jobspec: add diff for Task Group Scaling block

.changelog/18332.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+jobspec: Add diff for Task Group scaling block
+```

nomad/structs/diff.go

@@ -343,6 +343,11 @@ func (tg *TaskGroup) Diff(other *TaskGroup, contextual bool) (*TaskGroupDiff, er
 		diff.Objects = append(diff.Objects, nDiffs...)
 	}
 
+	// Scaling diff
+	if scDiff := scalingDiff(tg.Scaling, other.Scaling, contextual); scDiff != nil {
+		diff.Objects = append(diff.Objects, scDiff)
+	}
+
 	// Services diff
 	if sDiffs := serviceDiffs(tg.Services, other.Services, contextual); sDiffs != nil {
 		diff.Objects = append(diff.Objects, sDiffs...)
@@ -626,6 +631,66 @@ func (t TaskDiffs) Len() int           { return len(t) }
 func (t TaskDiffs) Swap(i, j int)      { t[i], t[j] = t[j], t[i] }
 func (t TaskDiffs) Less(i, j int) bool { return t[i].Name < t[j].Name }
 
+// scalingDiff returns the diff of two Scaling objects. If contextual diff is enabled, unchanged
+// fields within objects nested in the tasks will be returned.
+func scalingDiff(old, new *ScalingPolicy, contextual bool) *ObjectDiff {
+	diff := &ObjectDiff{Type: DiffTypeNone, Name: "Scaling"}
+	var oldPrimitiveFlat, newPrimitiveFlat map[string]string
+
+	filter := []string{"CreateIndex", "ModifyIndex", "ID", "Type", "Target[Job]", "Target[Group]", "Target[Namespace]"}
+
+	if reflect.DeepEqual(old, new) {
+		return nil
+	} else if old == nil {
+		old = &ScalingPolicy{}
+		diff.Type = DiffTypeAdded
+		newPrimitiveFlat = flatmap.Flatten(new, filter, true)
+	} else if new == nil {
+		new = &ScalingPolicy{}
+		diff.Type = DiffTypeDeleted
+		oldPrimitiveFlat = flatmap.Flatten(old, filter, true)
+	} else {
+		diff.Type = DiffTypeEdited
+		oldPrimitiveFlat = flatmap.Flatten(old, filter, true)
+		newPrimitiveFlat = flatmap.Flatten(new, filter, true)
+	}
+
+	// Diff the primitive fields.
+	diff.Fields = fieldDiffs(oldPrimitiveFlat, newPrimitiveFlat, false)
+
+	// Diff Policy
+	if pDiff := policyDiff(old.Policy, new.Policy, contextual); pDiff != nil {
+		diff.Objects = append(diff.Objects, pDiff)
+	}
+
+	sort.Sort(FieldDiffs(diff.Fields))
+	sort.Sort(ObjectDiffs(diff.Objects))
+
+	return diff
+}
+
+// policyDiff returns the diff of two Scaling Policy objects. If contextual diff is enabled, unchanged
+// fields within objects nested in the tasks will be returned.
+func policyDiff(old, new map[string]interface{}, contextual bool) *ObjectDiff {
+	diff := &ObjectDiff{Type: DiffTypeNone, Name: "Policy"}
+	if reflect.DeepEqual(old, new) {
+		return nil
+	} else if len(old) == 0 {
+		diff.Type = DiffTypeAdded
+	} else if len(new) == 0 {
+		diff.Type = DiffTypeDeleted
+	} else {
+		diff.Type = DiffTypeEdited
+	}
+
+	// Diff the primitive fields.
+	oldPrimitiveFlat := flatmap.Flatten(old, nil, false)
+	newPrimitiveFlat := flatmap.Flatten(new, nil, false)
+	diff.Fields = fieldDiffs(oldPrimitiveFlat, newPrimitiveFlat, false)
+
+	return diff
+}
+
 // serviceDiff returns the diff of two service objects. If contextual diff is
 // enabled, all fields will be returned, even if no diff occurred.
 func serviceDiff(old, new *Service, contextual bool) *ObjectDiff {

