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Fix broken spans in diffs (#14678) 

Gitea runs diff on highlighted code fragment for each line in order to provide
code highlight diffs. Unfortunately this diff algorithm is not aware that span tags
and entities are atomic and cannot be split.

The current fixup code makes some attempt to fix these broken tags however, it cannot
handle situations where a tag is split over multiple blocks.

This PR provides a more algorithmic fixup mechanism whereby spans and entities are
completely coalesced into their respective blocks.

This may result in a incompletely reduced diff but - it will definitely prevent the
broken entities and spans that are currently possible.

As a result of this fixup several inconsistencies were discovered in our testcases
and these were also fixed.

Fix #14231

Signed-off-by: Andrew Thornton <art27@cantab.net>
This commit is contained in:
zeripath 2021-02-14 14:51:00 +00:00 committed by GitHub
parent f3847c9d82
commit beb2058186
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 228 additions and 6 deletions
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210
services/gitdiff/gitdiff.go
View File

@ -182,6 +182,8 @@ var (
removedCodePrefix = []byte(`<span class="removed-code">`)
codeTagSuffix = []byte(`</span>`)
)
var unfinishedtagRegex = regexp.MustCompile(`<[^>]*$`)
var trailingSpanRegex = regexp.MustCompile(`<span\s*[[:alpha:]="]*?[>]?$`)
var entityRegex = regexp.MustCompile(`&[#]*?[0-9[:alpha:]]*$`)
@ -196,10 +198,218 @@ func shouldWriteInline(diff diffmatchpatch.Diff, lineType DiffLineType) bool {
return false
}
func fixupBrokenSpans(diffs []diffmatchpatch.Diff) []diffmatchpatch.Diff {
// Create a new array to store our fixed up blocks
fixedup := make([]diffmatchpatch.Diff, 0, len(diffs))
// semantically label some numbers
const insert, delete, equal = 0, 1, 2
// record the positions of the last type of each block in the fixedup blocks
last := []int{-1, -1, -1}
operation := []diffmatchpatch.Operation{diffmatchpatch.DiffInsert, diffmatchpatch.DiffDelete, diffmatchpatch.DiffEqual}
// create a writer for insert and deletes
toWrite := []strings.Builder{
{},
{},
}
// make some flags for insert and delete
unfinishedTag := []bool{false, false}
unfinishedEnt := []bool{false, false}
// store stores the provided text in the writer for the typ
store := func(text string, typ int) {
(&(toWrite[typ])).WriteString(text)
}
// hasStored returns true if there is stored content
hasStored := func(typ int) bool {
return (&toWrite[typ]).Len() > 0
}
// stored will return that content
stored := func(typ int) string {
return (&toWrite[typ]).String()
}
// empty will empty the stored content
empty := func(typ int) {
(&toWrite[typ]).Reset()
}
// pop will remove the stored content appending to a diff block for that typ
pop := func(typ int, fixedup []diffmatchpatch.Diff) []diffmatchpatch.Diff {
if hasStored(typ) {
if last[typ] > last[equal] {
fixedup[last[typ]].Text += stored(typ)
} else {
fixedup = append(fixedup, diffmatchpatch.Diff{
Type: operation[typ],
Text: stored(typ),
})
}
empty(typ)
}
return fixedup
}
// Now we walk the provided diffs and check the type of each block in turn
for _, diff := range diffs {
typ := delete // flag for handling insert or delete typs
switch diff.Type {
case diffmatchpatch.DiffEqual:
// First check if there is anything stored
if hasStored(insert) || hasStored(delete) {
// There are two reasons for storing content:
// 1. Unfinished Entity <- Could be more efficient here by not doing this if we're looking for a tag
if unfinishedEnt[insert] || unfinishedEnt[delete] {
