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Add better error checking for inline html diff code (#13239)

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* Add better error checking for inline html diff code

A better fix for #13191 which cleans up this code a bit and adds basic checking which should avoid writing broken HTML in future situations.

* Update gitdiff_test.go

* better regex

Co-authored-by: techknowlogick <techknowlogick@gitea.io>
This commit is contained in:
mrsdizzie 2020-10-21 18:14:44 -04:00 • committed by GitHub
parent 83106c166d
commit f6ee7ce9b6
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2 changed files with 49 additions and 53 deletions
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98
services/gitdiff/gitdiff.go
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@ -181,64 +181,60 @@ var (
removedCodePrefix = []byte(`<span class="removed-code">`)
codeTagSuffix = []byte(`</span>`)
)
var addSpanRegex = regexp.MustCompile(`<span\s*[a-z="]*$`)
var trailingSpanRegex = regexp.MustCompile(`<span\s*[[:alpha:]="]*?[>]?$`)
// shouldWriteInline represents combinations where we manually write inline changes
func shouldWriteInline(diff diffmatchpatch.Diff, lineType DiffLineType) bool {
if true &&
diff.Type == diffmatchpatch.DiffEqual ||
diff.Type == diffmatchpatch.DiffInsert && lineType == DiffLineAdd ||
diff.Type == diffmatchpatch.DiffDelete && lineType == DiffLineDel {
return true
}
return false
}
func diffToHTML(fileName string, diffs []diffmatchpatch.Diff, lineType DiffLineType) template.HTML {
buf := bytes.NewBuffer(nil)
var addSpan string
for i := range diffs {
match := ""
for _, diff := range diffs {
if shouldWriteInline(diff, lineType) {
if len(match) > 0 {
diff.Text = match + diff.Text
match = ""
}
// Chroma HTML syntax highlighting is done before diffing individual lines in order to maintain consistency.
// Since inline changes might split in the middle of a chroma span tag, make we manually put it back together
// before writing so we don't try insert added/removed code spans in the middle of an existing chroma span
// and create broken HTML.
m := trailingSpanRegex.FindStringSubmatchIndex(diff.Text)
if m != nil {
match = diff.Text[m[0]:m[1]]
diff.Text = strings.TrimSuffix(diff.Text, match)
}
// Print an existing closing span first before opening added/remove-code span so it doesn't unintentionally close it
if strings.HasPrefix(diff.Text, "</span>") {
buf.WriteString("</span>")
diff.Text = strings.TrimPrefix(diff.Text, "</span>")
}
// If we weren't able to fix it then this should avoid broken HTML by not inserting more spans below
// The previous/next diff section will contain the rest of the tag that is missing here
if strings.Count(diff.Text, "<") != strings.Count(diff.Text, ">") {
buf.WriteString(diff.Text)
continue
}
}
switch {
case diffs[i].Type == diffmatchpatch.DiffEqual:
// Looking for the case where our 3rd party diff library previously detected a string difference
// in the middle of a span class because we highlight them first. This happens when added/deleted code
// also changes the chroma class name, either partially or fully. If found, just move the openining span code forward into the next section
// see TestDiffToHTML for examples
if len(addSpan) > 0 {
diffs[i].Text = addSpan + diffs[i].Text
addSpan = ""
}
m := addSpanRegex.FindStringSubmatchIndex(diffs[i].Text)
if m != nil {
addSpan = diffs[i].Text[m[0]:m[1]]
buf.WriteString(strings.TrimSuffix(diffs[i].Text, addSpan))
} else {
addSpan = ""
buf.WriteString(getLineContent(diffs[i].Text))
}
case diffs[i].Type == diffmatchpatch.DiffInsert && lineType == DiffLineAdd:
if len(addSpan) > 0 {
diffs[i].Text = addSpan + diffs[i].Text
addSpan = ""
}
// Print existing closing span first before opening added-code span so it doesn't unintentionally close it
if strings.HasPrefix(diffs[i].Text, "</span>") {
buf.WriteString("</span>")
diffs[i].Text = strings.TrimPrefix(diffs[i].Text, "</span>")
}
m := addSpanRegex.FindStringSubmatchIndex(diffs[i].Text)
if m != nil {
addSpan = diffs[i].Text[m[0]:m[1]]
diffs[i].Text = strings.TrimSuffix(diffs[i].Text, addSpan)
}
case diff.Type == diffmatchpatch.DiffEqual:
buf.WriteString(diff.Text)
case diff.Type == diffmatchpatch.DiffInsert && lineType == DiffLineAdd:
buf.Write(addedCodePrefix)
buf.WriteString(diffs[i].Text)
buf.WriteString(diff.Text)
buf.Write(codeTagSuffix)
case diffs[i].Type == diffmatchpatch.DiffDelete && lineType == DiffLineDel:
if len(addSpan) > 0 {
diffs[i].Text = addSpan + diffs[i].Text
addSpan = ""
}
if strings.HasPrefix(diffs[i].Text, "</span>") {
buf.WriteString("</span>")
diffs[i].Text = strings.TrimPrefix(diffs[i].Text, "</span>")
}
m := addSpanRegex.FindStringSubmatchIndex(diffs[i].Text)
if m != nil {
addSpan = diffs[i].Text[m[0]:m[1]]
diffs[i].Text = strings.TrimSuffix(diffs[i].Text, addSpan)
}
case diff.Type == diffmatchpatch.DiffDelete && lineType == DiffLineDel:
buf.Write(removedCodePrefix)
buf.WriteString(diffs[i].Text)
buf.WriteString(diff.Text)
buf.Write(codeTagSuffix)
}
}