commit:     680276cc4d4faa653203366cbe3c896ac3883cf2
Author:     Zac Medico <zmedico <AT> gentoo <DOT> org>
AuthorDate: Wed Dec 25 08:37:18 2019 +0000
Commit:     Zac Medico <zmedico <AT> gentoo <DOT> org>
CommitDate: Thu Dec 26 22:56:39 2019 +0000
URL:        https://gitweb.gentoo.org/proj/portage.git/commit/?id=680276cc

_serialize_tasks: limit scope of dropped circular dependencies

Ensure that all members of a buildtime dependency cycle are merged
as a group, such that packages which depend on one or more members
of the group will only be merged *after* the entire group has been
merged.

This extends runtime cycle handling to also handle buildtime cycles
in cases where the buildtime dependencies happen to be satisfied by
installed packages. In situations when this is necessary, it is
desirable to rely on the old installed instances of these packages
as little as possible, since they might have been broken by the
upgrade of a package that is a member of the dependency cycle.
Upgrading members of the cycle as a group effectively minimizes
reliance on the old installed package instances, avoiding some cases
of bug 199856. For example, it should avoid bug 703676, where
libspectre reportedly failed to build against an old installed
instance of ghostscript-gpl.

Bug: https://bugs.gentoo.org/199856
Bug: https://bugs.gentoo.org/689644
Bug: https://bugs.gentoo.org/690436
Bug: https://bugs.gentoo.org/703676
Signed-off-by: Zac Medico <zmedico <AT> gentoo.org>

 lib/_emerge/depgraph.py                        | 94 +++++++++++++++-----------
 lib/portage/tests/resolver/test_merge_order.py | 25 ++++++-
 2 files changed, 78 insertions(+), 41 deletions(-)

diff --git a/lib/_emerge/depgraph.py b/lib/_emerge/depgraph.py
index 0ee50d5de..bf8882774 100644
--- a/lib/_emerge/depgraph.py
+++ b/lib/_emerge/depgraph.py
@@ -7640,21 +7640,6 @@ class depgraph(object):
                                break
                        removed_nodes.clear()
                self._merge_order_bias(mygraph)
-               def cmp_circular_bias(n1, n2):
-                       """
-                       RDEPEND is stronger than PDEPEND and this function
-                       measures such a strength bias within a circular
-                       dependency relationship.
-                       """
-                       n1_n2_medium = n2 in mygraph.child_nodes(n1,
-                               
ignore_priority=priority_range.ignore_medium_soft)
-                       n2_n1_medium = n1 in mygraph.child_nodes(n2,
-                               
ignore_priority=priority_range.ignore_medium_soft)
-                       if n1_n2_medium == n2_n1_medium:
-                               return 0
-                       elif n1_n2_medium:
-                               return 1
-                       return -1
                myblocker_uninstalls = 
self._dynamic_config._blocker_uninstalls.copy()
                retlist=[]
                # Contains uninstall tasks that have been scheduled to
@@ -7815,7 +7800,8 @@ class depgraph(object):
                        self._spinner_update()
                        selected_nodes = None
                        ignore_priority = None
-                       if drop_satisfied or (prefer_asap and asap_nodes):
+                       cycle_digraph = None
+                       if prefer_asap and asap_nodes:
                                priority_range = DepPrioritySatisfiedRange
                        else:
                                priority_range = DepPriorityNormalRange
@@ -7897,11 +7883,12 @@ class depgraph(object):
                                                        break
 
