james4ever0/hy

A dialect of lisp running in python, can change code at runtime, pop repl console on runtime exceptions by default

Resumeable exception patch for hy lang, a lisp embedded in python

Installation

It is tested on hy v0.25.

Original version of hy can be found here. This repo is a patch for hy, so you would install hy via pip, then run python3 patch_code_helper.py after modified your hy installation path in that file.

You have to install parse from pip, also reloading.

Also, I write a nice hy code formatter nelean depending on this modified version of hy.

If you want hy syntax highlighting: vim-hy

Intro

Why the modification?

I want a language capable of catching uncaught exceptions (a feature borrowed and improved from common lisp), hot-reloading function definitions (from reloading), and this project is what I've achieved so far. I'm pretty sure these functionalities are not precluded in most programming languages, so I do it myself, for you.

Since most people don't understand the fuzz, here we have some detailed discussion for your bed time reading.

I introduce four flags to both hy and hy2py executables:

-R
	disable automatic insertion of reloading decorator
-T
	disable toplevel try-except
-K
	disable toplevel show stacktrace
-L
	disable line-by-line try-except

As you can see it, these four behaviors are turned on by default unless you explicitly disable any of them by passing these flags like: hy -R -T -K -L <filepath>.

Which files have been patched?

All patched file names can be found under src.list. Currently, they are:

utils.py
models.py
importer.py
__init__.py
reader/__init__.py
reader/reader.py
reader/hy_reader.py
debugger.py
cmdline.py
config.py

If you want to dig into this project yourself, better check these files and diff against the original hy repo.

How does it work?

I miss common lisp dearly (by clisp --on-error debug <filename>), so I do similar things to hy.

In this modded hy intepreter, when you have exceptions, you can fix it right at the spot. Take a look for yourself ("justpush.sh" is a file you can find under this repo):

Hy 0.25.0 using CPython(main) 3.10.4 on Linux
=> (/ 1 0)
Traceback (most recent call last):
  File "stdin-7b3ace8766f1e1cfb3ae7c01a1a61cebed24f482", line 1, in <module>
    (/ 1 0)
ZeroDivisionError: division by zero
Entering debug REPL
:R1 SKIP (continue execution, value as None)
:R2 CONT CONTINUE (continue execution with last stored value)
:R3 RAISE (raise hy.HE exception)
D> :R3
=> (with [f (open "just_push.sh")] (print (.read f)))Traceback (most recent call last):
  File "stdin-eb4da89ad3793ee39d4d80616dbb52d9cf563ae9", line 1, in <module>
    (with [f (open "just_push.sh")] (print (.read f)))
FileNotFoundError: [Errno 2] No such file or directory: 'just_push.sh'
Entering debug REPL
:R1 SKIP (continue execution, value as None)
:R2 CONT CONTINUE (continue execution with last stored value)
:R3 RAISE (raise hy.HE exception)
D> (open "justpush.sh")
<_io.TextIOWrapper name='justpush.sh' mode='r' encoding='UTF-8'>
D> :R2
git add .
git commit -m "init"
git push origin master

=>

Want more?

How did you do that?

I change hy expressions during parsing. When a qualified expression comes through, I wrap it into a try...except expression with a REPL loop, which is not triggered unless an exception is raised.

This REPL provides different options (skip, continue, raise hy.HE exception (which will be raised for sure and nothing can stop it unless wrapped in top-level try...except or inside a reloading decorator)) and capabilities (whether able to evaluate return/yield/yield-from/break/continue statements) depending on different situations (whether inside function definitions/loops).

It will first scan the hy code, mark different regions according to different situations, then act correspondingly. Note that line-by-line try...except will not wrap any statements inside existing try...except expressions, and this behavior is expected, as the coder expects an try...except statement to handle exceptions by itself unless the exception is raised nevertheless, which creates an uncaught exception.

How would I contribute?

You don't need to contribute unless you are using it! Clone/fork this repo, follow the instructions, unbox and use it to do whatever you want!

I wrote some tests under ./hy_code_test_clisp_alike. These tests are rudimentary but maybe you can take a look to see what I mean, really.

If you want to fix bugs from this modded hy, first discover them first by writing programs in hy. You can check docs for hy and docs for hyrule for reference. Once you've discovered a bug, post the issue here. If you want to fix it yourself, please read my modded files (very helpful, because you are smart)!

In case you find more issues and want to post them to nelean or reloading, feel free to do so!

Future plans

• Add indicator to values fetched from debug REPL, so you can say CONT <value number> to selectively return that value instead of the last value.

• Ananlyze loop/function define statement scopes and add new options to REPL within these scopes accordingly.

• Save user inputed statements in debug REPL to replace original statement at runtime.