Improve dependency resolution (GH issue 318)

4 files changed, 273 insertions, 52 deletions

diff --git a/bpkg/pkg-build-collect.cxx b/bpkg/pkg-build-collect.cxx
index 436d629..e99557a 100644
--- a/bpkg/pkg-build-collect.cxx
+++ b/bpkg/pkg-build-collect.cxx
@@ -3367,7 +3367,7 @@ namespace bpkg
                                         pdb,
                                         nm,
                                         pkg.available_version (),
-                                        false /* selected_dependent */);
+                                        false /* existing_dependent */);
 
                     if (!satisfies (v2, c1.value))
                     {
@@ -3540,7 +3540,7 @@ namespace bpkg
                                             pdb,
                                             nm,
                                             pkg.available_version (),
-                                            false /* selected_dependent */);
+                                            false /* existing_dependent */);
 
             // Now collect this prerequisite. If it was actually collected
             // (i.e., it wasn't already there) and we are forcing a downgrade
@@ -7508,11 +7508,16 @@ namespace bpkg
         {
           using constraint_type = build_package::constraint_type;
 
+          // Pre-entered entries are always converted to adjustments (see
+          // above).
+          //
+          assert (dp.action);
+
           constraint_type c (move (*dc),
                              ddb,
                              move (dn),
                              dp.selected->version,
-                             true /* selected_dependent */);
+                             *dp.action != build_package::build);
 
           if (find_if (p.constraints.begin (), p.constraints.end (),
                        [&c] (const constraint_type& v)
@@ -7557,7 +7562,7 @@ namespace bpkg
                      const build_package& p,
                      string& indent,
                      set<package_key>& printed,
-                     optional<bool> selected_dependent) const
+                     optional<bool> existing_dependent) const
   {
     using constraint_type = build_package::constraint_type;
 
@@ -7573,8 +7578,8 @@ namespace bpkg
 
         for (const constraint_type& c: cs)
         {
-          if (!selected_dependent ||
-              *selected_dependent == c.selected_dependent)
+          if (!existing_dependent ||
+              *existing_dependent == c.existing_dependent)
           {
             if (const build_package* d = dependent_build (c))
             {
@@ -7582,7 +7587,7 @@ namespace bpkg
                  << ' ' << c.value << ')';
 
               indent += "  ";
-              print_constraints (dr, *d, indent, printed, selected_dependent);
+              print_constraints (dr, *d, indent, printed, existing_dependent);
               indent.resize (indent.size () - 2);
             }
             else
@@ -7595,8 +7600,8 @@ namespace bpkg
       {
         for (const constraint_type& c: cs)
         {
-          if (!selected_dependent ||
-              *selected_dependent == c.selected_dependent)
+          if (!existing_dependent ||
+              *existing_dependent == c.existing_dependent)
           {
             dr << '\n' << indent << "...";
             break;
@@ -7611,11 +7616,11 @@ namespace bpkg
                      const package_key& pk,
                      string& indent,
                      set<package_key>& printed,
-                     optional<bool> selected_dependent) const
+                     optional<bool> existing_dependent) const
   {
     const build_package* p (entered_build (pk));
     assert (p != nullptr); // Expected to be collected.
-    print_constraints (dr, *p, indent, printed, selected_dependent);
+    print_constraints (dr, *p, indent, printed, existing_dependent);
   }
 
   void build_packages::
@@ -7982,7 +7987,7 @@ namespace bpkg
                                     dpt.db,
                                     dpt.name,
                                     *dpt.version,
-                                    true /* selected_package */);
+                                    true /* existing_package */);
     }
 
     // Note: not recursive.
diff --git a/bpkg/pkg-build-collect.hxx b/bpkg/pkg-build-collect.hxx
index f84c86f..5c8a635 100644
--- a/bpkg/pkg-build-collect.hxx
+++ b/bpkg/pkg-build-collect.hxx
@@ -221,9 +221,9 @@ namespace bpkg
       package_version_key dependent;
 
