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Fix several render issues (#14986)

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* 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 2021-03-15 23:20:05 +00:00 • committed by GitHub
parent 044cd4d016
commit ed31ddc29a
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GPG key ID: 4AEE18F83AFDEB23
6 changed files with 211 additions and 61 deletions
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36
modules/markup/html.go
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@ -313,41 +313,27 @@ 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 := bytes.NewBuffer(make([]byte, 0, len(rawHTML)+50))
// prepend "<html><body>"
res = append(res, "<html><body>"...)
_, _ = res.WriteString("<html><body>")
// Strip out nuls - they're always invalid
start := bytes.IndexByte(rawHTML, '\000')
if start >= 0 {
res = append(res, rawHTML[:start]...)
start++
for start < len(rawHTML) {
end := bytes.IndexByte(rawHTML[start:], '\000')
if end < 0 {
res = append(res, rawHTML[start:]...)
break
} else if end > 0 {
res = append(res, rawHTML[start:start+end]...)
}
start += end + 1
}
} else {
res = append(res, rawHTML...)
}
_, _ = nulCleaner.WriteString(res, string(tagCleaner.ReplaceAll(rawHTML, []byte("&lt;$1"))))
// close the tags
res = append(res, "</body></html>"...)
_, _ = 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}
}
@ -384,17 +370,17 @@ 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) {