                        if not selected_nodes:
-                               nodes = 
get_nodes(ignore_priority=priority_range.ignore_medium)
-                               if nodes:
-                                       mergeable_nodes = set(nodes)
+
+                               def find_smallest_cycle(mergeable_nodes, 
priority_ranges):
                                        if prefer_asap and asap_nodes:
                                                nodes = asap_nodes
+                                       else:
+                                               nodes = mergeable_nodes
                                        # When gathering the nodes belonging to 
a runtime cycle,
                                        # we want to minimize the number of 
nodes gathered, since
                                        # this tends to produce a more optimal 
merge order.
@@ -7912,21 +7899,44 @@ class depgraph(object):
                                        # that depend on them. Therefore, we 
search for the
                                        # smallest cycle in order to try and 
identify and prefer
                                        # these smaller independent cycles.
-                                       ignore_priority = 
priority_range.ignore_medium_soft
                                        smallest_cycle = None
+                                       ignore_priority = None
                                        for node in nodes:
                                                if not 
mygraph.parent_nodes(node):
                                                        continue
-                                               selected_nodes = set()
-                                               if gather_deps(ignore_priority,
-                                                       mergeable_nodes, 
selected_nodes, node):
-                                                       if smallest_cycle is 
None or \
-                                                               
len(selected_nodes) < len(smallest_cycle):
-                                                               smallest_cycle 
= selected_nodes
+                                               for local_priority_range in 
priority_ranges:
+                                                       selected_nodes = set()
+                                                       if 
gather_deps(local_priority_range.ignore_medium_soft,
+                                                               
mergeable_nodes, selected_nodes, node):
+                                                               if 
smallest_cycle is None or \
+                                                                       
len(selected_nodes) < len(smallest_cycle):
+                                                                       
smallest_cycle = selected_nodes
+                                                                       
ignore_priority = local_priority_range.ignore_medium_soft
+                                                               break
+
+                                       return smallest_cycle, ignore_priority
 
-                                       selected_nodes = smallest_cycle
+                               priority_ranges = []
+                               if priority_range is not DepPriorityNormalRange:
+                                       
priority_ranges.append(DepPriorityNormalRange)
+                               priority_ranges.append(priority_range)
+                               if drop_satisfied and priority_range is not 
DepPrioritySatisfiedRange:
+                                       
priority_ranges.append(DepPrioritySatisfiedRange)
 
-                                       if selected_nodes is not None:
+                               for local_priority_range in priority_ranges:
+                                       mergeable_nodes = 
set(get_nodes(ignore_priority=local_priority_range.ignore_medium))
+                                       if mergeable_nodes:
+                                               selected_nodes, ignore_priority 
= find_smallest_cycle(mergeable_nodes, priority_ranges)
+                                               if selected_nodes:
+                                                       break
+
+                               if not selected_nodes:
+                                       if prefer_asap and asap_nodes:
+                                               # We failed to find any asap 
nodes to merge, so ignore
+                                               # them for the next iteration.
+                                               prefer_asap = False
+                                               continue
+                               else:
                                                cycle_digraph = mygraph.copy()
                                                
cycle_digraph.difference_update([x for x in
                                                        cycle_digraph if x not 
in selected_nodes])
@@ -7953,12 +7963,6 @@ class depgraph(object):
                                                                
writemsg("runtime cycle leaf: %s\n\n" %
                                                                        
(selected_nodes[0],), noiselevel=-1)
 
-                                       if prefer_asap and asap_nodes and not 
selected_nodes:
-                                               # We failed to find any asap 
nodes to merge, so ignore
-                                               # them for the next iteration.
-                                               prefer_asap = False
-                                               continue
-
                        if selected_nodes and ignore_priority is not None:
                                # Try to merge ignored medium_soft deps as soon 
as possible
                                # if they're not satisfied by installed 
packages.
@@ -7980,10 +7984,24 @@ class depgraph(object):
                                                # Merge PDEPEND asap for bug 
#180045.
                                                asap_nodes.append(child)
 
