Fix configuration negotiation machinery to postpone collecting cluster's existing dependent which is already a dependency in some cluster

2 files changed, 341 insertions, 73 deletions

diff --git a/bpkg/pkg-build-collect.cxx b/bpkg/pkg-build-collect.cxx
index f664bf7..c83645b 100644
--- a/bpkg/pkg-build-collect.cxx
+++ b/bpkg/pkg-build-collect.cxx
@@ -5158,28 +5158,28 @@ namespace bpkg
 
       build_package p {
         build_package::build,
-          db,
-          sp,
-          move (rp.first),
-          move (rp.second),
-          nullopt,                    // Dependencies.
-          nullopt,                    // Dependencies alternatives.
-          nullopt,                    // Package skeleton.
-          nullopt,                    // Postponed dependency alternatives.
-          false,                      // Recursive collection.
-          nullopt,                    // Hold package.
-          nullopt,                    // Hold version.
-          {},                         // Constraints.
-          sp->system (),
-          false,                      // Keep output directory.
-          false,                      // Disfigure (from-scratch reconf).
-          false,                      // Configure-only.
-          nullopt,                    // Checkout root.
-          false,                      // Checkout purge.
-          strings (),                 // Configuration variables.
-          move (required_by),         // Required by (dependencies).
-          false,                      // Required by dependents.
-          build_package::adjust_reconfigure | build_package::build_repoint};
+        db,
+        sp,
+        move (rp.first),
+        move (rp.second),
+        nullopt,                    // Dependencies.
+        nullopt,                    // Dependencies alternatives.
+        nullopt,                    // Package skeleton.
+        nullopt,                    // Postponed dependency alternatives.
+        false,                      // Recursive collection.
+        nullopt,                    // Hold package.
+        nullopt,                    // Hold version.
+        {},                         // Constraints.
+        sp->system (),
+        false,                      // Keep output directory.
+        false,                      // Disfigure (from-scratch reconf).
+        false,                      // Configure-only.
+        nullopt,                    // Checkout root.
+        false,                      // Checkout purge.
+        strings (),                 // Configuration variables.
+        move (required_by),         // Required by (dependencies).
+        false,                      // Required by dependents.
+        build_package::adjust_reconfigure | build_package::build_repoint};
 
       build_package_refs dep_chain;
 
@@ -5639,11 +5639,12 @@ namespace bpkg
               {
                 package_key pk (ed.db, ed.selected->name);
 
-                // If this dependent is present in postponed_deps, then it
-                // means someone depends on it with configuration and it's no
-                // longer considered an existing dependent (it will be
-                // reconfigured). However, this fact may not be reflected
-                // yet. And it can actually turn out bogus.
+                // If this dependent is present in postponed_deps or in some
+                // cluster as a dependency, then it means that someone depends
+                // on it with configuration and it's no longer considered an
+                // existing dependent (it will be reconfigured). However, this
+                // fact may not be reflected yet. And it can actually turn out
+                // bogus.
                 //
                 auto pi (postponed_deps.find (pk));
                 if (pi != postponed_deps.end ())
@@ -5660,6 +5661,20 @@ namespace bpkg
                   continue;
                 }
 
+                const postponed_configuration* pcfg (
+                  postponed_cfgs.find_dependency (pk));
+
+                if (pcfg != nullptr)
+                {
+                  l5 ([&]{trace << "skip existing dependent " << pk
+                                << " of dependency " << p << " since "
+                                << "dependent already in cluster " << *pcfg
+                                << " (as a dependency)";});
+
+                  postponed_existing_dependents.insert (pk);
+                  continue;
+                }
+
                 auto i (dependents.find (pk));
 
                 // If the existing dependent is not in the map yet, then add
@@ -5786,14 +5801,29 @@ namespace bpkg
         }
       }
 
