Better tracebacks when running as a script

[Akshay Agrawal]

The tracebacks when running as a script are inscrutable. This is particularly frustrating when a user runs a script that takes several hours, only to fail with a traceback that cannot be understood.

Ideally, the traceback would point to the exact line in the original script that raised the error.

Instead, tracebacks look like this today:

Script:

import marimo

__generated_with = "0.6.19"
app = marimo.App()


@app.cell
def __(y):
    x = 0
    y = y/x
    return x, y


if __name__ == "__main__":
    app.run()

Traceback:

Traceback (most recent call last):
  File "/home/akshay/src/marimo-team/marimo/tmp/script.py", line 15, in <module>
    app.run()
  File "/home/akshay/src/marimo-team/marimo/marimo/_ast/app.py", line 360, in run
    return self._run_sync(post_execute_hooks=post_execute_hooks)
  File "/home/akshay/src/marimo-team/marimo/marimo/_ast/app.py", line 275, in _run_sync
    outputs[cid] = execute_cell(cell._cell, glbls)
  File "/home/akshay/src/marimo-team/marimo/marimo/_ast/cell.py", line 459, in execute_cell
    exec(cell.body, glbls)
  File "/tmp/marimo_467203/__marimo__cell_Hbol_.py", line 2, in <module>
NameError: name 'y' is not defined

Notice how the user has no idea what __celll__Hbol__ is, the line number is relative to the cell and not the whole script (line 2 of what?), and the offending line is not even shown.

cc @delennc