When using `exec(string)`, the standard Python REPL, or `python -c` in a
terminal, the executed source code is not stored anywhere and cannot be
retrieved (except in the `-c` case by looking at `sys.argv`). This means that:
- The source line doesn't show up in tracebacks, e.g:
>>> exec("1/0")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 1, in <module>
ZeroDivisionError: division by zero
- Users cannot retrieve the source code using `inspect`, although many want to:
-
https://stackoverflow.com/questions/29850508/python-how-to-inspect-code-of-function-created-with-exec
-
https://stackoverflow.com/questions/12072252/cant-get-source-code-for-a-method-declared-through-exec-using-inspect-in-pyth/12072941#12072941
-
https://stackoverflow.com/questions/62160529/how-to-get-source-inside-exec-python
-
https://stackoverflow.com/questions/59244323/how-can-you-get-the-source-code-of-dynamically-defined-functions-in-python
-
https://stackoverflow.com/questions/50822656/source-code-for-an-evaled-dynamically-generated-function-in-python
-
https://stackoverflow.com/questions/50515651/why-does-the-python-linecache-affect-the-traceback-module-but-not-regular-traceb/50515847#50515847
- Libraries such as traceback formatters and debuggers which depend on source
code can't work. This often manifests when people try out a library for the
first time in the REPL and it doesn't seem to work. This leads to many similar
looking bug reports which sometimes take a while to resolve. Probably many more
people think these libraries don't work without ever opening an issue.
- https://github.com/cknd/stackprinter/issues/34
- https://github.com/Qix-/better-exceptions/issues/17
- https://github.com/Qix-/better-exceptions/issues/68
- https://github.com/aroberge/friendly-traceback/issues/23
- https://github.com/gruns/icecream/issues/17
- https://github.com/cool-RR/PySnooper/issues/135
- https://github.com/cool-RR/PySnooper/issues/164
- https://github.com/alexmojaki/sorcery/issues/3
- https://github.com/alexmojaki/sorcery/issues/5
- https://github.com/alexmojaki/sorcery/issues/6
I suggest that:
1. `exec(string)` assigns a unique generated filename to the compiled code
object and stores the source code in the `linecache` module under that
filename, similar to what the IPython REPL does. I imagine there might be
complaints about memory usage, security implications of revealing source code,
compatibility, etc. If that's an issue this could be off by default with a flag
to turn it on.
2. The REPL, `-c`, and other similar mechanisms (IDLE?) either follow the same
strategy as `exec` or defer to it.
3. The standard exception hook falls back to `linecache` for filenames that
don't exist. I don't know why it doesn't already. Here is a question on that
topic:
https://stackoverflow.com/questions/50515651/why-does-the-python-linecache-affect-the-traceback-module-but-not-regular-traceb
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