commit:     5095c2023595a75e2848f1ad3dbe25b5fb451a44
Author:     Zac Medico <zmedico <AT> gentoo <DOT> org>
AuthorDate: Mon Nov 16 05:55:54 2020 +0000
Commit:     Zac Medico <zmedico <AT> gentoo <DOT> org>
CommitDate: Sun Nov 22 03:19:29 2020 +0000
URL:        https://gitweb.gentoo.org/proj/portage.git/commit/?id=5095c202

find_smallest_cycle: enhance search prioritization

Enhance the find_smallest_cycle function to prioritize its
search so that it will minimize the use of installed packages
to break cycles. When installed packages must be used to
break cycles, it will now prefer to do this for runtime
dependencies over buildtime dependencies, since it's
preferable to build against latest versions of buildtime
dependencies whenever possible. This should solve some cases
of bug 199856 which have been triggered by unsafe reliance
on installed packages to break cycles.

The included unit test case demonstrates correct merge order
for a dependency calculation involving 6 independent cycles.
This test case fails with the master branch, due to a buildtime
dependency cycle of 3 packages being merged earlier than cycles
of 2 packages. We can generalize this to say that the master
branch may use an installed package to break an arbitrarily
sized cycle in a somewhat random location, even though that
cycle may be composed of smaller independent cycles which
would be safer to break individually.

Bug: https://bugs.gentoo.org/754903
Signed-off-by: Zac Medico <zmedico <AT> gentoo.org>

 lib/_emerge/DepPriorityNormalRange.py          |  2 +
 lib/_emerge/DepPrioritySatisfiedRange.py       | 53 ++++++++++++++++----------
 lib/_emerge/depgraph.py                        | 43 ++++++++++++---------
 lib/portage/tests/resolver/test_merge_order.py | 10 +++++
 4 files changed, 70 insertions(+), 38 deletions(-)

diff --git a/lib/_emerge/DepPriorityNormalRange.py 
b/lib/_emerge/DepPriorityNormalRange.py
index 5f3f3da70..10f205a3b 100644
--- a/lib/_emerge/DepPriorityNormalRange.py
+++ b/lib/_emerge/DepPriorityNormalRange.py
@@ -14,6 +14,7 @@ class DepPriorityNormalRange:
        """
        MEDIUM      = 3
        MEDIUM_SOFT = 2
+       MEDIUM_POST = 2
        SOFT        = 1
        NONE        = 0
 
@@ -37,6 +38,7 @@ class DepPriorityNormalRange:
 
        ignore_medium      = _ignore_runtime
        ignore_medium_soft = _ignore_runtime_post
+       ignore_medium_post = _ignore_runtime_post
        ignore_soft        = _ignore_optional
 
 DepPriorityNormalRange.ignore_priority = (

diff --git a/lib/_emerge/DepPrioritySatisfiedRange.py 
b/lib/_emerge/DepPrioritySatisfiedRange.py
index e056e676f..fb0d7db4e 100644
--- a/lib/_emerge/DepPrioritySatisfiedRange.py
+++ b/lib/_emerge/DepPrioritySatisfiedRange.py
@@ -8,17 +8,18 @@ class DepPrioritySatisfiedRange:
 
        not satisfied and buildtime                    HARD
        not satisfied and runtime              7       MEDIUM
-       not satisfied and runtime_post         6       MEDIUM_SOFT
-       satisfied and buildtime_slot_op        5       SOFT
-       satisfied and buildtime                4       SOFT
-       satisfied and runtime                  3       SOFT
-       satisfied and runtime_post             2       SOFT
+       satisfied and buildtime_slot_op        6       MEDIUM_SOFT
+       satisfied and buildtime                5       MEDIUM_SOFT
+       satisfied and runtime                  4       MEDIUM_SOFT
+       runtime_post                           3       MEDIUM_POST
+       satisfied and runtime_post             2       MEDIUM_POST
        optional                               1       SOFT
        (none of the above)                    0       NONE
        """
        MEDIUM      = 7
        MEDIUM_SOFT = 6
-       SOFT        = 5
+       MEDIUM_POST = 3
+       SOFT        = 1
        NONE        = 0
 
        @classmethod
@@ -35,42 +36,51 @@ class DepPrioritySatisfiedRange:
                        return True
                if not priority.satisfied:
                        return False
+               if priority.buildtime or priority.runtime:
+                       return False
                return bool(priority.runtime_post)
 
        @classmethod
-       def _ignore_satisfied_runtime(cls, priority):
+       def _ignore_runtime_post(cls, priority):
                if priority.__class__ is not DepPriority:
                        return False
                if priority.optional:
                        return True
-               if not priority.satisfied:
+               if priority.buildtime or priority.runtime:
                        return False
-               return not priority.buildtime
+               return bool(priority.runtime_post)
 
