Scoped labels (#22585)

Add a new "exclusive" option per label. This makes it so that when the
label is named `scope/name`, no other label with the same `scope/`
prefix can be set on an issue.

The scope is determined by the last occurence of `/`, so for example
`scope/alpha/name` and `scope/beta/name` are considered to be in
different scopes and can coexist.

Exclusive scopes are not enforced by any database rules, however they
are enforced when editing labels at the models level, automatically
removing any existing labels in the same scope when either attaching a
new label or replacing all labels.

In menus use a circle instead of checkbox to indicate they function as
radio buttons per scope. Issue filtering by label ensures that only a
single scoped label is selected at a time. Clicking with alt key can be
used to remove a scoped label, both when editing individual issues and
batch editing.

Label rendering refactor for consistency and code simplification:

* Labels now consistently have the same shape, emojis and tooltips
everywhere. This includes the label list and label assignment menus.
* In label list, show description below label same as label menus.
* Don't use exactly black/white text colors to look a bit nicer.
* Simplify text color computation. There is no point computing luminance
in linear color space, as this is a perceptual problem and sRGB is
closer to perceptually linear.
* Increase height of label assignment menus to show more labels. Showing
only 3-4 labels at a time leads to a lot of scrolling.
* Render all labels with a new RenderLabel template helper function.

Label creation and editing in multiline modal menu:

* Change label creation to open a modal menu like label editing.
* Change menu layout to place name, description and colors on separate
lines.
* Don't color cancel button red in label editing modal menu.
* Align text to the left in model menu for better readability and
consistent with settings layout elsewhere.

Custom exclusive scoped label rendering:

* Display scoped label prefix and suffix with slightly darker and
lighter background color respectively, and a slanted edge between them
similar to the `/` symbol.
* In menus exclusive labels are grouped with a divider line.

---------

Co-authored-by: Yarden Shoham <hrsi88@gmail.com>
Co-authored-by: Lauris BH <lauris@nix.lv>

11 files changed, 243 insertions, 53 deletions

diff --git a/models/fixtures/issue.yml b/models/fixtures/issue.yml
index 4dea8add1..174345ff5 100644
--- a/models/fixtures/issue.yml
+++ b/models/fixtures/issue.yml
@@ -287,3 +287,20 @@
   created_unix: 1602935696
   updated_unix: 1602935696
   is_locked: false
+
+-
+  id: 18
+  repo_id: 55
+  index: 1
+  poster_id: 2
+  original_author_id: 0
+  name: issue for scoped labels
+  content: content
+  milestone_id: 0
+  priority: 0
+  is_closed: false
+  is_pull: false
+  num_comments: 0
+  created_unix: 946684830
+  updated_unix: 978307200
+  is_locked: false
diff --git a/models/fixtures/label.yml b/models/fixtures/label.yml
index 57bf80445..ab4d5ef94 100644
--- a/models/fixtures/label.yml
+++ b/models/fixtures/label.yml
@@ -4,6 +4,7 @@
   org_id: 0
   name: label1
   color: '#abcdef'
+  exclusive: false
   num_issues: 2
   num_closed_issues: 0
 
@@ -13,6 +14,7 @@
   org_id: 0
   name: label2
   color: '#000000'
+  exclusive: false
   num_issues: 1
   num_closed_issues: 1
 
@@ -22,6 +24,7 @@
   org_id: 3
   name: orglabel3
   color: '#abcdef'
+  exclusive: false
   num_issues: 0
   num_closed_issues: 0
 
@@ -31,6 +34,7 @@
   org_id: 3
   name: orglabel4
   color: '#000000'
+  exclusive: false
   num_issues: 1
   num_closed_issues: 0
 
@@ -40,5 +44,46 @@
   org_id: 0
   name: pull-test-label
   color: '#000000'
+  exclusive: false
+  num_issues: 0
+  num_closed_issues: 0
+
+-
+  id: 6
+  repo_id: 55
+  org_id: 0
+  name: unscoped_label
+  color: '#000000'
+  exclusive: false
+  num_issues: 0
+  num_closed_issues: 0
+
+-
+  id: 7
+  repo_id: 55
+  org_id: 0
+  name: scope/label1
+  color: '#000000'
+  exclusive: true
+  num_issues: 0
+  num_closed_issues: 0
+
+-
+  id: 8
+  repo_id: 55
+  org_id: 0
+  name: scope/label2
+  color: '#000000'
+  exclusive: true
+  num_issues: 0
+  num_closed_issues: 0
+
+-
+  id: 9
+  repo_id: 55
+  org_id: 0
+  name: scope/subscope/label2
+  color: '#000000'
+  exclusive: true
   num_issues: 0
   num_closed_issues: 0
diff --git a/models/fixtures/repository.yml b/models/fixtures/repository.yml
index ef3cfbbbe..58f9b919a 100644
--- a/models/fixtures/repository.yml
+++ b/models/fixtures/repository.yml
@@ -1622,3 +1622,15 @@
   is_archived: false
   is_private: true
   status: 0
+
+-
+  id: 55
+  owner_id: 2
+  owner_name: user2
+  lower_name: scoped_label
+  name: scoped_label
+  is_empty: false
+  is_archived: false
+  is_private: true
+  num_issues: 1
+  status: 0
diff --git a/models/fixtures/user.yml b/models/fixtures/user.yml
index 63a5e0f89..0a1d85b48 100644
--- a/models/fixtures/user.yml
+++ b/models/fixtures/user.yml
@@ -66,7 +66,7 @@
   num_followers: 2
   num_following: 1
   num_stars: 2
-  num_repos: 10
+  num_repos: 11
   num_teams: 0
   num_members: 0
   visibility: 0
diff --git a/models/issues/issue.go b/models/issues/issue.go
index b1c7fdbf7..9d7dea017 100644
--- a/models/issues/issue.go
+++ b/models/issues/issue.go
@@ -538,6 +538,31 @@ func (ts labelSorter) Swap(i, j int) {
 	[]*Label(ts)[i], []*Label(ts)[j] = []*Label(ts)[j], []*Label(ts)[i]
 }
 
+// Ensure only one label of a given scope exists, with labels at the end of the
+// array getting preference over earlier ones.
+func RemoveDuplicateExclusiveLabels(labels []*Label) []*Label {
+	validLabels := make([]*Label, 0, len(labels))
+
+	for i, label := range labels {
+		scope := label.ExclusiveScope()
+		if scope != "" {
+			foundOther := false
+			for _, otherLabel := range labels[i+1:] {
+				if otherLabel.ExclusiveScope() == scope {
+					foundOther = true
+					break
+				}
+			}
+			if foundOther {
+				continue
+			}
+		}
+		validLabels = append(validLabels, label)
+	}
+
+	return validLabels
+}
+
 // ReplaceIssueLabels removes all current labels and add new labels to the issue.
 // Triggers appropriate WebHooks, if any.
 func ReplaceIssueLabels(issue *Issue, labels []*Label, doer *user_model.User) (err error) {
@@ -555,6 +580,8 @@ func ReplaceIssueLabels(issue *Issue, labels []*Label, doer *user_model.User) (e
 		return err
 	}
 
+	labels = RemoveDuplicateExclusiveLabels(labels)
+
 	sort.Sort(labelSorter(labels))
 	sort.Sort(labelSorter(issue.Labels))
 
diff --git a/models/issues/issue_test.go b/models/issues/issue_test.go
index de1da19ab..3a83d8d2b 100644
--- a/models/issues/issue_test.go
+++ b/models/issues/issue_test.go
@@ -25,7 +25,7 @@ import (
 func TestIssue_ReplaceLabels(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 
-	testSuccess := func(issueID int64, labelIDs []int64) {
+	testSuccess := func(issueID int64, labelIDs, expectedLabelIDs []int64) {
 		issue := unittest.AssertExistsAndLoadBean(t, &issues_model.Issue{ID: issueID})
 		repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: issue.RepoID})
 		doer := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: repo.OwnerID})
@@ -35,15 +35,20 @@ func TestIssue_ReplaceLabels(t *testing.T) {
 			labels[i] = unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: labelID, RepoID: repo.ID})
 		}
 		assert.NoError(t, issues_model.ReplaceIssueLabels(issue, labels, doer))
-		unittest.AssertCount(t, &issues_model.IssueLabel{IssueID: issueID}, len(labelIDs))
-		for _, labelID := range labelIDs {
+		unittest.AssertCount(t, &issues_model.IssueLabel{IssueID: issueID}, len(expectedLabelIDs))
+		for _, labelID := range expectedLabelIDs {
 			unittest.AssertExistsAndLoadBean(t, &issues_model.IssueLabel{IssueID: issueID, LabelID: labelID})
 		}
 	}
 
-	testSuccess(1, []int64{2})
-	testSuccess(1, []int64{1, 2})
-	testSuccess(1, []int64{})
+	testSuccess(1, []int64{2}, []int64{2})
+	testSuccess(1, []int64{1, 2}, []int64{1, 2})
+	testSuccess(1, []int64{}, []int64{})
+
+	// mutually exclusive scoped labels 7 and 8
+	testSuccess(18, []int64{6, 7}, []int64{6, 7})
+	testSuccess(18, []int64{7, 8}, []int64{8})
+	testSuccess(18, []int64{6, 8, 7}, []int64{6, 7})
 }
 
 func Test_GetIssueIDsByRepoID(t *testing.T) {
@@ -523,5 +528,5 @@ func TestCountIssues(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 	count, err := issues_model.CountIssues(db.DefaultContext, &issues_model.IssuesOptions{})
 	assert.NoError(t, err)
-	assert.EqualValues(t, 17, count)
+	assert.EqualValues(t, 18, count)
 }
diff --git a/models/issues/label.go b/models/issues/label.go
index dbb7a139e..0dd12fb5c 100644
--- a/models/issues/label.go
+++ b/models/issues/label.go
@@ -7,8 +7,6 @@ package issues
 import (
 	"context"
 	"fmt"
-	"html/template"
-	"math"
 	"regexp"
 	"strconv"
 	"strings"
@@ -89,6 +87,7 @@ type Label struct {
 	RepoID          int64 `xorm:"INDEX"`
 	OrgID           int64 `xorm:"INDEX"`
 	Name            string
+	Exclusive       bool
 	Description     string
 	Color           string `xorm:"VARCHAR(7)"`
 	NumIssues       int
@@ -128,18 +127,22 @@ func (label *Label) CalOpenOrgIssues(ctx context.Context, repoID, labelID int64)
 }
 
 // LoadSelectedLabelsAfterClick calculates the set of selected labels when a label is clicked
-func (label *Label) LoadSelectedLabelsAfterClick(currentSelectedLabels []int64) {
+func (label *Label) LoadSelectedLabelsAfterClick(currentSelectedLabels []int64, currentSelectedExclusiveScopes []string) {
 	var labelQuerySlice []string
 	labelSelected := false
 	labelID := strconv.FormatInt(label.ID, 10)
-	for _, s := range currentSelectedLabels {
+	labelScope := label.ExclusiveScope()
+	for i, s := range currentSelectedLabels {
 		if s == label.ID {
 			labelSelected = true
 		} else if -s == label.ID {
 			labelSelected = true
 			label.IsExcluded = true
 		} else if s != 0 {
-			labelQuerySlice = append(labelQuerySlice, strconv.FormatInt(s, 10))
+			// Exclude other labels in the same scope from selection
+			if s < 0 || labelScope == "" || labelScope != currentSelectedExclusiveScopes[i] {
+				labelQuerySlice = append(labelQuerySlice, strconv.FormatInt(s, 10))
+			}
 		}
 	}
 	if !labelSelected {
@@ -159,49 +162,43 @@ func (label *Label) BelongsToRepo() bool {
 	return label.RepoID > 0
 }
 
-// SrgbToLinear converts a component of an sRGB color to its linear intensity
-// See: https://en.wikipedia.org/wiki/SRGB#The_reverse_transformation_(sRGB_to_CIE_XYZ)
-func SrgbToLinear(color uint8) float64 {
-	flt := float64(color) / 255
-	if flt <= 0.04045 {
-		return flt / 12.92
+// Get color as RGB values in 0..255 range
+func (label *Label) ColorRGB() (float64, float64, float64, error) {
+	color, err := strconv.ParseUint(label.Color[1:], 16, 64)
+	if err != nil {
+		return 0, 0, 0, err
 	}
-	return math.Pow((flt+0.055)/1.055, 2.4)
-}
-
-// Luminance returns the luminance of an sRGB color
-func Luminance(color uint32) float64 {
-	r := SrgbToLinear(uint8(0xFF & (color >> 16)))
-	g := SrgbToLinear(uint8(0xFF & (color >> 8)))
-	b := SrgbToLinear(uint8(0xFF & color))
 
-	// luminance ratios for sRGB
-	return 0.2126*r + 0.7152*g + 0.0722*b
+	r := float64(uint8(0xFF & (uint32(color) >> 16)))
+	g := float64(uint8(0xFF & (uint32(color) >> 8)))
+	b := float64(uint8(0xFF & uint32(color)))
+	return r, g, b, nil
 }
 
-// LuminanceThreshold is the luminance at which white and black appear to have the same contrast
-// i.e. x such that 1.05 / (x + 0.05) = (x + 0.05) / 0.05
-// i.e. math.Sqrt(1.05*0.05) - 0.05
-const LuminanceThreshold float64 = 0.179
-
-// ForegroundColor calculates the text color for labels based
-// on their background color.
-func (label *Label) ForegroundColor() template.CSS {
+// Determine if label text should be light or dark to be readable on background color
+func (label *Label) UseLightTextColor() bool {
 	if strings.HasPrefix(label.Color, "#") {
-		if color, err := strconv.ParseUint(label.Color[1:], 16, 64); err == nil {
-			// NOTE: see web_src/js/components/ContextPopup.vue for similar implementation
-			luminance := Luminance(uint32(color))
-
-			// prefer white or black based upon contrast
-			if luminance < LuminanceThreshold {
-				return template.CSS("#fff")
-			}
-			return template.CSS("#000")
+		if r, g, b, err := label.ColorRGB(); err == nil {
+			// Perceived brightness from: https://www.w3.org/TR/AERT/#color-contrast
+			// In the future WCAG 3 APCA may be a better solution
+			brightness := (0.299*r + 0.587*g + 0.114*b) / 255
+			return brightness < 0.35
 		}
 	}
 
-	// default to black
-	return template.CSS("#000")
+	return false
+}
+
+// Return scope substring of label name, or empty string if none exists
+func (label *Label) ExclusiveScope() string {
+	if !label.Exclusive {
+		return ""
+	}
+	lastIndex := strings.LastIndex(label.Name, "/")
+	if lastIndex == -1 || lastIndex == 0 || lastIndex == len(label.Name)-1 {
+		return ""
+	}
+	return label.Name[:lastIndex]
 }
 
 // NewLabel creates a new label
@@ -253,7 +250,7 @@ func UpdateLabel(l *Label) error {
 	if !LabelColorPattern.MatchString(l.Color) {
 		return fmt.Errorf("bad color code: %s", l.Color)
 	}
-	return updateLabelCols(db.DefaultContext, l, "name", "description", "color")
+	return updateLabelCols(db.DefaultContext, l, "name", "description", "color", "exclusive")
 }
 
 // DeleteLabel delete a label
@@ -620,6 +617,29 @@ func newIssueLabel(ctx context.Context, issue *Issue, label *Label, doer *user_m
 	return updateLabelCols(ctx, label, "num_issues", "num_closed_issue")
 }
 