-      l5 ([&]{trace << "cfg-negotiate begin " << *pcfg;});
-
       // Negotiate the configuration.
       //
       // The overall plan is as follows: continue refining the configuration
       // until there are no more changes by giving each dependent a chance to
       // make further adjustments.
       //
+      l5 ([&]{trace << "cfg-negotiate begin " << *pcfg;});
+
+      // For the cluster's dependencies, the skeleton should not be present
+      // since we haven't yet started recursively collecting them. And we
+      // couldn't have started collecting them before we negotiated their
+      // configurations (that's in contrast to the up-negotiation). Let's
+      // assert for that here to make sure that's also true for dependencies
+      // of the postponed existing dependents of this cluster.
+      //
+#ifndef NDEBUG
+      for (const package_key& p: pcfg->dependencies)
+      {
+        build_package* b (entered_build (p));
+        assert (b != nullptr && !b->skeleton && !b->recursive_collection);
+      }
+#endif
+
       for (auto b (pcfg->dependents.begin ()),
                 i (b),
                 e (pcfg->dependents.end ()); i != e; )
@@ -5831,7 +5861,6 @@ namespace bpkg
         //
         pair<size_t, size_t> pos;
         small_vector<reference_wrapper<package_skeleton>, 1> depcs;
-        forward_list<package_skeleton> depcs_storage; // Ref stability.
         bool has_alt;
         {
           // A non-negotiated cluster must only have one depends position for
@@ -5856,21 +5885,14 @@ namespace bpkg
           for (const package_key& pk: ds)
           {
             build_package* b (entered_build (pk));
-            assert (b != nullptr);
 
-            package_skeleton* depc;
-            if (b->recursive_collection)
-            {
-              assert (b->skeleton);
+            // Shouldn't be here otherwise.
+            //
+            assert (b != nullptr && !b->recursive_collection);
 
-              depcs_storage.push_front (*b->skeleton);
-              depc = &depcs_storage.front ();
-              depc->reset ();
-            }
-            else
-              depc = &(b->skeleton
-                       ? *b->skeleton
-                       : b->init_skeleton (o /* options */));
+            package_skeleton* depc (&(b->skeleton
+                                      ? *b->skeleton
+                                      : b->init_skeleton (o /* options */)));
 
             depcs.push_back (*depc);
           }
diff --git a/tests/pkg-build.testscript b/tests/pkg-build.testscript
index a37ea9f..cc69b1a 100644
--- a/tests/pkg-build.testscript
+++ b/tests/pkg-build.testscript
@@ -13862,6 +13862,280 @@ test.arguments += --sys-no-query
       $pkg_drop tiz
     }
 