       // False for non-packages. Otherwise, indicates whether the constraint
-      // comes from the selected dependent or not.
+      // comes from the existing rather than the being built dependent.
       //
-      bool selected_dependent;
+      bool existing_dependent;
 
       // Create constraint for a package dependent.
       //
@@ -231,17 +231,17 @@ namespace bpkg
                        database& db,
                        package_name nm,
                        version ver,
-                       bool s)
+                       bool e)
           : value (move (v)),
             dependent (db, move (nm), move (ver)),
-            selected_dependent (s) {}
+            existing_dependent (e) {}
 
       // Create constraint for a non-package dependent.
       //
       constraint_type (version_constraint v, database& db, string nm)
           : value (move (v)),
             dependent (db, move (nm)),
-            selected_dependent (false) {}
+            existing_dependent (false) {}
     };
 
     vector<constraint_type> constraints;
@@ -1683,7 +1683,7 @@ namespace bpkg
     // constraints for the same package twice, printing "..." instead. Noop if
     // there are no constraints for this package.
     //
-    // Optionally, only print constraints from the selected or being built
+    // Optionally, only print constraints from the existing or being built
     // dependents (see build_package::constraint_type for details).
     //
     void
@@ -1691,14 +1691,14 @@ namespace bpkg
                        const build_package&,
                        string& indent,
                        std::set<package_key>& printed,
-                       optional<bool> selected_dependent = nullopt) const;
+                       optional<bool> existing_dependent = nullopt) const;
 
     void
     print_constraints (diag_record&,
                        const package_key&,
                        string& indent,
                        std::set<package_key>& printed,
-                       optional<bool> selected_dependent = nullopt) const;
+                       optional<bool> existing_dependent = nullopt) const;
 
     // Verify that builds ordering is consistent across all the data
     // structures and the ordering expectations are fulfilled (real build
diff --git a/bpkg/pkg-build.cxx b/bpkg/pkg-build.cxx
index 0802c40..6a9ad7d 100644
--- a/bpkg/pkg-build.cxx
+++ b/bpkg/pkg-build.cxx
@@ -2097,6 +2097,8 @@ namespace bpkg
   // Specifically, try to find the best available package version considering
   // all the imposed constraints as per unsatisfied_dependents description. If
   // succeed, return the command line adjustment reflecting the replacement.
+  // If allow_downgrade is false, then don't return a downgrade adjustment for
+  // the package, unless it is being deorphaned.
   //
   // Notes:
   //
@@ -2133,9 +2135,10 @@ namespace bpkg
   //     requested to be upgraded, patched, and/or deorphaned, then we
   //     shouldn't be silently up/down-grading it.
   //
-  optional<cmdline_adjustment>
+  static optional<cmdline_adjustment>
   try_replace_dependency (const common_options& o,
                           const build_package& p,
+                          bool allow_downgrade,
                           const build_packages& pkgs,
                           const vector<build_package>& hold_pkgs,
                           const dependency_packages& dep_pkgs,
@@ -2423,7 +2426,7 @@ namespace bpkg
         {
           r = false;
 
-          if (c.dependent.version && !c.selected_dependent)
+          if (c.dependent.version && !c.existing_dependent)
           {
             package_key pk (c.dependent.db, c.dependent.name);
 
