From aacff79e854d6d4eb22540339bc88c3efab353a2 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 5 Nov 2015 17:41:16 +0200
Subject: Implement package dependency resolution

---
 brep/package                             | 124 +++++++----
 brep/package-details.cxx                 |  24 +-
 brep/package-search.cxx                  |  17 +-
 brep/package-version-details.cxx         |  35 ++-
 brep/package.cxx                         |  10 +-
 brep/page.cxx                            |  27 ++-
 loader/loader.cxx                        | 266 ++++++++++++++++++++--
 tests/loader/driver.cxx                  | 366 ++++++++++++++++---------------
 tests/loader/external/1/staging/packages |  17 ++
 tests/loader/external/1/testing/packages |   6 +-
 tests/loader/internal/1/math/packages    |  16 ++
 tests/loader/internal/1/stable/packages  |  15 --
 web/module                               |   5 +-
 13 files changed, 644 insertions(+), 284 deletions(-)

diff --git a/brep/package b/brep/package
index 719a906..ef73542 100644
--- a/brep/package
+++ b/brep/package
@@ -10,6 +10,7 @@
 #include <vector>
 #include <chrono>
 #include <memory>  // shared_ptr
+#include <cassert>
 #include <cstddef> // size_t
 #include <utility> // move()
 #include <cstdint> // uint16
@@ -75,13 +76,11 @@ namespace brep
   class package;
 
   using strings = std::vector<std::string>;
-
-  template <typename T>
-  using optional = butl::optional<T>;
+  using butl::optional;
 
   // path
   //
-  using path = butl::path;
+  using butl::path;
 
   #pragma db map type(path) as(std::string)  \
     to((?).string ()) from(brep::path (?))
@@ -93,14 +92,14 @@ namespace brep
     to((?) ? (?)->string () : brep::optional_string ())        \
     from((?) ? brep::path (*(?)) : brep::optional_path ())
 
-  using dir_path = butl::dir_path;
+  using butl::dir_path;
 
   #pragma db map type(dir_path) as(std::string)  \
     to((?).string ()) from(brep::dir_path (?))
 
   // timestamp
   //
-  using timestamp = butl::timestamp;
+  using butl::timestamp;
 
   #pragma db map type(timestamp) as(std::uint64_t)   \
     to(std::chrono::system_clock::to_time_t (?))     \
@@ -108,7 +107,7 @@ namespace brep
 
   // version
   //
-  using version = bpkg::version;
+  using bpkg::version;
 
   #pragma db value
   struct canonical_version
@@ -116,6 +115,18 @@ namespace brep
     std::uint16_t epoch;
     std::string   canonical_upstream;
     std::uint16_t revision;
+
+    bool
+    empty () const noexcept
+    {
+      // No sense to test epoch and revision for 0 as a valid canonical_version
+      // object can not have them different from 0 if canonical_upstream is
+      // empty. The predicate semantics is equal to the one of the
+      // bpkg::version class.
+      //
+      assert (!canonical_upstream.empty () || (epoch == 0 && revision == 0));
+      return canonical_upstream.empty ();
+    }
   };
 
   #pragma db value transient
@@ -140,14 +151,14 @@ namespace brep
 
   // priority
   //
-  using priority = bpkg::priority;
+  using bpkg::priority;
 
   #pragma db value(priority) definition
   #pragma db member(priority::value) column("")
 
   // url
   //
-  using url = bpkg::url;
+  using bpkg::url;
 
   #pragma db value(url) definition
   #pragma db member(url::value) virtual(std::string) before access(this) \
@@ -155,7 +166,7 @@ namespace brep
 
   // email
   //
-  using email = bpkg::email;
+  using bpkg::email;
 
   #pragma db value(email) definition
   #pragma db member(email::value) virtual(std::string) before access(this) \
@@ -163,17 +174,33 @@ namespace brep
 
   // licenses
   //
-  using licenses = bpkg::licenses;
+  using bpkg::licenses;
   using license_alternatives = std::vector<licenses>;
 
   #pragma db value(licenses) definition
 
   // dependencies
   //
-  using comparison = bpkg::comparison;
-  using dependency_constraint = bpkg::dependency_constraint;
+  using bpkg::comparison;
+  using bpkg::dependency_constraint;
 
   #pragma db value(dependency_constraint) definition
+  #pragma db member(dependency_constraint::operation) column("")
+  #pragma db member(dependency_constraint::version) column("")
+
+  #pragma db value
+  struct package_id
+  {
+    std::string name;
+    canonical_version version;
+
+    package_id () = default;
+    package_id (std::string n, const brep::version& v)
+        : name (std::move (n)),
+          version {v.epoch, v.canonical_upstream, v.revision}
+    {
+    }
+  };
 
   // Notes:
   //
@@ -215,24 +242,51 @@ namespace brep
   //    * No need to complicate persisted object model with repository
   //      relations otherwise required just for dependency resolution.
   //
-  using dependency = bpkg::dependency;
-  using dependency_alternatives = bpkg::dependency_alternatives;
-  using dependencies = std::vector<dependency_alternatives>;
 
-  #pragma db value(dependency) definition
-  #pragma db member(dependency::constraint) column("")
-  #pragma db value(dependency_alternatives) definition
+  #pragma db value
+  struct dependency
+  {
+    using package_type = brep::package;
+
+    odb::lazy_shared_ptr<package_type> package;
+    optional<dependency_constraint> constraint;
+
+    // Prerequisite package name.
+    //
+    std::string
+    name () const;
+
+    // Database mapping.
+    //
+    #pragma db member(package) column("") not_null
+  };
+
+  #pragma db value
+  class dependency_alternatives: public std::vector<dependency>
+  {
+  public:
+    bool conditional;
+    std::string comment;
+
+    dependency_alternatives () = default;
+
+    explicit
+    dependency_alternatives (bool d, std::string c)
+        : conditional (d), comment (std::move (c)) {}
+  };
+
+  using dependencies = std::vector<dependency_alternatives>;
 
   // requirements
   //
-  using requirement_alternatives = bpkg::requirement_alternatives;
+  using bpkg::requirement_alternatives;
   using requirements = std::vector<requirement_alternatives>;
 
   #pragma db value(requirement_alternatives) definition
 
   // repository_location
   //
-  using repository_location = bpkg::repository_location;
+  using bpkg::repository_location;
 
   #pragma db map type(repository_location) as(std::string) \
     to((?).string ()) from(brep::repository_location (?))
@@ -270,6 +324,8 @@ namespace brep
     timestamp repositories_timestamp;
 
     bool internal;
+    std::vector<odb::lazy_weak_ptr<repository>> complements;
+    std::vector<odb::lazy_weak_ptr<repository>> prerequisites;
 
     // Database mapping.
     //
@@ -279,25 +335,17 @@ namespace brep
       set(this.location = std::move (?);                         \
           assert (this.name == this.location.canonical_name ()))
 