+    : skip-existing-dependent-cluster
+    :
+    : Similar to skip-existing-dependent but skip the existing dependent
+    : because it is already in a cluster as a dependency.
+    :
+    {
+      $clone_cfg;
+
+      #  Dependencies:
+      #
+      #  bac: depends: libbar(c)
+      #       depends: libbaz(c)
+      #       depends: libfoo(c)
+      #
+      #  bas: depends: libbar(c)
+      #       depends: bus(c)
+      #
+      #  bus: depends: libbaz(c)
+      #       depends: foo(c)
+      #
+      #  foo: depends: libfoo(c)
+      #
+      #  box: depends: {libbar libfoo} (c) | libbox
+      #
+      $* bac bas 2>!;
+
+      $pkg_status -r >>EOO;
+        !bac configured 1.0.0
+          libbar configured 1.0.0
+          libbaz configured 1.0.0
+          libfoo configured 1.0.0
+        !bas configured 1.0.0
+          bus configured 1.0.0
+            foo configured 1.0.0
+              libfoo configured 1.0.0
+            libbaz configured 1.0.0
+          libbar configured 1.0.0
+        EOO
+
+      $* box 2>&1 | $filter 2>>~%EOE%;
+        %.*
+        trace: pkg_build: refine package collection/plan execution from scratch
+        trace: collect_build: add box/1.0.0
+        trace: collect_build_prerequisites: begin box/1.0.0
+        trace: collect_build_prerequisites: alt-postpone dependent box/1.0.0 since max index is reached: 0
+          info: dependency alternative: {libbar libfoo}
+        {
+          require
+          {
+            config.libbar.extras = true
+            config.libfoo.extras = true
+          }
+        }
+        trace: collect_build_prerequisites: postpone box/1.0.0
+        trace: collect_build_postponed (0): begin
+        trace: collect_build_postponed (0): index 1 collect alt-postponed box/1.0.0
+        trace: collect_build_prerequisites: resume box/1.0.0
+        trace: collect_build: add libbar/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libbar/1.0.0 of dependent box/1.0.0
+        trace: collect_build: add libfoo/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libfoo/1.0.0 of dependent box/1.0.0
+        trace: postponed_configurations::add: create {box | libbar->{box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: postpone box/1.0.0
+        trace: collect_build_postponed (1): begin {box | libbar->{box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: pre-reeval bac/1.0.0
+        trace: collect_build_prerequisites: pre-reevaluated bac/1.0.0: 1,1
+        trace: collect_build_prerequisites: pre-reeval bas/1.0.0
+        trace: collect_build_prerequisites: pre-reevaluated bas/1.0.0: 1,1
+        trace: collect_build_prerequisites: pre-reeval foo/1.0.0
+        trace: collect_build_prerequisites: pre-reevaluated foo/1.0.0: 1,1
+        trace: collect_build_prerequisites: pre-reeval bac/1.0.0
+        trace: collect_build_prerequisites: pre-reevaluated bac/1.0.0: 1,1
+        trace: collect_build_postponed (1): re-evaluate existing dependents for {box | libbar->{box/1,1} libfoo->{box/1,1}}
+        trace: collect_build: add bac/1.0.0
+        trace: collect_build_prerequisites: reeval bac/1.0.0
+        trace: postponed_configurations::add: add {bac^ 1,1: libbar} to {box | libbar->{box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: re-evaluating dependent bac/1.0.0 results in {bac^ box | libbar->{bac/1,1 box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: re-evaluated bac/1.0.0
+        trace: collect_build: add bas/1.0.0
+        trace: collect_build_prerequisites: reeval bas/1.0.0
+        trace: postponed_configurations::add: add {bas^ 1,1: libbar} to {bac^ box | libbar->{bac/1,1 box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: re-evaluating dependent bas/1.0.0 results in {bac^ bas^ box | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: re-evaluated bas/1.0.0
+        trace: collect_build: add foo/1.0.0
+        trace: collect_build_prerequisites: reeval foo/1.0.0
+        trace: postponed_configurations::add: add {foo^ 1,1: libfoo} to {bac^ bas^ box | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: re-evaluating dependent foo/1.0.0 results in {bac^ bas^ box foo^ | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{box/1,1 foo/1,1}}
+        trace: collect_build_prerequisites: re-evaluated foo/1.0.0
+        trace: collect_build_postponed (1): cfg-negotiate begin {bac^ bas^ box foo^ | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{box/1,1 foo/1,1}}
+        %.*
+        trace: collect_build_postponed (1): recursively collect cfg-negotiated dependencies
+        trace: collect_build_prerequisites: skip configured libbar/1.0.0
