detached cdd2065

Fix mangled extended color sequences in syntax highlighting

commit
cdd2065c3401ea598d05fdcdb0422705f06270b5
author
Mike Smith · · 2026-09-26 19:43 UTC
parent
f2fef94
signature
unsigned
2 files · +191 -10
Unified
UnifiedSplit
M packages/tui/highlight.go +42 -10
@@ -121,6 +121,14 @@ func LanguageFromPath(p string) string {
121121 // Chroma's inherited styles can assign black backgrounds to a few tokens
122122 // (notably punctuation/error-ish spans), which looks like random black blocks
123123 // inside zot's dark-gray tool boxes. Foreground color is enough for code.
124+//
125+// Extended color parameters ("38;5;N", "38;2;R;G;B" and their "48;..."
126+// background twins) are consumed as whole units. The color index of an
127+// extended foreground is a value, not a standalone ANSI code: stripping a
128+// "45" or "101" out of "\x1b[38;5;45m" leaves the malformed "\x1b[38;5m",
129+// whose leftover "5" terminals read as blink (SGR 5), so the token loses its
130+// color and blinks. A truncated extended color cannot be rendered anyway,
131+// so it is dropped rather than forwarded.
124132 func stripANSIBackgrounds(s string) string {
125133 var out strings.Builder
126134 out.Grow(len(s))
@@ -143,21 +151,21 @@ func stripANSIBackgrounds(s string) string {
143151 for p := 0; p < len(params); p++ {
144152 param := params[p]
145153 switch param {
146- case "48":
147- // 48;5;N or 48;2;R;G;B background color.
148- if p+1 < len(params) && params[p+1] == "5" {
149- p += 2
150- continue
151- }
152- if p+1 < len(params) && params[p+1] == "2" {
153- p += 4
154- continue
154+ case "38", "48":
155+ span, complete := extendedColorSpan(params, p)
156+ if complete && param == "38" {
157+ kept = append(kept, span...)
155158 }
159+ // Consume the whole unit either way: a truncated
160+ // "38;5" must not leave its "5" to be read as blink.
161+ p += len(span) - 1
156162 continue
157163 case "49":
158164 continue
159165 }
160- // 40-47 and 100-107 are ANSI background colors.
166+ // 40-47 and 100-107 are ANSI background colors. Bare codes only:
167+ // extended colors were consumed above, so a color index in those
168+ // ranges cannot be mistaken for one here.
161169 if len(param) == 2 && param[0] == '4' && param[1] >= '0' && param[1] <= '7' {
162170 continue
163171 }
@@ -176,6 +184,30 @@ func stripANSIBackgrounds(s string) string {
176184 return out.String()
177185 }
178186
187+// extendedColorSpan returns the parameter run that belongs to the extended
188+// color starting at params[i] ("38" or "48"): "5;N" or "2;R;G;B". complete
189+// reports whether the run can be rendered; a truncated run is still returned
190+// so its parameters are consumed instead of being reprocessed as standalone
191+// codes (a bare "5" would mean blink).
192+func extendedColorSpan(params []string, i int) (span []string, complete bool) {
193+ if i+1 >= len(params) {
194+ return params[i : i+1], false
195+ }
196+ switch params[i+1] {
197+ case "5":
198+ if i+2 >= len(params) {
199+ return params[i : i+2], false
200+ }
201+ return params[i : i+3], true
202+ case "2":
203+ if i+5 > len(params) {
204+ return params[i:], false
205+ }
206+ return params[i : i+5], true
207+ }
208+ return params[i : i+1], false
209+}
210+
179211 func chooseLexer(lang string) chroma.Lexer {
180212 if lang == "" {
181213 return nil
@@ -121,6 +121,14 @@ func LanguageFromPath(p string) string {
121 // Chroma's inherited styles can assign black backgrounds to a few tokens121 // Chroma's inherited styles can assign black backgrounds to a few tokens
122 // (notably punctuation/error-ish spans), which looks like random black blocks122 // (notably punctuation/error-ish spans), which looks like random black blocks
123 // inside zot's dark-gray tool boxes. Foreground color is enough for code.123 // inside zot's dark-gray tool boxes. Foreground color is enough for code.
124+//
125+// Extended color parameters ("38;5;N", "38;2;R;G;B" and their "48;..."
126+// background twins) are consumed as whole units. The color index of an
127+// extended foreground is a value, not a standalone ANSI code: stripping a
128+// "45" or "101" out of "\x1b[38;5;45m" leaves the malformed "\x1b[38;5m",
129+// whose leftover "5" terminals read as blink (SGR 5), so the token loses its
130+// color and blinks. A truncated extended color cannot be rendered anyway,
131+// so it is dropped rather than forwarded.