@@ -2473,18 +2476,21 @@ namespace bpkg
       // then the selected one, then what we currently have is the best that
       // we can get. Thus, we use the selected version as a replacement,
       // unless it doesn't satisfy all the constraints or we are deorphaning.
+      // Bail out if we cannot stay with the selected version and downgrade is
+      // not allowed.
       //
       if (constraint == nullptr && sp != nullptr)
       {
         const version& sv (sp->version);
-        if (av < sv && !sp->system () && !p.deorphan)
+        if (av < sv && !p.deorphan)
         {
-          // Only consider the selected package if its version is satisfactory
-          // for its new dependents (note: must be checked first since has a
-          // byproduct), differs from the version being replaced, and was
-          // never used for the same command line (see above for details).
+          // Only consider to keep the selected non-system package if its
+          // version is satisfactory for its new dependents (note: must be
+          // checked first since has a byproduct), differs from the version
+          // being replaced, and was never used for the same command line (see
+          // above for details).
           //
-          if (satisfactory (sv) && sv != ver)
+          if (!sp->system () && satisfactory (sv) && sv != ver)
           {
             if (!cmdline_adjs.tried_earlier (db, nm, sv))
             {
@@ -2493,9 +2499,17 @@ namespace bpkg
             }
             else
               l5 ([&]{trace << "selected package replacement "
-                            << package_version_key (db, nm, sp->version)
-                            << " tried earlier for same command line, "
-                            << "skipping";});
+                            << package_version_key (db, nm, sv) << " tried "
+                            << "earlier for same command line, skipping";});
+          }
+
+          if (!allow_downgrade)
+          {
+            l5 ([&]{trace << "downgrade for "
+                          << package_version_key (db, nm, sv) << " is not "
+                          << "allowed, bailing out";});
+
+            break;
           }
         }
       }
@@ -2693,11 +2707,12 @@ namespace bpkg
   // of the specified dependency with a different available version,
   // satisfactory for all its new and existing dependents (if any). Return the
   // command line adjustment if such a replacement is deduced and nullopt
-  // otherwise. It is assumed that the dependency replacement has been
-  // (unsuccessfully) tried by using the try_replace_dependency() call and its
-  // resulting list of the dependents, unsatisfied by some of the dependency
-  // available versions, is also passed to the function call as the
-  // unsatisfied_dpts argument.
+  // otherwise. If allow_downgrade is false, then don't return a downgrade
+  // adjustment, except for a being deorphaned dependent. It is assumed that
+  // the dependency replacement has been (unsuccessfully) tried by using the
+  // try_replace_dependency() call and its resulting list of the dependents,
+  // unsatisfied by some of the dependency available versions, is also passed
+  // to the function call as the unsatisfied_dpts argument.
   //
   // Specifically, try to replace the dependents in the following order by
   // calling try_replace_dependency() for them:
@@ -2723,9 +2738,10 @@ namespace bpkg
   // - Dependents of all the above types of dependents, discovered by
   //   recursively calling try_replace_dependent() for them.
   //
-  optional<cmdline_adjustment>
+  static optional<cmdline_adjustment>
   try_replace_dependent (const common_options& o,
                          const build_package& p, // Dependency.
+                         bool allow_downgrade,
                          const vector<unsatisfied_constraint>* ucs,
                          const build_packages& pkgs,
                          const cmdline_adjustments& cmdline_adjs,
@@ -2758,6 +2774,7 @@ namespace bpkg
     //
     auto try_replace = [&o,
                         &p,
+                        allow_downgrade,
                         &pkgs,
                         &cmdline_adjs,
                         &hold_pkgs,
@@ -2793,6 +2810,7 @@ namespace bpkg
           if (optional<cmdline_adjustment> a = try_replace_dependency (
                 o,
                 *d,
+                allow_downgrade,
                 pkgs,
                 hold_pkgs,
                 dep_pkgs,
@@ -2816,7 +2834,7 @@ namespace bpkg
     {
       const package_version_key& dvk (c.dependent);
 
-      if (dvk.version && !c.selected_dependent && !satisfies (av, c.value))
+      if (dvk.version && !c.existing_dependent && !satisfies (av, c.value))
       {
         if (optional<cmdline_adjustment> a = try_replace (
               package_key (dvk.db, dvk.name), "unsatisfied dependent"))
@@ -2851,7 +2869,7 @@ namespace bpkg
     {
       const package_version_key& dvk (c1.dependent);
 