// we look for a ';' to finish an entity
idx := strings.IndexRune(diff.Text, ';')
if idx >= 0 {
// if we find a ';' store the preceding content to both insert and delete
store(diff.Text[:idx+1], insert)
store(diff.Text[:idx+1], delete)
// and remove it from this block
diff.Text = diff.Text[idx+1:]
// reset the ent flags
unfinishedEnt[insert] = false
unfinishedEnt[delete] = false
} else {
// otherwise store it all on insert and delete
store(diff.Text, insert)
store(diff.Text, delete)
// and empty this block
diff.Text = ""
}
}
// 2. Unfinished Tag
if unfinishedTag[insert] || unfinishedTag[delete] {
// we look for a '>' to finish a tag
idx := strings.IndexRune(diff.Text, '>')
if idx >= 0 {
store(diff.Text[:idx+1], insert)
store(diff.Text[:idx+1], delete)
diff.Text = diff.Text[idx+1:]
unfinishedTag[insert] = false
unfinishedTag[delete] = false
} else {
store(diff.Text, insert)
store(diff.Text, delete)
diff.Text = ""
}
}
// If we've completed the required tag/entities
if !(unfinishedTag[insert] || unfinishedTag[delete] || unfinishedEnt[insert] || unfinishedEnt[delete]) {
// pop off the stack
fixedup = pop(insert, fixedup)
fixedup = pop(delete, fixedup)
}
// If that has left this diff block empty then shortcut
if len(diff.Text) == 0 {
continue
}
}
// check if this block ends in an unfinished tag?
idx := unfinishedtagRegex.FindStringIndex(diff.Text)
if idx != nil {
unfinishedTag[insert] = true
unfinishedTag[delete] = true
} else {
// otherwise does it end in an unfinished entity?
idx = entityRegex.FindStringIndex(diff.Text)
if idx != nil {
unfinishedEnt[insert] = true
unfinishedEnt[delete] = true
}
}
// If there is an unfinished component
if idx != nil {
// Store the fragment
store(diff.Text[idx[0]:], insert)
store(diff.Text[idx[0]:], delete)
// and remove it from this block
diff.Text = diff.Text[:idx[0]]
}
// If that hasn't left the block empty
if len(diff.Text) > 0 {
// store the position of the last equal block and store it in our diffs
last[equal] = len(fixedup)
fixedup = append(fixedup, diff)
}
continue
case diffmatchpatch.DiffInsert:
typ = insert
fallthrough
case diffmatchpatch.DiffDelete:
// First check if there is anything stored for this type
if hasStored(typ) {
// if there is prepend it to this block, empty the storage and reset our flags
diff.Text = stored(typ) + diff.Text
empty(typ)
unfinishedEnt[typ] = false
unfinishedTag[typ] = false
}
// check if this block ends in an unfinished tag
idx := unfinishedtagRegex.FindStringIndex(diff.Text)
if idx != nil {
unfinishedTag[typ] = true
} else {
// otherwise does it end in an unfinished entity
idx = entityRegex.FindStringIndex(diff.Text)
if idx != nil {
unfinishedEnt[typ] = true
}
}
// If there is an unfinished component
if idx != nil {
// Store the fragment
store(diff.Text[idx[0]:], typ)
// and remove it from this block
diff.Text = diff.Text[:idx[0]]
}
// If that hasn't left the block empty
if len(diff.Text) > 0 {
// if the last block of this type was after the last equal block
if last[typ] > last[equal] {
// store this blocks content on that block
fixedup[last[typ]].Text += diff.Text
} else {
// otherwise store the position of the last block of this type and store the block
last[typ] = len(fixedup)
fixedup = append(fixedup, diff)
}
}
continue
}
}
// pop off any remaining stored content
fixedup = pop(insert, fixedup)
fixedup = pop(delete, fixedup)
return fixedup
}
func diffToHTML(fileName string, diffs []diffmatchpatch.Diff, lineType DiffLineType) template.HTML {
buf := bytes.NewBuffer(nil)
match := ""
diffs = fixupBrokenSpans(diffs)
for _, diff := range diffs {
if shouldWriteInline(diff, lineType) {
if len(match) > 0 {

