Merge pull request #2615 from pedronis/fix-patch4-vs-wip-install

make patch4 robust against in-progress install changes

Pending/in-progress install changes could be not far enough to have set a snap state. link-snap does this together with setting the flags that we were trying to upgrade here, so if there's no snap state, there's also nothing on the task to patch.

overlord/patch/patch4.go

@@ -21,6 +21,7 @@ package patch
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 
 	"github.com/snapcore/snapd/overlord/state"
@@ -141,6 +142,8 @@ func (p4 patch4T) taskSnapSetup(task *state.Task) (*patch4SnapSetup, error) {
 	return &snapsup, nil
 }
 
+var errNoSnapState = errors.New("no snap state")
+
 func (p4 patch4T) snapSetupAndState(task *state.Task) (*patch4SnapSetup, *patch4SnapState, error) {
 	var snapst patch4SnapState
 
@@ -152,11 +155,11 @@ func (p4 patch4T) snapSetupAndState(task *state.Task) (*patch4SnapSetup, *patch4
 	var snaps map[string]*json.RawMessage
 	err = task.State().Get("snaps", &snaps)
 	if err != nil {
-		return nil, nil, fmt.Errorf("cannot get snaps state: %v", err)
+		return nil, nil, errNoSnapState
 	}
 	raw, ok := snaps[snapsup.Name()]
 	if !ok {
-		return nil, nil, fmt.Errorf("cannot get snap state for %q: %v", snapsup.Name(), err)
+		return nil, nil, errNoSnapState
 	}
 	err = json.Unmarshal([]byte(*raw), &snapst)
 	if err != nil {
@@ -224,6 +227,16 @@ func (p4 patch4T) addCleanup(task *state.Task) error {
 
 func (p4 patch4T) mangle(task *state.Task) error {
 	snapsup, snapst, err := p4.snapSetupAndState(task)
+	if err == errNoSnapState {
+		change := task.Change()
+		if change.Kind() != "install-snap" {
+			return fmt.Errorf("cannot get snap state for task %s (%s) of change %s (%s != install-snap)", task.ID(), task.Kind(), change.ID(), change.Kind())
+		}
+		// we expect pending/in-progress install changes
+		// possibly not to have reached link-sanp yet and so
+		// have no snap state yet, nothing to do
+		return nil
+	}
 	if err != nil {
 		return err
 	}

overlord/patch/patch4_test.go

@@ -72,6 +72,14 @@ var statePatch4JSON = []byte(`
 			"status": 2,
 			"data": {"snap-names": ["b"]},
 			"task-ids": ["10","11","12","13","14","15","16"]
+		},
+		"3": {
+			"id": "3",
+			"kind": "install-snap",
+			"summary": "install c snap",
+			"status": 0,
+			"data": {"snap-names": ["c"]},
+			"task-ids": ["17", "18"]
 		}
 	},
 	"tasks": {
@@ -186,6 +194,30 @@ var statePatch4JSON = []byte(`
 			"data": {"snap-setup-task": "10", "had-candidate": false},
 			"wait-tasks": ["15"],
 			"change": "2"
+		},
+
+                "17": {
+			"id": "17",
+			"kind": "prepare-snap",
+			"summary": "",
+			"status": 4,
+			"data": {
+			    "snap-setup": {
+				"side-info": {"revision": "1", "name": "c"}
+			    }
+			},
+			"halt-tasks": ["18"],
+			"change": "1"
+		}, "18": {
+			"id": "18",
+			"kind": "link-snap",
+			"summary": "make snap avaiblabla",
+			"status": 0,
+			"data": {
+			    "snap-setup-task": "17"
+			},
+			"wait-tasks": ["17"],
+			"change": "3"
 		}
 	}
 }