+    #pragma db member(complements) id_column("repository") \
+      value_column("complement") value_not_null
+
+    #pragma db member(prerequisites) id_column("repository") \
+      value_column("prerequisite") value_not_null
+
   private:
     friend class odb::access;
     repository () = default;
   };
 
-  #pragma db value
-  struct package_id
-  {
-    std::string name;
-    canonical_version version;
-
-    package_id () = default;
-    package_id (std::string n, const brep::version& v)
-        : name (std::move (n)),
-          version {v.epoch, v.canonical_upstream, v.revision}
-    {
-    }
-  };
-
   // The 'to' expression calls the PostgreSQL to_tsvector(weighted_text)
   // function overload (package-extra.sql). Since we are only interested
   // in "write-only" members of this type, make the 'from' expression
@@ -382,7 +430,7 @@ namespace brep
     //
     optional<path> location;
 
-    std::vector<odb::lazy_shared_ptr<repository_type>> external_repositories;
+    std::vector<odb::lazy_shared_ptr<repository_type>> other_repositories;
 
     // Database mapping.
     //
@@ -446,9 +494,9 @@ namespace brep
       set(odb::nested_set (this.requirements, move (?))) \
       id_column("") key_column("") value_column("id")
 
-    // external_repositories
+    // other_repositories
     //
-    #pragma db member(external_repositories)                  \
+    #pragma db member(other_repositories)                  \
       id_column("") value_column("repository") value_not_null
 
     // search_index
diff --git a/brep/package-details.cxx b/brep/package-details.cxx
index f814ef8..0424d5b 100644
--- a/brep/package-details.cxx
+++ b/brep/package-details.cxx
@@ -10,6 +10,7 @@
 
 #include <xml/serializer>
 
+#include <odb/session.hxx>
 #include <odb/database.hxx>
 #include <odb/transaction.hxx>
 
@@ -119,6 +120,7 @@ namespace brep
       <<         A(HREF=url (!f, sq, pg)) << (f ? "[brief]" : "[full]") << ~A
       <<       ~DIV;
 
+    session sn;
     transaction t (db_->begin ());
 
     shared_ptr<package> p;
@@ -172,13 +174,12 @@ namespace brep
         "OFFSET" + to_string (pg * rp) +
         "LIMIT" + to_string (rp)));
 
-    s << FORM_SEARCH (sq.c_str ())
-      << DIV_COUNTER (pc, "Version", "Versions")
-
-      // Enclose the subsequent tables to be able to use nth-child CSS selector.
-      //
-      <<   DIV;
+    s << FORM_SEARCH (sq)
+      << DIV_COUNTER (pc, "Version", "Versions");
 
+    // Enclose the subsequent tables to be able to use nth-child CSS selector.
+    //
+    s << DIV;
     for (const auto& pr: r)
     {
       shared_ptr<package> p (db_->load<package> (pr.id));
@@ -187,7 +188,7 @@ namespace brep
         <<   TBODY
         <<     TR_VERSION (name, p->version.string ())
 
-        // @@ Shouldn't we skip low priority row ?
+        // @@ Shouldn't we skip low priority row ? Don't think so, why?
         //
         <<     TR_PRIORITY (p->priority);
 
@@ -200,24 +201,27 @@ namespace brep
       assert (p->internal_repository != nullptr);
 
       // @@ Shouldn't we make package location to be a link to the proper
-      //    place of the About page, describing corresponding repository ?
+      //    place of the About page, describing corresponding repository?
+      //    Yes, I think that's sounds reasonable, once we have about.
       //
       // @@ In most cases package location will be the same for all versions
       //    of the same package. Shouldn't we put package location to the
       //    package summary part and display it here only if it differes
       //    from the one in the summary ?
       //
+      //    Hm, I am not so sure about this. Consider: stable/testing/unstable.
+      //
       s <<     TR_LOCATION (p->internal_repository.object_id ())
         <<     TR_DEPENDS (p->dependencies)
         <<     TR_REQUIRES (p->requirements)
         <<   ~TBODY
         << ~TABLE;
     }
+    s << ~DIV;
 
     t.commit ();
 
-    s <<       ~DIV
-      <<       DIV_PAGER (pg, pc, rp, options_->pages_in_pager (), url (f, sq))
+    s <<       DIV_PAGER (pg, pc, rp, options_->pages_in_pager (), url (f, sq))
       <<     ~DIV
       <<   ~BODY
       << ~HTML;
diff --git a/brep/package-search.cxx b/brep/package-search.cxx
index 64e43f1..47f53e9 100644
--- a/brep/package-search.cxx
+++ b/brep/package-search.cxx
@@ -10,6 +10,7 @@
 
 #include <xml/serializer>
 
+#include <odb/session.hxx>
 #include <odb/database.hxx>
 #include <odb/transaction.hxx>
 
@@ -92,6 +93,7 @@ namespace brep
       <<     DIV_HEADER ()
       <<     DIV(ID="content");
 
+    session sn;
     transaction t (db_->begin ());
 
     auto pc (
@@ -105,13 +107,12 @@ namespace brep
         "OFFSET" + to_string (pg * rp) +
         "LIMIT" + to_string (rp)));
 
-    s << FORM_SEARCH (sq.c_str ())
-      << DIV_COUNTER (pc, "Package", "Packages")
-
-      // Enclose the subsequent tables to be able to use nth-child CSS selector.
-      //
-      <<   DIV;
+    s << FORM_SEARCH (sq)
+      << DIV_COUNTER (pc, "Package", "Packages");
 
+    // Enclose the subsequent tables to be able to use nth-child CSS selector.
+    //
+    s << DIV;
     for (const auto& pr: r)
     {
       shared_ptr<package> p (db_->load<package> (pr.id));
@@ -127,13 +128,13 @@ namespace brep
         <<   ~TBODY
         << ~TABLE;
     }
+    s << ~DIV;
 
     t.commit ();
 
     string url (qp.empty () ? "/" : ("/?" + qp));
 
-    s <<       ~DIV
-      <<       DIV_PAGER (pg, pc, rp, options_->pages_in_pager (), url)
+    s <<       DIV_PAGER (pg, pc, rp, options_->pages_in_pager (), url)
       <<     ~DIV
       <<   ~BODY
       << ~HTML;
diff --git a/brep/package-version-details.cxx b/brep/package-version-details.cxx
index 71559b9..a4fa95a 100644
--- a/brep/package-version-details.cxx
+++ b/brep/package-version-details.cxx
@@ -11,6 +11,7 @@
 
 #include <xml/serializer>
 
+#include <odb/session.hxx>
 #include <odb/database.hxx>
 #include <odb/transaction.hxx>
 
@@ -63,7 +64,7 @@ namespace brep
     }
 
     assert (i != rq.path ().rend ());
-    const string& n (*i);
+    const string& n (*i); // Package name.
 
