util.parse_URI: more granular exceptions

related: #5376

first report in #5376 was generated with these changes;
before, the exception was caught and a toast displayed "Not a Bitcoin URI"

electrum/gui/kivy/main_window.py

@@ -454,6 +454,8 @@ class ElectrumWindow(App):
                     String = autoclass("java.lang.String")
                     contents = intent.getStringExtra(String("text"))
                     on_complete(contents)
+            except Exception as e:  # exc would otherwise get lost
+                send_exception_to_crash_reporter(e)
             finally:
                 activity.unbind(on_activity_result=on_qr_result)
         activity.bind(on_activity_result=on_qr_result)

electrum/gui/kivy/uix/screens.py

@@ -21,7 +21,7 @@ from kivy.utils import platform
 from electrum.util import profiler, parse_URI, format_time, InvalidPassword, NotEnoughFunds, Fiat
 from electrum import bitcoin
 from electrum.transaction import TxOutput
-from electrum.util import send_exception_to_crash_reporter
+from electrum.util import send_exception_to_crash_reporter, parse_URI, InvalidBitcoinURI
 from electrum.paymentrequest import PR_UNPAID, PR_PAID, PR_UNKNOWN, PR_EXPIRED
 from electrum.plugin import run_hook
 from electrum.wallet import InternalAddressCorruption
@@ -174,11 +174,10 @@ class SendScreen(CScreen):
         if not self.app.wallet:
             self.payment_request_queued = text
             return
-        import electrum
         try:
-            uri = electrum.util.parse_URI(text, self.app.on_pr)
-        except:
-            self.app.show_info(_("Not a Bitcoin URI"))
+            uri = parse_URI(text, self.app.on_pr)
+        except InvalidBitcoinURI as e:
+            self.app.show_info(_("Error parsing URI") + f":\n{e}")
             return
         amount = uri.get('amount')
         self.screen.address = uri.get('address', '')

electrum/gui/qt/main_window.py

@@ -60,7 +60,8 @@ from electrum.util import (format_time, format_satoshis, format_fee_satoshis,
                            base_units, base_units_list, base_unit_name_to_decimal_point,
                            decimal_point_to_base_unit_name, quantize_feerate,
                            UnknownBaseUnit, DECIMAL_POINT_DEFAULT, UserFacingException,
-                           get_new_wallet_name, send_exception_to_crash_reporter)
+                           get_new_wallet_name, send_exception_to_crash_reporter,
+                           InvalidBitcoinURI)
 from electrum.transaction import Transaction, TxOutput
 from electrum.address_synchronizer import AddTransactionException
 from electrum.wallet import (Multisig_Wallet, CannotBumpFee, Abstract_Wallet,
@@ -1844,8 +1845,8 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
             return
         try:
             out = util.parse_URI(URI, self.on_pr)
-        except BaseException as e:
-            self.show_error(_('Invalid bitcoin URI:') + '\n' + str(e))
+        except InvalidBitcoinURI as e:
+            self.show_error(_("Error parsing URI") + f":\n{e}")
             return
         self.show_send_tab()
         r = out.get('r')

electrum/util.py

@@ -720,18 +720,25 @@ def block_explorer_URL(config: 'SimpleConfig', kind: str, item: str) -> Optional
 #_ud = re.compile('%([0-9a-hA-H]{2})', re.MULTILINE)
 #urldecode = lambda x: _ud.sub(lambda m: chr(int(m.group(1), 16)), x)
 
-def parse_URI(uri: str, on_pr: Callable=None) -> dict:
+class InvalidBitcoinURI(Exception): pass
+
+
+def parse_URI(uri: str, on_pr: Callable = None, *, loop=None) -> dict:
+    """Raises InvalidBitcoinURI on malformed URI."""
     from . import bitcoin
     from .bitcoin import COIN
 
+    if not isinstance(uri, str):
+        raise InvalidBitcoinURI(f"expected string, not {repr(uri)}")
+
     if ':' not in uri:
         if not bitcoin.is_address(uri):
-            raise Exception("Not a bitcoin address")
+            raise InvalidBitcoinURI("Not a bitcoin address")
         return {'address': uri}
 
     u = urllib.parse.urlparse(uri)
     if u.scheme != 'bitcoin':
-        raise Exception("Not a bitcoin URI")
+        raise InvalidBitcoinURI("Not a bitcoin URI")
     address = u.path
 
     # python for android fails to parse query
@@ -742,32 +749,44 @@ def parse_URI(uri: str, on_pr: Callable=None) -> dict:
         pq = urllib.parse.parse_qs(u.query)
 
     for k, v in pq.items():
-        if len(v)!=1:
-            raise Exception('Duplicate Key', k)
+        if len(v) != 1:
+            raise InvalidBitcoinURI(f'Duplicate Key: {repr(k)}')
 
     out = {k: v[0] for k, v in pq.items()}
     if address:
         if not bitcoin.is_address(address):
-            raise Exception("Invalid bitcoin address:" + address)
+            raise InvalidBitcoinURI(f"Invalid bitcoin address: {address}")
         out['address'] = address
     if 'amount' in out:
         am = out['amount']
-        m = re.match(r'([0-9.]+)X([0-9])', am)
-        if m:
-            k = int(m.group(2)) - 8
-            amount = Decimal(m.group(1)) * pow(  Decimal(10) , k)
-        else:
-            amount = Decimal(am) * COIN
-        out['amount'] = int(amount)
+        try:
+            m = re.match(r'([0-9.]+)X([0-9])', am)
+            if m:
+                k = int(m.group(2)) - 8
+                amount = Decimal(m.group(1)) * pow(  Decimal(10) , k)
+            else:
+                amount = Decimal(am) * COIN
+            out['amount'] = int(amount)
+        except Exception as e:
+            raise InvalidBitcoinURI(f"failed to parse 'amount' field: {repr(e)}") from e
     if 'message' in out:
         out['message'] = out['message']
         out['memo'] = out['message']
     if 'time' in out:
-        out['time'] = int(out['time'])
+        try:
+            out['time'] = int(out['time'])
+        except Exception as e:
+            raise InvalidBitcoinURI(f"failed to parse 'time' field: {repr(e)}") from e
     if 'exp' in out:
-        out['exp'] = int(out['exp'])
+        try:
+            out['exp'] = int(out['exp'])
+        except Exception as e:
+            raise InvalidBitcoinURI(f"failed to parse 'exp' field: {repr(e)}") from e
     if 'sig' in out:
-        out['sig'] = bh2u(bitcoin.base_decode(out['sig'], None, base=58))
+        try:
+            out['sig'] = bh2u(bitcoin.base_decode(out['sig'], None, base=58))
+        except Exception as e:
+            raise InvalidBitcoinURI(f"failed to parse 'sig' field: {repr(e)}") from e
 
     r = out.get('r')
     sig = out.get('sig')
@@ -782,7 +801,7 @@ def parse_URI(uri: str, on_pr: Callable=None) -> dict:
                 request = await pr.get_payment_request(r)
             if on_pr:
                 on_pr(request)
-        loop = asyncio.get_event_loop()
+        loop = loop or asyncio.get_event_loop()
         asyncio.run_coroutine_threadsafe(get_payment_request(), loop)
 
     return out