seed/seedwriter: consider modes when checking for deps availability

seed/seedwriter/helpers.go

@@ -21,6 +21,7 @@ package seedwriter
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/snapcore/snapd/asserts"
 	"github.com/snapcore/snapd/asserts/snapasserts"
@@ -120,6 +121,13 @@ func checkType(sn *SeedSnap, model *asserts.Model) error {
 	return nil
 }
 
+func errorMsgForModesSuffix(modes []string) string {
+	if len(modes) == 1 && modes[0] == "run" {
+		return ""
+	}
+	return fmt.Sprintf(" for all relevant modes (%s)", strings.Join(modes, ", "))
+}
+
 type seedSnapsByType []*SeedSnap
 
 func (s seedSnapsByType) Len() int      { return len(s) }

seed/seedwriter/seed16.go

@@ -86,7 +86,8 @@ func (pol *policy16) extraSnapDefaultChannel() string {
 	return "stable"
 }
 
-func (pol *policy16) checkBase(info *snap.Info, availableSnaps *naming.SnapSet) error {
+func (pol *policy16) checkBase(info *snap.Info, modes []string, availableByMode map[string]*naming.SnapSet) error {
+	availableSnaps := availableByMode["run"]
 	// snap needs no base (or it simply needs core which is never listed explicitly): nothing to do
 	if info.Base == "" {
 		if info.Type() == snap.TypeGadget || info.Type() == snap.TypeApp {
@@ -109,7 +110,13 @@ func (pol *policy16) checkBase(info *snap.Info, availableSnaps *naming.SnapSet)
 	return fmt.Errorf("cannot add snap %q without also adding its base %q explicitly", info.SnapName(), info.Base)
 }
 
-func (pol *policy16) needsImplicitSnaps(availableSnaps *naming.SnapSet) (bool, error) {
+func (pol *policy16) checkAvailable(snapRef naming.SnapRef, modes []string, availableByMode map[string]*naming.SnapSet) bool {
+	availableSnaps := availableByMode["run"]
+	return availableSnaps.Contains(snapRef)
+}
+
+func (pol *policy16) needsImplicitSnaps(availableByMode map[string]*naming.SnapSet) (bool, error) {
+	availableSnaps := availableByMode["run"]
 	// do we need to add implicitly either snapd (or core)
 	hasCore := availableSnaps.Contains(naming.Snap("core"))
 	if len(pol.needsCore) != 0 && !hasCore {
@@ -131,7 +138,8 @@ func (pol *policy16) needsImplicitSnaps(availableSnaps *naming.SnapSet) (bool, e
 	return false, nil
 }
 
-func (pol *policy16) implicitSnaps(availableSnaps *naming.SnapSet) []*asserts.ModelSnap {
+func (pol *policy16) implicitSnaps(availableByMode map[string]*naming.SnapSet) []*asserts.ModelSnap {
+	availableSnaps := availableByMode["run"]
 	if len(pol.needsCore) != 0 && !availableSnaps.Contains(naming.Snap("core")) {
 		return []*asserts.ModelSnap{makeSystemSnap("core")}
 	}
@@ -141,7 +149,8 @@ func (pol *policy16) implicitSnaps(availableSnaps *naming.SnapSet) []*asserts.Mo
 	return nil
 }
 
-func (pol *policy16) implicitExtraSnaps(availableSnaps *naming.SnapSet) []*OptionsSnap {
+func (pol *policy16) implicitExtraSnaps(availableByMode map[string]*naming.SnapSet) []*OptionsSnap {
+	availableSnaps := availableByMode["run"]
 	if len(pol.needsCore) != 0 && !availableSnaps.Contains(naming.Snap("core")) {
 		return []*OptionsSnap{{Name: "core"}}
 	}

seed/seedwriter/seed20.go

@@ -81,7 +81,7 @@ func (pol *policy20) extraSnapDefaultChannel() string {
 	return "latest/stable"
 }
 
-func (pol *policy20) checkBase(info *snap.Info, availableSnaps *naming.SnapSet) error {
+func (pol *policy20) checkBase(info *snap.Info, modes []string, availableByMode map[string]*naming.SnapSet) error {
 	base := info.Base
 	if base == "" {
 		if info.Type() != snap.TypeGadget && info.Type() != snap.TypeApp {
@@ -90,32 +90,57 @@ func (pol *policy20) checkBase(info *snap.Info, availableSnaps *naming.SnapSet)
 		base = "core"
 	}
 
