feat: pretty print errors on scan history access

bec_ipython_client/bec_ipython_client/main.py

@@ -24,7 +24,7 @@
 from bec_ipython_client.signals import ScanInterruption, SigintHandler
 from bec_lib import plugin_helper
 from bec_lib.alarm_handler import AlarmBase
-from bec_lib.bec_errors import DeviceConfigError
+from bec_lib.bec_errors import BECError, DeviceConfigError
 from bec_lib.bec_service import parse_cmdline_args
 from bec_lib.callback_handler import EventType
 from bec_lib.client import BECClient
@@ -207,38 +207,12 @@ def show_last_alarm(self, offset: int = 0):
         except IndexError:
             print("No alarm has been raised in this session.")
             return
-
-        console = Console()
-
-        # --- HEADER ---
-        header = Text()
-        header.append("Alarm Raised\n", style="bold red")
-        header.append(f"Severity: {alarm.severity.name}\n", style="bold")
-        header.append(f"Type: {alarm.alarm_type}\n", style="bold")
-        if alarm.alarm.info.device:
-            header.append(f"Device: {alarm.alarm.info.device}\n", style="bold")
-
-        console.print(Panel(header, title="Alarm Info", border_style="red", expand=False))
-
-        # --- SHOW SUMMARY
-        if alarm.alarm.info.compact_error_message:
-            console.print(
-                Panel(
-                    Text(alarm.alarm.info.compact_error_message, style="yellow"),
-                    title="Summary",
-                    border_style="yellow",
-                    expand=False,
-                )
-            )
-
-        # --- SHOW FULL TRACEBACK
-        tb_str = alarm.alarm.info.error_message
-        if tb_str:
-            try:
-                console.print(tb_str)
-            except Exception:
-                # fallback in case msg is not a traceback
-                console.print(Panel(tb_str, title="Message", border_style="cyan"))
+        if hasattr(alarm, "print_details"):
+            alarm.print_details()
+            return
+        if hasattr(alarm, "pretty_print"):
+            alarm.pretty_print()
+            return
 
 
 def _ip_exception_handler(
@@ -253,6 +227,12 @@ def _ip_exception_handler(
     if issubclass(etype, ValidationError):
         pretty_print_pydantic_validation_error(evalue)
         return
+    if issubclass(etype, BECError):
+        parent._alarm_history.append((etype, evalue, tb, tb_offset))
+        evalue.pretty_print()
+        print("For more details, use 'bec.show_last_alarm()'")
+        return
+
     if issubclass(etype, (ScanInterruption, DeviceConfigError)):
         print(f"\x1b[31m {evalue.__class__.__name__}:\x1b[0m {evalue}")
         return

bec_lib/bec_lib/alarm_handler.py

@@ -81,6 +81,39 @@ def pretty_print(self) -> None:
 
         console.print(Panel(body, title=text, border_style="red", expand=True))
 
+    def print_details(self) -> None:
+        console = Console()
+
+        # --- HEADER ---
+        header = Text()
+        header.append("Alarm Raised\n", style="bold red")
+        header.append(f"Severity: {self.severity.name}\n", style="bold")
+        header.append(f"Type: {self.alarm_type}\n", style="bold")
+        if self.alarm.info.device:
+            header.append(f"Device: {self.alarm.info.device}\n", style="bold")
+
+        console.print(Panel(header, title="Alarm Info", border_style="red", expand=False))
+
+        # --- SHOW SUMMARY
+        if self.alarm.info.compact_error_message:
+            console.print(
+                Panel(
+                    Text(self.alarm.info.compact_error_message, style="yellow"),
+                    title="Summary",
+                    border_style="yellow",
+                    expand=False,
+                )
+            )
+
+        # --- SHOW FULL TRACEBACK
+        tb_str = self.alarm.info.error_message
+        if tb_str:
+            try:
+                console.print(tb_str)
+            except Exception:
+                # fallback in case msg is not a traceback
+                console.print(Panel(tb_str, title="Message", border_style="cyan"))
+
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, AlarmBase):
             return False

bec_lib/bec_lib/bec_errors.py

@@ -2,6 +2,91 @@
 This module contains the custom exceptions used in the BEC library.
 """
 
