Have the apiserver watcher code translate unset application status.

apiserver/watcher.go

@@ -18,6 +18,7 @@ import (
 	"github.com/juju/juju/core/migration"
 	"github.com/juju/juju/core/multiwatcher"
 	"github.com/juju/juju/core/network"
+	"github.com/juju/juju/core/status"
 	"github.com/juju/juju/state"
 )
 
@@ -53,16 +54,18 @@ func NewAllWatcher(context facade.Context) (facade.Facade, error) {
 }
 
 type watcherCommon struct {
-	id        string
-	resources facade.Resources
-	dispose   func()
+	id         string
+	resources  facade.Resources
+	dispose    func()
+	controller *cache.Controller
 }
 
 func newWatcherCommon(context facade.Context) watcherCommon {
 	return watcherCommon{
 		context.ID(),
 		context.Resources(),
 		context.Dispose,
+		context.Controller(),
 	}
 }
 
@@ -176,6 +179,20 @@ func (aw *SrvAllWatcher) translateApplication(info multiwatcher.EntityInfo) para
 		logger.Criticalf("consistency error: %s", pretty.Sprint(info))
 		return nil
 	}
+
+	// Get the application status from the cache if it is unset.
+	applicationStatus := multiwatcher.StatusInfo{Current: status.Unknown}
+	if orig.Status.Current == status.Unset {
+		if model, err := aw.controller.Model(orig.ModelUUID); err == nil {
+			cachedApp, err := model.Application(orig.Name)
+			if err == nil {
+				applicationStatus = multiwatcher.NewStatusInfo(cachedApp.Status(), nil)
+			}
+		}
+	} else {
+		applicationStatus = orig.Status
+	}
+
 	return &params.ApplicationInfo{
 		ModelUUID:       orig.ModelUUID,
 		Name:            orig.Name,
@@ -187,7 +204,7 @@ func (aw *SrvAllWatcher) translateApplication(info multiwatcher.EntityInfo) para
 		Constraints:     orig.Constraints,
 		Config:          orig.Config,
 		Subordinate:     orig.Subordinate,
-		Status:          aw.translateStatus(orig.Status),
+		Status:          aw.translateStatus(applicationStatus),
 		WorkloadVersion: orig.WorkloadVersion,
 	}
 }

apiserver/watcher_internal_test.go

@@ -0,0 +1,135 @@
+// Copyright 2020 Canonical Ltd.
+// Licensed under the AGPLv3, see LICENCE file for details.
+
+package apiserver
+
+import (
+	"time"
+
+	"github.com/juju/worker/v2/workertest"
+	gc "gopkg.in/check.v1"
+
+	"github.com/juju/juju/apiserver/params"
+	"github.com/juju/juju/core/cache"
+	"github.com/juju/juju/core/life"
+	"github.com/juju/juju/core/multiwatcher"
+	"github.com/juju/juju/core/status"
+	"github.com/juju/juju/testing"
+	jc "github.com/juju/testing/checkers"
+)
+
+type allWatcherSuite struct {
+	testing.BaseSuite
+}
+
+var _ = gc.Suite(&allWatcherSuite{})
+
+func (s *allWatcherSuite) watcher() *SrvAllWatcher {
+	// We explicitly don't have a real watcher here as the tests
+	// are for the translation of types.
+	return &SrvAllWatcher{}
+}
+
+func (s *allWatcherSuite) TestTranslateApplicationWithStatus(c *gc.C) {
+	w := s.watcher()
+	input := &multiwatcher.ApplicationInfo{
+		ModelUUID: testing.ModelTag.Id(),
+		Name:      "test-app",
+		CharmURL:  "test-app",
+		Life:      life.Alive,
+		Status: multiwatcher.StatusInfo{
+			Current: status.Active,
+		},
+	}
+	output := w.translateApplication(input)
+	c.Assert(output, jc.DeepEquals, &params.ApplicationInfo{
+		ModelUUID: input.ModelUUID,
+		Name:      input.Name,
+		CharmURL:  input.CharmURL,
+		Life:      input.Life,
+		Status: params.StatusInfo{
+			Current: status.Active,
+		},
+	})
+}
+
+func (s *allWatcherSuite) setupCache(c *gc.C) *cache.Controller {
+	changes := make(chan interface{})
+	handled := make(chan interface{})
+	notify := func(evt interface{}) {
+		c.Logf("%#v", evt)
+		select {
+		case handled <- evt:
+		case <-time.After(testing.LongWait):
+			c.Fatalf("handled notify not retrieved")
+		}
+	}
+	sendEvent := func(event interface{}) {
+		select {
+		case changes <- event:
+		case <-time.After(testing.LongWait):
+			c.Fatal("cache did not accept event")
+		}
+		select {
+		case <-handled:
+		case <-time.After(testing.LongWait):
+			c.Fatal("cache did not handle event")
+		}
+	}
+
+	controller, err := cache.NewController(cache.ControllerConfig{
+		Changes: changes,
+		Notify:  notify,
+	})
+	c.Assert(err, jc.ErrorIsNil)
+	s.AddCleanup(func(c *gc.C) { workertest.CleanKill(c, controller) })
+
+	sendEvent(cache.ModelChange{
+		ModelUUID: testing.ModelTag.Id(),
+		// Defaults for everything else.
+	})
+	sendEvent(cache.ApplicationChange{
+		ModelUUID: testing.ModelTag.Id(),
+		Name:      "test-app",
+		Status: status.StatusInfo{
+			Status: status.Unset,
+		},
+		// Defaults for everything else.
+	})
+	sendEvent(cache.UnitChange{
+		ModelUUID:   testing.ModelTag.Id(),
+		Name:        "test-app/0",
+		Application: "test-app",
+		WorkloadStatus: status.StatusInfo{
+			Status: status.Active,
+		},
+		// Defaults for everything else.
+	})
+
+	return controller
+}
+
+func (s *allWatcherSuite) TestTranslateApplicationStatusUnset(c *gc.C) {
+	controller := s.setupCache(c)
+	w := s.watcher()
+	w.controller = controller
+	input := &multiwatcher.ApplicationInfo{
+		ModelUUID: testing.ModelTag.Id(),
+		Name:      "test-app",
+		CharmURL:  "test-app",
+		Life:      life.Alive,
+		Status: multiwatcher.StatusInfo{
+			Current: status.Unset,
+		},
+	}
+	output := w.translateApplication(input)
+	c.Assert(output, jc.DeepEquals, &params.ApplicationInfo{
+		ModelUUID: input.ModelUUID,
+		Name:      input.Name,
+		CharmURL:  input.CharmURL,
+		Life:      input.Life,
+		Status: params.StatusInfo{
+			Current: status.Active,
+		},
+	})
+}