     params::package_version_details pr;
 
@@ -120,6 +121,7 @@ namespace brep
     bool not_found (false);
     shared_ptr<package> p;
 
+    session sn;
     transaction t (db_->begin ());
 
     try
@@ -153,8 +155,6 @@ namespace brep
     const string du (p->internal_repository.load ()->location.string () +
                      "/" + p->location->string ());
 
-    t.commit ();
-
     s << TABLE(CLASS="proplist", ID="version")
       <<   TBODY
 
@@ -209,7 +209,32 @@ namespace brep
           if (&d != &da[0])
             s << " | ";
 
-          s << d; // @@ Should it be a link ?
+          shared_ptr<package> p (d.package.load ());
+          string en (mime_url_encode (p->id.name));
+
+          if (p->internal_repository != nullptr)
+            s << A << HREF << "/go/" << en << ~HREF << p->id.name << ~A;
+          else
+            // @@ Refer to package repository URL when supported in repository
+            //    manifest.
+            //
+            s << p->id.name;
+
+          if (d.constraint)
+          {
+            s << ' ';
+
+            if (p->internal_repository != nullptr)
+              s << A
+                << HREF << "/go/" << en << "/" << p->version.string () << ~HREF
+                <<   *d.constraint
+                << ~A;
+            else
+              // @@ Refer to package repository URL when supported in
+              //    repository manifest.
+              //
+              s << *d.constraint;
+          }
         }
 
         s <<     ~SPAN
@@ -222,6 +247,8 @@ namespace brep
         << ~TABLE;
     }
 
+    t.commit ();
+
     const auto& rt (p->requirements);
 
     if (!rt.empty ())
diff --git a/brep/package.cxx b/brep/package.cxx
index 9b7d24a..3c65ed8 100644
--- a/brep/package.cxx
+++ b/brep/package.cxx
@@ -16,6 +16,14 @@ using namespace odb::core;
 
 namespace brep
 {
+  // dependency
+  //
+  string dependency::
+  name () const
+  {
+    return package.object_id ().name;
+  }
+
   // package
   //
   package::
@@ -63,7 +71,7 @@ namespace brep
         version (move (vr))
   {
     assert (!rp->internal);
-    external_repositories.emplace_back (move (rp));
+    other_repositories.emplace_back (move (rp));
   }
 
   weighted_text package::
diff --git a/brep/page.cxx b/brep/page.cxx
index a23ce17..deee055 100644
--- a/brep/page.cxx
+++ b/brep/page.cxx
@@ -6,6 +6,7 @@
 
 #include <set>
 #include <string>
+#include <memory>    // shared_ptr
 #include <cassert>
 #include <utility>   // move()
 #include <algorithm> // min()
@@ -16,6 +17,7 @@
 #include <web/mime-url-encoding>
 
 #include <brep/package>
+#include <brep/package-odb>
 
 using namespace std;
 using namespace xml;
@@ -51,7 +53,7 @@ namespace brep
   void FORM_SEARCH::
   operator() (serializer& s) const
   {
-    // The 'action' attribute is optional in HTML5. While the standard don't
+    // The 'action' attribute is optional in HTML5. While the standard doesn't
     // specify browser behavior explicitly for the case the attribute is
     // ommited, the only reasonable behavior is to default it to the current
     // document URL.
@@ -260,26 +262,35 @@ namespace brep
       //
       set<string> ds;
       for (const auto& da: d)
-        ds.emplace (da.name);
+        ds.emplace (da.name ());
 
       bool m (ds.size () > 1);
 
       if (m)
         s << "(";
 
-      bool first (true);
+      bool f (true); // First dependency alternative.
       for (const auto& da: d)
       {
-        if (ds.find (da.name) != ds.end ())
+        string n (da.name ());
+        if (ds.find (n) != ds.end ())
         {
-          ds.erase (da.name);
+          ds.erase (n);
 
-          if (first)
-            first = false;
+          if (f)
+            f = false;
           else
             s << " | ";
 
-          s << da.name; // @@ Make it a link.
+          shared_ptr<package> p (da.package.load ());
+
+          if (p->internal_repository != nullptr)
+            s << A << HREF << "/go/" << mime_url_encode (n) << ~HREF << n << ~A;
+          else
+            // @@ Refer to package repository URL when supported in repository
+            //    manifest.
+            //
+            s << n;
         }
       }
 
diff --git a/loader/loader.cxx b/loader/loader.cxx
index ecc6032..74844f5 100644
--- a/loader/loader.cxx
+++ b/loader/loader.cxx
@@ -12,7 +12,9 @@
 #include <fstream>
 #include <iostream>
 #include <stdexcept> // runtime_error, invalid_argument
+#include <algorithm> // find(), find_if()
 
+#include <odb/session.hxx>
 #include <odb/database.hxx>
 #include <odb/transaction.hxx>
 
@@ -319,6 +321,22 @@ load_packages (const shared_ptr<repository>& rp, database& db)
           }
         }
 
+        dependencies ds;
+        for (auto& pda: pm.dependencies)
+        {
+          ds.emplace_back (pda.conditional, move (pda.comment));
+
+          for (auto& pd: pda)
+            // Proper version will be assigned during dependency resolution
+            // procedure. Here we rely on the fact the foreign key constraint
+            // check is deferred until the current transaction commit.
+            //
+            ds.back ().push_back ({
+                lazy_shared_ptr<package> (
+                  db, package_id (move (pd.name), version ())),
+                move (pd.constraint)});
+        }
+
         p = make_shared<package> (
           move (pm.name),
           move (pm.version),
@@ -332,7 +350,7 @@ load_packages (const shared_ptr<repository>& rp, database& db)
           move (pm.package_url),
           move (pm.email),
           move (pm.package_email),
-          move (pm.dependencies),
+          move (ds),
           move (pm.requirements),
           move (pm.location),
           rp);
@@ -351,21 +369,13 @@ load_packages (const shared_ptr<repository>& rp, database& db)
       //    for this purpose.
       //
 
-      if (rp->internal)
-      {
-        // Just skip the duplicate.
-        //
+      // As soon as internal repositories get loaded first, the internal
+      // package can duplicate an internal package only.
+      //
+      assert (!rp->internal || p->internal_repository != nullptr);
 
-        // As soon as internal repositories get loaded first, the internal
-        // package can duplicate an internal package only.
-        //
-        assert (p->internal_repository != nullptr);
-      }
-      else
-      {
-        p->external_repositories.push_back (rp);
-        db.update (p);
-      }
+      p->other_repositories.push_back (rp);
+      db.update (p);
     }
   }
 
@@ -374,7 +384,8 @@ load_packages (const shared_ptr<repository>& rp, database& db)
 
