Re: [PATCH setup 00/14] Use libsolv, solve all our problems... (WIP)

[Ken Brown <kbrown@cornell.edu>]

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On 12/13/2017 1:05 PM, Achim Gratz wrote:
> Ken Brown writes:
>> 1. Uninstall A.
>> 2. Don't uninstall B.
>>
>> On the surface, it would seem that libsolv chose 2 by default, because
>> it returned an empty transaction list.  This was reflected in the log
>> and was also clear when I selected 'Back'.
> 
> I don't think there is a default in this case.  I also see in zypper
> that the order of the proposed solutions (there can be way more than two
> if the dependencies are more complicated) is not always the same, so
> there is no preference implied by the order as well.
> 
>> Maybe we have to deal with this situation ourselves.  Whenever a
>> problem involves a missing dependency, we could choose as default
>> solution the one that installs/keeps the dependent package, as is
>> currently done.
> 
> That solution unfortunately isn't always the one that causes the least
> amount of transactions or even the least amount of breakage.

That may be true, but I still think it's a reasonable default.  The user 
doesn't have to accept it.  Also, it's consistent with what setup 
currently does, so it won't surprise anyone.

The attached patch attempts to implement my suggestion.

Ken


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From 65cb5413e81794829cbddeebc6826d04115f2a49 Mon Sep 17 00:00:00 2001
From: Ken Brown <kbrown@cornell.edu>
Date: Wed, 13 Dec 2017 17:20:26 -0500
Subject: [PATCH] Implement a default solution for SOLVER_RULE_PKG_REQUIRES

If libsolv reports a SOLVER_RULE_PKG_REQUIRES problem, it means that
the user chose to uninstall or skip a required package.  Add an
appropriate transInstall transaction if necessary, to override this
choice.  The user will have to uncheck the "Accept default problem
solutions" box to insist on the original choice.
---
 libsolv.cc | 18 +++++++++++++++---
 libsolv.h  |  2 +-
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/libsolv.cc b/libsolv.cc
index 0fb39c7..9977926 100644
--- a/libsolv.cc
+++ b/libsolv.cc
@@ -868,7 +868,7 @@ SolverSolution::transactions() const
 
 // Construct a string reporting the problems and solutions
 std::string
-SolverSolution::report() const
+SolverSolution::report()
 {
   packagedb db;
   std::string r = "";
@@ -881,8 +881,20 @@ SolverSolution::report() const
       Id probr = solver_findproblemrule(solv, problem);
       Id dep, source, target;
       SolverRuleinfo type = solver_ruleinfo(solv, probr, &source, &target, &dep);
-      if (source == db.basepkg.id)
-	r += "package " + std::string(pool_dep2str(pool.pool, dep)) + " is a Base package and is therefore required";
+      if (type == SOLVER_RULE_PKG_REQUIRES)
+	{
+	  packagemeta *pkg = db.findBinary(PackageSpecification(pool_dep2str(pool.pool, dep)));
+	  if (!pkg->desired && pkg->installed < pkg->default_version)
+	    // User chose to uninstall or skip a required package.
+	    trans.push_back(SolverTransaction(pkg->default_version,
+					      SolverTransaction::transInstall));
+	  if (source == db.basepkg.id)
+	    r += "package " + std::string(pool_dep2str(pool.pool, dep))
+	      + " is a Base package and is therefore required";
+	  else
+	    r += "package " + std::string(pool_dep2str(pool.pool, dep)) +
+	      " is  required by " + std::string(pool_solvid2str(pool.pool, source));
+	}
       else
 	r += solver_problemruleinfo2str(solv, type, source, target, dep);
       r += "\n";
diff --git a/libsolv.h b/libsolv.h
index cddf76f..391a96d 100644
--- a/libsolv.h
+++ b/libsolv.h
@@ -253,7 +253,7 @@ class SolverSolution
     updateForce, // distupdate: downgrade if necessary to best version in repo
   };
   bool update(SolverTasks &tasks, updateMode update, bool use_test_packages, bool include_source);
-  std::string report() const;
+  std::string report();
 
   const SolverTransactionList &transactions() const;
 
-- 
2.15.1