From b559b3d7d393360dbe238bfe73e6c02c62c427df Mon Sep 17 00:00:00 2001
From: Andrew Thornton <art27@cantab.net>
Date: Thu, 22 Jul 2021 18:13:30 +0100
Subject: [PATCH 1/6] Handle too long PR titles correctly

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>
---
 routers/web/repo/compare.go      |  9 +++++++++
 routers/web/repo/pull.go         | 10 ++++++++++
 templates/repo/diff/compare.tmpl |  8 ++++----
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/routers/web/repo/compare.go b/routers/web/repo/compare.go
index fddfc4a63a897..f00b35aaad86b 100644
--- a/routers/web/repo/compare.go
+++ b/routers/web/repo/compare.go
@@ -567,6 +567,15 @@ func PrepareCompareDiff(
 	} else {
 		title = headBranch
 	}
+	if len(title) > 255 {
+		if ctx.Data["content"] != nil {
+			ctx.Data["content"] = fmt.Sprintf("...%s\n\n%s", title[252:], ctx.Data["content"])
+		} else {
+			ctx.Data["content"] = "..." + title[252:] + "\n"
+		}
+		title = title[:252] + "..."
+	}
+
 	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..6ef5a09309b75 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 +1041,12 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 			return
 		}
 
+		if len(form.Title) > 255 {
+			form.Content = "..." + form.Title[252:] + "\n\n" + form.Content
+			form.Title = form.Title[:252] + "..."
+		}
+		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}}

From b1c229483ab8c1cee6e67c4384c409f984e0e563 Mon Sep 17 00:00:00 2001
From: Andrew Thornton <art27@cantab.net>
Date: Fri, 23 Jul 2021 08:50:03 +0100
Subject: [PATCH 2/6] =?UTF-8?q?use=20ellipsis=20=E2=80=A6?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Andrew Thornton <art27@cantab.net>
---
 routers/web/repo/compare.go | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/routers/web/repo/compare.go b/routers/web/repo/compare.go
index f00b35aaad86b..b6d877d5632fb 100644
--- a/routers/web/repo/compare.go
+++ b/routers/web/repo/compare.go
@@ -569,11 +569,11 @@ func PrepareCompareDiff(
 	}
 	if len(title) > 255 {
 		if ctx.Data["content"] != nil {
-			ctx.Data["content"] = fmt.Sprintf("...%s\n\n%s", title[252:], ctx.Data["content"])
+			ctx.Data["content"] = fmt.Sprintf("…%s\n\n%s", title[254:], ctx.Data["content"])
 		} else {
-			ctx.Data["content"] = "..." + title[252:] + "\n"
+			ctx.Data["content"] = "…" + title[254:] + "\n"
 		}
-		title = title[:252] + "..."
+		title = title[:254] + "…"
 	}
 
 	ctx.Data["title"] = title

From 6e1c07261255d84acdef1714d75d1d6e818b89b1 Mon Sep 17 00:00:00 2001
From: zeripath <art27@cantab.net>
Date: Fri, 23 Jul 2021 09:05:39 +0100
Subject: [PATCH 3/6] Update routers/web/repo/pull.go

---
 routers/web/repo/pull.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/routers/web/repo/pull.go b/routers/web/repo/pull.go
index 6ef5a09309b75..67096a87e5289 100644
--- a/routers/web/repo/pull.go
+++ b/routers/web/repo/pull.go
@@ -1042,7 +1042,7 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 		}
 
 		if len(form.Title) > 255 {
-			form.Content = "..." + form.Title[252:] + "\n\n" + form.Content
+			form.Content = "…" + form.Title[254:] + "\n\n" + form.Content
 			form.Title = form.Title[:252] + "..."
 		}
 		middleware.AssignForm(form, ctx.Data)

From 46deda4eb864d38f9b4f4fe8e06e10ec0c0fcdc8 Mon Sep 17 00:00:00 2001
From: zeripath <art27@cantab.net>
Date: Fri, 23 Jul 2021 09:06:14 +0100
Subject: [PATCH 4/6] Update routers/web/repo/pull.go

---
 routers/web/repo/pull.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/routers/web/repo/pull.go b/routers/web/repo/pull.go
index 67096a87e5289..a55d0f377505a 100644
--- a/routers/web/repo/pull.go
+++ b/routers/web/repo/pull.go
@@ -1043,7 +1043,7 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 
 		if len(form.Title) > 255 {
 			form.Content = "…" + form.Title[254:] + "\n\n" + form.Content
-			form.Title = form.Title[:252] + "..."
+			form.Title = form.Title[:254] + "…"
 		}
 		middleware.AssignForm(form, ctx.Data)
 

From 887c0f104fbc31de09f1c4bd876dd521f57e2b87 Mon Sep 17 00:00:00 2001
From: Andrew Thornton <art27@cantab.net>
Date: Sat, 24 Jul 2021 09:38:40 +0100
Subject: [PATCH 5/6] as per lunny

Signed-off-by: Andrew Thornton <art27@cantab.net>
---
 modules/util/truncate.go    | 34 ++++++++++++++++++++++++++++++++++
 routers/web/repo/compare.go | 14 +++++++++-----
 routers/web/repo/pull.go    |  6 ++++--
 3 files changed, 47 insertions(+), 7 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..93df3fe1ca270
--- /dev/null
+++ b/modules/util/truncate.go
@@ -0,0 +1,34 @@
+// 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"
+
+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 b6d877d5632fb..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"
 )
 
@@ -568,12 +569,15 @@ func PrepareCompareDiff(
 		title = headBranch
 	}
 	if len(title) > 255 {
-		if ctx.Data["content"] != nil {
-			ctx.Data["content"] = fmt.Sprintf("…%s\n\n%s", title[254:], ctx.Data["content"])
-		} else {
-			ctx.Data["content"] = "…" + title[254:] + "\n"
+		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"
+			}
 		}
-		title = title[:254] + "…"
 	}
 
 	ctx.Data["title"] = title
diff --git a/routers/web/repo/pull.go b/routers/web/repo/pull.go
index a55d0f377505a..703bbd837a9d2 100644
--- a/routers/web/repo/pull.go
+++ b/routers/web/repo/pull.go
@@ -1042,8 +1042,10 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 		}
 
 		if len(form.Title) > 255 {
-			form.Content = "…" + form.Title[254:] + "\n\n" + form.Content
-			form.Title = form.Title[:254] + "…"
+			var trailer string
+			form.Title, trailer = util.SplitStringAtByteN(form.Title, 255)
+
+			form.Content = trailer + "\n\n" + form.Content
 		}
 		middleware.AssignForm(form, ctx.Data)
 

From 6424efd3caee8851d8d3ff533ff42bbe41e43f34 Mon Sep 17 00:00:00 2001
From: Andrew Thornton <art27@cantab.net>
Date: Sat, 24 Jul 2021 09:58:04 +0100
Subject: [PATCH 6/6] placate lint

Signed-off-by: Andrew Thornton <art27@cantab.net>
---
 modules/util/truncate.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/modules/util/truncate.go b/modules/util/truncate.go
index 93df3fe1ca270..8d0f6309732d7 100644
--- a/modules/util/truncate.go
+++ b/modules/util/truncate.go
@@ -6,6 +6,7 @@ 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