move OP_RETURN ux rendition from chains to render_output

shared/auth.py

@@ -298,12 +298,26 @@ class ApproveTransaction(UserAuthorizedAction):
 
         # check for OP_RETURN
         data = self.chain.op_return(o.scriptPubKey)
-        if data:
-            data_hex, data_ascii = data
-            to_ret = '%s\n - OP_RETURN -\n%s' % (val, data_hex)
-            if data_ascii:
-                to_ret += " (ascii: %s)" % data_ascii
-            return to_ret + "\n", data_hex
+        if data is not None:
+            base = '%s\n - OP_RETURN -\n%s'
+            if not data:
+                return base % (val, "null-data\n"), ""
+            else:
+                data_ascii = None
+                if len(data) > 200:
+                    # completely arbitrary limit, prevents huge stories
+                    data_hex = b2a_hex(data[:100]).decode() + "\n ⋯\n" + b2a_hex(data[-100:]).decode()
+                else:
+                    data_hex = b2a_hex(data).decode()
+                    if (min(data) >= 32) and (max(data) < 127):  # printable & not huge
+                        try:
+                            data_ascii = data.decode("ascii")
+                        except: pass
+
+                to_ret = base % (val, data_hex)
+                if data_ascii:
+                    to_ret += " (ascii: %s)" % data_ascii
+                return to_ret + "\n", data_hex
 
         # Handle future things better: allow them to happen at least.
         dest = B2A(o.scriptPubKey)

shared/chains.py

@@ -258,21 +258,12 @@ class ChainsBase:
 
         try:
             data = next(gen)[0]
-            if data is None: raise RuntimeError
-        except (RuntimeError, StopIteration):
-            return "null-data", ""
+            if data:
+                return data
+        except StopIteration:
+            pass
 
-        data_ascii = None
-        if len(data) > 200:
-            # completely arbitrary limit, prevents huge stories
-            data_hex = b2a_hex(data[:100]).decode() + "\n ⋯\n" + b2a_hex(data[-100:]).decode()
-        else:
-            data_hex = b2a_hex(data).decode()
-            if min(data) >= 32 and max(data) < 127:  # printable
-                try:
-                    data_ascii = data.decode("ascii")
-                except: pass
-        return data_hex, data_ascii
+        return b""
 
     @classmethod
     def possible_address_fmt(cls, addr):

testing/test_sign.py

@@ -3038,9 +3038,11 @@ def test_txout_explorer(chain, data, fake_txn, start_sign, settings_set, txout_e
 @pytest.mark.parametrize("data", [
     [(1, b"Coinkite"), (0, b"Mk1 Mk2 Mk3 Mk4 Q"), (100, b"binarywatch.org"), (100, b"a" * 75)],
     [(0, b"a" * 300), (10, b"x" * 1000), (0, b"anchor output")],
+    [(0, b""), (10, b"")],
 ])
 def test_txout_explorer_op_return(finalize, data, fake_txn, start_sign, cap_story, is_q1,
-                                  need_keypress, press_cancel, press_select, end_sign):
+                                  need_keypress, press_cancel, press_select, end_sign,
+                                  cap_screen_qr):
     psbt = fake_txn(1, 20, segwit_in=False, op_return=data)
     start_sign(psbt, finalize=finalize)
     time.sleep(.1)
@@ -3073,7 +3075,7 @@ def test_txout_explorer_op_return(finalize, data, fake_txn, start_sign, cap_stor
     need_keypress(KEY_QR if is_q1 else "4")
     qr_list = []
     for _ in range(len(data)):
-        qr = cap_screen_qr().decode('ascii')
+        qr = cap_screen_qr().decode()
         qr_list.append(qr)
         need_keypress(KEY_RIGHT if is_q1 else "9")
         time.sleep(.5)
@@ -3089,14 +3091,21 @@ def test_txout_explorer_op_return(finalize, data, fake_txn, start_sign, cap_stor
             val, name, dd0, _, dd1 = sb.split("\n")
         assert "OP_RETURN" in name
         assert f'{amount / 100000000:.8f} XTN' == val
-        if dd:
+        if dd == "null-data":
+            assert qr_list[i - 20] == ""
+        elif dd:
             hex_str, ascii_str = dd.split(" ", 1)
             assert hex_str == qr_list[i-20]
             assert f"(ascii: {data.decode()})" == ascii_str
             assert data.hex() == hex_str
         else:
-            assert data.hex()[:200] == dd0
-            assert data.hex()[-200:] == dd1
+            s = data[:100].hex()
+            e = data[-100:].hex()
+            assert s == dd0
+            assert e == dd1
+            qr = qr_list[i - 20]
+            assert qr.startswith(s)
+            assert qr.endswith(e)
 
     press_cancel()  # exit txn out explorer
     end_sign(finalize=finalize)