-	if availableSnaps.Contains(naming.Snap(base)) {
+	if pol.checkAvailable(naming.Snap(base), modes, availableByMode) {
 		return nil
 	}
 
 	whichBase := fmt.Sprintf("its base %q", base)
 	if base == "core16" {
-		if availableSnaps.Contains(naming.Snap("core")) {
+		if pol.checkAvailable(naming.Snap("core"), modes, availableByMode) {
 			return nil
 		}
 		whichBase += ` (or "core")`
 	}
 
-	return fmt.Errorf("cannot add snap %q without also adding %s explicitly", info.SnapName(), whichBase)
+	return fmt.Errorf("cannot add snap %q without also adding %s explicitly%s", info.SnapName(), whichBase, errorMsgForModesSuffix(modes))
 }
 
-func (pol *policy20) needsImplicitSnaps(*naming.SnapSet) (bool, error) {
+func (pol *policy20) checkAvailable(snapRef naming.SnapRef, modes []string, availableByMode map[string]*naming.SnapSet) bool {
+	// checks that snapRef is available in all modes
+	for _, mode := range modes {
+		byMode := availableByMode[mode]
+		if !byMode.Contains(snapRef) {
+			if mode == "run" || mode == "ephemeral" {
+				// no additional fallback for these
+				// cases:
+				// * run is not ephemeral,
+				//   is covered only by run
+				// * ephemeral is only covered by ephemeral
+				return false
+			}
+			// all non-run modes (e.g. recover) are
+			// considered ephemeral, as a fallback check
+			// if the snap is listed under the ephemeral mode label
+			ephem := availableByMode["ephemeral"]
+			if ephem == nil || !ephem.Contains(snapRef) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func (pol *policy20) needsImplicitSnaps(map[string]*naming.SnapSet) (bool, error) {
 	// no implicit snaps with Core 20
 	// TODO: unless we want to support them for extra snaps
 	return false, nil
 }
 
-func (pol *policy20) implicitSnaps(*naming.SnapSet) []*asserts.ModelSnap {
+func (pol *policy20) implicitSnaps(map[string]*naming.SnapSet) []*asserts.ModelSnap {
 	return nil
 }
 
-func (pol *policy20) implicitExtraSnaps(*naming.SnapSet) []*OptionsSnap {
+func (pol *policy20) implicitExtraSnaps(map[string]*naming.SnapSet) []*OptionsSnap {
 	return nil
 }
 

seed/seedwriter/writer.go

@@ -90,6 +90,15 @@ type SeedSnap struct {
 	optionSnap *OptionsSnap
 }
 
+func (sn *SeedSnap) modes() []string {
+	if sn.modelSnap == nil {
+		// run is the assumed mode for extra snaps not listed
+		// in the model
+		return []string{"run"}
+	}
+	return sn.modelSnap.Modes
+}
+
 var _ naming.SnapRef = (*SeedSnap)(nil)
 
 /* Writer writes Core 16/18 and Core 20 seeds.
@@ -172,7 +181,8 @@ type Writer struct {
 	localSnaps      map[*OptionsSnap]*SeedSnap
 	byRefLocalSnaps *naming.SnapSet
 
-	availableSnaps *naming.SnapSet
+	availableSnaps  *naming.SnapSet
+	availableByMode map[string]*naming.SnapSet
 
 	// toDownload tracks which set of snaps SnapsToDownload should compute
 	// next
@@ -194,11 +204,13 @@ type policy interface {
 	modelSnapDefaultChannel() string
 	extraSnapDefaultChannel() string
 
-	checkBase(*snap.Info, *naming.SnapSet) error
+	checkBase(s *snap.Info, modes []string, availableByMode map[string]*naming.SnapSet) error
+
+	checkAvailable(snpRef naming.SnapRef, modes []string, availableByMode map[string]*naming.SnapSet) bool
 
-	needsImplicitSnaps(*naming.SnapSet) (bool, error)
-	implicitSnaps(*naming.SnapSet) []*asserts.ModelSnap
-	implicitExtraSnaps(*naming.SnapSet) []*OptionsSnap
+	needsImplicitSnaps(availableByMode map[string]*naming.SnapSet) (bool, error)
+	implicitSnaps(availableByMode map[string]*naming.SnapSet) []*asserts.ModelSnap
+	implicitExtraSnaps(availableByMode map[string]*naming.SnapSet) []*OptionsSnap
 }
 
 type tree interface {
@@ -769,11 +781,11 @@ func (w *Writer) SnapsToDownload() (snaps []*SeedSnap, err error) {
 		}
 		return toDownload, nil
 	case toDownloadImplicit:
-		return w.modelSnapsToDownload(w.policy.implicitSnaps(w.availableSnaps))
+		return w.modelSnapsToDownload(w.policy.implicitSnaps(w.availableByMode))
 	case toDownloadExtra:
 		return w.extraSnapsToDownload(w.optExtraSnaps())
 	case toDownloadExtraImplicit:
-		return w.extraSnapsToDownload(w.policy.implicitExtraSnaps(w.availableSnaps))
+		return w.extraSnapsToDownload(w.policy.implicitExtraSnaps(w.availableByMode))
 	default:
 		panic(fmt.Sprintf("unknown to-download set: %d", w.toDownload))
 	}
@@ -820,7 +832,7 @@ func (w *Writer) resolveChannel(whichSnap string, modSnap *asserts.ModelSnap, op
 	return resChannel, nil
 }
 
-func (w *Writer) checkBase(info *snap.Info) error {
+func (w *Writer) checkBase(info *snap.Info, modes []string) error {
 	// Sanity check, note that we could support this case
 	// if we have a use-case but it requires changes in the
 	// devicestate/firstboot.go ordering code.
@@ -833,19 +845,29 @@ func (w *Writer) checkBase(info *snap.Info) error {
 		return nil
 	}
 
-	return w.policy.checkBase(info, w.availableSnaps)
+	return w.policy.checkBase(info, modes, w.availableByMode)
 }
 
 func (w *Writer) downloaded(seedSnaps []*SeedSnap) error {
 	if w.availableSnaps == nil {
 		w.availableSnaps = naming.NewSnapSet(nil)
+		w.availableByMode = make(map[string]*naming.SnapSet)
+		w.availableByMode["run"] = naming.NewSnapSet(nil)
 	}
 
 	for _, sn := range seedSnaps {
 		if sn.Info == nil {
 			return fmt.Errorf("internal error: before seedwriter.Writer.Downloaded snap %q Info should have been set", sn.SnapName())
 		}
 		w.availableSnaps.Add(sn)
+		for _, mode := range sn.modes() {
+			byMode := w.availableByMode[mode]
+			if byMode == nil {
+				byMode = naming.NewSnapSet(nil)
+				w.availableByMode[mode] = byMode
+			}
+			byMode.Add(sn)
+		}
 	}
 
 	for _, sn := range seedSnaps {
@@ -873,14 +895,16 @@ func (w *Writer) downloaded(seedSnaps []*SeedSnap) error {
 			return fmt.Errorf("cannot use classic snap %q in a core system", info.SnapName())
 		}
 
-		if err := w.checkBase(info); err != nil {
+		modes := sn.modes()
+
+		if err := w.checkBase(info, modes); err != nil {
 			return err
 		}
 		// error about missing default providers
 		for dp := range snap.NeededDefaultProviders(info) {
-			if !w.availableSnaps.Contains(naming.Snap(dp)) {
+			if !w.policy.checkAvailable(naming.Snap(dp), modes, w.availableByMode) {
 				// TODO: have a way to ignore this issue on a snap by snap basis?
-				return fmt.Errorf("cannot use snap %q without its default content provider %q being added explicitly", info.SnapName(), dp)
+				return fmt.Errorf("cannot use snap %q without its default content provider %q being added explicitly%s", info.SnapName(), dp, errorMsgForModesSuffix(modes))
 			}
 		}
 
@@ -925,7 +949,7 @@ func (w *Writer) Downloaded() (complete bool, err error) {
 
 	switch w.toDownload {
 	case toDownloadModel:
-		implicitNeeded, err := w.policy.needsImplicitSnaps(w.availableSnaps)
+		implicitNeeded, err := w.policy.needsImplicitSnaps(w.availableByMode)
 		if err != nil {
 			return false, err
 		}
@@ -942,7 +966,7 @@ func (w *Writer) Downloaded() (complete bool, err error) {
 			return false, nil
 		}
 	case toDownloadExtra:
-		implicitNeeded, err := w.policy.needsImplicitSnaps(w.availableSnaps)
+		implicitNeeded, err := w.policy.needsImplicitSnaps(w.availableByMode)
 		if err != nil {
 			return false, err
 		}