a/snapasserts: report missing components when snaps are required

asserts/snapasserts/validation_sets.go

@@ -751,7 +751,12 @@ func (v *ValidationSets) CheckInstalledSnaps(snaps []*InstalledSnap, ignoreValid
 		return err
 	}
 
-	vcerrs, err := v.checkInstalledComponents(installed, ignoreValidation)
+	missingSnapNames := make(map[string]bool, len(missing))
+	for name := range missing {
+		missingSnapNames[name] = true
+	}
+
+	vcerrs, err := v.checkInstalledComponents(installed, ignoreValidation, missingSnapNames)
 	if err != nil {
 		return err
 	}
@@ -768,7 +773,7 @@ func (v *ValidationSets) CheckInstalledSnaps(snaps []*InstalledSnap, ignoreValid
 	return nil
 }
 
-func (v *ValidationSets) checkInstalledComponents(installedSnaps installedSnapSet, ignore map[string]bool) (map[string]*ValidationSetsComponentValidationError, error) {
+func (v *ValidationSets) checkInstalledComponents(installedSnaps installedSnapSet, ignore map[string]bool, missingSnaps map[string]bool) (map[string]*ValidationSetsComponentValidationError, error) {
 	componentInstalled := func(cstrs constraints) (snap.Revision, error) {
 		if cstrs.compRef == nil || cstrs.snapRef == nil {
 			return snap.Revision{}, errors.New("internal error: component constraint should have component and snap refs")
@@ -787,11 +792,13 @@ func (v *ValidationSets) checkInstalledComponents(installedSnaps installedSnapSe
 		// if we're ignoring the snap, then we don't consider its components
 		//
 		// if the snap is not installed, then nothing can be wrong with the
-		// components, since none will be installed.
+		// components, since none will be installed. however, for error
+		// reporting reasons, we consider components for snaps that are required
+		// by the validation sets.
 		//
 		// note that we consider "required" components to only be required if
 		// the snap itself is installed.
-		if ignore[sc.name] || !installedSnaps.Contains(sc.snapRef) {
+		if ignore[sc.name] || (!installedSnaps.Contains(sc.snapRef) && !missingSnaps[sc.name]) {
 			continue
 		}
 

asserts/snapasserts/validation_sets_test.go

@@ -737,6 +737,25 @@ func (s *validationSetsSuite) TestCheckInstalledSnapsWithComponents(c *C) {
 				},
 			},
 		},
+		"four": {
+			map[string]interface{}{
+				"name":     "snap-a",
+				"id":       snaptest.AssertedSnapID("snap-a"),
+				"presence": "required",
+				"components": map[string]interface{}{
+					"comp-3": map[string]interface{}{
+						"presence": "required",
+					},
+					"comp-4": map[string]interface{}{
+						"presence": "required",
+						"revision": "2",
+					},
+					"comp-5": map[string]interface{}{
+						"presence": "optional",
+					},
+				},
+			},
+		},
 	}
 
 	assertions := make(map[string]*asserts.ValidationSet)
@@ -862,14 +881,40 @@ func (s *validationSetsSuite) TestCheckInstalledSnapsWithComponents(c *C) {
 					"snap-a": {
 						MissingComponents: map[string]map[snap.Revision][]string{
 							"comp-2": {
-								{}:        {"acme/three"},
+								snap.R(0): {"acme/three"},
 								snap.R(3): {"acme/one"},
 							},
 						},
 					},
 				},
 			},
 		},
+		{
+			summary:    "missing required snap and required component",
+			assertions: []string{"four"},
+			verr: &snapasserts.ValidationSetsValidationError{
+				Sets: map[string]*asserts.ValidationSet{
+					"acme/four": assertions["four"],
+				},
+				ComponentErrors: map[string]*snapasserts.ValidationSetsComponentValidationError{
+					"snap-a": {
+						MissingComponents: map[string]map[snap.Revision][]string{
+							"comp-3": {
+								snap.R(0): {"acme/four"},
+							},
+							"comp-4": {
+								snap.R(2): {"acme/four"},
+							},
+						},
+					},
+				},
+				MissingSnaps: map[string]map[snap.Revision][]string{
+					"snap-a": {
+						snap.R(0): {"acme/four"},
+					},
+				},
+			},
+		},
 	}
 
 	for i, tc := range cases {