-      if (dvk.version && !c1.selected_dependent)
+      if (dvk.version && !c1.existing_dependent)
       {
         const version_constraint& v1 (c1.value);
 
@@ -2900,6 +2918,7 @@ namespace bpkg
       if (optional<cmdline_adjustment> a = try_replace_dependent (
             o,
             *d,
+            allow_downgrade,
             nullptr /* unsatisfied_constraints */,
             pkgs,
             cmdline_adjs,
@@ -4298,6 +4317,14 @@ namespace bpkg
     optional<cmdline_adjustment> cmdline_refine_adjustment;
     optional<size_t>             cmdline_refine_index;
 
+    // If an --upgrade* or --patch* option is used on the command line, then
+    // we try to avoid any package downgrades initially. However, if the
+    // resolution fails in this mode, we fall back to allowing such
+    // downgrades. Without this logic, we may end up downgrading one package
+    // in order to upgrade another, which would be incorrect.
+    //
+    bool cmdline_allow_downgrade (true);
+
     {
       // Check if the package is a duplicate. Return true if it is but
       // harmless.
@@ -4843,9 +4870,14 @@ namespace bpkg
             // configuration.
             //
             if (pdb != nullptr)
+            {
+              if (u)
+                cmdline_allow_downgrade = false;
+
               rec_pkgs.push_back (recursive_package {*pdb, pa.name,
                                                      r, u && *u,
                                                      d});
+            }
           }
         }
 
@@ -4901,6 +4933,10 @@ namespace bpkg
 
           bool hold_version (pa.constraint.has_value ());
 
+          optional<bool> upgrade (pa.options.upgrade () || pa.options.patch ()
+                                  ? pa.options.upgrade ()
+                                  : optional<bool> ());
+
           dep_pkgs.push_back (
             dependency_package {pdb,
                                 move (pa.name),
@@ -4909,9 +4945,7 @@ namespace bpkg
                                 move (sp),
                                 sys,
                                 existing,
-                                (pa.options.upgrade () || pa.options.patch ()
-                                 ? pa.options.upgrade ()
-                                 : optional<bool> ()),
+                                upgrade,
                                 pa.options.deorphan (),
                                 pa.options.keep_out (),
                                 pa.options.disfigure (),
@@ -4921,6 +4955,10 @@ namespace bpkg
                                 pa.options.checkout_purge (),
                                 move (pa.config_vars),
                                 pa.system_status});
+
+          if (upgrade)
+            cmdline_allow_downgrade = false;
+
           continue;
         }
 
@@ -5154,6 +5192,9 @@ namespace bpkg
 
         pkg_confs.emplace_back (p.db, p.name ());
 
+        if (p.upgrade)
+          cmdline_allow_downgrade = false;
+
         hold_pkgs.push_back (move (p));
       }
 
@@ -5279,6 +5320,9 @@ namespace bpkg
             l4 ([&]{trace << "stash held package "
                           << p.available_name_version_db ();});
 
+            if (p.upgrade)
+              cmdline_allow_downgrade = false;
+
             hold_pkgs.push_back (move (p));
 
             // If there are also -i|-r, then we are also upgrading and/or
@@ -7022,6 +7066,7 @@ namespace bpkg
 