 // Load the prerequsite repositories and their complements state from the
 // 'repositories' file. Update the repository persistent state to save
-// repositories_timestamp member. Should be called once per internal repository.
+// repositories_timestamp, prerequsites, and complements members.
+// Should be called once per persisted internal repository.
 //
 static void
 load_prerequisites (const shared_ptr<repository>& rp, database& db)
@@ -389,13 +400,16 @@ load_prerequisites (const shared_ptr<repository>& rp, database& db)
   //
   assert (!rp->local_path.empty ());
 
+  // Repository is already persisted by the load_packages() function call.
+  //
+  assert (db.find<repository> (rp->name) != nullptr);
+
   repository_manifests rpm;
 
   {
     ifstream ifs;
     path p (rp->local_path / path ("repositories"));
     rp->repositories_timestamp = manifest_stream (p, ifs);
-    db.update (rp);
 
     manifest_parser mp (ifs, p.string ());
     rpm = repository_manifests (mp);
@@ -408,6 +422,8 @@ load_prerequisites (const shared_ptr<repository>& rp, database& db)
          rm.effective_role () == repository_role::prerequisite))
       continue; // Ignore entry for this repository.
 
+    assert (rm.effective_role () != repository_role::base);
+
     repository_location rl;
 
     auto bad_location (
@@ -438,7 +454,18 @@ load_prerequisites (const shared_ptr<repository>& rp, database& db)
       bad_location ();
     }
 
-    shared_ptr<repository> pr (db.find<repository> (rl.canonical_name ()));
+    const auto& cn (rl.canonical_name ());
+
+    // Add repository to prerequisites or complements member of the dependent
+    // repository.
+    //
+    auto& rs (rm.effective_role () == repository_role::prerequisite
+              ? rp->prerequisites
+              : rp->complements);
+
+    rs.emplace_back (db, cn);
+
+    shared_ptr<repository> pr (db.find<repository> (cn));
 
     if (pr != nullptr)
       // The prerequisite repository is already loaded.
@@ -473,6 +500,189 @@ load_prerequisites (const shared_ptr<repository>& rp, database& db)
     load_packages (pr, db);
     load_prerequisites (pr, db);
   }
+
+  db.update (rp);
+}
+
+static ostream&
+operator<< (ostream& o,
+            const brep::dependency& d) // Ambiguity with bpkg::dependency.
+{
+  o << d.name ();
+
+  if (d.constraint)
+    o << ' ' << *d.constraint;
+
+  return o;
+}
+
+// Check if the package is available from the specified repository,
+// its prerequisite repositories, or one of their complements,
+// recursively.
+//
+static bool
+find (const lazy_shared_ptr<repository>& r,
+      const package& p,
+      bool prereq = true)
+{
+  assert (r != nullptr);
+
+  const auto& o (p.other_repositories);
+  if (r == p.internal_repository || find (o.begin (), o.end (), r) != o.end ())
+    return true;
+
+  auto rp (r.load ());
+  for (const auto& cr: rp->complements)
+  {
+    if (find (lazy_shared_ptr<repository> (cr), p, false))
+      return true;
+  }
+
+  if (prereq)
+  {
+    for (auto pr: rp->prerequisites)
+    {
+      if (find (lazy_shared_ptr<repository> (pr), p, false))
+        return true;
+    }
+  }
+
+  return false;
+}
+
+// Resolve package dependencies. Ensure that the best matching dependency
+// belongs to the package repositories, their immediate prerequisite
+// repositories, or their complements, recursively. Should be called once per
+// internal package.
+//
+static void
+resolve_dependencies (package& p, database& db)
+{
+  // Resolve dependencies for internal packages only.
+  //
+  // @@ add package::internal() predicate? Lots of place where you do
+  //    (p.internal_repository != nullptr).
+  //
+  assert (p.internal_repository != nullptr);
+
+  if (p.dependencies.empty ())
+    return;
+
+  for (auto& da: p.dependencies)
+  {
+    for (auto& d: da)
+    {
+      // Dependency should not be resolved yet.
+      //
+      assert (d.package.object_id ().version.empty ());
+
+      using query = query<package>;
+      query q (query::id.name == d.name ());
+
+      if (d.constraint)
+      {
+        auto c (*d.constraint);
+        switch (c.operation)
+        {
+        case comparison::eq: q = q && query::id.version == c.version; break;
+        case comparison::lt: q = q && query::id.version < c.version; break;
+        case comparison::gt: q = q && query::id.version > c.version; break;
+        case comparison::le: q = q && query::id.version <= c.version; break;
+        case comparison::ge: q = q && query::id.version >= c.version; break;
+        }
+      }
+
+      auto r (
+        db.query<package> (q + order_by_version_desc (query::id.version)));
+
+      for (const auto& pp: r)
+      {
+        if (find (p.internal_repository, pp))
+        {
+          d.package.reset (db, pp.id);
+          break;
+        }
+      }
+
+      if (d.package.object_id ().version.empty ())
+      {
+        ostringstream o;
+        o << "can't resolve dependency " << d << " of the package "
+          << p.id.name << " " << p.version.string ()
+          << " (" << p.internal_repository.load ()->name << ")";
+
+        // Practically it is enough to resolve at least one dependency
+        // alternative to build a package. Meanwhile here we consider an error
+        // specifying in the manifest file an alternative which can't be
+        // resolved.
+        //
+        throw runtime_error (o.str ());
+      }
+    }
+  }
+
+  db.update (p); // Update the package state.
+}
+
+using package_ids = vector<package_id>;
+
+// Ensure the package dependency chain do not contain the package id. Throw
+// runtime_error otherwise. Continue the chain with the package id and call
+// itself recursively for each prerequisite of the package. Should be called
+// once per internal package.
+//
+// @@ This should probably be eventually moved to bpkg.
+//
+static void
+detect_dependency_cycle (const package_id& id, package_ids& chain, database& db)
+{
+  // Package of one version depending on the same package of another version
+  // is something obscure. So the comparison is made up to a package name.
+  //
+  auto pr ([&id](const package_id& i) -> bool {return i.name == id.name;});
+  auto i (find_if (chain.begin (), chain.end (), pr));
+
+  if (i != chain.end ())
+  {
+    ostringstream o;
+    o << "package dependency cycle: ";
+
+    auto prn (
+      [&o, &db](const package_id& id)
+      {
+        shared_ptr<package> p (db.load<package> (id));
+
+        assert (p->internal_repository != nullptr ||
+                !p->other_repositories.empty ());
+
+        shared_ptr<repository> r (
+          p->internal_repository != nullptr
+          ? p->internal_repository.load ()
+          : p->other_repositories[0].load ());
+
+        o << id.name << " " << p->version.string () << " (" << r->name << ")";
+      });
+
+    for (; i != chain.end (); ++i)
+    {
+      prn (*i);
+      o << " -> ";
+    }
+
+    prn (id);
+    throw runtime_error (o.str ());
+  }
+
+  chain.push_back (id);
+
+  shared_ptr<package> p (db.load<package> (id));
+  for (const auto& da: p->dependencies)
+  {
+    for (const auto& d: da)
+      detect_dependency_cycle (d.package.object_id (), chain, db);
+  }
+
+  chain.pop_back ();
 }
 
