From 63e77f0ce4a11b0e3f4ce8476a74cc6f4b76d52b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bojan=20Poto=C4=8Dnik?= <info@bojanpotocnik.com>
Date: Thu, 22 Apr 2021 13:53:39 +0200
Subject: [PATCH] Add error description to BleakDBusError in addition to error
 name
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Converting BleakDBusError to string now adds detailed description of the
error, which can be very useful for debugging, as more than 12 different
errors are reported under org.bluez.Error.Failed error name.

Instead of
  bleak.exc.BleakDBusError: org.bluez.Error.Failed
one now gets
  bleak.exc.BleakDBusError: org.bluez.Error.Failed (Operation failed
  with ATT error: 0x0e = Connection Rejected Due To Security Reasons)

Some details are less useful, as example
  bleak.exc.BleakDBusError: org.bluez.Error.AuthenticationFailed
becomes
  bleak.exc.BleakDBusError: org.bluez.Error.AuthenticationFailed
  (Authentication Failed)

But looking at more possible error codes and their details (majority
from BlueZ sources gdbus/object.c and src/gatt-client.c), it becomes
clear that additional description of error can be very useful:
  org.freedesktop.DBus.Error.InvalidArgs
  org.freedesktop.DBus.Error.UnknownProperty
    No such interface '%s'
    No such property '%s'
    Invalid signature for '%s'
    Invalid argument type: '%c'
    Property '%s' is not readable
    Property '%s' is not writable
    No arguments given
  org.bluez.Error.Failed
    `strerror(-err)`
    Connect failed
    Not connected
    Invalid UUID
    Operation failed with ATT error: 0x%02x
    Failed to initiate write
    ... and many more

Signed-off-by: Bojan Potočnik <info@bojanpotocnik.com>
---
 CHANGELOG.rst                     |  1 +
 bleak/backends/bluezdbus/utils.py |  2 +-
 bleak/exc.py                      | 25 +++++++++++++++++++++++--
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index d5ea4138..50d8fc9e 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -23,6 +23,7 @@ Changed
 * Added ``Programming Language :: Python :: 3.9`` classifier in ``setup.py``
 * Deprecated ``BleakScanner.get_discovered_devices()`` async method.
 * Added capability to handle async functions as detection callbacks in ``BleakScanner``.
+* Added error description in addition to error name when ``BleakDBusError`` is converted to string
 
 Fixed
 ~~~~~
diff --git a/bleak/backends/bluezdbus/utils.py b/bleak/backends/bluezdbus/utils.py
index 537ef172..a4db0126 100644
--- a/bleak/backends/bluezdbus/utils.py
+++ b/bleak/backends/bluezdbus/utils.py
@@ -20,7 +20,7 @@ def assert_reply(reply: Message):
         AssentationError: if the message type is not ``MessageType.METHOD_RETURN``
     """
     if reply.message_type == MessageType.ERROR:
-        raise BleakDBusError(reply.error_name)
+        raise BleakDBusError(reply.error_name, reply.body)
     assert reply.message_type == MessageType.METHOD_RETURN
 
 
diff --git a/bleak/exc.py b/bleak/exc.py
index 1388d639..42feb02d 100644
--- a/bleak/exc.py
+++ b/bleak/exc.py
@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
+from typing import Optional
 
 
 class BleakError(Exception):
@@ -16,18 +17,38 @@ class BleakDotNetTaskError(BleakError):
 class BleakDBusError(BleakError):
     """Specialized exception type for D-Bus errors."""
 
-    def __init__(self, dbus_error: str):
+    def __init__(self, dbus_error: str, error_body: list):
         """
         Args:
             dbus_error (str): The D-Bus error, e.g. ``org.freedesktop.DBus.Error.UnknownObject``.
+            error_body (list): Body of the D-Bus error, sometimes containing error description or details.
         """
-        super().__init__(dbus_error)
+        super().__init__(dbus_error, *error_body)
 
     @property
     def dbus_error(self) -> str:
         """Gets the D-Bus error name, e.g. ``org.freedesktop.DBus.Error.UnknownObject``."""
         return self.args[0]
 
+    @property
+    def dbus_error_details(self) -> Optional[str]:
+        """Gets the optional D-Bus error details, e.g. 'Invalid UUID'."""
+        if len(self.args) > 1:
+            details = self.args[1]
+            # Some error descriptions can be further parsed to be even more helpful
+            if "ATT error: 0x" in details:
+                more_detail = CONTROLLER_ERROR_CODES.get(
+                    int(details.rsplit("x")[1], 16), "Unknown code"
+                )
+                details += f" ({more_detail})"
+            return details
+        return None
+
+    def __str__(self) -> str:
+        name = f"[{self.dbus_error}]"
+        details = self.dbus_error_details
+        return (name + " " + details) if details else name
+
 
 CONTROLLER_ERROR_CODES = {
     0x00: "Success",