Allow poster to choose reviewers (#21084)

Allow the poster of a PR to choose reviewers (add only). 

Solve #20746

routers/web/repo/issue.go

@@ -1336,13 +1336,18 @@ func ViewIssue(ctx *context.Context) {
 
 	if issue.IsPull {
 		canChooseReviewer := ctx.Repo.CanWrite(unit.TypePullRequests)
-		if !canChooseReviewer && ctx.Doer != nil && ctx.IsSigned {
+		if ctx.Doer != nil && ctx.IsSigned {
+			if !canChooseReviewer {
+				canChooseReviewer = ctx.Doer.ID == issue.PosterID
+			}
+			if !canChooseReviewer {
 				canChooseReviewer, err = issues_model.IsOfficialReviewer(ctx, issue, ctx.Doer)
 				if err != nil {
 					ctx.ServerError("IsOfficialReviewer", err)
 					return
 				}
 			}
+		}
 
 		RetrieveRepoReviewers(ctx, repo, issue, canChooseReviewer)
 		if ctx.Written() {

services/issue/assignee.go

@@ -131,7 +131,10 @@ func IsValidReviewRequest(ctx context.Context, reviewer, doer *user_model.User,
 			return nil
 		}
 
+		pemResult = doer.ID == issue.PosterID
+		if !pemResult {
 			pemResult = permDoer.CanAccessAny(perm.AccessModeWrite, unit.TypePullRequests)
+		}
 		if !pemResult {
 			pemResult, err = issues_model.IsOfficialReviewer(ctx, issue, doer)
 			if err != nil {
@@ -201,7 +204,7 @@ func IsValidTeamReviewRequest(ctx context.Context, reviewer *organization.Team,
 		}
 
 		doerCanWrite := permission.CanAccessAny(perm.AccessModeWrite, unit.TypePullRequests)
-		if !doerCanWrite {
+		if !doerCanWrite && doer.ID != issue.PosterID {
 			official, err := issues_model.IsOfficialReviewer(ctx, issue, doer)
 			if err != nil {
 				log.Error("Unable to Check if IsOfficialReviewer for %-v in %-v#%d", doer, issue.Repo, issue.Index)