124 func stripANSIBackgrounds(s string) string {132 func stripANSIBackgrounds(s string) string {
125 var out strings.Builder133 var out strings.Builder
126 out.Grow(len(s))134 out.Grow(len(s))
@@ -143,21 +151,21 @@ func stripANSIBackgrounds(s string) string {
143 for p := 0; p < len(params); p++ {151 for p := 0; p < len(params); p++ {
144 param := params[p]152 param := params[p]
145 switch param {153 switch param {
146- case "48":154+ case "38", "48":
147- // 48;5;N or 48;2;R;G;B background color.155+ span, complete := extendedColorSpan(params, p)
148- if p+1 < len(params) && params[p+1] == "5" {156+ if complete && param == "38" {
149- p += 2157+ kept = append(kept, span...)
150- continue
151- }
152- if p+1 < len(params) && params[p+1] == "2" {
153- p += 4
154- continue
155 }158 }
159+ // Consume the whole unit either way: a truncated
160+ // "38;5" must not leave its "5" to be read as blink.
161+ p += len(span) - 1
156 continue162 continue
157 case "49":163 case "49":
158 continue164 continue
159 }165 }
160- // 40-47 and 100-107 are ANSI background colors.166+ // 40-47 and 100-107 are ANSI background colors. Bare codes only:
167+ // extended colors were consumed above, so a color index in those
168+ // ranges cannot be mistaken for one here.
161 if len(param) == 2 && param[0] == '4' && param[1] >= '0' && param[1] <= '7' {169 if len(param) == 2 && param[0] == '4' && param[1] >= '0' && param[1] <= '7' {
162 continue170 continue
163 }171 }
@@ -176,6 +184,30 @@ func stripANSIBackgrounds(s string) string {
176 return out.String()184 return out.String()
177 }185 }
178 186
187+// extendedColorSpan returns the parameter run that belongs to the extended
188+// color starting at params[i] ("38" or "48"): "5;N" or "2;R;G;B". complete
189+// reports whether the run can be rendered; a truncated run is still returned
190+// so its parameters are consumed instead of being reprocessed as standalone
191+// codes (a bare "5" would mean blink).
192+func extendedColorSpan(params []string, i int) (span []string, complete bool) {
193+ if i+1 >= len(params) {
194+ return params[i : i+1], false
195+ }
196+ switch params[i+1] {
197+ case "5":
198+ if i+2 >= len(params) {
199+ return params[i : i+2], false
200+ }
201+ return params[i : i+3], true
202+ case "2":
203+ if i+5 > len(params) {
204+ return params[i:], false
205+ }
206+ return params[i : i+5], true
207+ }
208+ return params[i : i+1], false
209+}
210+
179 func chooseLexer(lang string) chroma.Lexer {211 func chooseLexer(lang string) chroma.Lexer {
180 if lang == "" {212 if lang == "" {
181 return nil213 return nil
A packages/tui/highlight_test.go +149 -0
@@ -0,0 +1,149 @@
1+package tui
2+
3+import (
4+ "regexp"
5+ "strings"
6+ "testing"
7+)
8+
9+// The stripper must treat "38;5;N" / "38;2;R;G;B" as one unit. Pulling the
10+// color index out on its own (when it happens to look like an ANSI
11+// background code, e.g. 45, 48, 49 or 101) leaves "\x1b[38;5m", whose leftover
12+// "5" terminals read as blink, so the token loses its color and blinks.
