Add debhelper marker in postinst script

Without this we don't get any of the generated debhelper postinst
scripts.

Signed-off-by: Brian Goff <[email protected]>

Author: cpuguy83

packaging/linux/deb/debroot.go

@@ -160,18 +160,9 @@ func Debroot(ctx context.Context, sOpt dalec.SourceOpts, spec *dalec.Spec, worke
 		states = append(states, dalecDir.File(llb.Mkfile(filepath.Join(dir, "dalec/"+customSystemdPostinstFile), 0o600, customEnable), opts...))
 	}
 
-	postinst := bytes.NewBuffer(nil)
-	artifacts := spec.GetArtifacts(target)
-	writeUsersPostInst(postinst, artifacts.Users)
-	writeGroupsPostInst(postinst, artifacts.Groups)
-	setArtifactOwnershipPostInst(postinst, spec, target)
-	setArtifactCapabilitiesPostInst(postinst, spec, target)
-
-	if postinst.Len() > 0 {
-		dt := []byte("#!/usr/bin/env sh\nset -e\n")
-		dt = append(dt, postinst.Bytes()...)
-
-		states = append(states, dalecDir.File(llb.Mkfile(filepath.Join(dir, "postinst"), 0o700, dt), opts...))
+	postinst := generatePostinst(spec, target)
+	if len(postinst) > 0 {
+		states = append(states, dalecDir.File(llb.Mkfile(filepath.Join(dir, "postinst"), 0o700, postinst), opts...))
 	}
 
 	patchDir := dalecDir.File(llb.Mkdir(filepath.Join(dir, "dalec/patches"), 0o755), opts...)
@@ -181,6 +172,7 @@ func Debroot(ctx context.Context, sOpt dalec.SourceOpts, spec *dalec.Spec, worke
 		states = append(states, pls...)
 	}
 
+	artifacts := spec.GetArtifacts(target)
 	if len(artifacts.Links) > 0 {
 		buf := bytes.NewBuffer(nil)
 
@@ -196,6 +188,28 @@ func Debroot(ctx context.Context, sOpt dalec.SourceOpts, spec *dalec.Spec, worke
 	return dalec.MergeAtPath(in, states, "/")
 }
 
+func generatePostinst(spec *dalec.Spec, target string) []byte {
+	buf := bytes.NewBuffer(nil)
+
+	artifacts := spec.GetArtifacts(target)
+	writeUsersPostInst(buf, artifacts.Users)
+	writeGroupsPostInst(buf, artifacts.Groups)
+	setArtifactOwnershipPostInst(buf, spec, target)
+	setArtifactCapabilitiesPostInst(buf, spec, target)
+
+	if buf.Len() == 0 {
+		return nil
+	}
+
+	// NOTE: `#DEBHELPER#` is a special marker that will be replaced by
+	// debhelper when it generates the final postinst script.
+	// Very important that this is included.
+	dt := []byte("#!/usr/bin/env sh\nset -e\n\n#DEBHELPER#\n\n")
+	dt = append(dt, buf.Bytes()...)
+
+	return dt
+}
+
 func fixupArtifactPerms(spec *dalec.Spec, target string, cfg *SourcePkgConfig) []byte {
 	buf := bytes.NewBuffer(nil)
 	writeScriptHeader(buf, cfg)

packaging/linux/deb/debroot_postinst_test.go

@@ -0,0 +1,72 @@
+package deb
+
+import (
+	"bytes"
+	"context"
+	"path/filepath"
+	"testing"
+
+	"github.com/moby/buildkit/client/llb"
+	"github.com/moby/buildkit/solver/pb"
+	"github.com/project-dalec/dalec"
+	"gotest.tools/v3/assert"
+)
+
+func TestDebrootPostinstIncludesDebhelperMarker(t *testing.T) {
+	t.Parallel()
+
+	ctx := context.Background()
+	spec := &dalec.Spec{
+		Name:        "example",
+		Description: "Example package",
+		Website:     "https://example.invalid",
+		Version:     "1.0.0",
+		Revision:    "1",
+		License:     "Apache-2.0",
+		Artifacts: dalec.Artifacts{
+			Users: []dalec.AddUserConfig{
+				{Name: "dalecuser"},
+			},
+		},
+	}
+
+	st := Debroot(ctx, dalec.SourceOpts{}, spec, llb.Scratch(), llb.Scratch(), "", "", "", SourcePkgConfig{})
+	def, err := st.Marshal(ctx)
+	assert.NilError(t, err)
+
+	mkfile, err := findMkfile(t, def.ToPB(), filepath.Join("/debian", "postinst"))
+	assert.NilError(t, err)
+	assert.Assert(t, mkfile != nil)
+
+	assert.Equal(t, int32(0o700), mkfile.Mode)
+	assert.Assert(t, bytes.Contains(mkfile.Data, []byte("#DEBHELPER#")))
+	assert.Assert(t, bytes.Contains(mkfile.Data, []byte("useradd dalecuser")))
+}
+
+func findMkfile(t *testing.T, def *pb.Definition, path string) (*pb.FileActionMkFile, error) {
+	for _, dt := range def.Def {
+		var op pb.Op
+		if err := op.Unmarshal(dt); err != nil {
+			return nil, err
+		}
+
+		fileOp := op.GetFile()
+		if fileOp == nil {
+			continue
+		}
+
+		for _, action := range fileOp.Actions {
+			mkfile := action.GetMkfile()
+			if mkfile == nil {
+				continue
+			}
+
+			t.Log(mkfile.Path)
+			if filepath.Clean(mkfile.Path) == filepath.Clean(path) {
+				return mkfile, nil
+			}
+		}
+	}
+
+	return nil, nil
+}