edsp: try 2 to read responses even if writing failed

Commit b60c8a89c281f2bb945d426d2215cbf8f5760738 improved the situation,
but due to inconsistency mostly for planners, not for solvers. As the
idea of hiding errors if we show another error is a bit scary (as the
extern error might be a followup of our intern error, rather than the
reason for our intern error as it is at the moment) we don't discard the
errors, but if we got an extern error we show them directly removing
them from the error list at the end of the run – that list will contain
the extern error which hopefully gives us the best of both worlds.

The problem itself is the same as before: The externals exiting before
apt is done talking to them.

Reported-By: Johannes 'josch' Schauer on IRC

apt-pkg/edsp.cc

@@ -648,13 +648,19 @@ bool EDSP::ReadResponse(int const input, pkgDepCache &Cache, OpProgress *Progres
 			}
 			continue;
 		} else if (section.Exists("Error") == true) {
+			if (_error->PendingError()) {
+				if (Progress != nullptr)
+					Progress->Done();
+				Progress = nullptr;
+				_error->DumpErrors(std::cerr, GlobalError::DEBUG, false);
+			}
 			std::string msg = SubstVar(SubstVar(section.FindS("Message"), "\n .\n", "\n\n"), "\n ", "\n");
 			if (msg.empty() == true) {
 				msg = _("External solver failed without a proper error message");
 				_error->Error("%s", msg.c_str());
 			} else
 				_error->Error("External solver failed with: %s", msg.substr(0,msg.find('\n')).c_str());
-			if (Progress != NULL)
+			if (Progress != nullptr)
 				Progress->Done();
 			std::cerr << "The solver encountered an error of type: " << section.FindS("Error") << std::endl;
 			std::cerr << "The following information might help you to understand what is wrong:" << std::endl;
@@ -1051,8 +1057,9 @@ bool EDSP::ResolveExternal(const char* const solver, pkgDepCache &Cache,
 		Okay &= EDSP::WriteRequest(Cache, output, flags, nullptr);
 		return Okay && EDSP::WriteScenario(Cache, output, nullptr);
 	}
+	_error->PushToStack();
 	int solver_in, solver_out;
-	pid_t const solver_pid = EDSP::ExecuteSolver(solver, &solver_in, &solver_out, true);
+	pid_t const solver_pid = ExecuteSolver(solver, &solver_in, &solver_out, true);
 	if (solver_pid == 0)
 		return false;
 
@@ -1071,11 +1078,11 @@ bool EDSP::ResolveExternal(const char* const solver, pkgDepCache &Cache,
 
 	if (Okay && Progress != NULL)
 		Progress->OverallProgress(25, 100, 75, _("Execute external solver"));
-	if (Okay && EDSP::ReadResponse(solver_out, Cache, Progress) == false)
-		return false;
-
-	bool const waited = ExecWait(solver_pid, solver);
-	return Okay && waited;
+	bool const ret = EDSP::ReadResponse(solver_out, Cache, Progress);
+	_error->MergeWithStack();
+	if (ExecWait(solver_pid, solver))
+		return ret;
+	return false;
 }
 bool EDSP::ResolveExternal(const char* const solver, pkgDepCache &Cache,
 			 bool const upgrade, bool const distUpgrade,
@@ -1108,7 +1115,7 @@ bool EIPP::OrderInstall(char const * const solver, pkgPackageManager * const PM,
       Okay &= EIPP::WriteRequest(PM->Cache, output, flags, nullptr);
       return Okay && EIPP::WriteScenario(PM->Cache, output, nullptr);
    }
-
+   _error->PushToStack();
    int solver_in, solver_out;
    pid_t const solver_pid = ExecuteExternal("planner", solver, "Dir::Bin::Planners", &solver_in, &solver_out);
    if (solver_pid == 0)
@@ -1139,12 +1146,11 @@ bool EIPP::OrderInstall(char const * const solver, pkgPackageManager * const PM,
 	    PM->Remove(Pkg, true);
       }
    }
-
-   if (EIPP::ReadResponse(solver_out, PM, Progress) == false)
-      return false;
-
-   bool const waited = ExecWait(solver_pid, solver);
-   return Okay && waited;
+   bool const ret = EIPP::ReadResponse(solver_out, PM, Progress);
+   _error->MergeWithStack();
+   if (ExecWait(solver_pid, solver))
+      return ret;
+   return false;
 }
 									/*}}}*/
 bool EIPP::WriteRequest(pkgDepCache &Cache, FileFd &output,		/*{{{*/
@@ -1341,13 +1347,19 @@ bool EIPP::ReadResponse(int const input, pkgPackageManager * const PM, OpProgres
 	 }
 	 continue;
       } else if (section.Exists("Error") == true) {
+	 if (_error->PendingError()) {
+	    if (Progress != nullptr)
+	       Progress->Done();
+	    Progress = nullptr;
+	    _error->DumpErrors(std::cerr, GlobalError::DEBUG, false);
+	 }
 	 std::string msg = SubstVar(SubstVar(section.FindS("Message"), "\n .\n", "\n\n"), "\n ", "\n");
 	 if (msg.empty() == true) {
 	    msg = _("External planner failed without a proper error message");
 	    _error->Error("%s", msg.c_str());
 	 } else
 	    _error->Error("External planner failed with: %s", msg.substr(0,msg.find('\n')).c_str());
-	 if (Progress != NULL)
+	 if (Progress != nullptr)
 	    Progress->Done();
 	 std::cerr << "The planner encountered an error of type: " << section.FindS("Error") << std::endl;
 	 std::cerr << "The following information might help you to understand what is wrong:" << std::endl;

