From 8d8d1dba0f204a42451741c7e7d937f76bb455ca Mon Sep 17 00:00:00 2001
From: SomberNight <somber.night@protonmail.com>
Date: Fri, 22 Aug 2025 13:30:26 +0000
Subject: [PATCH] util.format_satoshis: floating-point paranoia

---
 electrum/commands.py   |  2 +-
 electrum/util.py       | 10 ++++++++--
 electrum/wallet.py     |  2 +-
 tests/test_commands.py |  1 +
 4 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/electrum/commands.py b/electrum/commands.py
index 5b1688c43..a886197a4 100644
--- a/electrum/commands.py
+++ b/electrum/commands.py
@@ -101,7 +101,7 @@ def satoshis(amount):
     return int(COIN*to_decimal(amount)) if amount is not None else None
 
 
-def format_satoshis(x: Union[str, float, int, Decimal, None]) -> Optional[str]:
+def format_satoshis(x: Union[float, int, Decimal, None]) -> Optional[str]:
     """
     input: satoshis as a Number
     output: str formatted as bitcoin amount
diff --git a/electrum/util.py b/electrum/util.py
index 915f7ce21..0a57b68a2 100644
--- a/electrum/util.py
+++ b/electrum/util.py
@@ -234,6 +234,8 @@ def to_decimal(x: Union[str, float, int, Decimal]) -> Decimal:
     #   Decimal('41754.681')
     if isinstance(x, Decimal):
         return x
+    if isinstance(x, int):
+        return Decimal(x)
     return Decimal(str(x))
 
 
@@ -800,8 +802,10 @@ def format_satoshis_plain(
     if is_max_allowed and parse_max_spend(x):
         return f'max({x})'
     assert isinstance(x, (int, float, Decimal)), f"{x!r} should be a number"
+    # TODO(ghost43) just hard-fail if x is a float. do we even use floats for money anywhere?
+    x = to_decimal(x)
     scale_factor = pow(10, decimal_point)
-    return "{:.8f}".format(Decimal(x) / scale_factor).rstrip('0').rstrip('.')
+    return "{:.8f}".format(x / scale_factor).rstrip('0').rstrip('.')
 
 
 # Check that Decimal precision is sufficient.
@@ -833,8 +837,10 @@ def format_satoshis(
     if parse_max_spend(x):
         return f'max({x})'
     assert isinstance(x, (int, float, Decimal)), f"{x!r} should be a number"
+    # TODO(ghost43) just hard-fail if x is a float. do we even use floats for money anywhere?
+    x = to_decimal(x)
     # lose redundant precision
-    x = Decimal(x).quantize(Decimal(10) ** (-precision))
+    x = x.quantize(Decimal(10) ** (-precision))
     # format string
     overall_precision = decimal_point + precision  # max digits after final decimal point
     decimal_format = "." + str(overall_precision) if overall_precision > 0 else ""
diff --git a/electrum/wallet.py b/electrum/wallet.py
index 894c3a963..e28778abd 100644
--- a/electrum/wallet.py
+++ b/electrum/wallet.py
@@ -1759,7 +1759,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
             fee = self.adb.get_tx_fee(tx_hash)
             if fee is not None:
                 size = tx.estimated_size()
-                fee_per_byte = fee / size
+                fee_per_byte = Decimal(fee) / size
                 extra.append(format_fee_satoshis(fee_per_byte) + f" {util.UI_UNIT_NAME_FEERATE_SAT_PER_VB}")
             if fee is not None and height in (TX_HEIGHT_UNCONF_PARENT, TX_HEIGHT_UNCONFIRMED) \
                and self.network and self.network.has_fee_mempool():
diff --git a/tests/test_commands.py b/tests/test_commands.py
index 2d88431be..f1169ec40 100644
--- a/tests/test_commands.py
+++ b/tests/test_commands.py
@@ -185,6 +185,7 @@ class TestCommands(ElectrumTestCase):
         self.assertEqual(format_satoshis(Decimal(123.456)), "0.00000123")
         self.assertEqual(format_satoshis(Decimal(123.5)), "0.00000124")
         self.assertEqual(format_satoshis(Decimal(123.789)), "0.00000124")
+        self.assertEqual(format_satoshis(41754.681), "0.00041755")
 
 
 class TestCommandsTestnet(ElectrumTestCase):