13+func TestStripANSIBackgroundsKeepsExtendedColors(t *testing.T) {
14+ cases := []struct{ name, in, want string }{
15+ {"256 fg in background range", "\x1b[38;5;45mstring\x1b[0m", "\x1b[38;5;45mstring\x1b[0m"},
16+ {"256 fg index 48", "\x1b[38;5;48mx\x1b[0m", "\x1b[38;5;48mx\x1b[0m"},
17+ {"256 fg index 49", "\x1b[38;5;49mx\x1b[0m", "\x1b[38;5;49mx\x1b[0m"},
18+ {"256 fg bright range", "\x1b[38;5;101mcomment\x1b[0m", "\x1b[38;5;101mcomment\x1b[0m"},
19+ {"256 fg index 107", "\x1b[38;5;107mx\x1b[0m", "\x1b[38;5;107mx\x1b[0m"},
20+ {"256 fg index 41", "\x1b[38;5;41mx\x1b[0m", "\x1b[38;5;41mx\x1b[0m"},
21+ {"bold plus 256 fg", "\x1b[1;38;5;45mstring\x1b[0m", "\x1b[1;38;5;45mstring\x1b[0m"},
22+ {"truecolor fg", "\x1b[38;2;0;229;255mstring\x1b[0m", "\x1b[38;2;0;229;255mstring\x1b[0m"},
23+ {"plain text", "hello", "hello"},
24+ {"reset", "\x1b[0m", "\x1b[0m"},
25+
26+ {"256 bg dropped", "\x1b[48;5;45mbg\x1b[0m", "bg\x1b[0m"},
27+ {"256 bg dropped, fg kept", "\x1b[38;5;45m\x1b[48;5;0mtext", "\x1b[38;5;45mtext"},
28+ {"truecolor bg dropped", "\x1b[48;2;9;0;21mbg\x1b[0m", "bg\x1b[0m"},
29+ {"default bg dropped", "\x1b[49mbg", "bg"},
30+ {"ansi bg 41 dropped", "\x1b[41mbg", "bg"},
31+ {"ansi bg 101 dropped", "\x1b[101mbg", "bg"},
32+ {"truncated fg dropped", "\x1b[38;5mstring", "string"},
33+ {"truncated bg dropped", "\x1b[48;5mstring", "string"},
34+ {"truncated fg inside row", "\x1b[1m\x1b[38;5;109mfunc\x1b[0m\x1b[38;5m(", "\x1b[1m\x1b[38;5;109mfunc\x1b[0m("},
35+ }
36+ for _, c := range cases {
37+ if got := stripANSIBackgrounds(c.in); got != c.want {
38+ t.Errorf("%s:\n in %q\n got %q\n want %q", c.name, c.in, got, c.want)
39+ }
40+ }
41+}
42+
43+// incompleteExtendedColor returns the first SGR sequence in s whose extended
44+// color introducer ("38" or "48") is missing part of its parameter run, for
45+// example "\x1b[38;5m", which terminals read as a color-less SGR 38 followed
46+// by SGR 5 (blink). Validation here is independent of the production helper.
47+func incompleteExtendedColor(s string) string {
48+ numeric := func(p string) bool {
49+ if p == "" {
50+ return false
51+ }
52+ for _, r := range p {
53+ if r < '0' || r > '9' {
54+ return false
55+ }
56+ }
57+ return true
58+ }
59+ for i := 0; i < len(s); {
60+ if s[i] != 0x1b || i+1 >= len(s) || s[i+1] != '[' {
61+ i++
62+ continue
63+ }
64+ j := i + 2
65+ for j < len(s) && !(s[j] >= 0x40 && s[j] <= 0x7e) {
66+ j++
67+ }
68+ if j >= len(s) {
69+ return s[i:]
70+ }
71+ if s[j] == 'm' {
72+ params := strings.Split(s[i+2:j], ";")
73+ for p := 0; p < len(params); p++ {
74+ if params[p] != "38" && params[p] != "48" {
75+ continue
76+ }
77+ need := 0
78+ switch {
79+ case p+1 < len(params) && params[p+1] == "5":
80+ need = 2
81+ case p+1 < len(params) && params[p+1] == "2":
82+ need = 4
83+ default:
84+ return s[i : j+1]
85+ }
86+ if p+need >= len(params) || !numeric(params[p+2]) {
87+ return s[i : j+1]
88+ }
89+ if need == 4 {
90+ for k := p + 2; k <= p+4 && k < len(params); k++ {
91+ if !numeric(params[k]) {
92+ return s[i : j+1]
93+ }
94+ }
95+ }
96+ p += need
97+ }
98+ }
99+ i = j + 1
100+ }
101+ return ""
102+}
103+
104+// A theme color that chroma maps to xterm index 45 ("#00e5ff") must survive
105+// highlighting with a renderable sequence: a complete "\x1b[38;5;45m", never
106+// the malformed "\x1b[38;5m".
107+func TestHighlightCodeExtendedColorIsWellFormed(t *testing.T) {
108+ th := Dark
109+ th.Syntax = SyntaxTheme{
110+ KeywordType: "#00e5ff",
111+ NameBuiltin: "#00e5ff",
112+ }
113+ rows := th.HighlightCode("func splitFrontmatter(raw string) (string, string) {\n", "go")
114+ joined := strings.Join(rows, "\n")
115+ if strings.Contains(joined, "\x1b[38;5m") || strings.Contains(joined, "\x1b[48;5m") {
116+ t.Fatalf("highlighting emitted a malformed extended color: %q", joined)
117+ }
118+ if bad := incompleteExtendedColor(joined); bad != "" {
119+ t.Fatalf("highlighting emitted an incomplete extended color %q: %q", bad, joined)
120+ }
121+ // The type keyword keeps a full 256-color foreground.
