Support list / tuple of strings for format

[nhairs]

Many other JSON formatting libraries allow or directly use a list of strings for the format. This suggests that it might be worth us adding in support for it.

Pros:

• No parsing means no testing for a correct format - we can directly use the list.
• Allows for clearer config when using dictConfig with the () user-defined object indicator, or instantiating within Python itself.

Cons:

• Must always use the () custom class indicator when using dictConfig.
• Not compatible with fileConfig.
• Not compatible with other formatters

[FichteFoll]

Could you elaborate why it is not compatible with fileConfig? I assume because the file config format does not support deserialization of lists there?

[FichteFoll]

Okay, after checking the documentation a bit on this, since I've never used a fileConfig in the past, I've answerd the question myself.

1. The handler's args are evaluated while the formatters are not
2. Formatters are instead instantiated using special paramater names by default, or a kwargs dict if the custom method with key () is used
3. These kwargs dicts values are parsed "as-is" and presumably using the configparser stdlib.
4. configparser does not have a getlist method or similar.

docs:

• https://docs.python.org/3/library/logging.config.html#logging-config-fileformat
• https://docs.python.org/3/library/logging.config.html#logging-config-dictschema-formatters
• https://docs.python.org/3/library/logging.config.html#logging-config-dict-userdef
• https://docs.python.org/3/library/configparser.html#configparser.ConfigParser

I guess accepting a comma-separated string of the field names to include would be a decent workaround here but does not provide a significant enough reason to break compatibility with the current method.

Still, regarding the issue at hand, the constructor could simply be overloaded to also accept a list of strings and determine in code whether a list of fields was already provided or whether it must be extracted from a format string in the same format as a standard formatter.