        @classmethod
-       def _ignore_satisfied_buildtime(cls, priority):
+       def _ignore_satisfied_runtime(cls, priority):
                if priority.__class__ is not DepPriority:
                        return False
                if priority.optional:
                        return True
-               if priority.buildtime_slot_op:
+               if priority.buildtime:
                        return False
+               if not priority.runtime:
+                       return True
                return bool(priority.satisfied)
 
        @classmethod
-       def _ignore_satisfied_buildtime_slot_op(cls, priority):
+       def _ignore_satisfied_buildtime(cls, priority):
                if priority.__class__ is not DepPriority:
                        return False
-               return bool(priority.optional or \
-                       priority.satisfied)
+               if priority.optional:
+                       return True
+               if priority.buildtime_slot_op:
+                       return False
+               return bool(priority.satisfied)
 
        @classmethod
-       def _ignore_runtime_post(cls, priority):
+       def _ignore_satisfied_buildtime_slot_op(cls, priority):
                if priority.__class__ is not DepPriority:
                        return False
-               return bool(priority.optional or \
-                       priority.satisfied or \
-                       priority.runtime_post)
+               if priority.optional:
+                       return True
+               if priority.satisfied:
+                       return True
+               return not priority.buildtime and not priority.runtime
 
        @classmethod
        def _ignore_runtime(cls, priority):
@@ -81,17 +91,18 @@ class DepPrioritySatisfiedRange:
                        not priority.buildtime)
 
        ignore_medium      = _ignore_runtime
-       ignore_medium_soft = _ignore_runtime_post
-       ignore_soft        = _ignore_satisfied_buildtime
+       ignore_medium_soft = _ignore_satisfied_buildtime_slot_op
+       ignore_medium_post = _ignore_runtime_post
+       ignore_soft        = _ignore_optional
 
 
 DepPrioritySatisfiedRange.ignore_priority = (
        None,
        DepPrioritySatisfiedRange._ignore_optional,
        DepPrioritySatisfiedRange._ignore_satisfied_runtime_post,
+       DepPrioritySatisfiedRange._ignore_runtime_post,
        DepPrioritySatisfiedRange._ignore_satisfied_runtime,
        DepPrioritySatisfiedRange._ignore_satisfied_buildtime,
        DepPrioritySatisfiedRange._ignore_satisfied_buildtime_slot_op,
-       DepPrioritySatisfiedRange._ignore_runtime_post,
        DepPrioritySatisfiedRange._ignore_runtime
 )

diff --git a/lib/_emerge/depgraph.py b/lib/_emerge/depgraph.py
index a994caea7..d10474ab3 100644
--- a/lib/_emerge/depgraph.py
+++ b/lib/_emerge/depgraph.py
@@ -7905,7 +7905,7 @@ class depgraph:
                                                                if 
check_asap_parent:
                                                                        for 
node in nodes:
                                                                                
parents = mygraph.parent_nodes(node,
-                                                                               
        ignore_priority=DepPrioritySatisfiedRange.ignore_soft)
+                                                                               
        ignore_priority=DepPrioritySatisfiedRange.ignore_medium_soft)
                                                                                
if any(x in asap_nodes for x in parents):
                                                                                
        selected_nodes = [node]
                                                                                
        break
@@ -7921,7 +7921,7 @@ class depgraph:
 
                        if not selected_nodes:
 
-                               def find_smallest_cycle(mergeable_nodes, 
priority_ranges):
+                               def find_smallest_cycle(mergeable_nodes, 
local_priority_range):
                                        if prefer_asap and asap_nodes:
                                                nodes = asap_nodes
                                        else:
@@ -7938,18 +7938,27 @@ class depgraph:
                                        # these smaller independent cycles.
                                        smallest_cycle = None
                                        ignore_priority = None
-                                       for node in nodes:
-                                               if not 
mygraph.parent_nodes(node):
-                                                       continue
-                                               for local_priority_range in 
priority_ranges:
+
+                                       # Sort nodes for deterministic results.
+                                       nodes = sorted(nodes)
+                                       for priority in 
(local_priority_range.ignore_priority[i] for i in range(
+                                               
local_priority_range.MEDIUM_POST,
+                                               
local_priority_range.MEDIUM_SOFT + 1)):
+                                               for node in nodes:
+                                                       if not 
mygraph.parent_nodes(node):
+                                                               continue
                                                        selected_nodes = set()
-                                                       if 
gather_deps(local_priority_range.ignore_medium_soft,
+                                                       if gather_deps(priority,
                                                                