122+ idx := strings.Index(joined, "string")
123+ if idx < 0 {
124+ t.Fatalf("type keyword missing from highlighted output: %q", joined)
125+ }
126+ prefix := joined[:idx]
127+ esc := prefix[strings.LastIndex(prefix, "\x1b["):]
128+ if !regexp.MustCompile(`^\x1b\[(?:[0-9]+;)*38;5;[0-9]+m$`).MatchString(esc) {
129+ t.Fatalf("type keyword lost its color, got %q in %q", esc, joined)
130+ }
131+}
132+
133+// Every syntax color in the built-in palettes must come out of the
134+// highlighting path as a complete SGR sequence.
135+func TestHighlightCodeAllPalettesWellFormed(t *testing.T) {
136+ samples := map[string]string{
137+ "go": "package main\n\n// note\nfunc main() { s := \"x\"; _ = len(s) }\n",
138+ "python": "def f(x: int) -> str:\n # note\n return str(x)\n",
139+ "markdown": "# Title\n\nSome *emphasis* and **bold** and `code`.\n",
140+ }
141+ for _, th := range []Theme{Dark, Light} {
142+ for lang, src := range samples {
143+ joined := strings.Join(th.HighlightCode(src, lang), "\n")
144+ if bad := incompleteExtendedColor(joined); bad != "" {
145+ t.Errorf("%s emitted an incomplete extended color %q: %q", lang, bad, joined)
146+ }
147+ }
148+ }
149+}
@@ -0,0 +1,149 @@
1+package tui
2+
3+import (
4+ "regexp"
5+ "strings"
6+ "testing"
7+)
8+
9+// The stripper must treat "38;5;N" / "38;2;R;G;B" as one unit. Pulling the
10+// color index out on its own (when it happens to look like an ANSI
11+// background code, e.g. 45, 48, 49 or 101) leaves "\x1b[38;5m", whose leftover
12+// "5" terminals read as blink, so the token loses its color and blinks.
13+func TestStripANSIBackgroundsKeepsExtendedColors(t *testing.T) {
14+ cases := []struct{ name, in, want string }{
15+ {"256 fg in background range", "\x1b[38;5;45mstring\x1b[0m", "\x1b[38;5;45mstring\x1b[0m"},
16+ {"256 fg index 48", "\x1b[38;5;48mx\x1b[0m", "\x1b[38;5;48mx\x1b[0m"},
17+ {"256 fg index 49", "\x1b[38;5;49mx\x1b[0m", "\x1b[38;5;49mx\x1b[0m"},
18+ {"256 fg bright range", "\x1b[38;5;101mcomment\x1b[0m", "\x1b[38;5;101mcomment\x1b[0m"},
19+ {"256 fg index 107", "\x1b[38;5;107mx\x1b[0m", "\x1b[38;5;107mx\x1b[0m"},
20+ {"256 fg index 41", "\x1b[38;5;41mx\x1b[0m", "\x1b[38;5;41mx\x1b[0m"},
21+ {"bold plus 256 fg", "\x1b[1;38;5;45mstring\x1b[0m", "\x1b[1;38;5;45mstring\x1b[0m"},
22+ {"truecolor fg", "\x1b[38;2;0;229;255mstring\x1b[0m", "\x1b[38;2;0;229;255mstring\x1b[0m"},
23+ {"plain text", "hello", "hello"},
24+ {"reset", "\x1b[0m", "\x1b[0m"},
25+
26+ {"256 bg dropped", "\x1b[48;5;45mbg\x1b[0m", "bg\x1b[0m"},
27+ {"256 bg dropped, fg kept", "\x1b[38;5;45m\x1b[48;5;0mtext", "\x1b[38;5;45mtext"},
28+ {"truecolor bg dropped", "\x1b[48;2;9;0;21mbg\x1b[0m", "bg\x1b[0m"},
29+ {"default bg dropped", "\x1b[49mbg", "bg"},
30+ {"ansi bg 41 dropped", "\x1b[41mbg", "bg"},
31+ {"ansi bg 101 dropped", "\x1b[101mbg", "bg"},
32+ {"truncated fg dropped", "\x1b[38;5mstring", "string"},
33+ {"truncated bg dropped", "\x1b[48;5mstring", "string"},
34+ {"truncated fg inside row", "\x1b[1m\x1b[38;5;109mfunc\x1b[0m\x1b[38;5m(", "\x1b[1m\x1b[38;5;109mfunc\x1b[0m("},
35+ }
36+ for _, c := range cases {
37+ if got := stripANSIBackgrounds(c.in); got != c.want {
38+ t.Errorf("%s:\n in %q\n got %q\n want %q", c.name, c.in, got, c.want)
39+ }
40+ }
41+}
42+
43+// incompleteExtendedColor returns the first SGR sequence in s whose extended
44+// color introducer ("38" or "48") is missing part of its parameter run, for
45+// example "\x1b[38;5m", which terminals read as a color-less SGR 38 followed
46+// by SGR 5 (blink). Validation here is independent of the production helper.
