prow/plugin: Extends label plugin to use Unique Prefixes

prow/plugins/config.go

@@ -391,6 +391,9 @@ type Label struct {
 	// defines to which repos this applies and can be `*` for global, an org
 	// or a repo in org/repo notation.
 	RestrictedLabels map[string][]RestrictedLabel `json:"restricted_labels,omitempty"`
+	// UniquePrefixes is the list of label prefixes that can only exist
+	// once per issue,
+	UniquePrefixes []string `json:"unique_prefixes,omitempty"`
 }
 
 func (l Label) RestrictedLabelsFor(org, repo string) map[string]RestrictedLabel {
@@ -1077,6 +1080,15 @@ func (c *Configuration) ValidatePluginsUnknown() error {
 	return utilerrors.NewAggregate(errors)
 }
 
+func validateUniquePrefixes(uniquePrefixes []string) error {
+	for _, prefix := range uniquePrefixes {
+		if len(prefix) == 0 {
+			return fmt.Errorf("prefix cannot be an empty string")
+		}
+	}
+	return nil
+}
+
 func validateSizes(size Size) error {
 	if size.S > size.M || size.M > size.L || size.L > size.Xl || size.Xl > size.Xxl {
 		return errors.New("invalid size plugin configuration - one of the smaller sizes is bigger than a larger one")
@@ -1344,8 +1356,13 @@ func (c *Configuration) Validate() error {
 	if err := validateTrigger(c.Triggers); err != nil {
 		return err
 	}
+
 	validateRepoMilestone(c.RepoMilestone)
 
+	if err := validateUniquePrefixes(c.Label.UniquePrefixes); err != nil {
+		return err
+	}
+
 	return nil
 }
 
@@ -2043,7 +2060,7 @@ func getLabelConfigFromRestrictedLabelsSlice(s []RestrictedLabel, label string)
 func (c *Configuration) HasConfigFor() (global bool, orgs sets.String, repos sets.String) {
 	equals := reflect.DeepEqual(c,
 		&Configuration{Approve: c.Approve, Bugzilla: c.Bugzilla, ExternalPlugins: c.ExternalPlugins,
-			Label: Label{RestrictedLabels: c.Label.RestrictedLabels}, Lgtm: c.Lgtm, Plugins: c.Plugins,
+			Label: Label{RestrictedLabels: c.Label.RestrictedLabels, UniquePrefixes: c.Label.UniquePrefixes}, Lgtm: c.Lgtm, Plugins: c.Plugins,
 			Triggers: c.Triggers, Welcome: c.Welcome})
 
 	if !equals || c.Bugzilla.Default != nil {

prow/plugins/config_test.go

@@ -104,6 +104,35 @@ func TestValidateExternalPlugins(t *testing.T) {
 	}
 }
 
+func TestValidateUniquePrefixes(t *testing.T) {
+	testCases := []struct {
+		name           string
+		uniquePrefixes []string
+		isErrorNil     bool
+	}{
+		{
+			name:           "non-zero length prefixes",
+			uniquePrefixes: []string{"prefix1/", "prefix2"},
+			isErrorNil:     true,
+		},
+		{
+			name:           "zero length prefixes",
+			uniquePrefixes: []string{"", "prefix2"},
+			isErrorNil:     false,
+		},
+	}
+	for _, tC := range testCases {
+		t.Run(tC.name, func(t *testing.T) {
+			err := validateUniquePrefixes(tC.uniquePrefixes)
+			if tC.isErrorNil && err != nil {
+				t.Errorf("expected nil error got %s", err)
+			} else if !tC.isErrorNil && err == nil {
+				t.Errorf("expected non nil error, got nil")
+			}
+		})
+	}
+}
+
 func TestSetDefault_Maps(t *testing.T) {
 	cases := []struct {
 		name     string

prow/plugins/label/label.go

@@ -49,6 +49,20 @@ func init() {
 	plugins.RegisterPullRequestHandler(PluginName, handlePullRequest, helpProvider)
 }
 