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
+                                                                       
ignore_priority = priority
+
+                                               # Exit this loop with the 
lowest possible priority, which
+                                               # minimizes the use of 
installed packages to break cycles.
+                                               if smallest_cycle is not None:
+                                                       break
 
                                        return smallest_cycle, ignore_priority
 
@@ -7963,7 +7972,7 @@ class depgraph:
                                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)
+                                               selected_nodes, ignore_priority 
= find_smallest_cycle(mergeable_nodes, local_priority_range)
                                                if selected_nodes:
                                                        break
 
@@ -8001,19 +8010,19 @@ class depgraph:
                                                                        
(selected_nodes[0],), noiselevel=-1)
 
                        if selected_nodes and ignore_priority is not None:
-                               # Try to merge ignored medium_soft deps as soon 
as possible
+                               # Try to merge ignored medium_post deps as soon 
as possible
                                # if they're not satisfied by installed 
packages.
                                for node in selected_nodes:
                                        children = 
set(mygraph.child_nodes(node))
                                        soft = children.difference(
-                                               mygraph.child_nodes(node,
-                                               
ignore_priority=DepPrioritySatisfiedRange.ignore_soft))
-                                       medium_soft = children.difference(
                                                mygraph.child_nodes(node,
                                                        ignore_priority = \
-                                                       
DepPrioritySatisfiedRange.ignore_medium_soft))
-                                       medium_soft -= soft
-                                       for child in medium_soft:
+                                                       
DepPrioritySatisfiedRange.ignore_soft))
+                                       medium_post = children.difference(
+                                               mygraph.child_nodes(node,
+                                               
ignore_priority=DepPrioritySatisfiedRange.ignore_medium_post))
+                                       medium_post -= soft
+                                       for child in medium_post:
                                                if child in selected_nodes:
                                                        continue
                                                if child in asap_nodes:

diff --git a/lib/portage/tests/resolver/test_merge_order.py 
b/lib/portage/tests/resolver/test_merge_order.py
index 0003cd7d8..f81fd2f6f 100644
--- a/lib/portage/tests/resolver/test_merge_order.py
+++ b/lib/portage/tests/resolver/test_merge_order.py
@@ -490,6 +490,16 @@ class MergeOrderTestCase(TestCase):
                                success=True,
                                all_permutations = True,
                                mergelist = ['x11-base/xorg-server-1.14.1', 
'media-libs/mesa-9.1.3']),
+                       # Test prioritization of the find_smallest_cycle 
function, which should
+                       # minimize the use of installed packages to break 
cycles. If installed
+                       # packages must be used to break cycles, then it should 
prefer to do this
+                       # for runtime dependencies over buildtime dependencies. 
If a package needs
+                       # to be uninstalled in order to solve a blocker, then 
it should prefer to
+                       # do this before it uses an installed package to break 
a cycle.
+                       ResolverPlaygroundTestCase(
+                               ["app-misc/some-app-a", "app-misc/some-app-b", 
"app-misc/some-app-c", "app-misc/circ-buildtime-a", 
"app-misc/blocker-buildtime-unbuilt-a", "media-libs/mesa", 
"x11-base/xorg-server", "app-misc/circ-direct-a", "app-misc/circ-direct-b", 
"app-misc/circ-satisfied-a", "app-misc/circ-satisfied-b", 
"app-misc/circ-satisfied-c"],
+                               success = True,
+                               mergelist = ['app-misc/circ-post-runtime-a-1', 
'app-misc/circ-post-runtime-c-1', 'app-misc/circ-post-runtime-b-1', 
'app-misc/some-app-b-1', 'app-misc/circ-runtime-a-1', 
'app-misc/circ-runtime-b-1', 'app-misc/circ-runtime-c-1', 
'app-misc/some-app-a-1', 'app-misc/blocker-buildtime-unbuilt-a-1', 
'[uninstall]app-misc/installed-blocker-a-1', '!app-misc/installed-blocker-a', 
'app-misc/circ-direct-a-1', 'app-misc/circ-direct-b-1', 
'x11-base/xorg-server-1.14.1', 'media-libs/mesa-9.1.3', 
'app-misc/circ-buildtime-a-1', 'app-misc/circ-buildtime-b-1', 
'app-misc/circ-buildtime-c-1', 'app-misc/some-app-c-1', 
'app-misc/circ-satisfied-a-1', 'app-misc/circ-satisfied-b-1', 
'app-misc/circ-satisfied-c-1']),
                )
 
                playground = ResolverPlayground(ebuilds=ebuilds, 
installed=installed)

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