               if ((a = try_replace_dependency (o,
                                                *p,
+                                               cmdline_allow_downgrade,
                                                pkgs,
                                                hold_pkgs,
                                                dep_pkgs,
@@ -7030,6 +7075,7 @@ namespace bpkg
                                                "unsatisfactory dependency")) ||
                   (a = try_replace_dependent (o,
                                               *p,
+                                              cmdline_allow_downgrade,
                                               &ic.unsatisfied_constraints,
                                               pkgs,
                                               cmdline_adjs,
@@ -7055,7 +7101,27 @@ namespace bpkg
                 prepare_recollect ();
               }
               else
-                unsatisfied_depts.diag (pkgs); // Issue the diagnostics and fail.
+              {
+                // If we fail to resolve the unsatisfied dependency
+                // constraints with the downgrades disallowed, then allow
+                // downgrades and retry from the very beginning.
+                //
+                if (!cmdline_allow_downgrade)
+                {
+                  l5 ([&]{trace << "cannot resolve unsatisfied dependency "
+                                << "constraints, now allowing downgrades";});
+
+                  cmdline_allow_downgrade = true;
+
+                  prepare_recollect ();
+                }
+                else
+                {
+                  // Issue the diagnostics and fail.
+                  //
+                  unsatisfied_depts.diag (pkgs);
+                }
+              }
             }
             else // We are in the command line adjustments refinement cycle.
             {
diff --git a/tests/pkg-build.testscript b/tests/pkg-build.testscript
index 9d19846..9326541 100644
--- a/tests/pkg-build.testscript
+++ b/tests/pkg-build.testscript
@@ -2369,8 +2369,8 @@ test.arguments += --sys-no-query
           trace: execute_plan: simulate: yes
           %.*
           trace: pkg_build: try to replace unsatisfactory dependency libbar/2.0.0 with some other version
-          trace: try_replace_dependent: try to replace unsatisfiable dependent libbaz/2.0.0 of dependency libbar/2.0.0 with some other version
-          trace: try_replace_dependency: replace unsatisfiable dependent version libbaz/2.0.0 with 1.0.0 by adding constraint '?libbaz' -> '?libbaz == 1.0.0' on command line
+          trace: try_replace_dependent: try to replace unsatisfied dependent libbaz/2.0.0 of dependency libbar/2.0.0 with some other version
+          trace: try_replace_dependency: replace unsatisfied dependent version libbaz/2.0.0 with 1.0.0 by adding constraint '?libbaz' -> '?libbaz == 1.0.0' on command line
           trace: pkg_build: refine package collection/plan execution from scratch
           trace: execute_plan: simulate: yes
           %.*
@@ -2584,8 +2584,8 @@ test.arguments += --sys-no-query
           trace: execute_plan: simulate: yes
           %.*
           trace: pkg_build: try to replace unsatisfactory dependency libbar/2.0.0 with some other version
-          trace: try_replace_dependent: try to replace unsatisfiable dependent libbaz/2.0.0 of dependency libbar/2.0.0 with some other version
-          trace: try_replace_dependency: replace unsatisfiable dependent version libbaz/2.0.0 with 1.0.0 by adding constraint '?libbaz' -> '?libbaz == 1.0.0' on command line
+          trace: try_replace_dependent: try to replace unsatisfied dependent libbaz/2.0.0 of dependency libbar/2.0.0 with some other version
+          trace: try_replace_dependency: replace unsatisfied dependent version libbaz/2.0.0 with 1.0.0 by adding constraint '?libbaz' -> '?libbaz == 1.0.0' on command line
           trace: pkg_build: refine package collection/plan execution from scratch
           trace: collect_build: add foo/1.0.0
           trace: collect_build_prerequisites: skip configured foo/1.0.0
@@ -2663,8 +2663,8 @@ test.arguments += --sys-no-query
           trace: execute_plan: simulate: yes
           %.*
           trace: pkg_build: try to replace unsatisfactory dependency libbar/2.0.0 with some other version
-          trace: try_replace_dependent: try to replace unsatisfiable dependent libbaz/2.0.0 of dependency libbar/2.0.0 with some other version
-          trace: try_replace_dependency: replace unsatisfiable dependent version libbaz/2.0.0 with 1.0.0 by adding constraint '?libbaz' -> '?libbaz == 1.0.0' on command line
+          trace: try_replace_dependent: try to replace unsatisfied dependent libbaz/2.0.0 of dependency libbar/2.0.0 with some other version
+          trace: try_replace_dependency: replace unsatisfied dependent version libbaz/2.0.0 with 1.0.0 by adding constraint '?libbaz' -> '?libbaz == 1.0.0' on command line
           trace: pkg_build: refine package collection/plan execution from scratch
           trace: collect_build: add foo/1.0.0
           trace: collect_build_prerequisites: skip configured foo/1.0.0
@@ -5217,7 +5217,7 @@ test.arguments += --sys-no-query
           $pkg_drop libfoo libfox
         }
 
