Fix section linking and editing

canvas_test.go

@@ -252,3 +252,35 @@ func TestCanvasListedWithIcon(t *testing.T) {
 		t.Error("canvas files do not get the canvas icon")
 	}
 }
+
+func TestCanvasSubpath(t *testing.T) {
+	doc := []byte("# LAN Party 2026\nIntro.\n## Teilnehmer\n| Nr. | Name |\n| --- | --- |\n| 1. | Marci |\n")
+	cases := []struct {
+		subpath, want string
+		ok            bool
+	}{
+		{"", string(doc), true},
+		// The last section of the file runs to its end.
+		{"#teilnehmer", "## Teilnehmer\n| Nr. | Name |\n| --- | --- |\n| 1. | Marci |\n", true},
+		// A heading takes the sections nested under it along.
+		{"#LAN Party 2026", string(doc), true},
+		{"#Gäste", "", false},
+		{"#^block", "", false},
+	}
+	for _, c := range cases {
+		got, ok := canvasSubpath(doc, c.subpath)
+		if ok != c.ok || string(got) != c.want {
+			t.Errorf("canvasSubpath(%q) = %q, %v; want %q, %v", c.subpath, got, ok, c.want, c.ok)
+		}
+	}
+}
+
+func TestSectionSpanEndAtLastSection(t *testing.T) {
+	sections := splitSections([]byte("# A\n## B\ntext\n"))
+	if end := secionSpanEnd(sections, 2); end != 3 {
+		t.Errorf("span of the last section ends at %d, want 3", end)
+	}
+	if end := secionSpanEnd(sections, 1); end != 3 {
+		t.Errorf("span of the top section ends at %d, want 3", end)
+	}
+}