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Blame · server/web/diff.go

Line attribution on main · 184 line(s)

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78912785 Keenan Nemetz 17d ago	1	package web
	2
	3	// Unified diff parsing for the web views. Git is the source of truth for what
	4	// changed, so nothing here computes a diff: it reads the patch git prints and
	5	// shapes it for a template. Two rules matter: every line is escaped by
	6	// html/template on the way out, and a patch that is cut off (the cap) is shown
	7	// as cut off rather than as a smaller change.
	8
	9	import (
f6f4b1db Keenan Nemetz 15d ago	10	"html/template"
78912785 Keenan Nemetz 17d ago	11	"regexp"
	12	"strconv"
	13	"strings"
f6f4b1db Keenan Nemetz 15d ago	14	"time"
78912785 Keenan Nemetz 17d ago	15	)
	16
	17	type diffFile struct {
e7982ac5 Keenan Nemetz 12d ago	18	OldPath string
	19	NewPath string
	20	Binary bool
	21	Language string // the Prism language for Label, or "" when it is not known
	22	Hunks []diffHunk
	23	Added int
	24	Removed int
78912785 Keenan Nemetz 17d ago	25	}
	26
	27	// Label is what to show as the file's name: the new path, or the old one for a
	28	// deletion.
	29	func (f diffFile) Label() string {
	30	if f.NewPath != "" {
	31	return f.NewPath
	32	}
	33	return f.OldPath
	34	}
	35
628d4523 Keenan Nemetz 11d ago	36	// pathspec is what git has to be told to print this file's patch. A rename needs
	37	// both of its paths: filtered to the destination alone, git reports what is left
	38	// as a new file and the rename is lost.
bef0c093 Keenan Nemetz 9d ago	39	//
	40	// A deletion has one path, on the old side, and must not hand git the empty new
	41	// side: git refuses an empty pathspec outright, so asking for a deleted file used
	42	// to fail the whole page. Nothing at all is the one answer a caller has to
	43	// handle: it means there is no patch to ask for, not "every path".
628d4523 Keenan Nemetz 11d ago	44	func (f diffFile) pathspec() []string {
bef0c093 Keenan Nemetz 9d ago	45	if f.OldPath == "" && f.NewPath == "" {
	46	return nil
	47	}
	48	if f.OldPath != "" && f.NewPath != "" && f.OldPath != f.NewPath {
628d4523 Keenan Nemetz 11d ago	49	return []string{f.OldPath, f.NewPath}
	50	}
	51	if f.NewPath != "" {
	52	return []string{f.NewPath}
	53	}
	54	return []string{f.OldPath}
	55	}
	56
78912785 Keenan Nemetz 17d ago	57	type diffHunk struct {
	58	Header string
	59	Lines []diffLine
	60	}
	61
	62	type diffLine struct {
	63	Kind string // "add", "del" or "ctx"
	64	OldNo int
	65	NewNo int
	66	Text string
9cc2f087 Keenan Nemetz 17d ago	67	// Comments are review comments anchored to this line, filled in by the request
f6f4b1db Keenan Nemetz 15d ago	68	// view rather than by the parser. They are rendered beneath the line so the
f6f4b1db Keenan Nemetz 15d ago	69	// reviewer can read the note where it applies.
9cc2f087 Keenan Nemetz 17d ago	70	Comments []diffComment
	71	}
	72
f6f4b1db Keenan Nemetz 15d ago	73	// diffComment is one review comment shown beneath the line it is anchored to.
9cc2f087 Keenan Nemetz 17d ago	74	type diffComment struct {
f6f4b1db Keenan Nemetz 15d ago	75	ID string
	76	Author string
	77	Created time.Time
	78	Body template.HTML
78912785 Keenan Nemetz 17d ago	79	}
	80
	81	var (
	82	hunkRE = regexp.MustCompile(`^@@ -(\d+)(?:,\d+)? \+(\d+)(?:,\d+)? @@`)
	83	metaRE = regexp.MustCompile(`^(index \|old mode\|new mode\|similarity index\|rename (from\|to)\|copy (from\|to)\|new file mode\|deleted file mode)`)
	84	quoteRE = regexp.MustCompile(`^"(.*)"$`)
	85	)
	86
	87	// parseDiff turns `git diff`/`git show` output into files, hunks and numbered
	88	// lines. Unrecognised metadata is dropped: a viewer that shows "index 3f2a.." is
	89	// showing the plumbing, not the change.
	90	func parseDiff(patch string) []diffFile {
	91	var files []diffFile
	92	var cur *diffFile
	93	var hunk *diffHunk
	94	oldNo, newNo := 0, 0
	95
	96	flushHunk := func() {
	97	if cur != nil && hunk != nil {
	98	cur.Hunks = append(cur.Hunks, *hunk)
	99	hunk = nil
	100	}
	101	}
	102	flushFile := func() {
	103	flushHunk()
	104	if cur != nil {
e7982ac5 Keenan Nemetz 12d ago	105	name := cur.NewPath
	106	if name == "" {
	107	name = cur.OldPath
	108	}
	109	cur.Language = prismLanguage(name)
78912785 Keenan Nemetz 17d ago	110	files = append(files, *cur)
	111	cur = nil
	112	}
	113	}
	114
	115	for _, line := range strings.Split(patch, "\n") {
	116	switch {
	117	case strings.HasPrefix(line, "diff --git "):
	118	flushFile()
	119	cur = &diffFile{}
	120	case cur == nil:
	121	continue
	122	case strings.HasPrefix(line, "--- "):
	123	cur.OldPath = diffPath(strings.TrimPrefix(line, "--- "))
	124	case strings.HasPrefix(line, "+++ "):
	125	cur.NewPath = diffPath(strings.TrimPrefix(line, "+++ "))
	126	case strings.HasPrefix(line, "Binary files ") \|\| strings.HasPrefix(line, "GIT binary patch"):
	127	cur.Binary = true
	128	case metaRE.MatchString(line):
	129	// plumbing: shown nowhere
	130	case hunkRE.MatchString(line):
	131	flushHunk()
	132	m := hunkRE.FindStringSubmatch(line)
	133	oldNo, _ = strconv.Atoi(m[1])
	134	newNo, _ = strconv.Atoi(m[2])
	135	hunk = &diffHunk{Header: line}
	136	case hunk != nil && strings.HasPrefix(line, "+"):
	137	hunk.Lines = append(hunk.Lines, diffLine{Kind: "add", NewNo: newNo, Text: line[1:]})
	138	cur.Added++
	139	newNo++
	140	case hunk != nil && strings.HasPrefix(line, "-"):
	141	hunk.Lines = append(hunk.Lines, diffLine{Kind: "del", OldNo: oldNo, Text: line[1:]})
	142	cur.Removed++
	143	oldNo++
	144	case hunk != nil && strings.HasPrefix(line, " "):
	145	hunk.Lines = append(hunk.Lines, diffLine{Kind: "ctx", OldNo: oldNo, NewNo: newNo, Text: line[1:]})
	146	oldNo++
	147	newNo++
	148	case hunk != nil && strings.HasPrefix(line, `\`):
	149	// "\ No newline at end of file" belongs to the previous line.
	150	}
	151	}
	152	flushFile()
	153	return files
	154	}
	155
	156	// diffPath normalises a ---/+++ path: strips the a/ or b/ prefix and the tab
	157	// git appends when a path contains spaces.
	158	func diffPath(p string) string {
	159	if i := strings.IndexByte(p, '\t'); i >= 0 {
	160	p = p[:i]
	161	}
	162	p = strings.TrimSpace(p)
	163	if m := quoteRE.FindStringSubmatch(p); m != nil {
	164	if q, err := strconv.Unquote(`"` + m[1] + `"`); err == nil {
	165	p = q
	166	}
	167	}
	168	if p == "/dev/null" {
	169	return ""
	170	}
	171	if len(p) > 2 && (strings.HasPrefix(p, "a/") \|\| strings.HasPrefix(p, "b/")) {
	172	return p[2:]
	173	}
174	return p
175	}
176
177	// diffSummary is the "3 files changed, +12 −4" line under a heading.
178	func diffSummary(files []diffFile) (added, removed int) {
179	for _, f := range files {
180	added += f.Added
181	removed += f.Removed
182	}
183	return added, removed
184	}