 int
@@ -581,6 +791,26 @@ main (int argc, char* argv[])
 
         load_prerequisites (r, db);
       }
+
+      session s;
+      using query = query<package>;
+
+      // Resolve internal packages dependencies.
+      //
+      {
+        auto r (db.query<package> (query::internal_repository.is_not_null ()));
+        for (auto& p: r)
+          resolve_dependencies (p, db);
+      }
+
+      // Ensure there is no package dependency cycles.
+      //
+      {
+        package_ids chain;
+        auto r (db.query<package> (query::internal_repository.is_not_null ()));
+        for (const auto& p: r)
+          detect_dependency_cycle (p.id, chain, db);
+      }
     }
 
     t.commit ();
diff --git a/tests/loader/driver.cxx b/tests/loader/driver.cxx
index 74c6966..2222fde 100644
--- a/tests/loader/driver.cxx
+++ b/tests/loader/driver.cxx
@@ -30,7 +30,7 @@ using namespace brep;
 static inline bool
 operator== (const dependency& a, const dependency& b)
 {
-  return a.name == b.name && !a.constraint == !b.constraint &&
+  return a.name () == b.name () && !a.constraint == !b.constraint &&
     (!a.constraint || (a.constraint->operation == b.constraint->operation &&
                       a.constraint->version == b.constraint->version));
 }
@@ -45,9 +45,22 @@ check_location (shared_ptr<package>& p)
       path (p->id.name + "-" + p->version.string () + ".tar.gz");
 }
 
+static bool
+check_external (const package& p)
+{
+  return p.summary.empty () && p.tags.empty () && !p.description &&
+    p.url.empty () && !p.package_url && p.email.empty () && !p.package_email &&
+    p.internal_repository == nullptr && p.other_repositories.size () > 0 &&
+    p.priority == priority () && p.changes.empty () &&
+    p.license_alternatives.empty () && p.dependencies.empty () &&
+    p.requirements.empty ();
+}
+
 int
 main (int argc, char* argv[])
 {
+  using brep::optional; // Ambiguity with butl::optional.
+
   if (argc != 7)
   {
     cerr << "usage: " << argv[0]
@@ -90,7 +103,7 @@ main (int argc, char* argv[])
       transaction t (db.begin ());
 
       assert (db.query<repository> ().size () == 5);
-      assert (db.query<package> ().size () == 12);
+      assert (db.query<package> ().size () == 14);
 
       shared_ptr<repository> sr (db.load<repository> ("cppget.org/stable"));
       shared_ptr<repository> mr (db.load<repository> ("cppget.org/math"));
@@ -129,48 +142,10 @@ main (int argc, char* argv[])
         db.load<package> (package_id ("libfoo", version ("1.2.4"))));
       assert (check_location (fpv4));
 
-      shared_ptr<package> xpv (
-        db.load<package> (package_id ("libstudxml", version ("1.0.0-1"))));
-      assert (check_location (xpv));
-
-      // Verify libstudxml package version.
-      //
-      assert (xpv->summary == "Modern C++ XML API");
-      assert (xpv->tags == strings ({"c++", "xml", "parser", "serializer",
-              "pull", "streaming", "modern"}));
-      assert (!xpv->description);
-      assert (xpv->url == "http://www.codesynthesis.com/projects/libstudxml/");
-      assert (!xpv->package_url);
-      assert (xpv->email ==
-              email ("studxml-users@codesynthesis.com",
-                     "Public mailing list, posts by  non-members "
-                     "are allowed but moderated."));
-      assert (xpv->package_email &&
-              *xpv->package_email == email ("boris@codesynthesis.com",
-                                            "Direct email to the author."));
-
-      assert (xpv->internal_repository.load () == sr);
-      assert (xpv->external_repositories.empty ());
-      assert (xpv->priority == priority::low);
-      assert (xpv->changes.empty ());
-
-      assert (xpv->license_alternatives.size () == 1);
-      assert (xpv->license_alternatives[0].size () == 1);
-      assert (xpv->license_alternatives[0][0] == "MIT");
-
-      assert (xpv->dependencies.size () == 2);
-      assert (xpv->dependencies[0].size () == 1);
-      assert (xpv->dependencies[0][0] ==
-              (dependency {
-                 "libexpat",
-                 brep::optional<dependency_constraint> (
-                   dependency_constraint{
-                     comparison::ge, version ("2.0.0")})}));
-
-      assert (xpv->dependencies[1].size () == 1);
-      assert (xpv->dependencies[1][0] == (dependency {"libgenx", nullopt}));
-
-      assert (xpv->requirements.empty ());
+      assert (sr->complements.empty ());
+      assert (sr->prerequisites.size () == 2);
+      assert (sr->prerequisites[0].load () == cr);
+      assert (sr->prerequisites[1].load () == mr);
 
       // Verify libfoo package versions.
       //
@@ -185,8 +160,10 @@ main (int argc, char* argv[])
       assert (!fpv1->package_email);
 
       assert (fpv1->internal_repository.load () == sr);
-      assert (fpv1->external_repositories.size () == 1);
-      assert (fpv1->external_repositories[0].load () == cr);
+      assert (fpv1->other_repositories.size () == 2);
+      assert (fpv1->other_repositories[0].load () == mr);
+      assert (fpv1->other_repositories[1].load () == cr);
+
       assert (fpv1->priority == priority::low);
       assert (fpv1->changes.empty ());
 
@@ -208,7 +185,7 @@ main (int argc, char* argv[])
       assert (!fpv2->package_email);
 
       assert (fpv2->internal_repository.load () == sr);
-      assert (fpv2->external_repositories.empty ());
+      assert (fpv2->other_repositories.empty ());
       assert (fpv2->priority == priority::low);
       assert (fpv2->changes.empty ());
 
@@ -220,17 +197,24 @@ main (int argc, char* argv[])
       assert (fpv2->dependencies[0].size () == 1);
       assert (fpv2->dependencies[1].size () == 1);
 
+      auto dep (
+        [&db](const char* n,
+              const optional<dependency_constraint>& c) -> dependency
+        {
+          return {lazy_shared_ptr<package> (db, package_id (n, version ())), c};
+        });
+
       assert (fpv2->dependencies[0][0] ==
-              (dependency {
-                 "libbar",
-                 brep::optional<dependency_constraint> (
-                   dependency_constraint{comparison::le, version ("2.4.0")})}));
+              dep (
+                "libbar",
+                optional<dependency_constraint> (
+                  dependency_constraint{comparison::le, version ("2.4.0")})));
 
       assert (fpv2->dependencies[1][0] ==
-              (dependency {
-                 "libexp",
-                 brep::optional<dependency_constraint> (
-                   dependency_constraint{comparison::eq, version ("1+1.2")})}));
+              dep (
+                "libexp",
+                brep::optional<dependency_constraint> (
+                  dependency_constraint{comparison::eq, version ("1+1.2")})));
 
       assert (fpv2->requirements.empty ());
 