nomad/structs/diff_test.go

@@ -4444,12 +4444,208 @@ func TestTaskGroupDiff(t *testing.T) {
 				},
 			},
 		},
+		{
+			TestCase: "Scaling added",
+			Old:      &TaskGroup{},
+			New: &TaskGroup{
+				Scaling: &ScalingPolicy{
+					Enabled: true,
+					Max:     10,
+					Min:     1,
+					Policy: map[string]interface{}{
+						"cooldown":            "1m",
+						"evaluation_interval": "5s",
+					},
+				},
+			},
+			Expected: &TaskGroupDiff{
+				Type: DiffTypeEdited,
+				Objects: []*ObjectDiff{
+					{
+						Type: DiffTypeAdded,
+						Name: "Scaling",
+						Fields: []*FieldDiff{
+							{
+								Type: DiffTypeAdded,
+								Name: "Enabled",
+								Old:  "",
+								New:  "true",
+							},
+							{
+								Type: DiffTypeAdded,
+								Name: "Max",
+								Old:  "",
+								New:  "10",
+							},
+							{
+								Type: DiffTypeAdded,
+								Name: "Min",
+								Old:  "",
+								New:  "1",
+							},
+						},
+						Objects: []*ObjectDiff{
+							{
+								Type: DiffTypeAdded,
+								Name: "Policy",
+								Fields: []*FieldDiff{
+									{
+										Type: DiffTypeAdded,
+										Name: "cooldown",
+										Old:  "",
+										New:  "1m",
+									},
+									{
+										Type: DiffTypeAdded,
+										Name: "evaluation_interval",
+										Old:  "",
+										New:  "5s",
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+		{
+			TestCase: "Scaling deleted",
+			Old: &TaskGroup{
+				Scaling: &ScalingPolicy{
+					Enabled: true,
+					Max:     10,
+					Min:     1,
+					Policy: map[string]interface{}{
+						"cooldown":            "1m",
+						"evaluation_interval": "5s",
+					},
+				},
+			},
+			New: &TaskGroup{},
+			Expected: &TaskGroupDiff{
+				Type: DiffTypeEdited,
+				Objects: []*ObjectDiff{
+					{
+						Type: DiffTypeDeleted,
+						Name: "Scaling",
+						Fields: []*FieldDiff{
+							{
+								Type: DiffTypeDeleted,
+								Name: "Enabled",
+								Old:  "true",
+								New:  "",
+							},
+							{
+								Type: DiffTypeDeleted,
+								Name: "Max",
+								Old:  "10",
+								New:  "",
+							},
+							{
+								Type: DiffTypeDeleted,
+								Name: "Min",
+								Old:  "1",
+								New:  "",
+							},
+						},
+						Objects: []*ObjectDiff{
+							{
+								Type: DiffTypeDeleted,
+								Name: "Policy",
+								Fields: []*FieldDiff{
+									{
+										Type: DiffTypeDeleted,
+										Name: "cooldown",
+										Old:  "1m",
+										New:  "",
+									},
+									{
+										Type: DiffTypeDeleted,
+										Name: "evaluation_interval",
+										Old:  "5s",
+										New:  "",
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+		{
+			TestCase: "Scaling edited",
+			Old: &TaskGroup{
+				Scaling: &ScalingPolicy{
+					Enabled: true,
+					Max:     10,
+					Min:     1,
+					Policy: map[string]interface{}{
+						"cooldown":            "1m",
+						"evaluation_interval": "5s",
+					},
+				},
+			},
+			New: &TaskGroup{
+				Scaling: &ScalingPolicy{
+					Enabled: true,
+					Max:     15,
+					Min:     5,
+					Policy: map[string]interface{}{
+						"cooldown":            "2m",
+						"evaluation_interval": "10s",
+					},
+				},
+			},
+			Expected: &TaskGroupDiff{
+				Type: DiffTypeEdited,
+				Objects: []*ObjectDiff{
+					{
+						Type: DiffTypeEdited,
+						Name: "Scaling",
+						Fields: []*FieldDiff{
+							{
+								Type: DiffTypeEdited,
+								Name: "Max",
+								Old:  "10",
+								New:  "15",
+							},
+							{
+								Type: DiffTypeEdited,
+								Name: "Min",
+								Old:  "1",
+								New:  "5",
+							},
+						},
+						Objects: []*ObjectDiff{
+							{
+								Type: DiffTypeEdited,
+								Name: "Policy",
+								Fields: []*FieldDiff{
+									{
+										Type: DiffTypeEdited,
+										Name: "cooldown",
+										Old:  "1m",
+										New:  "2m",
+									}, {
+										Type: DiffTypeEdited,
+										Name: "evaluation_interval",
+										Old:  "5s",
+										New:  "10s",
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
 	}
 
 	for i, c := range cases {
 		require.NotEmpty(t, c.TestCase, "case #%d needs a name", i+1)
 
 		t.Run(c.TestCase, func(t *testing.T) {
+
 			result, err := c.Old.Diff(c.New, c.Contextual)
 			switch c.ExpErr {
 			case true: