Closed milestones with no issues now show as 100% completed

models/issues/milestone.go

@@ -75,6 +75,8 @@ func init() {
 func (m *Milestone) BeforeUpdate() {
 	if m.NumIssues > 0 {
 		m.Completeness = m.NumClosedIssues * 100 / m.NumIssues
+	} else if m.IsClosed {
+		m.Completeness = 100
 	} else {
 		m.Completeness = 0
 	}
@@ -195,8 +197,8 @@ func UpdateMilestoneCounters(ctx context.Context, id int64) error {
 	if err != nil {
 		return err
 	}
-	_, err = e.Exec("UPDATE `milestone` SET completeness=100*num_closed_issues/(CASE WHEN num_issues > 0 THEN num_issues ELSE 1 END) WHERE id=?",
-		id,
+	_, err = e.Exec("UPDATE `milestone` SET completeness=(CASE WHEN is_closed = ? AND num_issues = 0 THEN 100 ELSE 100*num_closed_issues/(CASE WHEN num_issues > 0 THEN num_issues ELSE 1 END) END) WHERE id=?",
+		true, id,
 	)
 	return err
 }
@@ -240,6 +242,11 @@ func changeMilestoneStatus(ctx context.Context, m *Milestone, isClosed bool) err
 	if count < 1 {
 		return nil
 	}
+
+	if err := UpdateMilestoneCounters(ctx, m.ID); err != nil {
+		return err
+	}
+
 	return updateRepoMilestoneNum(ctx, m.RepoID)
 }
 

models/migrations/migrations.go

@@ -398,6 +398,7 @@ func prepareMigrationTasks() []*migration {
 		// Gitea 1.25.0 ends at migration ID number 322 (database version 323)
 
 		newMigration(323, "Add support for actions concurrency", v1_26.AddActionsConcurrency),
+		newMigration(324, "Fix closed milestone completeness for milestones with no issues", v1_26.FixClosedMilestoneCompleteness),
 	}
 	return preparedMigrations
 }

models/migrations/v1_26/v324.go

@@ -0,0 +1,24 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_26
+
+import (
+	"fmt"
+
+	"xorm.io/xorm"
+)
+
+func FixClosedMilestoneCompleteness(x *xorm.Engine) error {
+	// Update all milestones to recalculate completeness with the new logic:
+	// - Closed milestones with 0 issues should show 100%
+	// - All other milestones should calculate based on closed/total ratio
+	_, err := x.Exec("UPDATE `milestone` SET completeness=(CASE WHEN is_closed = ? AND num_issues = 0 THEN 100 ELSE 100*num_closed_issues/(CASE WHEN num_issues > 0 THEN num_issues ELSE 1 END) END)",
+		true,
+	)
+	if err != nil {
+		return fmt.Errorf("error updating milestone completeness: %w", err)
+	}
+
+	return nil
+}