-                       if selected_nodes and len(selected_nodes) > 1:
-                               if not isinstance(selected_nodes, list):
-                                       selected_nodes = list(selected_nodes)
-                               
selected_nodes.sort(key=cmp_sort_key(cmp_circular_bias))
+                       if selected_nodes and len(selected_nodes) > 1 and 
cycle_digraph is not None:
+                               # Sort nodes to account for direct circular 
relationships. Relevant
+                               # priorities here are: runtime < buildtime < 
buildtime slot operator
+                               ignore_priorities = list(filter(None, chain(
+                                       DepPriorityNormalRange.ignore_priority,
+                                       
DepPrioritySatisfiedRange.ignore_priority,
+                               )))
+                               selected_nodes = []
+                               while cycle_digraph:
+                                       for ignore_priority in 
ignore_priorities:
+                                               leaves = 
cycle_digraph.leaf_nodes(ignore_priority=ignore_priority)
+                                               if leaves:
+                                                       
cycle_digraph.difference_update(leaves)
+                                                       
selected_nodes.extend(leaves)
+                                                       break
+                                       else:
+                                               
selected_nodes.extend(cycle_digraph)
+                                               break
 
                        if not selected_nodes and myblocker_uninstalls:
                                # An Uninstall task needs to be executed in 
order to

diff --git a/lib/portage/tests/resolver/test_merge_order.py 
b/lib/portage/tests/resolver/test_merge_order.py
index 74e826661..11752d71e 100644
--- a/lib/portage/tests/resolver/test_merge_order.py
+++ b/lib/portage/tests/resolver/test_merge_order.py
@@ -81,6 +81,13 @@ class MergeOrderTestCase(TestCase):
                                "DEPEND": "app-misc/circ-satisfied-a",
                                "RDEPEND": "app-misc/circ-satisfied-a",
                        },
+                       "app-misc/circ-direct-a-1": {
+                               "RDEPEND": "app-misc/circ-direct-b",
+                       },
+                       "app-misc/circ-direct-b-1": {
+                               "RDEPEND": "app-misc/circ-direct-a",
+                               "DEPEND": "app-misc/circ-direct-a",
+                       },
                        "app-misc/circ-smallest-a-1": {
                                "RDEPEND": "app-misc/circ-smallest-b",
                        },
@@ -220,6 +227,13 @@ class MergeOrderTestCase(TestCase):
                }
 
                installed = {
+                       "app-misc/circ-direct-a-1": {
+                               "RDEPEND": "app-misc/circ-direct-b",
+                       },
+                       "app-misc/circ-direct-b-1": {
+                               "RDEPEND": "app-misc/circ-direct-a",
+                               "DEPEND": "app-misc/circ-direct-a",
+                       },
                        "app-misc/circ-buildtime-a-0": {},
                        "app-misc/circ-satisfied-a-0": {
                                "RDEPEND": "app-misc/circ-satisfied-b",
@@ -295,6 +309,12 @@ class MergeOrderTestCase(TestCase):
                }
 
                test_cases = (
+                       ResolverPlaygroundTestCase(
+                               ["app-misc/circ-direct-a", 
"app-misc/circ-direct-b"],
+                               success = True,
+                               all_permutations = True,
+                               mergelist = ["app-misc/circ-direct-a-1", 
"app-misc/circ-direct-b-1"],
+                       ),
                        ResolverPlaygroundTestCase(
                                ["app-misc/some-app-a"],
                                success = True,
@@ -321,9 +341,8 @@ class MergeOrderTestCase(TestCase):
                                ambiguous_merge_order = True,
                                # The following merge order assertion reflects 
optimal order for
                                # a circular relationship which is DEPEND in 
one direction and
-                               # RDEPEND in the other. The assertion currently 
fails, and the
-                               # patch for bug 690436 will fix it.
-                               #merge_order_assertions = 
(("app-misc/circ-buildtime-a-1", "app-misc/circ-buildtime-c-1"),),
+                               # RDEPEND in the other.
+                               merge_order_assertions = 
(("app-misc/circ-buildtime-a-1", "app-misc/circ-buildtime-c-1"),),
                                mergelist = [("app-misc/circ-buildtime-b-1", 
"app-misc/circ-buildtime-c-1", "app-misc/circ-buildtime-a-1"), 
"app-misc/some-app-c-1"]),
                        # Test optimal merge order for a circular dep that is
                        # RDEPEND in one direction and PDEPEND in the other.

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