Fix external renderer (go-gitea#16401)

* fix external renderer

* use GBackground context as fallback

* no fallback, return error

Co-authored-by: Lauris BH <lauris@nix.lv>

modules/markup/external/external.go

@@ -98,6 +98,10 @@ func (p *Renderer) Render(ctx *markup.RenderContext, input io.Reader, output io.
 		args = append(args, f.Name())
 	}
 
+	if ctx == nil || ctx.Ctx == nil {
+		return fmt.Errorf("RenderContext did not provide context")
+	}
+
 	processCtx, cancel := context.WithCancel(ctx.Ctx)
 	defer cancel()
 

routers/web/repo/view.go

@@ -336,6 +336,7 @@ func renderDirectory(ctx *context.Context, treeLink string) {
 					ctx.Data["MarkupType"] = string(markupType)
 					var result strings.Builder
 					err := markup.Render(&markup.RenderContext{
+						Ctx:       ctx,
 						Filename:  readmeFile.name,
 						URLPrefix: readmeTreelink,
 						Metas:     ctx.Repo.Repository.ComposeDocumentMetas(),
@@ -511,6 +512,7 @@ func renderFile(ctx *context.Context, entry *git.TreeEntry, treeLink, rawLink st
 			ctx.Data["MarkupType"] = markupType
 			var result strings.Builder
 			err := markup.Render(&markup.RenderContext{
+				Ctx:       ctx,
 				Filename:  blob.Name(),
 				URLPrefix: path.Dir(treeLink),
 				Metas:     ctx.Repo.Repository.ComposeDocumentMetas(),
@@ -570,6 +572,7 @@ func renderFile(ctx *context.Context, entry *git.TreeEntry, treeLink, rawLink st
 			ctx.Data["MarkupType"] = markupType
 			var result strings.Builder
 			err := markup.Render(&markup.RenderContext{
+				Ctx:       ctx,
 				Filename:  blob.Name(),
 				URLPrefix: path.Dir(treeLink),
 				Metas:     ctx.Repo.Repository.ComposeDocumentMetas(),