feat(python): detect busy device as a separate condition

fixes #1026

python/.changelog.d/1026.added

@@ -0,0 +1 @@
+New exception type `DeviceIsBusy` indicates that the device is in use by another process.

python/.changelog.d/1026.fixed

@@ -0,0 +1 @@
+trezorctl will correctly report that device is in use.

python/src/trezorlib/cli/__init__.py

@@ -21,9 +21,8 @@ from typing import TYPE_CHECKING, Any, Callable, Dict, Optional
 
 import click
 
-from .. import exceptions
+from .. import exceptions, transport
 from ..client import TrezorClient
-from ..transport import get_transport
 from ..ui import ClickUI, ScriptUI
 
 if TYPE_CHECKING:
@@ -67,14 +66,14 @@ class TrezorConnection:
     def get_transport(self) -> "Transport":
         try:
             # look for transport without prefix search
-            return get_transport(self.path, prefix_search=False)
+            return transport.get_transport(self.path, prefix_search=False)
         except Exception:
             # most likely not found. try again below.
             pass
 
         # look for transport with prefix search
         # if this fails, we want the exception to bubble up to the caller
-        return get_transport(self.path, prefix_search=True)
+        return transport.get_transport(self.path, prefix_search=True)
 
     def get_ui(self) -> "TrezorClientUI":
         if self.script:
@@ -101,6 +100,9 @@ class TrezorConnection:
         """
         try:
             client = self.get_client()
+        except transport.DeviceIsBusy:
+            click.echo("Device is in use by another process.")
+            sys.exit(1)
         except Exception:
             click.echo("Failed to find a Trezor device.")
             if self.path is not None:

python/src/trezorlib/cli/trezorctl.py

@@ -26,7 +26,7 @@ import click
 
 from .. import log, messages, protobuf, ui
 from ..client import TrezorClient
-from ..transport import enumerate_devices
+from ..transport import DeviceIsBusy, enumerate_devices
 from ..transport.udp import UdpTransport
 from . import (
     AliasedGroup,
@@ -247,9 +247,15 @@ def list_devices(no_resolve: bool) -> Optional[Iterable["Transport"]]:
         return enumerate_devices()
 
     for transport in enumerate_devices():
+        try:
             client = TrezorClient(transport, ui=ui.ClickUI())
-        click.echo(f"{transport} - {format_device_name(client.features)}")
+            description = format_device_name(client.features)
             client.end_session()
+        except DeviceIsBusy:
+            description = "Device is in use by another process"
+        except Exception:
+            description = "Failed to read details"
+        click.echo(f"{transport} - {description}")
     return None
 
 

python/src/trezorlib/transport/__init__.py

@@ -48,6 +48,10 @@ class TransportException(TrezorException):
     pass
 
 
+class DeviceIsBusy(TransportException):
+    pass
+
+
 class Transport:
     """Raw connection to a Trezor device.
 

python/src/trezorlib/transport/bridge.py

@@ -21,7 +21,7 @@ from typing import TYPE_CHECKING, Any, Dict, Iterable, Optional
 import requests
 
 from ..log import DUMP_PACKETS
-from . import MessagePayload, Transport, TransportException
+from . import DeviceIsBusy, MessagePayload, Transport, TransportException
 
 if TYPE_CHECKING:
     from ..models import TrezorModel
@@ -37,14 +37,19 @@ CONNECTION = requests.Session()
 CONNECTION.headers.update(TREZORD_ORIGIN_HEADER)
 
 
-def call_bridge(uri: str, data: Optional[str] = None) -> requests.Response:
-    url = TREZORD_HOST + "/" + uri
+class BridgeException(TransportException):
+    def __init__(self, path: str, status: int, message: str) -> None:
+        self.path = path
+        self.status = status
+        self.message = message
+        super().__init__(f"trezord: {path} failed with code {status}: {message}")
+
+
+def call_bridge(path: str, data: Optional[str] = None) -> requests.Response:
+    url = TREZORD_HOST + "/" + path
     r = CONNECTION.post(url, data=data)
     if r.status_code != 200:
-        error_str = (
-            f"trezord: {uri} failed with code {r.status_code}: {r.json()['error']}"
-        )
-        raise TransportException(error_str)
+        raise BridgeException(path, r.status_code, r.json()["error"])
     return r
 
 
@@ -150,7 +155,12 @@ class BridgeTransport(Transport):
             return []
 
     def begin_session(self) -> None:
+        try:
             data = self._call("acquire/" + self.device["path"])
+        except BridgeException as e:
+            if e.message == "wrong previous session":
+                raise DeviceIsBusy(self.device["path"]) from e
+            raise
         self.session = data.json()["session"]
 
     def end_session(self) -> None:

python/src/trezorlib/transport/webusb.py

@@ -22,7 +22,7 @@ from typing import Iterable, List, Optional
 
 from ..log import DUMP_PACKETS
 from ..models import TREZORS, TrezorModel
-from . import UDEV_RULES_STR, TransportException
+from . import UDEV_RULES_STR, DeviceIsBusy, TransportException
 from .protocol import ProtocolBasedTransport, ProtocolV1
 
 LOG = logging.getLogger(__name__)
@@ -57,7 +57,10 @@ class WebUsbHandle:
             else:
                 args = ()
             raise IOError("Cannot open device", *args)
+        try:
             self.handle.claimInterface(self.interface)
+        except usb1.USBErrorAccess as e:
+            raise DeviceIsBusy(self.device) from e
 
     def close(self) -> None:
         if self.handle is not None: