feat(format): case_collapse uses line_width via Doc-IR

pkg/format/dml_test.go

@@ -632,3 +632,18 @@ func TestWhereWhenLong(t *testing.T) {
 		t.Errorf("broken when_long should equal always:\n%s\n---\n%s", long, want)
 	}
 }
+
+func TestDMLCaseCollapseUsesLineWidth(t *testing.T) {
+	st := config.Default()
+	st.CaseWhenWrap = true
+	st.CaseCollapse = true
+	src := "select case when a = 1 then 'one' when a = 2 then 'two' else 'other' end from t;"
+	st.LineWidth = 120
+	if got := File(parser.Parse(src), st); strings.Contains(got, "\n  WHEN") {
+		t.Errorf("fits in 120, should collapse:\n%s", got)
+	}
+	st.LineWidth = 30
+	if got := File(parser.Parse(src), st); !strings.Contains(got, "\n  WHEN") {
+		t.Errorf("exceeds 30, should wrap:\n%s", got)
+	}
+}