TOML file: crash when given keyword misses quotes

[FransRoelofsen]

The TOML file contains several keywords, for instance "dll". These keywords expect a reference to a file. In case such a fille name doesn't contain spaces, users might give an unquoted line, like dll = \path\to\MetaSWAP.dll
However, this causes a crash and a message "Invalid value (at line 10, column 7)."
I found out that the TOML must contain a "python linke" string, so always including quotes. That is not clear for a user.

Suggestion: build in a check for a string value and if not present, please close the program with a clear message about this string requirement.

[Huite]

This is arguably a failure of the TOML parser; it could give a more meaningful error. But that's an upstream issue.

See:
python/cpython#115516

One possible solution is catching this error and wrapping it. I'm not sure that a very sustainable solution: we use TOML everywhere, and I don't think we would want error wrapping everywhere.

To be fair, the "invalid value" error is not that bad; the phrasing is too terse, and ideally it should mention the key, maybe mention that types matter, and not just the line number. It's just that people will see a configuration file, think "I get it", not read any specification and then get unpleasantly surprised when they got something as simple as a config file wrong.

[Huite]

For comparison, the JSON parser doesn't give a lot more info either.

JSON keys need to be quoted too, error's okay:

In [11]: json.loads('{stuff: stuff}')
JSONDecodeError: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)

But if you screw up the value:

json.loads('{"stuff": stuff}')
JSONDecodeError: Expecting value: line 1 column 11 (char 10)

It's pretty much the tomllib error.

[Huite]

@FransRoelofsen, how did you make the TOML file?

As @HendrikKok mentioned, most of the time the TOML file will be generated by Python as well.
Did you take an example and copy-pasted a new path, deleting quotes that were there before? Or is the example incorrect too?