Implement state filter for get PR by base head

Add the `isClosed` flag to the function and filter the pull requests accordingly. Filter on the issue state as the indicator if a PR is closed or not. The default behaves like the previous implementation, returning the first one regardless of issue state

models/issues/pull.go

@@ -20,6 +20,7 @@ import (
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/util"
@@ -691,11 +692,15 @@ func GetPullRequestByIssueID(ctx context.Context, issueID int64) (*PullRequest,
 }
 
 // GetPullRequestByBaseHeadInfo returns the pull request by given base and head
-func GetPullRequestByBaseHeadInfo(ctx context.Context, baseID, headID int64, base, head string) (*PullRequest, error) {
+func GetPullRequestByBaseHeadInfo(ctx context.Context, baseID, headID int64, base, head string, isClosed optional.Option[bool]) (*PullRequest, error) {
 	pr := &PullRequest{}
 	sess := db.GetEngine(ctx).
 		Join("INNER", "issue", "issue.id = pull_request.issue_id").
 		Where("base_repo_id = ? AND base_branch = ? AND head_repo_id = ? AND head_branch = ?", baseID, base, headID, head)
+	if isClosed.Has() {
+		sess = sess.And("issue.is_closed = ?", isClosed.Value())
+	}
+
 	has, err := sess.Get(pr)
 	if err != nil {
 		return nil, err

routers/api/v1/repo/pull.go

@@ -25,6 +25,7 @@ import (
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/gitrepo"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/setting"
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/timeutil"
@@ -261,6 +262,11 @@ func GetPullRequestByBaseHead(ctx *context.APIContext) {
 	//   description: head of the pull request to get
 	//   type: string
 	//   required: true
+	// - name: state
+	//   in: query
+	//   description: state of pull request to get
+	//   type: string
+	//   enum: [closed, open, all]
 	// responses:
 	//   "200":
 	//     "$ref": "#/responses/PullRequest"
@@ -297,7 +303,17 @@ func GetPullRequestByBaseHead(ctx *context.APIContext) {
 		headBranch = head
 	}
 
-	pr, err := issues_model.GetPullRequestByBaseHeadInfo(ctx, ctx.Repo.Repository.ID, headRepoID, ctx.Params(":base"), headBranch)
+	var isClosed optional.Option[bool]
+	switch ctx.FormString("state") {
+	case "closed":
+		isClosed = optional.Some(true)
+	case "open":
+		isClosed = optional.Some(false)
+	default:
+		isClosed = optional.None[bool]()
+	}
+
+	pr, err := issues_model.GetPullRequestByBaseHeadInfo(ctx, ctx.Repo.Repository.ID, headRepoID, ctx.Params(":base"), headBranch, isClosed)
 	if err != nil {
 		if issues_model.IsErrPullRequestNotExist(err) {
 			ctx.NotFound()