Another attempt at fixing the duplication

src/action.go

@@ -39,7 +39,7 @@ func updateOrCreateDraftRelease(a *Action, cfg *config.RepoConfig) (*gitea.Relea
 		return nil, err
 	}
 
-	changelog, err := GenerateChangelog(a.client, a.config.RepoOwner, a.config.RepoName, last)
+	changelog, err := GenerateChangelog(a.client, a.config.RepoOwner, a.config.RepoName, last, cfg.Categories)
 	if err != nil {
 		return nil, err
 	}

src/changelog.go

@@ -2,14 +2,23 @@ package src
 
 import (
 	"code.gitea.io/sdk/gitea"
+	"git.beisel.it/florian/gitea-release-drafter/src/config"
 	"github.com/sethvargo/go-githubactions"
 )
 
 type Changelog map[string][]*gitea.PullRequest
 
-// GenerateChangelog fetches all the pull requests merged into the default branch since the last release and groups them by label. note that duplicates might occur if a pull request has multiple labels.
-func GenerateChangelog(c *gitea.Client, owner string, repo string, lastRelease *gitea.Release) (*Changelog, error) {
+// GenerateChangelog fetches all the pull requests merged into the default branch since the last release and groups them by label.
+func GenerateChangelog(c *gitea.Client, owner string, repo string, lastRelease *gitea.Release, categories []config.Category) (*Changelog, error) {
 	changelogByLabels := make(Changelog)
+	validLabels := make(map[string]string)
+
+	// Construct a set of valid labels from the categories
+	for _, category := range categories {
+		for _, label := range category.Labels {
+			validLabels[label] = category.Title
+		}
+	}
 
 	// FIXME: use pagination
 	prs, _, err := c.ListRepoPullRequests(owner, repo, gitea.ListPullRequestsOptions{
@@ -20,21 +29,21 @@ func GenerateChangelog(c *gitea.Client, owner string, repo string, lastRelease *
 	}
 
 	for _, pr := range prs {
-		// only consider merged pull requests. note that we can't filter by that in the API
 		if pr.HasMerged {
-			// if there was a release, only take into account pull requests that have been merged after that
-			if lastRelease == nil || lastRelease != nil && pr.Merged.After(lastRelease.CreatedAt) {
-				for _, l := range pr.Labels {
-					_, ok := changelogByLabels[l.Name]
-
+			if lastRelease == nil || (lastRelease != nil && pr.Merged.After(lastRelease.CreatedAt)) {
+				addedToChangelog := false
+				for _, prLabel := range pr.Labels {
+					categoryTitle, ok := validLabels[prLabel.Name]
 					if ok {
-						changelogByLabels[l.Name] = append(changelogByLabels[l.Name], pr)
-					} else {
-						changelogByLabels[l.Name] = []*gitea.PullRequest{pr}
+						changelogByLabels[categoryTitle] = append(changelogByLabels[categoryTitle], pr)
+						addedToChangelog = true
+						break
 					}
 				}
 
-				if len(pr.Labels) == 0 {
+				if !addedToChangelog && len(pr.Labels) > 0 {
+					githubactions.Warningf("PR #%d has labels but none match configured categories", pr.ID)
+				} else if len(pr.Labels) == 0 {
 					githubactions.Warningf("PR #%d doesn't have any labels", pr.ID)
 				}
 			}