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from rich.console import Console
+from rich.panel import Panel
+from rich.syntax import Syntax
+from rich.text import Text
+
+if TYPE_CHECKING:  # pragma: no cover
+    from bec_lib import messages
+
+
+class BECError(Exception):
+    """Base class for all BEC exceptions"""
+
+    def __init__(self, message: str, error_info: messages.ErrorInfo) -> None:
+        super().__init__(message)
+        self.error_info = error_info
+
+    def pretty_print(self) -> None:
+        """
+        Use Rich to pretty print the alarm message,
+        following the same logic used in __str__().
+        """
+        console = Console()
+
+        msg = self.error_info.compact_error_message or self.error_info.error_message
+
+        text = Text()
+        text.append(f"{self.error_info.exception_type}", style="bold")
+        if self.error_info.context:
+            text.append(f" | {self.error_info.context}", style="bold")
+
+        if self.error_info.device:
+            text.append(f" | Device {self.error_info.device}\n", style="bold")
+        text.append("\n")
+
+        # Format message inside a syntax box if it looks like traceback
+        if "Traceback (most recent call last):" in msg:
+            body = Syntax(msg.strip(), "python", word_wrap=True)
+        else:
+            body = Text(msg.strip())
+
+        if self.error_info.device:
+            body.append(
+                f"\n\nThe error is likely unrelated to BEC. Please check the device '{self.error_info.device}'.",
+                style="bold",
+            )
+
+        console.print(Panel(body, title=text, border_style="red", expand=True))
+
+    def print_details(self) -> None:
+        console = Console()
+
+        # --- HEADER ---
+        header = Text()
+        header.append("Error Occurred\n", style="bold red")
+        header.append(f"Type: {self.error_info.exception_type}\n", style="bold")
+        if self.error_info.context:
+            header.append(f"Context: {self.error_info.context}\n", style="bold")
+        if self.error_info.device:
+            header.append(f"Device: {self.error_info.device}\n", style="bold")
+
+        console.print(Panel(header, title="Error Info", border_style="red", expand=False))
+
+        # --- SHOW SUMMARY
+        if self.error_info.compact_error_message:
+            console.print(
+                Panel(
+                    Text(self.error_info.compact_error_message),
+                    title="Error Summary",
+                    border_style="red",
+                    expand=False,
+                )
+            )
+
+        # --- SHOW FULL TRACEBACK
+        tb_str = self.error_info.error_message
+        if tb_str:
+            try:
+                console.print(tb_str)
+            except Exception as e:
+                console.print(f"Error printing traceback: {e}", style="bold red")
+
 
 class ScanAbortion(Exception):
     """Scan abortion exception"""

bec_lib/bec_lib/messages.py

@@ -432,6 +432,7 @@ class ErrorInfo(BaseModel):
     compact_error_message: str | None
     exception_type: str
     device: str | list[str] | None = None
+    context: str | None = None
 
 
 class DeviceInstructionResponse(BECMessage):

bec_lib/bec_lib/scan_history.py

@@ -6,14 +6,16 @@
 
 import os
 import threading
+import traceback
 from typing import TYPE_CHECKING
 
+from bec_lib import messages
+from bec_lib.bec_errors import BECError
 from bec_lib.callback_handler import EventType
 from bec_lib.endpoints import MessageEndpoints
 from bec_lib.scan_data_container import ScanDataContainer
 
 if TYPE_CHECKING:  # pragma: no cover
-    from bec_lib import messages
     from bec_lib.client import BECClient
 
 
@@ -143,7 +145,27 @@ def __len__(self) -> int:
     def __getitem__(self, index: int | slice) -> ScanDataContainer | list[ScanDataContainer]:
         with self._scan_data_lock:
             if isinstance(index, int):
-                target_id = self._scan_ids[index]
+                try:
+                    target_id = self._scan_ids[index]
+                except IndexError:
+                    if len(self._scan_ids) == 0:
+                        compact_msg = (
+                            f"ScanHistory is empty. This may be due to no scans being "
+                            f"run yet or the current user {os.getlogin()} not having access to the data files."
+                        )
+                    else:
+                        compact_msg = (
+                            f"Index {index} out of range for ScanHistory of length {len(self)}"
+                        )
+                    error_info = messages.ErrorInfo(
+                        error_message=traceback.format_exc(),
+                        compact_error_message=compact_msg,
+                        exception_type="IndexError",
+                        context="ScanHistory",
+                        device=None,
+                    )
+                    raise BECError(compact_msg, error_info)
+
                 return self.get_by_scan_id(target_id)
             if isinstance(index, slice):
                 return [self.get_by_scan_id(scan_id) for scan_id in self._scan_ids[index]]