manifest: make packageSpecs optional

Allow manifests to be instantiated without providing packageSpecs.
This allows manifests without packageSpecs to be introspected, but
not serialized.

The only reason we used to require packegaSpecs to be passed at
instantiation time was to compute the kernelVer based on the
kernelName and the NEVRAs in the package set. Now move this to be
done at serialize time.

This means that in order to serialize a manifest, you need to pass
the packageSpecs at initialization time, but if you don't need to
serialize, only to introspect it, then you don't need to pass it
at all.

In a future patch packageSpecs will be passed at serialization time
to not have to make that commitment up front.

The new logic is now that before a pipeline can be serialized, all
the pipelines in the manifest must be "prepared" for serialization
by calling serialize_start() on each of them, which does whatever
would in the past have been done at initialization time which
required the pacakgeSpecs. Once serialization has been finished
serialize_end() must be called on each of the pipelines to undo
any of the preparation, making sure we can serialize repeatedly,
possibly while changing the fields of our pipeline in-between,
and that serialization appears from the outside to not have any
side-effects.

In a future PR we may want to rework this logic to instead use a
serialization context.

internal/manifest/anaconda.go

@@ -27,6 +27,7 @@ type AnacondaPipeline struct {
 
 	repos        []rpmmd.RepoConfig
 	packageSpecs []rpmmd.PackageSpec
+	kernelName   string
 	kernelVer    string
 	arch         string
 	product      string
@@ -46,12 +47,11 @@ func NewAnacondaPipeline(buildPipeline *BuildPipeline,
 	arch,
 	product,
 	version string) *AnacondaPipeline {
-	kernelVer := rpmmd.GetVerStrFromPackageSpecListPanic(packages, kernelName)
 	p := &AnacondaPipeline{
 		BasePipeline: NewBasePipeline("anaconda-tree", buildPipeline, nil),
 		repos:        repos,
 		packageSpecs: packages,
-		kernelVer:    kernelVer,
+		kernelName:   kernelName,
 		arch:         arch,
 		product:      product,
 		version:      version,
@@ -74,6 +74,20 @@ func (p *AnacondaPipeline) getPackageSpecs() []rpmmd.PackageSpec {
 	return p.packageSpecs
 }
 
+func (p *AnacondaPipeline) serializeStart() {
+	if p.kernelVer != "" {
+		panic("double call to serializeStart()")
+	}
+	p.kernelVer = rpmmd.GetVerStrFromPackageSpecListPanic(p.packageSpecs, p.kernelName)
+}
+
+func (p *AnacondaPipeline) serializeEnd() {
+	if p.kernelVer == "" {
+		panic("serializeEnd() call when serialization not in progress")
+	}
+	p.kernelVer = ""
+}
+
 func (p *AnacondaPipeline) serialize() osbuild2.Pipeline {
 	pipeline := p.BasePipeline.serialize()
 

internal/manifest/manifest.go

@@ -79,9 +79,15 @@ func (m Manifest) Serialize() (distro.Manifest, error) {
 	}
 
 	pipelines := make([]osbuild2.Pipeline, 0)
+	for _, pipeline := range m.pipelines {
+		pipeline.serializeStart()
+	}
 	for _, pipeline := range m.pipelines {
 		pipelines = append(pipelines, pipeline.serialize())
 	}
+	for _, pipeline := range m.pipelines {
+		pipeline.serializeEnd()
+	}
 
 	return json.Marshal(
 		osbuild2.Manifest{

internal/manifest/os.go

@@ -92,6 +92,7 @@ type OSPipeline struct {
 	partitionTable *disk.PartitionTable
 	bootLoader     BootLoader
 	grubLegacy     string
+	kernelName     string
 	kernelVer      string
 }
 
@@ -115,10 +116,6 @@ func NewOSPipeline(buildPipeline *BuildPipeline,
 	if osTree {
 		name = "ostree-tree"
 	}
-	var kernelVer string
-	if kernelName != "" {
-		kernelVer = rpmmd.GetVerStrFromPackageSpecListPanic(packages, kernelName)
-	}
 	p := &OSPipeline{
 		BasePipeline:   NewBasePipeline(name, buildPipeline, nil),
 		osTree:         osTree,
@@ -129,7 +126,7 @@ func NewOSPipeline(buildPipeline *BuildPipeline,
 		partitionTable: partitionTable,
 		bootLoader:     bootLoader,
 		grubLegacy:     grubLegacy,
-		kernelVer:      kernelVer,
+		kernelName:     kernelName,
 		Language:       "C.UTF-8",
 		Hostname:       "localhost.localdomain",
 		Timezone:       "UTC",
@@ -174,6 +171,26 @@ func (p *OSPipeline) getPackageSpecs() []rpmmd.PackageSpec {
 	return p.packageSpecs
 }
 
+func (p *OSPipeline) serializeStart() {
+	if p.kernelName == "" {
+		return
+	}
+	if p.kernelVer != "" {
+		panic("double call to serializeStart()")
+	}
+	p.kernelVer = rpmmd.GetVerStrFromPackageSpecListPanic(p.packageSpecs, p.kernelName)
+}
+
+func (p *OSPipeline) serializeEnd() {
+	if p.kernelName == "" {
+		return
+	}
+	if p.kernelVer == "" {
+		panic("serializeEnd() call when serialization not in progress")
+	}
+	p.kernelVer = ""
+}
+
 func (p *OSPipeline) serialize() osbuild2.Pipeline {
 	pipeline := p.BasePipeline.serialize()
 

internal/manifest/pipeline.go

@@ -15,6 +15,8 @@ type Pipeline interface {
 	Name() string
 	getBuildPackages() []string
 	getPackageSetChain() []rpmmd.PackageSet
+	serializeStart()
+	serializeEnd()
 	serialize() osbuild2.Pipeline
 	getPackageSpecs() []rpmmd.PackageSpec
 	getOSTreeCommits() []osTreeCommit
@@ -79,6 +81,16 @@ func NewBasePipeline(name string, build *BuildPipeline, runner *string) BasePipe
 	return p
 }
 
+// serializeStart must be called exactly once before each call
+// to serialize().
+func (p BasePipeline) serializeStart() {
+}
+
+// serializeEnd must be called exactly once after each call to
+// serialize().
+func (p BasePipeline) serializeEnd() {
+}
+
 // Serialize turns a given pipeline into an osbuild2.Pipeline object. This object is
 // meant to be treated as opaque and not to be modified further outside of the pipeline
 // package.