Fix 500 on PR files API (#21602)

qwerty287 · lunny · 6543 · web-flow · commit 8430f738e296 · 2022-10-26T23:46:11.000+08:00
Fixes an 500 error/panic if using the changed PR files API with pages
that should return empty lists because there are no items anymore.
`start-end` is then &lt; 0 which ends in panic.

Co-authored-by: Lunny Xiao &lt;xiaolunwen@gmail.com&gt;
Co-authored-by: 6543 &lt;6543@obermui.de&gt;
Co-authored-by: delvh &lt;dev.lh@web.de&gt;
diff --git a/routers/api/v1/repo/pull.go b/routers/api/v1/repo/pull.go
@@ -1443,7 +1443,11 @@ func GetPullRequestFiles(ctx *context.APIContext) {
 		end = totalNumberOfFiles
 	}
 
-	apiFiles := make([]*api.ChangedFile, 0, end-start)
+	lenFiles := end - start
+	if lenFiles < 0 {
+		lenFiles = 0
+	}
+	apiFiles := make([]*api.ChangedFile, 0, lenFiles)
 	for i := start; i < end; i++ {
 		apiFiles = append(apiFiles, convert.ToChangedFile(diff.Files[i], pr.HeadRepo, endCommitID))
 	}

Original file line number	Diff line number	Diff line change
`@@ -1443,7 +1443,11 @@ func GetPullRequestFiles(ctx *context.APIContext) {`
`1443`	`1443`	`end = totalNumberOfFiles`
`1444`	`1444`	`}`
`1445`	`1445`
`1446`		`- apiFiles := make([]*api.ChangedFile, 0, end-start)`
	`1446`	`+ lenFiles := end - start`
	`1447`	`+ if lenFiles < 0 {`
	`1448`	`+ lenFiles = 0`
	`1449`	`+ }`
	`1450`	`+ apiFiles := make([]*api.ChangedFile, 0, lenFiles)`
`1447`	`1451`	`for i := start; i < end; i++ {`
`1448`	`1452`	`apiFiles = append(apiFiles, convert.ToChangedFile(diff.Files[i], pr.HeadRepo, endCommitID))`
`1449`	`1453`	`}`