@@ -245,7 +229,7 @@ main (int argc, char* argv[])
       assert (!fpv3->package_email);
 
       assert (fpv3->internal_repository.load () == sr);
-      assert (fpv3->external_repositories.empty ());
+      assert (fpv3->other_repositories.empty ());
       assert (fpv3->priority == priority::low);
 
       assert (fpv3->changes.empty ());
@@ -257,10 +241,10 @@ main (int argc, char* argv[])
       assert (fpv3->dependencies.size () == 1);
       assert (fpv3->dependencies[0].size () == 1);
       assert (fpv3->dependencies[0][0] ==
-              (dependency {
-                 "libmisc",
-                 brep::optional<dependency_constraint> (
-                   dependency_constraint{comparison::ge, version ("2.0.0")})}));
+              dep (
+                "libmisc",
+                brep::optional<dependency_constraint> (
+                  dependency_constraint{comparison::ge, version ("2.0.0")})));
 
       // libfoo-1.2.4
       //
@@ -273,7 +257,7 @@ main (int argc, char* argv[])
       assert (!fpv4->package_email);
 
       assert (fpv4->internal_repository.load () == sr);
-      assert (fpv4->external_repositories.empty ());
+      assert (fpv4->other_repositories.empty ());
       assert (fpv4->priority == priority::low);
       assert (fpv4->changes == "some changes 1\nsome changes 2");
 
@@ -286,10 +270,10 @@ main (int argc, char* argv[])
       assert (fpv4->dependencies.size () == 1);
       assert (fpv4->dependencies[0].size () == 1);
       assert (fpv4->dependencies[0][0] ==
-              (dependency {
-                 "libmisc",
-                 brep::optional<dependency_constraint> (
-                   dependency_constraint{comparison::ge, version ("2.0.0")})}));
+              dep (
+                "libmisc",
+                brep::optional<dependency_constraint> (
+                  dependency_constraint{comparison::ge, version ("2.0.0")})));
 
       // Verify 'math' repository.
       //
@@ -315,6 +299,52 @@ main (int argc, char* argv[])
         db.load<package> (package_id ("libfoo", version ("1.2.4-1"))));
       assert (check_location (fpv5));
 
+      shared_ptr<package> xpv (
+        db.load<package> (package_id ("libstudxml", version ("1.0.0-1"))));
+      assert (check_location (xpv));
+
+      assert (mr->complements.empty ());
+      assert (mr->prerequisites.size () == 1);
+      assert (mr->prerequisites[0].load () == cr);
+
+      // Verify libstudxml package version.
+      //
+      assert (xpv->summary == "Modern C++ XML API");
+      assert (xpv->tags == strings ({"c++", "xml", "parser", "serializer",
+              "pull", "streaming", "modern"}));
+      assert (!xpv->description);
+      assert (xpv->url == "http://www.codesynthesis.com/projects/libstudxml/");
+      assert (!xpv->package_url);
+      assert (xpv->email ==
+              email ("studxml-users@codesynthesis.com",
+                     "Public mailing list, posts by  non-members "
+                     "are allowed but moderated."));
+      assert (xpv->package_email &&
+              *xpv->package_email == email ("boris@codesynthesis.com",
+                                            "Direct email to the author."));
+
+      assert (xpv->internal_repository.load () == mr);
+      assert (xpv->other_repositories.empty ());
+      assert (xpv->priority == priority::low);
+      assert (xpv->changes.empty ());
+
+      assert (xpv->license_alternatives.size () == 1);
+      assert (xpv->license_alternatives[0].size () == 1);
+      assert (xpv->license_alternatives[0][0] == "MIT");
+
+      assert (xpv->dependencies.size () == 2);
+      assert (xpv->dependencies[0].size () == 1);
+      assert (xpv->dependencies[0][0] ==
+              dep (
+                "libexpat",
+                optional<dependency_constraint> (
+                  dependency_constraint{comparison::ge, version ("2.0.0")})));
+
+      assert (xpv->dependencies[1].size () == 1);
+      assert (xpv->dependencies[1][0] == dep ("libgenx", nullopt));
+
+      assert (xpv->requirements.empty ());
+
       // Verify libfoo package versions.
       //
       // libfoo-1.2.4-1
@@ -335,8 +365,8 @@ main (int argc, char* argv[])
               *fpv5->package_email == "pack@example.com");
 
       assert (fpv5->internal_repository.load () == mr);
-      assert (fpv5->external_repositories.size () == 1);
-      assert (fpv5->external_repositories[0].load () == cr);
+      assert (fpv5->other_repositories.size () == 1);
+      assert (fpv5->other_repositories[0].load () == cr);
 
       assert (fpv5->priority == priority::high);
       assert (fpv5->priority.comment ==
@@ -362,28 +392,36 @@ main (int argc, char* argv[])
       assert (fpv5->license_alternatives[1].size () == 1);
       assert (fpv5->license_alternatives[1][0] == "BSD");
 
-      assert (fpv5->dependencies.size () == 2);
+      assert (fpv5->dependencies.size () == 3);
       assert (fpv5->dependencies[0].size () == 2);
       assert (fpv5->dependencies[0].comment ==
               "Crashes with 1.1.0-2.3.0.");
 
       assert (fpv5->dependencies[0][0] ==
-              (dependency {
-                 "libmisc",
-                 brep::optional<dependency_constraint> (
-                   dependency_constraint{comparison::lt, version ("1.1")})}));
+              dep (
+                "libmisc",
+                brep::optional<dependency_constraint> (
+                  dependency_constraint{comparison::lt, version ("1.1")})));
 
       assert (fpv5->dependencies[0][1] ==
-              (dependency {
-                 "libmisc",
-                 brep::optional<dependency_constraint> (
-                   dependency_constraint{comparison::gt, version ("2.3.0")})}));
+              dep (
+                "libmisc",
+                brep::optional<dependency_constraint> (
+                  dependency_constraint{comparison::gt, version ("2.3.0")})));
+
+      assert (fpv5->dependencies[1].size () == 1);
+      assert (fpv5->dependencies[1].comment.empty ());
 
-      assert (fpv5->dependencies[1].size () == 2);
-      assert (fpv5->dependencies[1].comment == "The newer the better.");
+      assert (fpv5->dependencies[1][0] ==
+              dep ("libexp",
+                   brep::optional<dependency_constraint> (
+                     dependency_constraint{comparison::ge, version ("1.0")})));
 
