From 7ee6f2644e30613170074aac23fade658488d986 Mon Sep 17 00:00:00 2001
From: zeripath <art27@cantab.net>
Date: Sun, 25 Jul 2021 03:59:27 +0100
Subject: [PATCH] Handle too long PR titles correctly (#16517)

Backport #16517

The CompareAndPullRequestPost handler for POST to /compare
incorrectly handles returning errors to the user. For a start
it does not set the necessary markers to switch SimpleMDE
but it also does not immediately return to the form.

This PR fixes this by setting the appropriate values, fixing
the templates and preventing the suggestion of a too long
title.

Fix #16507

Signed-off-by: Andrew Thornton <art27@cantab.net>
---
 modules/util/truncate.go         | 35 ++++++++++++++++++++++++++++++++
 routers/web/repo/compare.go      | 13 ++++++++++++
 routers/web/repo/pull.go         | 12 +++++++++++
 templates/repo/diff/compare.tmpl |  8 ++++----
 4 files changed, 64 insertions(+), 4 deletions(-)
 create mode 100644 modules/util/truncate.go

diff --git a/modules/util/truncate.go b/modules/util/truncate.go
new file mode 100644
index 0000000000000..8d0f6309732d7
--- /dev/null
+++ b/modules/util/truncate.go
@@ -0,0 +1,35 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package util
+
+import "unicode/utf8"
+
+// SplitStringAtByteN splits a string at byte n accounting for rune boundaries. (Combining characters are not accounted for.)
+func SplitStringAtByteN(input string, n int) (left, right string) {
+	if len(input) <= n {
+		left = input
+		return
+	}
+
+	if !utf8.ValidString(input) {
+		left = input[:n-3] + "..."
+		right = "..." + input[n-3:]
+		return
+	}
+
+	// in UTF8 "…" is 3 bytes so doesn't really gain us anything...
+	end := 0
+	for end <= n-3 {
+		_, size := utf8.DecodeRuneInString(input[end:])
+		if end+size > n-3 {
+			break
+		}
+		end += size
+	}
+
+	left = input[:end] + "…"
+	right = "…" + input[end:]
+	return
+}
diff --git a/routers/web/repo/compare.go b/routers/web/repo/compare.go
index fddfc4a63a897..e66aa614cb0a4 100644
--- a/routers/web/repo/compare.go
+++ b/routers/web/repo/compare.go
@@ -24,6 +24,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/upload"
+	"code.gitea.io/gitea/modules/util"
 	"code.gitea.io/gitea/services/gitdiff"
 )
 
@@ -567,6 +568,18 @@ func PrepareCompareDiff(
 	} else {
 		title = headBranch
 	}
+	if len(title) > 255 {
+		var trailer string
+		title, trailer = util.SplitStringAtByteN(title, 255)
+		if len(trailer) > 0 {
+			if ctx.Data["content"] != nil {
+				ctx.Data["content"] = fmt.Sprintf("%s\n\n%s", trailer, ctx.Data["content"])
+			} else {
+				ctx.Data["content"] = trailer + "\n"
+			}
+		}
+	}
+
 	ctx.Data["title"] = title
 	ctx.Data["Username"] = headUser.Name
 	ctx.Data["Reponame"] = headRepo.Name
diff --git a/routers/web/repo/pull.go b/routers/web/repo/pull.go
index a299799647777..703bbd837a9d2 100644
--- a/routers/web/repo/pull.go
+++ b/routers/web/repo/pull.go
@@ -1001,10 +1001,14 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 	ctx.Data["Title"] = ctx.Tr("repo.pulls.compare_changes")
 	ctx.Data["PageIsComparePull"] = true
 	ctx.Data["IsDiffCompare"] = true
+	ctx.Data["IsRepoToolbarCommits"] = true
+	ctx.Data["RequireTribute"] = true
+	ctx.Data["RequireSimpleMDE"] = true
 	ctx.Data["RequireHighlightJS"] = true
 	ctx.Data["PullRequestWorkInProgressPrefixes"] = setting.Repository.PullRequest.WorkInProgressPrefixes
 	ctx.Data["IsAttachmentEnabled"] = setting.Attachment.Enabled
 	upload.AddUploadContext(ctx, "comment")
+	ctx.Data["HasIssuesOrPullsWritePermission"] = ctx.Repo.CanWrite(models.UnitTypePullRequests)
 
 	var (
 		repo        = ctx.Repo.Repository
@@ -1037,6 +1041,14 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 			return
 		}
 
+		if len(form.Title) > 255 {
+			var trailer string
+			form.Title, trailer = util.SplitStringAtByteN(form.Title, 255)
+
+			form.Content = trailer + "\n\n" + form.Content
+		}
+		middleware.AssignForm(form, ctx.Data)
+
 		ctx.HTML(http.StatusOK, tplCompareDiff)
 		return
 	}
diff --git a/templates/repo/diff/compare.tmpl b/templates/repo/diff/compare.tmpl
index 7959ef7bb5173..2beca579601f8 100644
--- a/templates/repo/diff/compare.tmpl
+++ b/templates/repo/diff/compare.tmpl
@@ -176,10 +176,10 @@
 	{{if .IsNothingToCompare}}
 		{{if and $.IsSigned $.AllowEmptyPr (not .Repository.IsArchived) }}
 			<div class="ui segment">{{.i18n.Tr "repo.pulls.nothing_to_compare_and_allow_empty_pr"}}</div>
-			<div class="ui info message show-form-container">
+			<div class="ui info message show-form-container" {{if .Flash}}style="display: none"{{end}}>
 				<button class="ui button green show-form">{{.i18n.Tr "repo.pulls.new"}}</button>
 			</div>
-			<div class="pullrequest-form" style="display: none">
+			<div class="pullrequest-form" {{if not .Flash}}style="display: none"{{end}}>
 				{{template "repo/issue/new_form" .}}
 			</div>
 		{{else}}
@@ -192,7 +192,7 @@
 			</div>
 		{{else}}
 			{{if and $.IsSigned (not .Repository.IsArchived)}}
-				<div class="ui info message show-form-container">
+				<div class="ui info message show-form-container" {{if .Flash}}style="display: none"{{end}}>
 					<button class="ui button green show-form">{{.i18n.Tr "repo.pulls.new"}}</button>
 				</div>
 			{{else if .Repository.IsArchived}}
@@ -201,7 +201,7 @@
 				</div>
 			{{end}}
 			{{if $.IsSigned}}
-				<div class="pullrequest-form" style="display: none">
+				<div class="pullrequest-form" {{if not .Flash}}style="display: none"{{end}}>
 					{{template "repo/issue/new_form" .}}
 				</div>
 			{{end}}