filtering tweaks

[alexcjohnson]

Filtering got a major overhaul with #397 and #410. This issue is just to document and discuss some loose ends we may want to clean up.

• eq and ne are not exact complements. For example 123, "123", and "123.0" are all both eq and ne to each other. I think we should extend number casting to at least ne and probably all the inequalities.
• If you enter an invalid column type, no error is generated (even in debug mode) but there's no default operator. Either we should treat this as an any column, we should display an error, or both.
• datetime columns should have their own comparisons. Currently a lot of things pass that probably shouldn't, like '2018-01-01 00:00' > '2018-01-01', not to mention effects of poorly-specified (yet still interpretable) dates like '18-1-1'. It may be as simple as, if both values are dates, converting them to milliseconds and comparing those, although we should consider some edge cases before settling on this: for example, if you say > '2017' we would convert that to the very first instant of 2017, so '2017-01-01 00:00:01' would pass. Is that what we want, or would we want only datetimes in the year 2018 and later to pass?
• Option to filter on every keypress, ie without pressing enter, perhaps with a configurable debounce rate.

[xgdgsc]

Is there plan to make the default behavior simpler and intuitive? User would usually only expect to do a substring matching as start typing, instead of learning the eq "double quoted string" syntax. I like the search in https://vuetifyjs.com/en/components/data-tables#search-with-custom-no-results-slot

[alexcjohnson]

Isn't that what we're doing now? Any text or any (untyped) column defaults to the contains operator, so you can just start typing, no eq, no quotes, and you'll get a substring match. You can use quotes and operators for more specific results, but you don't need to.

The docs haven't caught up to this yet (This PR shows the new behavior https://github.com/plotly/dash-docs/pull/489) but you should see that behavior using the latest dash version.

[xgdgsc]

Great, thanks. I was using 0.42. 0.43 is fine, is there an option to start filtering without pressing "enter"?

[alexcjohnson]

Filtering without pressing enter is something we haven't implemented yet. We've discussed it internally, but I don't think there's an issue for it yet. I've added it to the list above. Thanks for mentioning it!