+// getExistingUniquePrefixLabels returns a list of labels for every label prefix that can only exist once per issue
+func getExistingUniquePrefixLabels(config plugins.Label, labels []github.Label) map[string][]string {
+	labelsMap := make(map[string][]string)
+	prefixList := config.UniquePrefixes
+	for _, prefix := range prefixList {
+		for _, label := range labels {
+			if matched := strings.HasPrefix(label.Name, prefix); matched {
+				labelsMap[prefix] = append(labelsMap[prefix], label.Name)
+			}
+		}
+	}
+	return labelsMap
+}
+
 func configString(labels []string) string {
 	var formattedLabels []string
 	for _, label := range labels {
@@ -168,7 +182,6 @@ func handleComment(gc githubClient, log *logrus.Entry, config plugins.Label, e *
 	if err != nil {
 		return err
 	}
-
 	RepoLabelsExisting := sets.String{}
 	for _, l := range repoLabels {
 		RepoLabelsExisting.Insert(strings.ToLower(l.Name))
@@ -180,6 +193,7 @@ func handleComment(gc githubClient, log *logrus.Entry, config plugins.Label, e *
 		labelsToAdd             []string
 		labelsToRemove          []string
 		nonMemberTriageAccepted bool
+		labelPrefix             string
 	)
 
 	additionalLabelSet := sets.String{}
@@ -228,12 +242,29 @@ func handleComment(gc githubClient, log *logrus.Entry, config plugins.Label, e *
 			gc.CreateComment(org, repo, e.Number, plugins.FormatResponseRaw(bodyWithoutComments, e.HTMLURL, e.User.Login, canNotSetLabelReason))
 			continue
 		}
-
+		uniqueLabelsMap := getExistingUniquePrefixLabels(config, labels)
+		var labelsWithPrefixExist = false
+		for prefix := range uniqueLabelsMap {
+			if matched := strings.HasPrefix(labelToAdd, prefix); matched {
+				labelPrefix = prefix
+				labelsWithPrefixExist = true
+			}
+		}
+		// if the labelToAdd matches a unique prefix, remove all pre existing
+		// labels that match this unique prefix, and then add the new label
+		if labelsWithPrefixExist {
+			for _, label := range uniqueLabelsMap[labelPrefix] {
+				if label != labelToAdd && github.HasLabel(label, labels) {
+					if err := gc.RemoveLabel(org, repo, e.Number, label); err != nil {
+						log.WithError(err).Errorf("GitHub failed to remove the following label: %s", label)
+					}
+				}
+			}
+		}
 		if err := gc.AddLabel(org, repo, e.Number, labelToAdd); err != nil {
 			log.WithError(err).WithField("label", labelToAdd).Error("GitHub failed to add the label")
 		}
 	}
-
 	// Remove labels
 	for _, labelToRemove := range labelsToRemove {
 		if !github.HasLabel(labelToRemove, labels) {

prow/plugins/label/label_test.go

@@ -64,6 +64,7 @@ func TestHandleComment(t *testing.T) {
 		expectedCommentText   string
 		action                github.GenericCommentEventAction
 		teams                 map[string]map[string]fakegithub.TeamWithMembers
+		uniquePrefixes        []string
 	}
 	testcases := []testCase{
 		{
@@ -475,6 +476,17 @@ func TestHandleComment(t *testing.T) {
 			commenter:             orgMember,
 			action:                github.GenericCommentActionCreated,
 		},
+		{
+			name:                  "Add label that has a prefix that can only exist once per issue",
+			body:                  "/priority urgent",
+			repoLabels:            []string{"area/go", "priority/urgent", "priority/critical", "priority/l"},
+			issueLabels:           []string{"area/go", "priority/critical", "priority/l"},
+			expectedNewLabels:     formatWithPRInfo("priority/urgent"),
+			expectedRemovedLabels: formatWithPRInfo("priority/critical", "priority/l"),
+			commenter:             orgMember,
+			action:                github.GenericCommentActionCreated,
+			uniquePrefixes:        []string{"priority/"},
+		},
 		{
 			name:                  "Do nothing with empty /label command",
 			body:                  "/label",
@@ -762,7 +774,8 @@ func TestHandleComment(t *testing.T) {
 				Repo:   github.Repo{Owner: github.User{Login: "org"}, Name: "repo"},
 				User:   github.User{Login: tc.commenter},
 			}
-			err := handleComment(fakeClient, logrus.WithField("plugin", PluginName), plugins.Label{AdditionalLabels: tc.extraLabels, RestrictedLabels: tc.restrictedLabels}, e)
+			err := handleComment(fakeClient, logrus.WithField("plugin", PluginName), plugins.Label{AdditionalLabels: tc.extraLabels, RestrictedLabels: tc.restrictedLabels, UniquePrefixes: tc.uniquePrefixes}, e)
+
 			if err != nil {
 				t.Fatalf("didn't expect error from handle comment test: %v", err)
 			}

prow/plugins/plugin-config-documented.yaml

@@ -487,6 +487,11 @@ label:
     # or a repo in org/repo notation.
     restricted_labels:
         "": null
+
+    # UniquePrefixes is the list of label prefixes that can only exist
+    # once per issue.
+    unique_prefixes:
+      - ""
 lgtm:
   - # Repos is either of the form org/repos or just org.
     repos: