    if (_imp->use_newlines)
+        _imp->s << _imp->pretty_printer.newline();
+    else
+        _imp->need_space = true;
+
+    {
+        Save<unsigned> old_indent(&_imp->indent, _imp->indent + 1);
+        Save<bool> extra_label_indent(&_imp->extra_label_indent, false);
+        std::for_each(indirect_iterator(node.begin()), indirect_iterator(node.end()), accept_visitor(*this));
+    }
+
+    if (_imp->use_newlines)
+        _imp->s << _imp->pretty_printer.indentify(_imp->indent);
+    else if (_imp->need_space)
+        _imp->s << " ";
+    _imp->s << ")";
+
+    do_annotations(*node.spec());
+
+    if (_imp->use_newlines)
+        _imp->s << _imp->pretty_printer.newline();
+    else
+        _imp->need_space = true;
+}
+
+void
 SpecTreePrettyPrinter::visit(const GenericSpecTree::NodeType<ConditionalDepSpec>::Type & node)
 {
     Save<bool> old_outer(&_imp->outer_block, false);
diff --git a/paludis/repositories/e/spec_tree_pretty_printer.hh b/paludis/repositories/e/spec_tree_pretty_printer.hh
index 373a7affb..5451ef119 100644
--- a/paludis/repositories/e/spec_tree_pretty_printer.hh
+++ b/paludis/repositories/e/spec_tree_pretty_printer.hh
@@ -53,6 +53,7 @@ namespace paludis
                 void visit(const GenericSpecTree::NodeType<AllDepSpec>::Type & node);
                 void visit(const GenericSpecTree::NodeType<AnyDepSpec>::Type & node);
                 void visit(const GenericSpecTree::NodeType<ExactlyOneDepSpec>::Type & node);
+                void visit(const GenericSpecTree::NodeType<AtMostOneDepSpec>::Type & node);
                 void visit(const GenericSpecTree::NodeType<ConditionalDepSpec>::Type & node);
                 void visit(const GenericSpecTree::NodeType<PackageDepSpec>::Type & node);
                 void visit(const GenericSpecTree::NodeType<BlockDepSpec>::Type & node);
diff --git a/paludis/spec_tree-fwd.hh b/paludis/spec_tree-fwd.hh
index fb4bcf9a0..831cf4e78 100644
--- a/paludis/spec_tree-fwd.hh
+++ b/paludis/spec_tree-fwd.hh
@@ -84,6 +84,7 @@ namespace paludis
             SpecTreeInnerNodeType<AllDepSpec>,
             SpecTreeInnerNodeType<AnyDepSpec>,
             SpecTreeInnerNodeType<ExactlyOneDepSpec>,
+            SpecTreeInnerNodeType<AtMostOneDepSpec>,
             SpecTreeInnerNodeType<ConditionalDepSpec>
         >::Type, AllDepSpec> GenericSpecTree;
 
@@ -112,6 +113,7 @@ namespace paludis
             SpecTreeInnerNodeType<AllDepSpec>,
             SpecTreeInnerNodeType<AnyDepSpec>,
             SpecTreeInnerNodeType<ExactlyOneDepSpec>,
+            SpecTreeInnerNodeType<AtMostOneDepSpec>,
             SpecTreeInnerNodeType<ConditionalDepSpec>
         >::Type, AllDepSpec> RequiredUseSpecTree;
 
diff --git a/paludis/spec_tree.cc b/paludis/spec_tree.cc
index c67fbf801..0adb27f8d 100644
--- a/paludis/spec_tree.cc
+++ b/paludis/spec_tree.cc
@@ -192,6 +192,7 @@ namespace paludis
             SpecTreeInnerNodeType<AllDepSpec>,
             SpecTreeInnerNodeType<AnyDepSpec>,
             SpecTreeInnerNodeType<ExactlyOneDepSpec>,
+            SpecTreeInnerNodeType<AtMostOneDepSpec>,
             SpecTreeInnerNodeType<ConditionalDepSpec>
         >::Type, AllDepSpec>;
 
@@ -233,6 +234,7 @@ namespace paludis
             SpecTreeInnerNodeType<AllDepSpec>,
             SpecTreeInnerNodeType<AnyDepSpec>,
             SpecTreeInnerNodeType<ExactlyOneDepSpec>,
+            SpecTreeInnerNodeType<AtMostOneDepSpec>,
             SpecTreeInnerNodeType<ConditionalDepSpec>
         >::Type, AllDepSpec>;
 
@@ -287,6 +289,7 @@ namespace paludis
         template class PALUDIS_VISIBLE InnerNode<GenericSpecTree, AllDepSpec>;
         template class PALUDIS_VISIBLE InnerNode<GenericSpecTree, AnyDepSpec>;
         template class PALUDIS_VISIBLE InnerNode<GenericSpecTree, ExactlyOneDepSpec>;
+        template class PALUDIS_VISIBLE InnerNode<GenericSpecTree, AtMostOneDepSpec>;
         template class PALUDIS_VISIBLE InnerNode<GenericSpecTree, ConditionalDepSpec>;
     }
 }
@@ -435,6 +438,11 @@ template const std::shared_ptr<RequiredUseSpecTree::NodeType<ExactlyOneDepSpec>:
 template const std::shared_ptr<RequiredUseSpecTree::NodeType<ExactlyOneDepSpec>::Type>
     BasicInnerNode<RequiredUseSpecTree>::append<ExactlyOneDepSpec>(const std::shared_ptr<ExactlyOneDepSpec> &);
 
+template const std::shared_ptr<RequiredUseSpecTree::NodeType<AtMostOneDepSpec>::Type>
+    BasicInnerNode<RequiredUseSpecTree>::append<AtMostOneDepSpec>(const std::shared_ptr<const AtMostOneDepSpec> &);
+template const std::shared_ptr<RequiredUseSpecTree::NodeType<AtMostOneDepSpec>::Type>
+    BasicInnerNode<RequiredUseSpecTree>::append<AtMostOneDepSpec>(const std::shared_ptr<AtMostOneDepSpec> &);
+
 template const std::shared_ptr<RequiredUseSpecTree::NodeType<ConditionalDepSpec>::Type>
     BasicInnerNode<RequiredUseSpecTree>::append<ConditionalDepSpec>(const std::shared_ptr<const ConditionalDepSpec> &);
 template const std::shared_ptr<RequiredUseSpecTree::NodeType<ConditionalDepSpec>::Type>
@@ -452,6 +460,7 @@ namespace paludis
         template class PALUDIS_VISIBLE InnerNode<RequiredUseSpecTree, AllDepSpec>;
         template class PALUDIS_VISIBLE InnerNode<RequiredUseSpecTree, AnyDepSpec>;
         template class PALUDIS_VISIBLE InnerNode<RequiredUseSpecTree, ExactlyOneDepSpec>;
+        template class PALUDIS_VISIBLE InnerNode<RequiredUseSpecTree, AtMostOneDepSpec>;
         template class PALUDIS_VISIBLE InnerNode<RequiredUseSpecTree, ConditionalDepSpec>;
     }
 }
@@ -615,6 +624,7 @@ template LeafNode<PlainTextSpecTree, PlainTextLabelDepSpec>::operator LeafNode<G
 template InnerNode<RequiredUseSpecTree, AllDepSpec>::operator InnerNode<GenericSpecTree, AllDepSpec> () const;
 template InnerNode<RequiredUseSpecTree, AnyDepSpec>::operator InnerNode<GenericSpecTree, AnyDepSpec> () const;
 template InnerNode<RequiredUseSpecTree, ExactlyOneDepSpec>::operator InnerNode<GenericSpecTree, ExactlyOneDepSpec> () const;
+template InnerNode<RequiredUseSpecTree, AtMostOneDepSpec>::operator InnerNode<GenericSpecTree, AtMostOneDepSpec> () const;
 template InnerNode<RequiredUseSpecTree, ConditionalDepSpec>::operator InnerNode<GenericSpecTree, ConditionalDepSpec> () const;
 template LeafNode<RequiredUseSpecTree, PlainTextDepSpec>::operator LeafNode<GenericSpecTree, PlainTextDepSpec> () const;
 
diff --git a/paludis/spec_tree.hh b/paludis/spec_tree.hh
index 9629fd9c9..95b33b23d 100644
--- a/paludis/spec_tree.hh
+++ b/paludis/spec_tree.hh
@@ -191,6 +191,7 @@ namespace paludis
             SpecTreeInnerNodeType<AllDepSpec>,
             SpecTreeInnerNodeType<AnyDepSpec>,
             SpecTreeInnerNodeType<ExactlyOneDepSpec>,
+            SpecTreeInnerNodeType<AtMostOneDepSpec>,
             SpecTreeInnerNodeType<ConditionalDepSpec>
         >::Type, AllDepSpec>;
 
@@ -232,6 +233,7 @@ namespace paludis
             SpecTreeInnerNodeType<AllDepSpec>,
             SpecTreeInnerNodeType<AnyDepSpec>,
             SpecTreeInnerNodeType<ExactlyOneDepSpec>,
+            SpecTreeInnerNodeType<AtMostOneDepSpec>,
             SpecTreeInnerNodeType<ConditionalDepSpec>
         >::Type, AllDepSpec>;
 
diff --git a/paludis/user_dep_spec.cc b/paludis/user_dep_spec.cc
index 4e810d0d6..f810e4c24 100644
--- a/paludis/user_dep_spec.cc
+++ b/paludis/user_dep_spec.cc
@@ -505,6 +505,12 @@ namespace
                     accept_visitor_returning<bool>(*this));
         }
 
+        bool visit(const GenericSpecTree::NodeType<AtMostOneDepSpec>::Type & n) const
+        {
+            return indirect_iterator(n.end()) != std::find_if(indirect_iterator(n.begin()), indirect_iterator(n.end()),
+                    accept_visitor_returning<bool>(*this));
+        }
+
         bool visit(const GenericSpecTree::NodeType<ConditionalDepSpec>::Type & n) const
         {
             if (n.spec()->condition_met(env, id))
diff --git a/python/dep_spec.cc b/python/dep_spec.cc
index 9f544929a..7e109162b 100644
--- a/python/dep_spec.cc
+++ b/python/dep_spec.cc
@@ -152,6 +152,14 @@ PythonExactlyOneDepSpec::PythonExactlyOneDepSpec(const ExactlyOneDepSpec &)
 {
 }
 
+PythonAtMostOneDepSpec::PythonAtMostOneDepSpec()
+{
+}
+
+PythonAtMostOneDepSpec::PythonAtMostOneDepSpec(const AtMostOneDepSpec &)
+{
+}
+
 PythonAllDepSpec::PythonAllDepSpec()
 {
 }
@@ -539,6 +547,15 @@ SpecTreeToPython::visit(const GenericSpecTree::NodeType<ExactlyOneDepSpec>::Type
 }
 
 void
+SpecTreeToPython::visit(const GenericSpecTree::NodeType<AtMostOneDepSpec>::Type & node)
+{
+    std::shared_ptr<PythonAtMostOneDepSpec> py_cds(std::make_shared<PythonAtMostOneDepSpec>(*node.spec()));
+    _current_parent->add_child(py_cds);
+    Save<std::shared_ptr<PythonCompositeDepSpec> > old_parent(&_current_parent, py_cds);
+    std::for_each(indirect_iterator(node.begin()), indirect_iterator(node.end()), accept_visitor(*this));
+}
+
+void
 SpecTreeToPython::visit(const GenericSpecTree::NodeType<ConditionalDepSpec>::Type & node)
 {
     std::shared_ptr<PythonConditionalDepSpec> py_cds(std::make_shared<PythonConditionalDepSpec>(*node.spec()));
@@ -657,6 +674,7 @@ struct AllowedTypes<RequiredUseSpecTree>
     AllowedTypes(const AllDepSpec &) {};
     AllowedTypes(const AnyDepSpec &) {};
     AllowedTypes(const ExactlyOneDepSpec &) {};
+    AllowedTypes(const AtMostOneDepSpec &) {};
     AllowedTypes(const ConditionalDepSpec &) {};
     AllowedTypes(const PlainTextDepSpec &) {};
 };
@@ -758,6 +776,13 @@ SpecTreeFromPython<H_>::visit(const PythonExactlyOneDepSpec & d)
 
 template <typename H_>
 void
+SpecTreeFromPython<H_>::visit(const PythonAtMostOneDepSpec & d)
+{
+    dispatch<H_, AtMostOneDepSpec>(this, d);
+}
+
+template <typename H_>
+void
 SpecTreeFromPython<H_>::visit(const PythonConditionalDepSpec & d)
 {
     dispatch<H_, ConditionalDepSpec>(this, d);
@@ -859,6 +884,14 @@ SpecTreeFromPython<H_>::real_visit(const PythonExactlyOneDepSpec & d)
 
 template <typename H_>
 void
+SpecTreeFromPython<H_>::real_visit(const PythonAtMostOneDepSpec & d)
+{
+    Save<std::shared_ptr<typename H_::BasicInnerNode> > old_add_to(&_add_to, _add_to->append(std::make_shared<AtMostOneDepSpec>()));
+    std::for_each(indirect_iterator(d.begin()), indirect_iterator(d.end()), accept_visitor(*this));
+}
+
+template <typename H_>
+void
 SpecTreeFromPython<H_>::real_visit(const PythonConditionalDepSpec & d)
 {
     Save<std::shared_ptr<typename H_::BasicInnerNode> > old_add_to(&_add_to, _add_to->append(std::make_shared<ConditionalDepSpec>(d.data())));
@@ -1123,6 +1156,16 @@ void expose_dep_spec()
         );
 