apt-private/private-install.cc

@@ -48,6 +48,10 @@ bool CheckNothingBroken(CacheFile &Cache)				/*{{{*/
    if (Cache->BrokenCount() == 0)
       return true;
 
+   // FIXME: if an external solver showed an error, we shouldn't show one here
+   if (_error->PendingError() && _config->Find("APT::Solver") == "dump")
+      return false;
+
    c1out <<
       _("Some packages could not be installed. This may mean that you have\n"
 	    "requested an impossible situation or if you are using the unstable\n"

test/integration/test-external-dependency-solver-protocol

@@ -262,3 +262,24 @@ EOF
 chmod +x rootdir/usr/lib/apt/solvers/installall
 testfailure apt full-upgrade -s --solver installall
 testsuccess grep "is already installed!" rootdir/tmp/testfailure.output
+
+testsolverfailuremsg() {
+	local SOLVER="rootdir/usr/lib/apt/solvers/$1"
+	echo "$2" > "$SOLVER"
+	chmod +x "$SOLVER"
+	testfailuremsg "$3" apt full-upgrade -s --solver $1
+}
+
+testsolverfailuremsg 'exit0withmsg' "#!/bin/sh
+echo 'Error: instant-exit
+Message: This solver exits instantly'
+exit 0" 'E: External solver failed with: This solver exits instantly'
+
+testsolverfailuremsg 'exit1withoutmsg' "#!/bin/sh
+exit 1" 'E: Sub-process exit1withoutmsg returned an error code (1)'
+
+testsolverfailuremsg 'exit1withmsg' "#!/bin/sh
+echo 'Error: instant-exit
+Message: This solver exits instantly'
+exit 1" 'E: External solver failed with: This solver exits instantly
+E: Sub-process exit1withmsg returned an error code (1)'

test/integration/test-external-installation-planner-protocol

@@ -70,3 +70,24 @@ Remove: foo:amd64
 Planner: internal' head -n 5 "$EIPPLOG"
 aptinternalplanner < "$EIPPLOG" > planner.log || true
 testsuccessequal 'Remove: 4' grep -e '^Unpack:' -e '^Install:' -e '^Configure:' -e '^Remove:' planner.log
+
+testplannerfailuremsg() {
+	local PLANNER="rootdir/usr/lib/apt/planners/$1"
+	echo "$2" > "$PLANNER"
+	chmod +x "$PLANNER"
+	testfailuremsg "$3" apt install foo -s --planner $1
+}
+
+testplannerfailuremsg 'exit0withmsg' "#!/bin/sh
+echo 'Error: instant-exit
+Message: This planner exits instantly'
+exit 0" 'E: External planner failed with: This planner exits instantly'
+
+testplannerfailuremsg 'exit1withoutmsg' "#!/bin/sh
+exit 1" 'E: Sub-process exit1withoutmsg returned an error code (1)'
+
+testplannerfailuremsg 'exit1withmsg' "#!/bin/sh
+echo 'Error: instant-exit
+Message: This planner exits instantly'
+exit 1" 'E: External planner failed with: This planner exits instantly
+E: Sub-process exit1withmsg returned an error code (1)'