+        trace: collect_build_prerequisites: skip configured libfoo/1.0.0
+        trace: collect_build_postponed (1): recursively collect cfg-negotiated dependents
+        trace: collect_build_postponed (1): select cfg-negotiated dependency alternative for dependent bac/1.0.0
+        trace: collect_build_prerequisites: resume bac/1.0.0
+        trace: collect_build: add libbaz/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libbaz/1.0.0 of dependent bac/1.0.0
+        trace: postponed_configurations::add: create {bac | libbaz->{bac/2,1}}
+        trace: collect_build_prerequisites: postpone bac/1.0.0
+        trace: collect_build_postponed (1): select cfg-negotiated dependency alternative for dependent bas/1.0.0
+        trace: collect_build_prerequisites: resume bas/1.0.0
+        trace: collect_build: add bus/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency bus/1.0.0 of dependent bas/1.0.0
+        trace: postponed_configurations::add: create {bas | bus->{bas/2,1}}
+        trace: collect_build_prerequisites: postpone bas/1.0.0
+        trace: collect_build_postponed (1): select cfg-negotiated dependency alternative for dependent box/1.0.0
+        trace: collect_build_prerequisites: resume box/1.0.0
+        trace: collect_build_prerequisites: end box/1.0.0
+        trace: collect_build_postponed (1): select cfg-negotiated dependency alternative for dependent foo/1.0.0
+        trace: collect_build_prerequisites: resume foo/1.0.0
+        trace: collect_build_prerequisites: end foo/1.0.0
+        trace: collect_build_postponed (1): cfg-negotiate end {bac^ bas^ box foo^ | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{box/1,1 foo/1,1}}!
+        trace: collect_build_postponed (2): begin {bac | libbaz->{bac/2,1}}
+        trace: collect_build_prerequisites: pre-reeval bus/1.0.0
+        trace: collect_build_prerequisites: pre-reevaluated bus/1.0.0: 1,1
+        trace: collect_build_postponed (2): skip being built existing dependent bac of dependency libbaz
+        trace: collect_build_postponed (2): skip existing dependent bus of dependency libbaz since dependent already in cluster {bas | bus->{bas/2,1}} (as a dependency)
+        trace: collect_build_postponed (2): cfg-negotiate begin {bac | libbaz->{bac/2,1}}
+        %.*
+        trace: collect_build_postponed (2): recursively collect cfg-negotiated dependencies
+        trace: collect_build_prerequisites: skip configured libbaz/1.0.0
+        trace: collect_build_postponed (2): recursively collect cfg-negotiated dependents
+        trace: collect_build_postponed (2): select cfg-negotiated dependency alternative for dependent bac/1.0.0
+        trace: collect_build_prerequisites: resume bac/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libfoo/1.0.0 of dependent bac/1.0.0
+        trace: postponed_configurations::add: add {bac 3,1: libfoo} to {bac^ bas^ box foo^ | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{box/1,1 foo/1,1}}!
+        trace: collect_build_prerequisites: configuration for cfg-postponed dependencies of dependent bac/1.0.0 is negotiated
+        trace: collect_build_prerequisites: dependency libfoo/1.0.0 of dependent bac/1.0.0 is already (being) recursively collected, skipping
+        trace: collect_build_prerequisites: end bac/1.0.0
+        trace: collect_build_postponed (2): cfg-negotiate end {bac | libbaz->{bac/2,1}}!
+        trace: collect_build_postponed (3): begin {bas | bus->{bas/2,1}}
+        trace: collect_build_postponed (3): skip being built existing dependent bas of dependency bus
+        trace: collect_build_postponed (3): cfg-negotiate begin {bas | bus->{bas/2,1}}
+        %.*
+        trace: collect_build_postponed (3): recursively collect cfg-negotiated dependencies
+        trace: collect_build_prerequisites: begin bus/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libbaz/1.0.0 of dependent bus/1.0.0
+        trace: postponed_configurations::add: add {bus 1,1: libbaz} to {bac | libbaz->{bac/2,1}}!
+        trace: collect_build_prerequisites: configuration for cfg-postponed dependencies of dependent bus/1.0.0 is negotiated
+        trace: collect_build_prerequisites: dependency libbaz/1.0.0 of dependent bus/1.0.0 is already (being) recursively collected, skipping
+        trace: collect_build_prerequisites: cannot cfg-postpone dependency foo/1.0.0 of dependent bus/1.0.0 (collected prematurely), throwing postpone_dependency
+        trace: pkg_build: collection failed due to prematurely collected dependency (foo), retry from scratch