     /**
+     * AtMostOneDepSpec
+     */
+    bp::class_<PythonAtMostOneDepSpec, bp::bases<PythonCompositeDepSpec>, boost::noncopyable>
+        (
+         "AtMostOneDepSpec",
+         "Represents a \"?? ( )\" dependency block.",
+         bp::init<>("__init__()")
+        );
+
+    /**
      * AllDepSpec
      */
     bp::class_<PythonAllDepSpec, bp::bases<PythonCompositeDepSpec>, boost::noncopyable>
diff --git a/python/dep_spec.hh b/python/dep_spec.hh
index 1a10fc191..bd4825193 100644
--- a/python/dep_spec.hh
+++ b/python/dep_spec.hh
@@ -33,6 +33,7 @@ namespace paludis
         class PythonAllDepSpec;
         class PythonAnyDepSpec;
         class PythonExactlyOneDepSpec;
+        class PythonAtMostOneDepSpec;
         class PythonConditionalDepSpec;
         class PythonStringDepSpec;
         class PythonPlainTextDepSpec;
@@ -50,6 +51,7 @@ namespace paludis
             public virtual DeclareAbstractAcceptMethods<PythonDepSpec, MakeTypeList<
                     PythonAnyDepSpec,
                     PythonExactlyOneDepSpec,
+                    PythonAtMostOneDepSpec,
                     PythonAllDepSpec,
                     PythonConditionalDepSpec,
                     PythonBlockDepSpec,
@@ -115,6 +117,15 @@ namespace paludis
                 PythonExactlyOneDepSpec(const ExactlyOneDepSpec &);
         };
 
+        class PALUDIS_VISIBLE PythonAtMostOneDepSpec :
+            public PythonCompositeDepSpec,
+            public ImplementAcceptMethods<PythonDepSpec, PythonAtMostOneDepSpec>
+        {
+            public:
+                PythonAtMostOneDepSpec();
+                PythonAtMostOneDepSpec(const AtMostOneDepSpec &);
+        };
+
         class PALUDIS_VISIBLE PythonAllDepSpec :
             public PythonCompositeDepSpec,
             public ImplementAcceptMethods<PythonDepSpec, PythonAllDepSpec>
@@ -302,6 +313,7 @@ namespace paludis
                 void visit(const GenericSpecTree::NodeType<AllDepSpec>::Type &);
                 void visit(const GenericSpecTree::NodeType<AnyDepSpec>::Type &);
                 void visit(const GenericSpecTree::NodeType<ExactlyOneDepSpec>::Type &);
+                void visit(const GenericSpecTree::NodeType<AtMostOneDepSpec>::Type &);
                 void visit(const GenericSpecTree::NodeType<ConditionalDepSpec>::Type &);
 
                 void visit(const GenericSpecTree::NodeType<PackageDepSpec>::Type &);
@@ -339,6 +351,7 @@ namespace paludis
                 void visit(const PythonAllDepSpec &);
                 void visit(const PythonAnyDepSpec &);
                 void visit(const PythonExactlyOneDepSpec &);
+                void visit(const PythonAtMostOneDepSpec &);
                 void visit(const PythonConditionalDepSpec &);
                 void visit(const PythonPackageDepSpec &);
                 void visit(const PythonPlainTextDepSpec &);
@@ -354,6 +367,7 @@ namespace paludis
                 void real_visit(const PythonAllDepSpec &);
                 void real_visit(const PythonAnyDepSpec &);
                 void real_visit(const PythonExactlyOneDepSpec &);
+                void real_visit(const PythonAtMostOneDepSpec &);
                 void real_visit(const PythonConditionalDepSpec &);
                 void real_visit(const PythonPackageDepSpec &);
                 void real_visit(const PythonPlainTextDepSpec &);
diff --git a/python/nice_names.nn b/python/nice_names.nn
index 8494d26a0..da233373b 100644
--- a/python/nice_names.nn
+++ b/python/nice_names.nn
@@ -28,6 +28,7 @@ make_nn_NiceNames() {
     name "AllDepSpec"
     name "AnyDepSpec"
     name "ExactlyOneDepSpec"
+    name "AtMostOneDepSpec"
     name "ConditionalDepSpec"
     name "BlockDepSpec"
     name "StringDepSpec"
diff --git a/ruby/dep_spec.cc b/ruby/dep_spec.cc
index 91766cc18..32d07b023 100644
--- a/ruby/dep_spec.cc
+++ b/ruby/dep_spec.cc
@@ -59,6 +59,7 @@ namespace
     static VALUE c_all_dep_spec;
     static VALUE c_any_dep_spec;
     static VALUE c_exactly_one_dep_spec;
+    static VALUE c_at_most_one;
     static VALUE c_conditional_dep_spec;
 
