On Sun, Sep 19, 2021 at 7:36 AM Ben Weidig <b...@netzgut.net> wrote: > Hi, >
Hello! I'm sorry for the very late answer. I thought I had answered this already. > I'm working on TAP5-2688, which is about the TypeCoercer picking the > "wrong" CoercionTuple. > Because JSONArray became a real Collection, its String->JSONArray > CoercionTuple is picked over the Object->List CoercionTuple. > > https://issues.apache.org/jira/browse/TAP5-2688 > > I've created a patch and added it to the ticket, but I wanted to have some > feedback before committing and pushing. > Nice! > The patch contains: > > - Preferring exact targetType matches over cheaper (less intermediate) > coercions. > Awesome! > - Add an explicit String->Collection CoercionTuple in tapestry-json > Cool! But why in tapestry-json instead of commons? > What's up to discussion IMO is the general question about cost vs. quality. > Previously "cost" was favored over quality because no quality checks > existed except the exact source and target type checks. > > The patch I've added to the ticket now prefers quality over cost. > That means that the first coercion of a value will check all coercion > tuples if a better match with an exact targetType is found. > The only problem I see with this approach is costlier first checks (it's > cached afterward), and maybe a more costly way is chosen even if a cheaper > "good enough" CoercionTuple would suffice. > I believe this is exactly the way to go. Calculating the best coercion is something very quick and the result is permanently cached. > Possible changes: > > - Restrict intermediate lookups if a "good enough" CoercionTuple is found. > A one or two-step coercion should be preferable over a 5+ coercion. > But what would be a good number? > A maximum of one or two additional level checks sounds good to me. > I was wondering whether we could check for direct coercions (i.e. one step) first, then 2-step ones, then 3-step ones, and so on. Is this what you're proposing, Ben? Since this is a very quick computation that will only be done once, I think we could stop at level 5. > > What do you think? > > Cheers, > Ben > -- Thiago
