test(tui-selection): freeze the OSC 52 capability-detection law (#2532 )

The drag-select + auto-copy behavior shipped in 1ea093ad, but its detection seam — the wireOSC52Detection law the real main() installs — had no coverage: the degrade was only asserted through the injectable osc52Allowed gate. This freezes the honest-degrade contract: known non-carrier terminals (dumb et al.) and emacs shells highlight without copying, a modern carrier copies, and the explicit RUNE_NO_OSC52 opt-out wins over detection.
2026-10-24 22:42:59 +01:00
1 changed files with 38 additions and 0 deletions
@@ -196,3 +196,41 @@ func TestMotionRoutesThroughShell(t *testing.T) {
 		t.Fatal("the release must finish the selection")
 	}
 }
+
+// The capability-detection law itself (the wireOSC52Detection seam the
+// real main() installs): known non-carrier terminals and the explicit
+// RUNE_NO_OSC52 opt-out degrade to highlight-only; a modern carrier
+// copies.
+func TestOSC52DetectionDegradesHonestly(t *testing.T) {
+	term := os.Getenv("TERM")
+	noosc := os.Getenv("RUNE_NO_OSC52")
+	emacs := os.Getenv("INSIDE_EMACS")
+	t.Setenv("RUNE_NO_OSC52", "")
+	t.Setenv("INSIDE_EMACS", "")
+	defer func() {
+		os.Setenv("TERM", term)
+		os.Setenv("RUNE_NO_OSC52", noosc)
+		os.Setenv("INSIDE_EMACS", emacs)
+	}()
+
+	wireOSC52Detection()
+	defer func() { osc52Allowed = func() bool { return false } }()
+
+	t.Setenv("TERM", "dumb")
+	if osc52Allowed() {
+		t.Fatal("a known non-carrier (dumb) must degrade to highlight-only")
+	}
+	t.Setenv("TERM", "xterm-256color")
+	if !osc52Allowed() {
+		t.Fatal("a modern carrier terminal must be allowed to copy")
+	}
+	t.Setenv("RUNE_NO_OSC52", "1")
+	if osc52Allowed() {
+		t.Fatal("the explicit RUNE_NO_OSC52 opt-out must win over detection")
+	}
+	t.Setenv("RUNE_NO_OSC52", "")
+	t.Setenv("INSIDE_EMACS", "t")
+	if osc52Allowed() {
+		t.Fatal("an emacs shell must degrade to highlight-only")
+	}
+}