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Fix several render issues (#14986) (#15013)

Backport #14986

* Fix an issue with panics related to attributes
* Wrap goldmark render in a recovery function
* Reduce memory use in render emoji
* Use a pipe for rendering goldmark - still needs more work and a limiter

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>
This commit is contained in:
zeripath
2021-03-17 08:58:58 +00:00
committed by GitHub
parent fff66eb016
commit 8c461eb261
6 changed files with 216 additions and 44 deletions

View File

@@ -298,19 +298,27 @@ func RenderEmoji(
return ctx.postProcess(rawHTML)
}
var tagCleaner = regexp.MustCompile(`<((?:/?\w+/\w+)|(?:/[\w ]+/)|(/?[hH][tT][mM][lL][ />]))`)
var nulCleaner = strings.NewReplacer("\000", "")
func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
if ctx.procs == nil {
ctx.procs = defaultProcessors
}
// give a generous extra 50 bytes
res := make([]byte, 0, len(rawHTML)+50)
res = append(res, "<html><body>"...)
res = append(res, rawHTML...)
res = append(res, "</body></html>"...)
res := bytes.NewBuffer(make([]byte, 0, len(rawHTML)+50))
// prepend "<html><body>"
_, _ = res.WriteString("<html><body>")
// Strip out nuls - they're always invalid
_, _ = nulCleaner.WriteString(res, string(tagCleaner.ReplaceAll(rawHTML, []byte("&lt;$1"))))
// close the tags
_, _ = res.WriteString("</body></html>")
// parse the HTML
nodes, err := html.ParseFragment(bytes.NewReader(res), nil)
nodes, err := html.ParseFragment(res, nil)
if err != nil {
return nil, &postProcessError{"invalid HTML", err}
}
@@ -347,17 +355,17 @@ func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
// Create buffer in which the data will be placed again. We know that the
// length will be at least that of res; to spare a few alloc+copy, we
// reuse res, resetting its length to 0.
buf := bytes.NewBuffer(res[:0])
res.Reset()
// Render everything to buf.
for _, node := range nodes {
err = html.Render(buf, node)
err = html.Render(res, node)
if err != nil {
return nil, &postProcessError{"error rendering processed HTML", err}
}
}
// Everything done successfully, return parsed data.
return buf.Bytes(), nil
return res.Bytes(), nil
}
func (ctx *postProcessCtx) visitNode(node *html.Node, visitText bool) {