From ed0a589561604dd6d61ee90dd17ab617dbd16ade Mon Sep 17 00:00:00 2001
From: Manuel Naranjo <naranjo.manuel@gmail.com>
Date: Mon, 13 Jan 2025 14:33:20 +0100
Subject: [PATCH] sat: sort inputs to the sat solver for determinism

Make sure the sat solver output is deterministic and reproducible by
making the input order stable
---
 .bazelrc            |  3 +++
 MODULE.bazel        |  1 +
 pkg/sat/BUILD.bazel |  1 +
 pkg/sat/sat.go      | 60 +++++++++++++++++++++++++++++++++++++++------
 4 files changed, 58 insertions(+), 7 deletions(-)

diff --git a/.bazelrc b/.bazelrc
index 2d3524b..4e2ab67 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -12,6 +12,9 @@ common --incompatible_enable_proto_toolchain_resolution
 # inside the rules project we build from source
 common --extra_toolchains=//cmd:bazeldnf-host-toolchain
 
+# make sure bazel doesn't complain on hosts without java
+common --java_runtime_version=remotejdk_21
+
 # Load any settings & overrides specific to the current user from `.bazelrc.user`.
 # This file should appear in `.gitignore` so that settings are not shared with team members. This
 # should be last statement in this config so the user configuration is able to overwrite flags from
diff --git a/MODULE.bazel b/MODULE.bazel
index 6770cd2..e6af7b4 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -33,6 +33,7 @@ use_repo(
     "com_github_spf13_cobra",
     "io_k8s_sigs_yaml",
     "org_golang_x_crypto",
+    "org_golang_x_exp",
 )
 
 # deps only needed for the repo internals
diff --git a/pkg/sat/BUILD.bazel b/pkg/sat/BUILD.bazel
index 2eb0ecb..2432fa2 100644
--- a/pkg/sat/BUILD.bazel
+++ b/pkg/sat/BUILD.bazel
@@ -13,6 +13,7 @@ go_library(
         "@com_github_crillab_gophersat//explain",
         "@com_github_crillab_gophersat//maxsat",
         "@com_github_sirupsen_logrus//:logrus",
+        "@org_golang_x_exp//slices",
     ],
 )
 
diff --git a/pkg/sat/sat.go b/pkg/sat/sat.go
index 1a2f9ca..7ee3bce 100644
--- a/pkg/sat/sat.go
+++ b/pkg/sat/sat.go
@@ -2,6 +2,7 @@ package sat
 
 import (
 	"bufio"
+	"cmp"
 	"fmt"
 	"io"
 	"regexp"
@@ -16,6 +17,7 @@ import (
 	"github.com/rmohr/bazeldnf/pkg/reducer"
 	"github.com/rmohr/bazeldnf/pkg/rpm"
 	"github.com/sirupsen/logrus"
+	"golang.org/x/exp/slices"
 )
 
 type VarType string
@@ -34,6 +36,13 @@ type VarContext struct {
 	Version  api.Version
 }
 
+func varContextSort(a VarContext, b VarContext) int {
+	return cmp.Or(
+		cmp.Compare(a.Package, b.Package),
+		rpm.Compare(a.Version, b.Version),
+	)
+}
+
 type Var struct {
 	satVarName      string
 	varType         VarType
@@ -129,8 +138,15 @@ func (r *Resolver) LoadInvolvedPackages(packages []*api.Package, ignoreRegex []s
 			deduplicated[pkg.String()] = packages[i]
 		}
 	}
+
+	deduplicatedKeys := make([]string, 0, len(deduplicated))
+	for k := range deduplicated {
+		deduplicatedKeys = append(deduplicatedKeys, k)
+	}
+	slices.Sort(deduplicatedKeys)
+
 	packages = nil
-	for k, _ := range deduplicated {
+	for _, k := range deduplicatedKeys {
 		reducer.FixPackages(deduplicated[k])
 		packages = append(packages, deduplicated[k])
 	}
@@ -146,8 +162,13 @@ func (r *Resolver) LoadInvolvedPackages(packages []*api.Package, ignoreRegex []s
 
 	if !r.nobest {
 		packages = nil
-		for _, v := range r.bestPackages {
-			packages = append(packages, v)
+		bestPackagesKeys := make([]string, 0, len(r.bestPackages))
+		for k := range r.bestPackages {
+			bestPackagesKeys = append(bestPackagesKeys, k)
+		}
+		slices.Sort(bestPackagesKeys)
+		for _, v := range bestPackagesKeys {
+			packages = append(packages, r.bestPackages[v])
 		}
 	}
 	// Generate variables
@@ -161,17 +182,31 @@ func (r *Resolver) LoadInvolvedPackages(packages []*api.Package, ignoreRegex []s
 		}
 	}
 
-	for x, _ := range r.packages {
+	packagesKeys := make([]string, 0, len(r.packages))
+	for k := range r.packages {
+		packagesKeys = append(packagesKeys, k)
+	}
+	slices.Sort(packagesKeys)
+
+	for _, x := range packagesKeys {
 		sort.SliceStable(r.packages[x], func(i, j int) bool {
 			return rpm.Compare(r.packages[x][i].Package.Version, r.packages[x][j].Package.Version) < 0
 		})
 	}
 
 	logrus.Infof("Loaded %v packages.", len(r.pkgProvides))
+
+	pkgProvideKeys := make([]VarContext, 0, len(r.pkgProvides))
+	for vc := range r.pkgProvides {
+		pkgProvideKeys = append(pkgProvideKeys, vc)
+	}
+	slices.SortFunc(pkgProvideKeys, varContextSort)
+
 	// Generate imply rules
-	for _, resourceVars := range r.pkgProvides {
+	for _, provided := range pkgProvideKeys {
 		// Create imply rules for every package and add them to the formula
 		// one provided dependency implies all dependencies from that package
+		resourceVars := r.pkgProvides[provided]
 		bfVar := bf.And(toBFVars(resourceVars)...)
 		var ands []bf.Formula
 		for _, res := range resourceVars {
@@ -250,8 +285,14 @@ func (res *Resolver) Resolve() (install []*api.Package, excluded []*api.Package,
 			}
 		}
 		// write soft rules. We don't want to install any package
-		for _, pkgs := range res.packages {
-			weight := 1901
+		packageKeys := make([]string, 0, len(res.packages))
+		for k := range res.packages {
+			packageKeys = append(packageKeys, k)
+		}
+
+		for _, name := range packageKeys {
+			pkgs := res.packages[name]
+			weight := 2999
 			fmt.Fprintf(pwMaxSatWriter, "c prefer %s\n", pkgs[len(pkgs)-1].Package.String())
 			if len(pkgs) > 1 {
 				for _, pkg := range pkgs[0 : len(pkgs)-1] {
@@ -533,6 +574,11 @@ func (r *Resolver) explodeSingleRequires(entry api.Entry, provides []*Var) (acce
 		return nil, fmt.Errorf("Nothing can satisfy %s", entry.Name)
 	}
 
+	slices.SortFunc(accepts, func(a *Var, b *Var) int {
+		// there's a single var context for a given package
+		return varContextSort(a.Context, b.Context)
+	})
+
 	return accepts, nil
 }