     static VALUE c_version_requirements_mode;
@@ -131,6 +132,7 @@ namespace
             WrappedSpec<AllDepSpec>,
             WrappedSpec<AnyDepSpec>,
             WrappedSpec<ExactlyOneDepSpec>,
+            WrappedSpec<AtMostOneDepSpec>,
             WrappedSpec<ConditionalDepSpec>
         >::Type>
     {
@@ -272,6 +274,12 @@ namespace
             wrapped.reset((new WrappedSpec<ExactlyOneDepSpec>(std::static_pointer_cast<ExactlyOneDepSpec>(node.spec()->clone())))->add_children(node.begin(), node.end()));
             klass = c_exactly_one_dep_spec;
         }
+
+        void visit(const GenericSpecTree::NodeType<AtMostOneDepSpec>::Type & node)
+        {
+            wrapped.reset((new WrappedSpec<AtMostOneDepSpec>(std::static_pointer_cast<AtMostOneDepSpec>(node.spec()->clone())))->add_children(node.begin(), node.end()));
+            klass = c_at_most_one;
+        }
     };
 
     template <typename T_>
@@ -1017,6 +1025,17 @@ namespace
         rb_define_method(c_exactly_one_dep_spec, "each", RUBY_FUNC_CAST((&Composite<AllDepSpec>::each)), 0);
 
         /*
+         * Document-class: Paludis::AtMostOneDepSpec
+         *
+         * Represents a "?? ( )" dependency block. Includes
+         * Enumerable[http://www.ruby-doc.org/core/classes/Enumerable.html].
+         */
+        c_at_most_one = rb_define_class_under(paludis_module(), "AtMostOneDepSpec", c_dep_spec);
+        rb_funcall(c_at_most_one, rb_intern("private_class_method"), 1, rb_str_new2("new"));
+        rb_include_module(c_at_most_one, rb_mEnumerable);
+        rb_define_method(c_at_most_one, "each", RUBY_FUNC_CAST((&Composite<AllDepSpec>::each)), 0);
+
+        /*
          * Document-class: Paludis::ConditionalDepSpec
          *
          * Represents a use? ( ) dependency spec. Includes
diff --git a/ruby/nice_names.nn b/ruby/nice_names.nn
index c90f18f8a..60dab855a 100644
--- a/ruby/nice_names.nn
+++ b/ruby/nice_names.nn
@@ -24,6 +24,7 @@ make_nn_NiceNames() {
     name "SimpleURIDepSpec"
     name "AllDepSpec"
     name "AnyDepSpec"
+    name "AtMostOneDepSpec"
     name "ExactlyOneDepSpec"
     name "ConditionalDepSpec"
     name "BlockDepSpec"
diff --git a/src/clients/cave/cmd_match.cc b/src/clients/cave/cmd_match.cc
index 129f6d4ee..f422ae639 100644
--- a/src/clients/cave/cmd_match.cc
+++ b/src/clients/cave/cmd_match.cc
@@ -190,6 +190,11 @@ namespace
             std::for_each(indirect_iterator(node.begin()), indirect_iterator(node.end()), accept_visitor(*this));
         }
 
+        void visit(const GenericSpecTree::NodeType<AtMostOneDepSpec>::Type & node)
+        {
+            std::for_each(indirect_iterator(node.begin()), indirect_iterator(node.end()), accept_visitor(*this));
+        }
+
         void visit(const GenericSpecTree::NodeType<SimpleURIDepSpec>::Type & node)
         {
             texts.push_back(stringify(*node.spec()));