47+func incompleteExtendedColor(s string) string {
48+ numeric := func(p string) bool {
49+ if p == "" {
50+ return false
51+ }
52+ for _, r := range p {
53+ if r < '0' || r > '9' {
54+ return false
55+ }
56+ }
57+ return true
58+ }
59+ for i := 0; i < len(s); {
60+ if s[i] != 0x1b || i+1 >= len(s) || s[i+1] != '[' {
61+ i++
62+ continue
63+ }
64+ j := i + 2
65+ for j < len(s) && !(s[j] >= 0x40 && s[j] <= 0x7e) {
66+ j++
67+ }
68+ if j >= len(s) {
69+ return s[i:]
70+ }
71+ if s[j] == 'm' {
72+ params := strings.Split(s[i+2:j], ";")
73+ for p := 0; p < len(params); p++ {
74+ if params[p] != "38" && params[p] != "48" {
75+ continue
76+ }
77+ need := 0
78+ switch {
79+ case p+1 < len(params) && params[p+1] == "5":
80+ need = 2
81+ case p+1 < len(params) && params[p+1] == "2":
82+ need = 4
83+ default:
84+ return s[i : j+1]
85+ }
86+ if p+need >= len(params) || !numeric(params[p+2]) {
87+ return s[i : j+1]
88+ }
89+ if need == 4 {
90+ for k := p + 2; k <= p+4 && k < len(params); k++ {
91+ if !numeric(params[k]) {
92+ return s[i : j+1]
93+ }
94+ }
95+ }
96+ p += need
97+ }
98+ }
99+ i = j + 1
100+ }
101+ return ""
102+}
103+
104+// A theme color that chroma maps to xterm index 45 ("#00e5ff") must survive
105+// highlighting with a renderable sequence: a complete "\x1b[38;5;45m", never
106+// the malformed "\x1b[38;5m".
107+func TestHighlightCodeExtendedColorIsWellFormed(t *testing.T) {
108+ th := Dark
109+ th.Syntax = SyntaxTheme{
110+ KeywordType: "#00e5ff",
111+ NameBuiltin: "#00e5ff",
112+ }
113+ rows := th.HighlightCode("func splitFrontmatter(raw string) (string, string) {\n", "go")
114+ joined := strings.Join(rows, "\n")
115+ if strings.Contains(joined, "\x1b[38;5m") || strings.Contains(joined, "\x1b[48;5m") {
116+ t.Fatalf("highlighting emitted a malformed extended color: %q", joined)
117+ }
118+ if bad := incompleteExtendedColor(joined); bad != "" {
119+ t.Fatalf("highlighting emitted an incomplete extended color %q: %q", bad, joined)
120+ }
121+ // The type keyword keeps a full 256-color foreground.
122+ idx := strings.Index(joined, "string")
123+ if idx < 0 {
124+ t.Fatalf("type keyword missing from highlighted output: %q", joined)
125+ }
126+ prefix := joined[:idx]
127+ esc := prefix[strings.LastIndex(prefix, "\x1b["):]
128+ if !regexp.MustCompile(`^\x1b\[(?:[0-9]+;)*38;5;[0-9]+m$`).MatchString(esc) {
129+ t.Fatalf("type keyword lost its color, got %q in %q", esc, joined)
130+ }
131+}
132+
133+// Every syntax color in the built-in palettes must come out of the
134+// highlighting path as a complete SGR sequence.
135+func TestHighlightCodeAllPalettesWellFormed(t *testing.T) {
136+ samples := map[string]string{
137+ "go": "package main\n\n// note\nfunc main() { s := \"x\"; _ = len(s) }\n",
138+ "python": "def f(x: int) -> str:\n # note\n return str(x)\n",
139+ "markdown": "# Title\n\nSome *emphasis* and **bold** and `code`.\n",
140+ }
141+ for _, th := range []Theme{Dark, Light} {
142+ for lang, src := range samples {
143+ joined := strings.Join(th.HighlightCode(src, lang), "\n")
144+ if bad := incompleteExtendedColor(joined); bad != "" {
145+ t.Errorf("%s emitted an incomplete extended color %q: %q", lang, bad, joined)
146+ }
147+ }
148+ }
149+}

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