+        trace: pkg_build: refine package collection/plan execution from scratch
+        trace: collect_build: add box/1.0.0
+        trace: collect_build_prerequisites: begin box/1.0.0
+        trace: collect_build_prerequisites: alt-postpone dependent box/1.0.0 since max index is reached: 0
+          info: dependency alternative: {libbar libfoo}
+        {
+          require
+          {
+            config.libbar.extras = true
+            config.libfoo.extras = true
+          }
+        }
+        trace: collect_build_prerequisites: postpone box/1.0.0
+        trace: collect_build_postponed (0): begin
+        trace: collect_build_postponed (0): index 1 collect alt-postponed box/1.0.0
+        trace: collect_build_prerequisites: resume box/1.0.0
+        trace: collect_build: add libbar/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libbar/1.0.0 of dependent box/1.0.0
+        trace: collect_build: add libfoo/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libfoo/1.0.0 of dependent box/1.0.0
+        trace: postponed_configurations::add: create {box | libbar->{box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: postpone box/1.0.0
+        trace: collect_build_postponed (1): begin {box | libbar->{box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: pre-reeval bac/1.0.0
+        trace: collect_build_prerequisites: pre-reevaluated bac/1.0.0: 1,1
+        trace: collect_build_prerequisites: pre-reeval bas/1.0.0
+        trace: collect_build_prerequisites: pre-reevaluated bas/1.0.0: 1,1
+        trace: collect_build_prerequisites: pre-reeval foo/1.0.0
+        trace: collect_build_prerequisites: pre-reevaluated foo/1.0.0: 1,1
+        trace: collect_build_prerequisites: pre-reeval bac/1.0.0
+        trace: collect_build_prerequisites: pre-reevaluated bac/1.0.0: 1,1
+        trace: collect_build_postponed (1): skip dep-postponed existing dependent foo of dependency libfoo
+        trace: collect_build_postponed (1): re-evaluate existing dependents for {box | libbar->{box/1,1} libfoo->{box/1,1}}
+        trace: collect_build: add bac/1.0.0
+        trace: collect_build_prerequisites: reeval bac/1.0.0
+        trace: postponed_configurations::add: add {bac^ 1,1: libbar} to {box | libbar->{box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: re-evaluating dependent bac/1.0.0 results in {bac^ box | libbar->{bac/1,1 box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: re-evaluated bac/1.0.0
+        trace: collect_build: add bas/1.0.0
+        trace: collect_build_prerequisites: reeval bas/1.0.0
+        trace: postponed_configurations::add: add {bas^ 1,1: libbar} to {bac^ box | libbar->{bac/1,1 box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: re-evaluating dependent bas/1.0.0 results in {bac^ bas^ box | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_prerequisites: re-evaluated bas/1.0.0
+        trace: collect_build_postponed (1): cfg-negotiate begin {bac^ bas^ box | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_postponed (1): recursively collect cfg-negotiated dependencies
+        trace: collect_build_prerequisites: skip configured libbar/1.0.0
+        trace: collect_build_prerequisites: skip configured libfoo/1.0.0
+        trace: collect_build_postponed (1): recursively collect cfg-negotiated dependents
+        trace: collect_build_postponed (1): select cfg-negotiated dependency alternative for dependent bac/1.0.0
+        trace: collect_build_prerequisites: resume bac/1.0.0
+        trace: collect_build: add libbaz/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libbaz/1.0.0 of dependent bac/1.0.0
+        trace: postponed_configurations::add: create {bac | libbaz->{bac/2,1}}
+        trace: collect_build_prerequisites: postpone bac/1.0.0
+        trace: collect_build_postponed (1): select cfg-negotiated dependency alternative for dependent bas/1.0.0
+        trace: collect_build_prerequisites: resume bas/1.0.0
+        trace: collect_build: add bus/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency bus/1.0.0 of dependent bas/1.0.0
+        trace: postponed_configurations::add: create {bas | bus->{bas/2,1}}
+        trace: collect_build_prerequisites: postpone bas/1.0.0
+        trace: collect_build_postponed (1): select cfg-negotiated dependency alternative for dependent box/1.0.0
+        trace: collect_build_prerequisites: resume box/1.0.0
+        trace: collect_build_prerequisites: end box/1.0.0
+        trace: collect_build_postponed (1): cfg-negotiate end {bac^ bas^ box | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{box/1,1}}!
