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 5:31 PM, Ken Brown wrote:
> 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
> 
> 
> 0001-Implement-a-default-solution-for-SOLVER_RULE_PKG_REQ.patch
> 
> +      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));

This isn't quite right.  We also need a transErase if the package is 
installed.  Revised patch attached.

Ken

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From 1930460c9f5c8a4c1aea0837778d76d8322642fa Mon Sep 17 00:00:00 2001
From: Ken Brown <kbrown@cornell.edu>
Date: Wed, 13 Dec 2017 17:20:26 -0500
Subject: [PATCH setup libsolv v2] 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
appropriate transactions, 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 | 26 +++++++++++++++++++++++---
 libsolv.h  |  2 +-
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/libsolv.cc b/libsolv.cc
index 0fb39c7..48c24c4 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 +881,28 @@ 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)
+	{
+	  // The user chose to uninstall or skip a required package.
+	  // libsolv will not create an erase transaction, but we
+	  // might need to create our own transactions to implement a
+	  // default solution to the problem.
+	  packagemeta *pkg = db.findBinary(PackageSpecification(pool_dep2str(pool.pool, dep)));
+	  if (!pkg->desired && pkg->installed < pkg->default_version)
+	    {
+	      trans.push_back(SolverTransaction(pkg->default_version,
+						SolverTransaction::transInstall));
+	      if (pkg->installed)
+		trans.push_back(SolverTransaction(pkg->installed,
+						  SolverTransaction::transErase));
+	    }
+	  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