-        : unsatisfied-dependent
+        : unsatisfied-dependent-noop
         :
         : This test demonstrates a case when the dependency resolution
         : machinery resolves unsatisfied dependency constraints by
@@ -5231,6 +5231,16 @@ test.arguments += --sys-no-query
         {
           $clone_cfg;
 
+          #  Dependencies:
+          #
+          #  libbox/2.0.0: depends: libbax == 1.0.0
+          #  libbox/1.0.0: depends: libbax
+          #
+          #  libbix/1.0.0: depends: libbax == 1.0.0
+          #  libbix/2.0.0: depends: libbax == 2.0.0
+          #
+          #  libbux: depends: libbix
+          #
           $* libbox ?libbix/1.0.0 libbux 2>!;
 
           $pkg_status -ar >>EOO;
@@ -5272,8 +5282,10 @@ test.arguments += --sys-no-query
             trace: execute_plan: simulate: yes
             %.*
             trace: pkg_build: try to replace unsatisfactory dependency libbax/2.0.0 with some other version
-            trace: try_replace_dependent: try to replace unsatisfiable dependent libbix/2.0.0 of dependency libbax/2.0.0 with some other version
-            trace: try_replace_dependency: replace unsatisfiable dependent version libbix/2.0.0 with 1.0.0 by adding package spec '?libbix == 1.0.0' to command line
+            trace: try_replace_dependent: try to replace unsatisfied dependent libbox/2.0.0 of dependency libbax/2.0.0 with some other version
+            trace: try_replace_dependency: downgrade for libbox/2.0.0 is not allowed, bailing out
+            trace: try_replace_dependent: try to replace unsatisfied dependent libbix/2.0.0 of dependency libbax/2.0.0 with some other version
+            trace: try_replace_dependency: replace unsatisfied dependent version libbix/2.0.0 with 1.0.0 by adding package spec '?libbix == 1.0.0' to command line
             trace: pkg_build: refine package collection/plan execution from scratch
             trace: collect_build: add libbox/2.0.0
             trace: collect_build: add libbux/1.0.0
@@ -5299,6 +5311,144 @@ test.arguments += --sys-no-query
           $pkg_drop libbox libbux
         }
 