+        trace: collect_build_postponed (2): begin {bac | libbaz->{bac/2,1}}
+        trace: collect_build_prerequisites: pre-reeval bus/1.0.0
+        trace: collect_build_prerequisites: pre-reevaluated bus/1.0.0: 1,1
+        trace: collect_build_postponed (2): skip being built existing dependent bac of dependency libbaz
+        trace: collect_build_postponed (2): skip existing dependent bus of dependency libbaz since dependent already in cluster {bas | bus->{bas/2,1}} (as a dependency)
+        trace: collect_build_postponed (2): cfg-negotiate begin {bac | libbaz->{bac/2,1}}
+        trace: collect_build_postponed (2): recursively collect cfg-negotiated dependencies
+        trace: collect_build_prerequisites: skip configured libbaz/1.0.0
+        trace: collect_build_postponed (2): recursively collect cfg-negotiated dependents
+        trace: collect_build_postponed (2): select cfg-negotiated dependency alternative for dependent bac/1.0.0
+        trace: collect_build_prerequisites: resume bac/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libfoo/1.0.0 of dependent bac/1.0.0
+        trace: postponed_configurations::add: add {bac 3,1: libfoo} to {bac^ bas^ box | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{box/1,1}}!
+        trace: collect_build_prerequisites: configuration for cfg-postponed dependencies of dependent bac/1.0.0 is negotiated
+        trace: collect_build_prerequisites: dependency libfoo/1.0.0 of dependent bac/1.0.0 is already (being) recursively collected, skipping
+        trace: collect_build_prerequisites: end bac/1.0.0
+        trace: collect_build_postponed (2): cfg-negotiate end {bac | libbaz->{bac/2,1}}!
+        trace: collect_build_postponed (3): begin {bas | bus->{bas/2,1}}
+        trace: collect_build_postponed (3): skip being built existing dependent bas of dependency bus
+        trace: collect_build_postponed (3): cfg-negotiate begin {bas | bus->{bas/2,1}}
+        trace: collect_build_postponed (3): recursively collect cfg-negotiated dependencies
+        trace: collect_build_prerequisites: begin bus/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libbaz/1.0.0 of dependent bus/1.0.0
+        trace: postponed_configurations::add: add {bus 1,1: libbaz} to {bac | libbaz->{bac/2,1}}!
+        trace: collect_build_prerequisites: configuration for cfg-postponed dependencies of dependent bus/1.0.0 is negotiated
+        trace: collect_build_prerequisites: dependency libbaz/1.0.0 of dependent bus/1.0.0 is already (being) recursively collected, skipping
+        trace: collect_build: add foo/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency foo/1.0.0 of dependent bus/1.0.0
+        trace: postponed_configurations::add: create {bus | foo->{bus/2,1}}
+        trace: collect_build_prerequisites: postpone bus/1.0.0
+        trace: collect_build_postponed (3): recursively collect cfg-negotiated dependents
+        trace: collect_build_postponed (3): select cfg-negotiated dependency alternative for dependent bas/1.0.0
+        trace: collect_build_prerequisites: resume bas/1.0.0
+        trace: collect_build_prerequisites: end bas/1.0.0
+        trace: collect_build_postponed (3): cfg-negotiate end {bas | bus->{bas/2,1}}!
+        trace: collect_build_postponed (4): begin {bus | foo->{bus/2,1}}
+        trace: collect_build_postponed (4): skip being built existing dependent bus of dependency foo
+        trace: collect_build_postponed (4): cfg-negotiate begin {bus | foo->{bus/2,1}}
+        %.*
+        trace: collect_build_postponed (4): recursively collect cfg-negotiated dependencies
+        trace: collect_build_prerequisites: begin foo/1.0.0
+        trace: collect_build_prerequisites: cfg-postpone dependency libfoo/1.0.0 of dependent foo/1.0.0
+        trace: postponed_configurations::add: add {foo 1,1: libfoo} to {bac^ bas^ box | libbar->{bac/1,1 bas/1,1 box/1,1} libfoo->{bac/3,1 box/1,1}}!
+        trace: collect_build_prerequisites: configuration for cfg-postponed dependencies of dependent foo/1.0.0 is negotiated
+        trace: collect_build_prerequisites: dependency libfoo/1.0.0 of dependent foo/1.0.0 is already (being) recursively collected, skipping
+        trace: collect_build_prerequisites: end foo/1.0.0
+        trace: collect_build_postponed (4): recursively collect cfg-negotiated dependents
+        trace: collect_build_postponed (4): select cfg-negotiated dependency alternative for dependent bus/1.0.0
+        trace: collect_build_prerequisites: resume bus/1.0.0
+        trace: collect_build_prerequisites: end bus/1.0.0
+        trace: collect_build_postponed (4): cfg-negotiate end {bus | foo->{bus/2,1}}!
