From a91b713dcec4d17f76155f0cd6b26903c59b9c19 Mon Sep 17 00:00:00 2001
From: Lukasz Kasprzak <lukas@labunix.xyz>
Date: Mon, 14 Sep 2026 22:31:12 +0200
Subject: plan 10: stderr messages cannot be split by quoted newlines; config
 paths escaped; krino new refuses control characters; independent terminal
 oracle

---
 cmd/krino/display_test.go | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

(limited to 'cmd/krino/display_test.go')

diff --git a/cmd/krino/display_test.go b/cmd/krino/display_test.go
index 0f4cf90..a1b199c 100644
--- a/cmd/krino/display_test.go
+++ b/cmd/krino/display_test.go
@@ -6,15 +6,24 @@ import (
 	"fmt"
 	"strings"
 	"testing"
-	"unicode"
 	"unicode/utf8"
 )
 
-// firstUnsafe names the first thing in s a terminal could act on - a
-// control character (a newline too, unless allowNewline), a Unicode
-// bidirectional control, a line or paragraph separator, or invalid UTF-8 -
-// or returns "" when there is none. It is built from Go's Unicode tables,
-// not from display's own ranges, so it can catch a class display misses.
+// terminalRunes is the test's own, hand-written list of code points a
+// terminal acts on or that reorder what it shows: C0 controls, DEL, C1
+// controls, the Unicode bidirectional marks, embeddings, overrides and
+// isolates (UAX #9), and the line and paragraph separators. It is written
+// out, not derived from Go's tables or from display, so it can catch a
+// class display misses (re-review term F3).
+var terminalRunes = [][2]rune{
+	{0x00, 0x1f}, {0x7f, 0x9f},
+	{0x061c, 0x061c}, {0x200e, 0x200f}, {0x202a, 0x202e}, {0x2066, 0x2069},
+	{0x2028, 0x2029},
+}
+
+// firstUnsafe names the first thing in s from terminalRunes (a newline
+// allowed when allowNewline), or invalid UTF-8, or returns "" when there is
+// none.
 func firstUnsafe(s string, allowNewline bool) string {
 	if !utf8.ValidString(s) {
 		return "invalid UTF-8"
@@ -23,8 +32,10 @@ func firstUnsafe(s string, allowNewline bool) string {
 		if r == '\n' && allowNewline {
 			continue
 		}
-		if unicode.IsControl(r) || unicode.Is(unicode.Bidi_Control, r) || unicode.In(r, unicode.Zl, unicode.Zp) {
-			return fmt.Sprintf("%U", r)
+		for _, span := range terminalRunes {
+			if r >= span[0] && r <= span[1] {
+				return fmt.Sprintf("%U", r)
+			}
 		}
 	}
 	return ""
@@ -92,8 +103,8 @@ func TestReviewEscapesHostileNames(t *testing.T) {
 }
 
 // TestSafeWriterEscapesButKeepsNewlines: everything written to stderr goes
-// through display line by line, so a quoted file name cannot act on the
-// terminal while messages keep their lines (review M5).
+// through display, so a quoted file name cannot act on the terminal; each
+// Write keeps its final newline (review M5).
 func TestSafeWriterEscapesButKeepsNewlines(t *testing.T) {
 	var b strings.Builder
 	in := "a\x1b[2J\nb\u202e\n"
@@ -101,7 +112,9 @@ func TestSafeWriterEscapesButKeepsNewlines(t *testing.T) {
 	if err != nil || n != len(in) {
 		t.Fatalf("Write = %d, %v", n, err)
 	}
-	if got, want := b.String(), "a\\x1b[2J\nb\\u202e\n"; got != want {
+	// Only the Write's final newline ends a line; one inside it came from
+	// quoted text and could fake a line of krino's own (re-review term F1).
+	if got, want := b.String(), "a\\x1b[2J\\x0ab\\u202e\n"; got != want {
 		t.Errorf("wrote %q, want %q", got, want)
 	}
 }
-- 
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