Evaluate and fall back to the 3.0 solver

Always run the 3.0 solver after the internal solver. If the internal
solver failed, and the 3.0 solver did not, use the 3.0 result.

If 3.0 solver failed or produced a worse result than the internal
solver, write an apport crash dump.

We exclude situations which we now the solver can't handle, i.e.
removals are forbidden and you requested removals, and stuff like
that.

3 files changed, 222 insertions, 0 deletions

diff --git a/test/integration/test-bug-745046-candidate-propagation-fails b/test/integration/test-bug-745046-candidate-propagation-fails
index 8475a4ea1..f4fc15e0e 100755
--- a/test/integration/test-bug-745046-candidate-propagation-fails
+++ b/test/integration/test-bug-745046-candidate-propagation-fails
@@ -17,6 +17,7 @@ setupaptarchive
 testfailureequal "Reading package lists...
 Building dependency tree...
 Selected version '2' (experimental [amd64]) for 'gedit'
+Selected version '2' (experimental [amd64]) for 'gedit'
 Some packages could not be installed. This may mean that you have
 requested an impossible situation or if you are using the unstable
 distribution that some required packages have not yet been created
diff --git a/test/integration/test-release-candidate-switching b/test/integration/test-release-candidate-switching
index be5b3f997..52d3e5a12 100755
--- a/test/integration/test-release-candidate-switching
+++ b/test/integration/test-release-candidate-switching
@@ -424,6 +424,7 @@ E: Trivial Only specified but this is not a trivial operation." aptget install a
 testfailureequal "Reading package lists...
 Building dependency tree...
 Selected version '1.0' (experimental [all]) for 'uninstallablepkg'
+Selected version '1.0' (experimental [all]) for 'uninstallablepkg'
 Some packages could not be installed. This may mean that you have
 requested an impossible situation or if you are using the unstable
 distribution that some required packages have not yet been created
diff --git a/test/integration/test-solver3-evaluation b/test/integration/test-solver3-evaluation
new file mode 100755
index 000000000..d3521e9c6
--- /dev/null
+++ b/test/integration/test-solver3-evaluation
@@ -0,0 +1,220 @@
+#!/bin/sh
+set -e
+
+TESTDIR="$(readlink -f "$(dirname "$0")")"
+. "$TESTDIR/framework"
+setupenvironment
+configarchitecture 'amd64'
+
+insertinstalledpackage 'apport' 'all' '3'
+
+insertpackage 'unstable' 'x' 'all' '3' 'Depends: a | b'
+insertpackage 'unstable' 'y' 'all' '3' 'Depends: b | a'
+insertpackage 'unstable' 'a' 'all' '3' 'Depends: c'
+insertpackage 'unstable' 'b' 'all' '3'
+insertpackage 'unstable' 'c' 'all' '3'
+
+setupaptarchive
+
+mkdir rootdir/var/log/apt
+
+testsuccess aptget install y x --solver internal -s -o Dir::Apport=var/crash
+
+testsuccess sed -i "s/^Date:.*/Date: Sun Mar  9 00:08:41 2025/" rootdir/var/crash/apt-edsp.$(id -u).crash
+
+testsuccessequal "ProblemType: AptSolver
+Architecture: amd64
+Date: Sun Mar  9 00:08:41 2025
+Package: apt 
+Title: Failure: The 3.0 solver produced a worse result
+SourcePackage: apt
+ErrorMessage:
+AptSolverDump:
+ Request: EDSP 0.5
+ Architecture: amd64
+ Architectures: amd64
+ Machine-ID: 912e43bd1c1d4ba481f9f8ccab25f9ee
+ Install: x:amd64 y:amd64
+ Solver: internal
+ 
+ Package: a
+ Architecture: all
+ Version: 3
+ APT-ID: 2
+ Source: a
+ Source-Version: 3
+ Priority: optional
+ Section: other
+ Size: 42
+ APT-Release:
+  a=unstable,n=sid,c=main,b=all
+ APT-Pin: 500
+ APT-Candidate: yes
+ Depends: c
+ 
+ Package: b
+ Architecture: all
+ Version: 3
+ APT-ID: 3
+ Source: b
+ Source-Version: 3
+ Priority: optional
+ Section: other
+ Size: 42
+ APT-Release:
+  a=unstable,n=sid,c=main,b=all
+ APT-Pin: 500
+ APT-Candidate: yes
+ 
+ Package: c
+ Architecture: all
+ Version: 3
+ APT-ID: 4
+ Source: c
+ Source-Version: 3
+ Priority: optional
+ Section: other
+ Size: 42
+ APT-Release:
+  a=unstable,n=sid,c=main,b=all
+ APT-Pin: 500
+ APT-Candidate: yes
+ 
+ Package: x
+ Architecture: all
+ Version: 3
+ APT-ID: 0
+ Source: x
+ Source-Version: 3
+ Priority: optional
+ Section: other
+ Size: 42
+ APT-Release:
+  a=unstable,n=sid,c=main,b=all
+ APT-Pin: 500
+ APT-Candidate: yes
+ Depends: a | b
+ 
+ Package: y
+ Architecture: all
+ Version: 3
+ APT-ID: 1
+ Source: y
+ Source-Version: 3
+ Priority: optional
+ Section: other
+ Size: 42
+ APT-Release:
+  a=unstable,n=sid,c=main,b=all
+ APT-Pin: 500
+ APT-Candidate: yes
+ Depends: b | a
+ 
+ Package: apport
+ Architecture: all
+ Version: 3
+ APT-ID: 5
+ Source: apport
+ Source-Version: 3
+ Priority: optional
+ Section: other
+ Installed: yes
+ APT-Pin: 100
+ APT-Candidate: yes
+ " cat rootdir/var/crash/apt-edsp.$(id -u).crash
+
+
+testsuccessequal "Request: EDSP 0.5
+Architecture: amd64
+Architectures: amd64
+Machine-ID: 912e43bd1c1d4ba481f9f8ccab25f9ee
+Install: x:amd64 y:amd64
+Solver: internal
+
+Package: a
+Architecture: all
+Version: 3
+APT-ID: 2
+Source: a
+Source-Version: 3
+Priority: optional
+Section: other
+Size: 42
+APT-Release:
+ a=unstable,n=sid,c=main,b=all
+APT-Pin: 500
+APT-Candidate: yes
+Depends: c
+
+Package: b
+Architecture: all
+Version: 3
+APT-ID: 3
+Source: b
+Source-Version: 3
+Priority: optional
+Section: other
+Size: 42
+APT-Release:
+ a=unstable,n=sid,c=main,b=all
+APT-Pin: 500
+APT-Candidate: yes
+
+Package: c
+Architecture: all
+Version: 3
+APT-ID: 4
+Source: c
+Source-Version: 3
+Priority: optional
+Section: other
+Size: 42
+APT-Release:
+ a=unstable,n=sid,c=main,b=all
+APT-Pin: 500
+APT-Candidate: yes
+
+Package: x
+Architecture: all
+Version: 3
+APT-ID: 0
+Source: x
+Source-Version: 3
+Priority: optional
+Section: other
+Size: 42
+APT-Release:
+ a=unstable,n=sid,c=main,b=all
+APT-Pin: 500
+APT-Candidate: yes
+Depends: a | b
+
+Package: y
+Architecture: all
+Version: 3
+APT-ID: 1
+Source: y
+Source-Version: 3
+Priority: optional
+Section: other
+Size: 42
+APT-Release:
+ a=unstable,n=sid,c=main,b=all
+APT-Pin: 500
+APT-Candidate: yes
+Depends: b | a
+
+Package: apport
+Architecture: all
+Version: 3
+APT-ID: 5
+Source: apport
+Source-Version: 3
+Priority: optional
+Section: other
+Installed: yes
+APT-Pin: 100
+APT-Candidate: yes
+" cat rootdir/var/log/apt/edsp.log
+
+