-      assert (fpv5->dependencies[1][0] == (dependency {"libstudxml", nullopt}));
-      assert (fpv5->dependencies[1][1] == (dependency {"libexpat", nullopt}));
+      assert (fpv5->dependencies[2].size () == 2);
+      assert (fpv5->dependencies[2].comment == "The newer the better.");
+
+      assert (fpv5->dependencies[2][0] == dep ("libstudxml", nullopt));
+      assert (fpv5->dependencies[2][1] == dep ("libexpat", nullopt));
 
       requirements& fpvr5 (fpv5->requirements);
       assert (fpvr5.size () == 4);
@@ -419,7 +457,7 @@ main (int argc, char* argv[])
       assert (!epv->package_email);
 
       assert (epv->internal_repository.load () == mr);
-      assert (epv->external_repositories.empty ());
+      assert (epv->other_repositories.empty ());
       assert (epv->priority == priority (priority::low));
       assert (epv->changes.empty ());
 
@@ -429,7 +467,7 @@ main (int argc, char* argv[])
 
       assert (epv->dependencies.size () == 1);
       assert (epv->dependencies[0].size () == 1);
-      assert (epv->dependencies[0][0] == (dependency {"libmisc", nullopt}));
+      assert (epv->dependencies[0][0] == dep ("libmisc", nullopt));
 
       assert (epv->requirements.empty ());
 
@@ -461,72 +499,31 @@ main (int argc, char* argv[])
         db.load<package> (package_id ("libfoo", version ("1.2.4-2"))));
       assert (check_location (fpv6));
 
+      assert (cr->prerequisites.empty ());
+      assert (cr->complements.size () == 1);
+      assert (cr->complements[0].load () == tr);
+
       // Verify libbar package version.
       //
       // libbar-2.3.5
       //
-      assert (bpv->summary.empty ());
-      assert (bpv->tags.empty ());
-      assert (!bpv->description);
-      assert (bpv->url.empty ());
-      assert (!bpv->package_url);
-      assert (bpv->email.empty ());
-      assert (!bpv->package_email);
-
-      assert (bpv->internal_repository == nullptr);
-      assert (bpv->external_repositories.size () == 1);
-      assert (bpv->external_repositories[0].load () == cr);
-
-      assert (bpv->priority == priority ());
-      assert (bpv->changes.empty ());
-
-      assert (bpv->license_alternatives.empty ());
-      assert (bpv->dependencies.empty ());
-      assert (bpv->requirements.empty ());
+      assert (check_external (*bpv));
+      assert (bpv->other_repositories.size () == 1);
+      assert (bpv->other_repositories[0].load () == cr);
 
       // Verify libfoo package versions.
       //
       // libfoo-0.1
       //
-      assert (fpv0->summary.empty ());
-      assert (fpv0->tags.empty ());
-      assert (!fpv0->description);
-      assert (fpv0->url.empty ());
-      assert (!fpv0->package_url);
-      assert (fpv0->email.empty ());
-      assert (!fpv0->package_email);
-
-      assert (fpv0->internal_repository == nullptr);
-      assert (fpv0->external_repositories.size () == 1);
-      assert (fpv0->external_repositories[0].load () == cr);
-      assert (fpv0->priority == priority::low);
-      assert (fpv0->changes.empty ());
-
-      assert (fpv0->license_alternatives.empty ());
-
-      assert (fpv0->dependencies.empty ());
-      assert (fpv0->requirements.empty ());
+      assert (check_external (*fpv0));
+      assert (fpv0->other_repositories.size () == 1);
+      assert (fpv0->other_repositories[0].load () == cr);
 
       // libfoo-1.2.4-2
       //
-      assert (fpv6->summary.empty ());
-      assert (fpv6->tags.empty ());
-      assert (!fpv6->description);
-      assert (fpv6->url.empty ());
-      assert (!fpv6->package_url);
-      assert (fpv6->email.empty ());
-      assert (!fpv6->package_email);
-
-      assert (fpv6->internal_repository == nullptr);
-      assert (fpv6->external_repositories.size () == 1);
-      assert (fpv6->external_repositories[0].load () == cr);
-      assert (fpv6->priority == priority::low);
-      assert (fpv6->changes.empty ());
-
-      assert (fpv6->license_alternatives.empty ());
-
-      assert (fpv6->dependencies.empty ());
-      assert (fpv6->requirements.empty ());
+      assert (check_external (*fpv6));
+      assert (fpv6->other_repositories.size () == 1);
+      assert (fpv6->other_repositories[0].load () == cr);
 
       // Verify 'testing' repository.
       //
@@ -544,59 +541,76 @@ main (int argc, char* argv[])
               file_mtime (dir_path (tr->local_path) / path ("repositories")));
       assert (!tr->internal);
 
-      shared_ptr<package> mpv (
-        db.load<package> (package_id ("libmisc", version ("1.1"))));
-      assert (check_location (mpv));
+      shared_ptr<package> mpv0 (
+        db.load<package> (package_id ("libmisc", version ("2.4.0"))));
+      assert (check_location (mpv0));
 
-      shared_ptr<package> tpv (
-        db.load<package> (package_id ("libexpat", version ("5.1"))));
-      assert (check_location (tpv));
+      assert (tr->prerequisites.empty ());
+      assert (tr->complements.size () == 1);
+      assert (tr->complements[0].load () == gr);
 
       // Verify libmisc package version.
       //
-      // libmisc-1.1
+      // libmisc-2.4.0
+      //
+      assert (check_external (*mpv0));
+      assert (mpv0->other_repositories.size () == 1);
+      assert (mpv0->other_repositories[0].load () == tr);
+
+      // Verify 'staging' repository.
       //
-      assert (mpv->summary.empty ());
-      assert (mpv->tags.empty ());
-      assert (!mpv->description);
-      assert (mpv->url.empty ());
-      assert (!mpv->package_url);
-      assert (mpv->email.empty ());
-      assert (!mpv->package_email);
+      assert (gr->location.canonical_name () == "cppget.org/staging");
+      assert (gr->location.string () ==
+              "http://pkg.cppget.org/external/1/staging");
+      assert (gr->display_name.empty ());
 
-      assert (mpv->internal_repository == nullptr);
-      assert (mpv->external_repositories.size () == 1);
-      assert (mpv->external_repositories[0].load () == tr);
+      dir_path grp (cp.directory () / dir_path ("external/1/staging"));
+      assert (gr->local_path == grp.normalize ());
 
-      assert (mpv->priority == priority ());
-      assert (mpv->changes.empty ());
+      assert (gr->packages_timestamp ==
+              file_mtime (dir_path (gr->local_path) / path ("packages")));
+      assert (gr->repositories_timestamp ==
+              file_mtime (dir_path (gr->local_path) / path ("repositories")));
+      assert (!gr->internal);
 
-      assert (mpv->license_alternatives.empty ());
-      assert (mpv->dependencies.empty ());
-      assert (mpv->requirements.empty ());
+      shared_ptr<package> tpv (
+        db.load<package> (package_id ("libexpat", version ("5.1"))));
+      assert (check_location (tpv));
+
+      shared_ptr<package> gpv (
+        db.load<package> (package_id ("libgenx", version ("1.0"))));
+      assert (check_location (gpv));
+
+      shared_ptr<package> mpv1 (
+        db.load<package> (package_id ("libmisc", version ("1.0"))));
+      assert (check_location (mpv1));
+
+      assert (gr->prerequisites.empty ());
+      assert (gr->complements.empty ());
 
       // Verify libexpat package version.
       //
       // libexpat-5.1
       //
-      assert (tpv->summary.empty ());
-      assert (tpv->tags.empty ());
-      assert (!tpv->description);
-      assert (tpv->url.empty ());
-      assert (!tpv->package_url);
-      assert (tpv->email.empty ());
-      assert (!tpv->package_email);
-
-      assert (tpv->internal_repository == nullptr);
-      assert (tpv->external_repositories.size () == 1);
-      assert (tpv->external_repositories[0].load () == gr);
-
-      assert (tpv->priority == priority ());
-      assert (tpv->changes.empty ());
-
-      assert (tpv->license_alternatives.empty ());
-      assert (tpv->dependencies.empty ());
-      assert (tpv->requirements.empty ());
+      assert (check_external (*tpv));
+      assert (tpv->other_repositories.size () == 1);
+      assert (tpv->other_repositories[0].load () == gr);
+
+      // Verify libgenx package version.
+      //
+      // libgenx-1.0
+      //
+      assert (check_external (*gpv));
+      assert (gpv->other_repositories.size () == 1);
+      assert (gpv->other_repositories[0].load () == gr);
+
+      // Verify libmisc package version.
+      //
+      // libmisc-1.0
+      //
+      assert (check_external (*mpv1));
+      assert (mpv1->other_repositories.size () == 1);
+      assert (mpv1->other_repositories[0].load () == gr);
 
       // Change package summary, update the object persistent state, rerun
       // loader and ensure the model were not rebuilt.
diff --git a/tests/loader/external/1/staging/packages b/tests/loader/external/1/staging/packages
index 86c20c1..e7b22b0 100644
--- a/tests/loader/external/1/staging/packages
+++ b/tests/loader/external/1/staging/packages
@@ -6,3 +6,20 @@ license: MIT
 url: http://www.example.com/expat/
 email: expat-users@example.com
 location: libexpat-5.1.tar.gz
+:
+name: libgenx
+version: 1.0
+summary: The Genx Library
+license: MIT
+url: http://www.example.com/genx/
+email: genx-users@example.com
+location: libgenx-1.0.tar.gz
+:
+name: libmisc
+version: 1.0
+summary: The Misc Library
+license: MIT
+url: http://www.example.com/misc/
+email: misc-users@example.com
+depends: libexpat >= 5.0
+location: libmisc-1.0.tar.gz
diff --git a/tests/loader/external/1/testing/packages b/tests/loader/external/1/testing/packages
index ac5ab95..bdebece 100644
--- a/tests/loader/external/1/testing/packages
+++ b/tests/loader/external/1/testing/packages
@@ -1,9 +1,9 @@
 : 1
 name: libmisc
-version: 1.1
-summary: The Expat Library
+version: 2.4.0
+summary: The Misc Library
 license: MIT
 url: http://www.example.com/misc/
 email: misc-users@example.com
 depends: libexpat >= 5.0
-location: libmisc-1.1.tar.gz
+location: libmisc-2.4.0.tar.gz
diff --git a/tests/loader/internal/1/math/packages b/tests/loader/internal/1/math/packages
index d55a9e3..4d34c13 100644
--- a/tests/loader/internal/1/math/packages
+++ b/tests/loader/internal/1/math/packages
@@ -1,4 +1,19 @@
 : 1
+name: libstudxml
+version: 1.0.0-1
+summary: Modern C++ XML API
+license: MIT
+tags: c++, xml, parser, serializer, pull, streaming, modern
+description-file: README
+changes-file: NEWS
+url: http://www.codesynthesis.com/projects/libstudxml/
+email: studxml-users@codesynthesis.com; Public mailing list, posts by\
+ non-members are allowed but moderated.
+package-email: boris@codesynthesis.com; Direct email to the author.
+depends: libexpat >= 2.0.0
+depends: libgenx
+location: libstudxml-1.0.0-1.tar.gz
+:
 name: libexp
 version: 1+1.2
 summary: The exponent
@@ -31,6 +46,7 @@ email: foo-users@example.com; Public mailing list. Read FAQ before posting.
 package-url: http://www.example.com/foo/pack; Package details.
 package-email: pack@example.com; Current packager.
 depends: libmisc < 1.1 | libmisc > 2.3.0; Crashes with 1.1.0-2.3.0.
+depends: libexp >= 1.0
 depends: ? libstudxml | libexpat; The newer the better.
 requires: linux | windows | macosx; Symbian support is coming.
 requires: c++11
diff --git a/tests/loader/internal/1/stable/packages b/tests/loader/internal/1/stable/packages
index 8d1e2fd..756a562 100644
--- a/tests/loader/internal/1/stable/packages
+++ b/tests/loader/internal/1/stable/packages
@@ -9,21 +9,6 @@ email: foo-users@example.com
 depends: libmisc >= 2.0.0
 location: libfoo-1.2.3-4.tar.gz
 :
-name: libstudxml
-version: 1.0.0-1
-summary: Modern C++ XML API
-license: MIT
-tags: c++, xml, parser, serializer, pull, streaming, modern
-description-file: README
-changes-file: NEWS
-url: http://www.codesynthesis.com/projects/libstudxml/
-email: studxml-users@codesynthesis.com; Public mailing list, posts by\
- non-members are allowed but moderated.
-package-email: boris@codesynthesis.com; Direct email to the author.
-depends: libexpat >= 2.0.0
-depends: libgenx
-location: libstudxml-1.0.0-1.tar.gz
-:
 name: libfoo
 version: 1.2.2
 summary: The Foo library
diff --git a/web/module b/web/module
index 25c4bf2..1774884 100644
--- a/web/module
+++ b/web/module
@@ -58,8 +58,7 @@ namespace web
     sequence_error (std::string d): std::runtime_error (std::move (d)) {}
   };
 
-  template <typename T>
-  using optional = butl::optional<T>;
+  using butl::optional;
 
   struct name_value
   {
@@ -74,7 +73,7 @@ namespace web
   };
 
   using name_values = std::vector<name_value>;
-  using path = butl::path;
+  using butl::path;
 
   class request
   {
-- 
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