24
services/gitdiff/gitdiff_test.go
View File

@ -15,6 +15,7 @@ import (
"code.gitea.io/gitea/models"
"code.gitea.io/gitea/modules/git"
"code.gitea.io/gitea/modules/highlight"
"code.gitea.io/gitea/modules/setting"
dmp "github.com/sergi/go-diff/diffmatchpatch"
"github.com/stretchr/testify/assert"
@ -23,7 +24,7 @@ import (
func assertEqual(t *testing.T, s1 string, s2 template.HTML) {
if s1 != string(s2) {
t.Errorf("%s should be equal %s", s2, s1)
t.Errorf("Did not receive expected results:\nExpected: %s\nActual: %s", s1, s2)
}
}
@ -61,7 +62,7 @@ func TestDiffToHTML(t *testing.T) {
{Type: dmp.DiffEqual, Text: "</span><span class=\"p\">)</span>"},
}, DiffLineDel))
assertEqual(t, "<span class=\"nx\">r</span><span class=\"p\">.</span><span class=\"nf\">WrapperRenderer</span><span class=\"p\">(</span><span class=\"nx\">w</span><span class=\"p\">,</span> <span class=\"removed-code\"><span class=\"nx\">language</span></span><span class=\"removed-code\"><span class=\"p\">,</span> <span class=\"kc\">true</span><span class=\"p\">,</span> <span class=\"nx\">attrs</span></span><span class=\"p\">,</span> <span class=\"kc\">false</span><span class=\"p\">)</span>", diffToHTML("", []dmp.Diff{
assertEqual(t, "<span class=\"nx\">r</span><span class=\"p\">.</span><span class=\"nf\">WrapperRenderer</span><span class=\"p\">(</span><span class=\"nx\">w</span><span class=\"p\">,</span> <span class=\"removed-code\"><span class=\"nx\">language</span><span class=\"p\">,</span> <span class=\"kc\">true</span><span class=\"p\">,</span> <span class=\"nx\">attrs</span></span><span class=\"p\">,</span> <span class=\"kc\">false</span><span class=\"p\">)</span>", diffToHTML("", []dmp.Diff{
{Type: dmp.DiffEqual, Text: "<span class=\"nx\">r</span><span class=\"p\">.</span><span class=\"nf\">WrapperRenderer</span><span class=\"p\">(</span><span class=\"nx\">w</span><span class=\"p\">,</span> <span class=\"nx\">"},
{Type: dmp.DiffDelete, Text: "language</span><span "},
{Type: dmp.DiffEqual, Text: "c"},
@ -69,14 +70,14 @@ func TestDiffToHTML(t *testing.T) {
{Type: dmp.DiffEqual, Text: "</span><span class=\"p\">,</span> <span class=\"kc\">false</span><span class=\"p\">)</span>"},
}, DiffLineDel))
assertEqual(t, "<span class=\"added-code\">language</span></span><span class=\"added-code\"><span class=\"p\">,</span> <span class=\"kc\">true</span><span class=\"p\">,</span> <span class=\"nx\">attrs</span></span><span class=\"p\">,</span> <span class=\"kc\">false</span><span class=\"p\">)</span>", diffToHTML("", []dmp.Diff{
assertEqual(t, "<span class=\"added-code\">language</span><span class=\"p\">,</span> <span class=\"kc\">true</span><span class=\"p\">,</span> <span class=\"nx\">attrs</span></span><span class=\"p\">,</span> <span class=\"kc\">false</span><span class=\"p\">)</span>", diffToHTML("", []dmp.Diff{
{Type: dmp.DiffInsert, Text: "language</span><span "},
{Type: dmp.DiffEqual, Text: "c"},