+        trace: collect_build_postponed (4): end {bus | foo->{bus/2,1}}
+        trace: collect_build_postponed (3): end {bas | bus->{bas/2,1}}
+        trace: collect_build_postponed (2): end {bac | libbaz->{bac/2,1}}
+        trace: collect_build_postponed (1): end {box | libbar->{box/1,1} libfoo->{box/1,1}}
+        trace: collect_build_postponed (0): end
+        trace: execute_plan: simulate: yes
+        %.*
+        build plan:
+          new box/1.0.0
+        trace: execute_plan: simulate: no
+        %.*
+        EOE
+
+      $pkg_drop bac bas box
+    }
+
     : replace-configured-dependency
     :
     {
@@ -14840,35 +15114,7 @@ test.arguments += --sys-no-query
         trace: collect_build_prerequisites: pre-reevaluated tex/1.0.0: 1,1
         trace: collect_build_prerequisites: pre-reeval tiz/1.0.0
         trace: collect_build_prerequisites: pre-reevaluated tiz/1.0.0: 1,1
-        trace: collect_build_postponed (1): re-evaluate existing dependents for {tex^ | libbar->{tex/1,1}}
-        trace: collect_build_prerequisites: reeval tex/1.0.0
-        trace: collect_build: pick libbar/1.0.0 over libbar/0.1.0
-        trace: postponed_configurations::add: add {tex^ 1,1: libbar} to {tex^ | libbar->{tex/1,1}}
-        trace: collect_build_prerequisites: re-evaluating dependent tex/1.0.0 results in {tex^ | libbar->{tex/1,1}}
-        trace: collect_build_prerequisites: re-evaluated tex/1.0.0
-        trace: collect_build_prerequisites: reeval tiz/1.0.0
-        trace: collect_build_prerequisites: cannot re-evaluate existing dependent tiz/1.0.0 due to dependency tex/1.0.0 (collected prematurely), throwing postpone_dependency
-        trace: pkg_build: collection failed due to prematurely collected dependency (tex), retry from scratch
-        trace: pkg_build: refine package collection/plan execution from scratch
-        trace: collect_build: add libbar/1.0.0
-        trace: collect_build: add tiz/1.0.0
-        trace: collect_build_prerequisites: pre-reeval tex/1.0.0
-        trace: collect_build_prerequisites: pre-reevaluated tex/1.0.0: 1,1
-        trace: collect_build_prerequisites: pre-reeval tiz/1.0.0
-        trace: collect_build_prerequisites: pre-reevaluated tiz/1.0.0: 1,1
-        trace: collect_build_prerequisites: cfg-postpone dependency libbar/1.0.0 of existing dependent tex/1.0.0 due to dependency libbar/1.0.0
-        trace: collect_build: add tex/1.0.0
-        trace: postponed_configurations::add: create {tex^ | libbar->{tex/1,1}}
-        trace: collect_build_prerequisites: cfg-postpone dependency tex/1.0.0 of existing dependent tiz/1.0.0 due to dependency libbar/1.0.0
-        trace: postponed_configurations::add: create {tiz^ | tex->{tiz/1,1}}
-        trace: collect_build_prerequisites: skip configured tiz/1.0.0
-        trace: collect_build_postponed (0): begin
-        trace: collect_build_postponed (1): begin {tex^ | libbar->{tex/1,1}}
-        trace: collect_build_prerequisites: pre-reeval tex/1.0.0
-        trace: collect_build_prerequisites: pre-reevaluated tex/1.0.0: 1,1
-        trace: collect_build_prerequisites: pre-reeval tiz/1.0.0
-        trace: collect_build_prerequisites: pre-reevaluated tiz/1.0.0: 1,1
-        trace: collect_build_postponed (1): skip dep-postponed existing dependent tex of dependency libbar
+        trace: collect_build_postponed (1): skip existing dependent tex of dependency libbar since dependent already in cluster {tiz^ | tex->{tiz/1,1}} (as a dependency)
         trace: collect_build_postponed (1): re-evaluate existing dependents for {tex^ | libbar->{tex/1,1}}
         trace: collect_build_prerequisites: reeval tiz/1.0.0
         trace: postponed_configurations::add: add {tiz^ 1,1: tex} to {tiz^ | tex->{tiz/1,1}}
@@ -14897,7 +15143,7 @@ test.arguments += --sys-no-query
         trace: collect_build_prerequisites: pre-reevaluated tex/1.0.0: 1,1
         trace: collect_build_prerequisites: pre-reeval tiz/1.0.0
         trace: collect_build_prerequisites: pre-reevaluated tiz/1.0.0: 1,1
-        trace: collect_build_postponed (1): skip dep-postponed existing dependent tex of dependency libbar
+        trace: collect_build_postponed (1): skip existing dependent tex of dependency libbar since dependent already in cluster {tiz^ | tex->{tiz/1,1}} (as a dependency)
         trace: collect_build_postponed (1): re-evaluate existing dependents for {tex^ | libbar->{tex/1,1}}
         trace: collect_build_prerequisites: reeval tiz/1.0.0
         trace: postponed_configurations::add: add {tiz^ 1,1: tex} to {tiz^ | tex->{tiz/1,1}}