+// Remove all issue labels in the given exclusive scope
+func RemoveDuplicateExclusiveIssueLabels(ctx context.Context, issue *Issue, label *Label, doer *user_model.User) (err error) {
+	scope := label.ExclusiveScope()
+	if scope == "" {
+		return nil
+	}
+
+	var toRemove []*Label
+	for _, issueLabel := range issue.Labels {
+		if label.ID != issueLabel.ID && issueLabel.ExclusiveScope() == scope {
+			toRemove = append(toRemove, issueLabel)
+		}
+	}
+
+	for _, issueLabel := range toRemove {
+		if err = deleteIssueLabel(ctx, issue, issueLabel, doer); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // NewIssueLabel creates a new issue-label relation.
 func NewIssueLabel(issue *Issue, label *Label, doer *user_model.User) (err error) {
 	if HasIssueLabel(db.DefaultContext, issue.ID, label.ID) {
@@ -641,6 +661,10 @@ func NewIssueLabel(issue *Issue, label *Label, doer *user_model.User) (err error
 		return nil
 	}
 
+	if err = RemoveDuplicateExclusiveIssueLabels(ctx, issue, label, doer); err != nil {
+		return nil
+	}
+
 	if err = newIssueLabel(ctx, issue, label, doer); err != nil {
 		return err
 	}
diff --git a/models/issues/label_test.go b/models/issues/label_test.go
index 239e328d4..0e45e0db0 100644
--- a/models/issues/label_test.go
+++ b/models/issues/label_test.go
@@ -4,7 +4,6 @@
 package issues_test
 
 import (
-	"html/template"
 	"testing"
 
 	"code.gitea.io/gitea/models/db"
@@ -25,13 +24,22 @@ func TestLabel_CalOpenIssues(t *testing.T) {
 	assert.EqualValues(t, 2, label.NumOpenIssues)
 }
 
-func TestLabel_ForegroundColor(t *testing.T) {
+func TestLabel_TextColor(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 	label := unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 1})
-	assert.Equal(t, template.CSS("#000"), label.ForegroundColor())
+	assert.False(t, label.UseLightTextColor())
 
 	label = unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 2})
-	assert.Equal(t, template.CSS("#fff"), label.ForegroundColor())
+	assert.True(t, label.UseLightTextColor())
+}
+
+func TestLabel_ExclusiveScope(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	label := unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 7})
+	assert.Equal(t, "scope", label.ExclusiveScope())
+
+	label = unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 9})
+	assert.Equal(t, "scope/subscope", label.ExclusiveScope())
 }
 
 func TestNewLabels(t *testing.T) {
@@ -266,6 +274,7 @@ func TestUpdateLabel(t *testing.T) {
 		Color:       "#ffff00",
 		Name:        "newLabelName",
 		Description: label.Description,
+		Exclusive:   false,
 	}
 	label.Color = update.Color
 	label.Name = update.Name
@@ -323,6 +332,34 @@ func TestNewIssueLabel(t *testing.T) {
 	unittest.CheckConsistencyFor(t, &issues_model.Issue{}, &issues_model.Label{})
 }
 