{Type: dmp.DiffInsert, Text: "lass=\"p\">,</span> <span class=\"kc\">true</span><span class=\"p\">,</span> <span class=\"nx\">attrs"},
{Type: dmp.DiffEqual, Text: "</span><span class=\"p\">,</span> <span class=\"kc\">false</span><span class=\"p\">)</span>"},
}, DiffLineAdd))
assertEqual(t, "<span class=\"k\">print</span><span class=\"added-code\"></span><span class=\"added-code\"><span class=\"p\">(</span></span><span class=\"sa\"></span><span class=\"s2\">&#34;</span><span class=\"s2\">// </span><span class=\"s2\">&#34;</span><span class=\"p\">,</span> <span class=\"n\">sys</span><span class=\"o\">.</span><span class=\"n\">argv</span><span class=\"added-code\"><span class=\"p\">)</span></span>", diffToHTML("", []dmp.Diff{
assertEqual(t, "<span class=\"k\">print</span><span class=\"added-code\"><span class=\"p\">(</span></span><span class=\"sa\"></span><span class=\"s2\">&#34;</span><span class=\"s2\">// </span><span class=\"s2\">&#34;</span><span class=\"p\">,</span> <span class=\"n\">sys</span><span class=\"o\">.</span><span class=\"n\">argv</span><span class=\"added-code\"><span class=\"p\">)</span></span>", diffToHTML("", []dmp.Diff{
{Type: dmp.DiffEqual, Text: "<span class=\"k\">print</span>"},
{Type: dmp.DiffInsert, Text: "<span"},
{Type: dmp.DiffEqual, Text: " "},
@ -85,14 +86,14 @@ func TestDiffToHTML(t *testing.T) {
{Type: dmp.DiffInsert, Text: "<span class=\"p\">)</span>"},
}, DiffLineAdd))
assertEqual(t, "sh <span class=\"added-code\">&#39;useradd -u $(stat -c &#34;%u&#34; .gitignore) jenkins</span>&#39;", diffToHTML("", []dmp.Diff{
assertEqual(t, "sh <span class=\"added-code\">&#39;useradd -u $(stat -c &#34;%u&#34; .gitignore) jenkins&#39;</span>", diffToHTML("", []dmp.Diff{
{Type: dmp.DiffEqual, Text: "sh &#3"},
{Type: dmp.DiffDelete, Text: "4;useradd -u 111 jenkins&#34"},
{Type: dmp.DiffInsert, Text: "9;useradd -u $(stat -c &#34;%u&#34; .gitignore) jenkins&#39"},
{Type: dmp.DiffEqual, Text: ";"},
}, DiffLineAdd))
assertEqual(t, "<span class=\"x\"> &lt;h<span class=\"added-code\">4 class=</span><span class=\"added-code\">&#34;release-list-title df ac&#34;</span>&gt;</span>", diffToHTML("", []dmp.Diff{
assertEqual(t, "<span class=\"x\"> &lt;h<span class=\"added-code\">4 class=&#34;release-list-title df ac&#34;</span>&gt;</span>", diffToHTML("", []dmp.Diff{
{Type: dmp.DiffEqual, Text: "<span class=\"x\"> &lt;h"},
{Type: dmp.DiffInsert, Text: "4 class=&#"},
{Type: dmp.DiffEqual, Text: "3"},
@ -462,3 +463,14 @@ func TestGetDiffRangeWithWhitespaceBehavior(t *testing.T) {
}
}
}
func TestDiffToHTML_14231(t *testing.T) {
setting.Cfg = ini.Empty()
diffRecord := diffMatchPatch.DiffMain(highlight.Code("main.v", " run()\n"), highlight.Code("main.v", " run(db)\n"), true)
diffRecord = diffMatchPatch.DiffCleanupEfficiency(diffRecord)
expected := ` <span class="n">run</span><span class="added-code"><span class="o">(</span><span class="n">db</span></span><span class="o">)</span>`
output := diffToHTML("main.v", diffRecord, DiffLineAdd)
assertEqual(t, expected, output)
}