refactor tools: centralize error handling with explain_exc and ensure

[PiotrCzapla]

@jph00 What do you think about centralizing it in a single helper?

The could look like this:

def view(...):
    try:
        assert (1<=s<=len(lines)), f'Invalid start line {s}'
        assert e==-1 or s<=e<= len(lines), f'Invalid end line {e}'
        ...
    except: return explain_exc("viewing")

I’m leaning towards an explicit try/except with a helper func, rather than a decorator, as I worry a decorator might suggest some "magic" to convert a function to a tool.

Re. assert, I find them easier to reason about or skip than if statements, especially with complex logic. But they can be disabled with -O. If we would like to avoid this edge case what would you say about simple ensure(b, m) helper that raise ValueError Like:

def view(...):
    try:
        ensure(1 <= s <= len(lines), f'Invalid start line {s}')
        ensure(e == -1 or s <= e <= len(lines), f'Invalid end line {e}')
        ...
    except: return explain_exc("viewing")

Regarding the explain_exc it could look like:

def explain_exception(task=''):
    try: raise sys.exc_info()[1]
    except AssertionError as e: return f"Error: {e}"
    except Exception as e: return f"Error {task}: {repr(e)}"

or using python matching

def explain_exception(task=''):
    match sys.exc_info()[1]:
        case AssertionError() as e: return f"Error: {e}"
        case e: return f"Error {task}: {repr(e)}"

I've implemented rerise as it is easier to catch multiple exceptions

Here is how the current error handling looks like

def run_cmd
    if disallow_re ...: return 'Error: args disallowed'
    if allow_re ...: return 'Error: args not allowed'
    try: ... except Exception as e: return f'Error running cmd: {str(e)}'

def rg / def sed
    uses run_cmd

def view
    if not (1<=s<=len(lines)): return f'Error: Invalid start line {s}'
    if e!=-1 and not (s<=e<= len(lines)): return f'Error: Invalid end line {e}'
    except Exception as e: return f'Error viewing: {str(e)}'

def create
    if p.exists() and not overwrite: return f'Error: File already exists: {p}'
    except Exception as e: return f'Error creating file: {str(e)}'

def insert
    if not (0 <= insert_line <= len(content)): return f'Error: Invalid line number {insert_line}'
    except Exception as e: return f'Error inserting text: {str(e)}'

def str_replace
    if count == 0: return 'Error: Text not found in file'
    if count > 1: return f'Error: Multiple matches found ({count})'
    except Exception as e: return f'Error replacing text: {str(e)}'

def strs_replace
    uses str_replace

def replace_lines
    except Exception as e: return f'Error replacing lines: {str(e)}'

def move_lines
    assert 1 <= start_line <= end_line <= len(lines), f"Invalid range {start_line}-{end_line}"
    assert 1 <= dest_line <= len(lines) + 1, f"Invalid destination {dest_line}"
    assert not(start_line <= dest_line <= end_line + 1), "Destination within source range"
    except Exception as e: return f'Error: {str(e)}'