+func TestNewIssueExclusiveLabel(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	issue := unittest.AssertExistsAndLoadBean(t, &issues_model.Issue{ID: 18})
+	doer := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+
+	otherLabel := unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 6})
+	exclusiveLabelA := unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 7})
+	exclusiveLabelB := unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 8})
+
+	// coexisting regular and exclusive label
+	assert.NoError(t, issues_model.NewIssueLabel(issue, otherLabel, doer))
+	assert.NoError(t, issues_model.NewIssueLabel(issue, exclusiveLabelA, doer))
+	unittest.AssertExistsAndLoadBean(t, &issues_model.IssueLabel{IssueID: issue.ID, LabelID: otherLabel.ID})
+	unittest.AssertExistsAndLoadBean(t, &issues_model.IssueLabel{IssueID: issue.ID, LabelID: exclusiveLabelA.ID})
+
+	// exclusive label replaces existing one
+	assert.NoError(t, issues_model.NewIssueLabel(issue, exclusiveLabelB, doer))
+	unittest.AssertExistsAndLoadBean(t, &issues_model.IssueLabel{IssueID: issue.ID, LabelID: otherLabel.ID})
+	unittest.AssertExistsAndLoadBean(t, &issues_model.IssueLabel{IssueID: issue.ID, LabelID: exclusiveLabelB.ID})
+	unittest.AssertNotExistsBean(t, &issues_model.IssueLabel{IssueID: issue.ID, LabelID: exclusiveLabelA.ID})
+
+	// exclusive label replaces existing one again
+	assert.NoError(t, issues_model.NewIssueLabel(issue, exclusiveLabelA, doer))
+	unittest.AssertExistsAndLoadBean(t, &issues_model.IssueLabel{IssueID: issue.ID, LabelID: otherLabel.ID})
+	unittest.AssertExistsAndLoadBean(t, &issues_model.IssueLabel{IssueID: issue.ID, LabelID: exclusiveLabelA.ID})
+	unittest.AssertNotExistsBean(t, &issues_model.IssueLabel{IssueID: issue.ID, LabelID: exclusiveLabelB.ID})
+}
+
 func TestNewIssueLabels(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 	label1 := unittest.AssertExistsAndLoadBean(t, &issues_model.Label{ID: 1})
diff --git a/models/migrations/fixtures/Test_DeleteOrphanedIssueLabels/label.yml b/models/migrations/fixtures/Test_DeleteOrphanedIssueLabels/label.yml
index d651c87d5..085b7f088 100644
--- a/models/migrations/fixtures/Test_DeleteOrphanedIssueLabels/label.yml
+++ b/models/migrations/fixtures/Test_DeleteOrphanedIssueLabels/label.yml
@@ -4,6 +4,7 @@
   org_id: 0
   name: label1
   color: '#abcdef'
+  exclusive: false
   num_issues: 2
   num_closed_issues: 0
 
@@ -13,6 +14,7 @@
   org_id: 0
   name: label2
   color: '#000000'
+  exclusive: false
   num_issues: 1
   num_closed_issues: 1
 -
@@ -21,6 +23,7 @@
   org_id:  3
   name: orglabel3
   color: '#abcdef'
+  exclusive: false
   num_issues: 0
   num_closed_issues: 0
 
@@ -30,6 +33,7 @@
   org_id: 3
   name: orglabel4
   color: '#000000'
+  exclusive: false
   num_issues: 1
   num_closed_issues: 0
 
@@ -39,5 +43,6 @@
   org_id: 0
   name: pull-test-label
   color: '#000000'
+  exclusive: false
   num_issues: 0
   num_closed_issues: 0
diff --git a/models/migrations/migrations.go b/models/migrations/migrations.go
index 73c44f008..c7497becd 100644
--- a/models/migrations/migrations.go
+++ b/models/migrations/migrations.go
@@ -459,6 +459,8 @@ var migrations = []Migration{
 	NewMigration("Add card_type column to project table", v1_19.AddCardTypeToProjectTable),
 	// v242 -> v243
 	NewMigration("Alter gpg_key_import content TEXT field to MEDIUMTEXT", v1_19.AlterPublicGPGKeyImportContentFieldToMediumText),
+	// v243 -> v244
+	NewMigration("Add exclusive label", v1_19.AddExclusiveLabel),
 }
 
 // GetCurrentDBVersion returns the current db version
diff --git a/models/migrations/v1_19/v244.go b/models/migrations/v1_19/v244.go
new file mode 100644
index 000000000..55bbfafb2
--- /dev/null
+++ b/models/migrations/v1_19/v244.go
@@ -0,0 +1,16 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_19 //nolint
+
+import (
+	"xorm.io/xorm"
+)
+
+func AddExclusiveLabel(x *xorm.Engine) error {
+	type Label struct {
+		Exclusive bool
+	}
+
+	return x.Sync(new(Label))
+}