+        : unsatisfied-dependent
+        :
+        : Similar to the above, but this time noop is not a valid constraints
+        : resolution due to ?libbix/2.0.0. Thus, the dependency resolution
+        : machinery ends up with the downgrade of libbox/2.0.0 to 1.0.0.
+        :
+        {
+          $clone_cfg;
+
+          $* libbox ?libbix/1.0.0 libbux 2>!;
+
+          $pkg_status -ar >>EOO;
+            libbax configured 1.0.0 available 2.0.0
+            !libbox configured 2.0.0
+              libbax configured 1.0.0 available 2.0.0
+            libbix configured !1.0.0 available 2.0.0
+              libbax configured 1.0.0 available 2.0.0
+            !libbux configured 1.0.0
+              libbix configured !1.0.0 available 2.0.0
+                libbax configured 1.0.0 available 2.0.0
+            EOO
+
+          $* { libbox libbux ?libbax } +{ --upgrade --recursive } ?libbix/2.0.0 2>>~%EOE%;
+            %.*
+            trace: pkg_build: refine package collection/plan execution from scratch
+            trace: collect_build: add libbox/2.0.0
+            trace: collect_build: add libbux/1.0.0
+            trace: collect_build_prerequisites: skip configured libbox/2.0.0
+            trace: collect_build_prerequisites: skip configured libbux/1.0.0
+            trace: execute_plan: simulate: yes
+            %.*
+            trace: evaluate_dependency: libbix/1.0.0: update to libbix/2.0.0
+            %.*
+            trace: pkg_build: refine package collection/plan execution
+            trace: collect_build_prerequisites: pre-reeval libbux/1.0.0
+            trace: collect_build_prerequisites: pre-reevaluated libbux/1.0.0: end reached
+            trace: collect_build_prerequisites: begin libbix/2.0.0
+            trace: collect_build_prerequisites: no cfg-clause for dependency libbax/2.0.0 of dependent libbix/2.0.0
+            trace: collect_build_prerequisites: skip unsatisfied existing dependent libbox of dependency libbax/2.0.0 due to constraint (libbax == 1.0.0)
+            trace: collect_build_prerequisites: skip being built existing dependent libbix of dependency libbax
+            trace: collect_build_prerequisites: begin libbax/2.0.0
+            trace: collect_build_prerequisites: end libbax/2.0.0
+            trace: collect_build_prerequisites: end libbix/2.0.0
+            trace: collect_dependents: postpone failure for existing dependent libbox unsatisfied with dependency libbax/2.0.0 (== 1.0.0)
+            trace: execute_plan: simulate: yes
+            %.*
+            trace: pkg_build: try to replace unsatisfactory dependency libbax/2.0.0 with some other version
+            trace: try_replace_dependent: try to replace unsatisfied dependent libbox/2.0.0 of dependency libbax/2.0.0 with some other version
+            trace: try_replace_dependency: downgrade for libbox/2.0.0 is not allowed, bailing out
+            trace: try_replace_dependent: try to replace unsatisfied dependent libbix/2.0.0 of dependency libbax/2.0.0 with some other version
+            trace: try_replace_dependency: replacement of unsatisfied dependent version libbix/2.0.0 is denied since it is specified on command line as '?libbix == 2.0.0'
+            trace: pkg_build: cannot resolve unsatisfied dependency constraints, now allowing downgrades
+            trace: pkg_build: refine package collection/plan execution from scratch
+            trace: collect_build: add libbox/2.0.0
+            trace: collect_build: add libbux/1.0.0
+            trace: collect_build_prerequisites: skip configured libbox/2.0.0
+            trace: collect_build_prerequisites: skip configured libbux/1.0.0
+            trace: execute_plan: simulate: yes
+            %.*
+            trace: evaluate_dependency: libbix/1.0.0: update to libbix/2.0.0
+            %.*
+            trace: pkg_build: refine package collection/plan execution
+            trace: collect_build_prerequisites: pre-reeval libbux/1.0.0
+            trace: collect_build_prerequisites: pre-reevaluated libbux/1.0.0: end reached
+            trace: collect_build_prerequisites: begin libbix/2.0.0
+            trace: collect_build_prerequisites: no cfg-clause for dependency libbax/2.0.0 of dependent libbix/2.0.0
+            trace: collect_build_prerequisites: skip unsatisfied existing dependent libbox of dependency libbax/2.0.0 due to constraint (libbax == 1.0.0)
+            trace: collect_build_prerequisites: skip being built existing dependent libbix of dependency libbax
+            trace: collect_build_prerequisites: begin libbax/2.0.0
+            trace: collect_build_prerequisites: end libbax/2.0.0
+            trace: collect_build_prerequisites: end libbix/2.0.0
+            trace: collect_dependents: postpone failure for existing dependent libbox unsatisfied with dependency libbax/2.0.0 (== 1.0.0)
+            trace: execute_plan: simulate: yes
+            %.*
+            trace: pkg_build: try to replace unsatisfactory dependency libbax/2.0.0 with some other version
+            trace: try_replace_dependent: try to replace unsatisfied dependent libbox/2.0.0 of dependency libbax/2.0.0 with some other version
+            trace: try_replace_dependency: replace unsatisfied dependent version libbox/2.0.0 with 1.0.0 by adding constraint 'libbox' -> 'libbox == 1.0.0' on command line
+            trace: pkg_build: refine package collection/plan execution from scratch
+            trace: collect_build: add libbox/1.0.0
+            trace: collect_build: add libbux/1.0.0
+            trace: collect_build_prerequisites: begin libbox/1.0.0
+            trace: collect_build_prerequisites: no cfg-clause for dependency libbax/1.0.0 of dependent libbox/1.0.0
+            trace: collect_build_prerequisites: skip configured libbax/1.0.0
+            trace: collect_build_prerequisites: end libbox/1.0.0
+            trace: collect_build_prerequisites: skip configured libbux/1.0.0
+            trace: execute_plan: simulate: yes
+            %.*
+            trace: evaluate_dependency: libbix/1.0.0: update to libbix/2.0.0
+            %.*
+            trace: pkg_build: refine package collection/plan execution
+            trace: collect_build_prerequisites: pre-reeval libbux/1.0.0
+            trace: collect_build_prerequisites: pre-reevaluated libbux/1.0.0: end reached
+            trace: collect_build_prerequisites: begin libbix/2.0.0
+            trace: collect_build: pick libbax/2.0.0 over libbax/1.0.0
+            trace: collect_build: libbax/1.0.0 package version needs to be replaced with libbax/2.0.0
+            trace: pkg_build: collection failed due to package version replacement, retry from scratch
+            trace: pkg_build: refine package collection/plan execution from scratch
+            trace: collect_build: add libbox/1.0.0
+            trace: collect_build: add libbux/1.0.0
+            trace: collect_build_prerequisites: begin libbox/1.0.0
+            trace: collect_build: apply version replacement for libbax/1.0.0
+            trace: collect_build: replacement: libbax/2.0.0
+            trace: collect_build_prerequisites: no cfg-clause for dependency libbax/2.0.0 of dependent libbox/1.0.0
+            trace: collect_build_prerequisites: skip being built existing dependent libbox of dependency libbax
+            trace: collect_build_prerequisites: skip unsatisfied existing dependent libbix of dependency libbax/2.0.0 due to constraint (libbax == 1.0.0)
+            trace: collect_build_prerequisites: begin libbax/2.0.0
+            trace: collect_build_prerequisites: end libbax/2.0.0
+            trace: collect_build_prerequisites: end libbox/1.0.0
+            trace: collect_build_prerequisites: skip configured libbux/1.0.0
+            trace: collect_build_prerequisites: pre-reeval libbux/1.0.0
+            trace: collect_build_prerequisites: pre-reevaluated libbux/1.0.0: end reached
+            trace: collect_build_prerequisites: begin libbix/2.0.0
+            trace: collect_build_prerequisites: no cfg-clause for dependency libbax/2.0.0 of dependent libbix/2.0.0
+            trace: collect_build_prerequisites: end libbix/2.0.0
+            trace: execute_plan: simulate: yes
+            %.*
+              upgrade libbax/2.0.0
+              downgrade libbox/1.0.0
+              upgrade libbix/2.0.0
+              reconfigure libbux/1.0.0
+            trace: execute_plan: simulate: no
+            %.*
+            EOE
+
+          $pkg_status -ar >>EOO;
+            libbax configured 2.0.0
+            !libbox configured 1.0.0 available 2.0.0
+              libbax configured 2.0.0
+            libbix configured !2.0.0
+              libbax configured 2.0.0
+            !libbux configured 1.0.0
+              libbix configured !2.0.0
+                libbax configured 2.0.0
+            EOO
+
+          $pkg_drop libbox libbux
+        }
+
         : indirect
         :
         : Test replacement of indirect dependents of an unsatisfactory