Improve ParseException for better parsing

[moosefriend]

Problem Description

When calling the CLI of the compiler for a KSP script which has an error, then the message of the ParseException also contains the line number and the line content. So it's hard to extract the actual error message.

How to reproduce

I'm calling the compiler from CLI using the following command:

C:\Python312\python.exe compiler\ksp_compiler.py --extra_syntax_check --indent-size 4 test-in.ksp test-out.ksp

"test-in.ksp" contains the following code:

on init
    declare $b
    $a := $b + 1
end on

This will throw a ksp_compile.ParseException of the problem:

Traceback (most recent call last):
  ...
  File "C:\zz_Kontakt_Script_IDE\vscode-ksp-compiler\vscode_extension\sublime_ksp\compiler\ksp_compiler.py", line 1362, in modifyID
    raise ksp_ast.ParseException(node, "%s has not been declared!" % name)
  File "<string>", line 7
ksp_ast.ParseException: $a has not been declared!

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  ...
  File "C:\zz_Kontakt_Script_IDE\vscode-ksp-compiler\vscode_extension\sublime_ksp\compiler\ksp_compiler.py", line 2574, in compile
    raise ParseException(line, message)
ksp_compiler.ParseException: $a has not been declared! (line 7)

$a := $b + 1

<main script>: 3

Now even when writing a wrapper to extract the relevant information from the ParseException, the message also contains the actual line and the file and line number:

from ksp_compiler import main, ParseException

try:
    # Call the main function from ksp_compiler
    main()
except ParseException as ex:
        error_message = ex.message
        error_command = ex.line.command
        error_filename = ex.line.filename
        error_lineno = ex.line.lineno
        print(f">>> Message:\n{error_message}")
        print(f">>> Command:\n{error_command}")
        print(f">>> File:\n{error_filename}")
        print(f">>> Line:\n{error_lineno}")

Output:

>>> Message:
$a has not been declared! (line 7)

$a := $b + 1

<main script>: 3
>>> Command:
    $a := $b + 1
>>> File:
None
>>> Line:
3

Analysis

The code which constructs the message is in line 223:

SublimeKSP/compiler/ksp_compiler.py

Lines 210 to 227 in ee3ec9a

	class ParseException(ExceptionWithMessage):
	'''Parse Exceptions for parse errors raised before AST lex/yacc parsing'''
	def __init__(self, line, message, no_traceback = False):
	if no_traceback:
	utils.disable_traceback()
	if line.calling_lines:
	macro_chain = '\n'.join(['=> {}'.format(l.command.strip()) for l in line.calling_lines])
	line_content = 'Macro traceback:\n{}\n{}'.format(macro_chain, str(line).strip())
	else:
	line_content = str(line).strip()
	msg = "%s\n\n%s\n\n%s" % (message, line_content, line.get_locations_string())
	Exception.__init__(self, msg)
	self.line = line
	self.message = msg

Proposal

It would be great if the ParseException.message only contains the error message without further information.
If a string is requested of the ParseException (__str__ method) then the current output could be constructed.

[mkruselj]

Having the traceback can be useful to pinpoint where the issue in the transpiler is. But you're right, this is more useful to the developer of the transpiler than the end user. And it seems all we really need to do here is set no_traceback = True in __init__ method of ParseException and that would solve the issue.

This can then be changed to True when investigating a potential bug report. There could even be a non-menu exposed setting in the SublimeKSP extension to flip this behavior, which I think might be the real solution here.

[mkruselj]

Hmmm, actually doing that doesn't remove the traceback from the report... Dunno why.

EDIT: Traceback also needs to be disabled in ksp_ast.py, that was it.

[moosefriend]

I think this was a bit misunderstood (but it's also OK for end users to hide the stack trace 😃):
The intension of this issue was to improve the ParseException.message. My expectation would be that it just contains the message, but no further details on the command (can be retrieved from ParseException.line.command), script (can be retrieved from ParseException.line.file) or the line number (can be retrieved from ParseException.line.lineno). So, in the example above I would like ParseException.message to contain only (the (line 7) is now removed by solving the other issue):

$a has not been declared!

But currently it contains:

$a has not been declared! (line 7)

$a := $b + 1

<main script>: 3

To mitigate the change for end-users, you could implement an ParseException.__str__ method which for compatibility produces the second output. But this would allow me in Python to get the right message only.

[mkruselj]

Frankly I like the context that is provided by the message as it stands... I am not very keen on changing it further. 😅

[moosefriend]

No problems. I've found a way to monkey patch the exception, and with this it works:
https://github.com/moosefriend/vscode-ksp-compiler/blob/dd48ced3be3c610e7f6310729c4044aa9cbdbbc4/vscode_extension/bin/ksp_compiler_wrapper.py#L26-L56

[moosefriend]

I've added a pull request, which should solve this issue without changing the message: #536