Friday, June 16, 2017, 8:41:37 PM, Daniel Dekany wrote: > A problem in FM2 is that when calling a directive (as a macro), either > all parameters are positional (`<@message "Hi" 2 />`), or all > parameters are named (`<@message content="Hi" height=2 />`); you can't > mix the two (`<@message "Hi" height=2 />`). Also you can't use named > parameters for functions/methods, only for directives. Worse, core > directives don't even use named parameters, but some keyword like > `as`, `using`... their syntax is hard coded into the parser, which is > not nice, and will be a problem for the custom dialects feature. > > I think that with the exception of a few core directives (see them > later) all directive calls should be like this, if for now (in this > thread) we ignore loop variables: > > <#name posPar1 posPar2 namedPar1Name=namedPar1Value > namedPar2=namedPar2Value>
An adjustment to the above... I think that we should require comma between positional arguments (but not between positional and named arguments and between named arguments): <#name posPar1, posPar2 namedPar1Name=namedPar1Value namedPar2=namedPar2Value> FM2 supports both the <@foo 1, 2, 3 /> and <@foo 1 2 3 /> variation (and has no core directive with more the one positional argument, hence I demonstrated it with a custom directive). I believe it's better stick to one syntax or the other in FM3, not supporting both. Question is, which one. While <@foo 1 2 3 /> fits HTML style better, it can be ambiguous. Consider: - In `<@foo x - 1 />` is the argument `x - 1`, or we have an `x` and a `-1` argument? - In `<@foo x! 1 />` is the argument `x!1`, or we have an `x!` and a `1` argument? Technically, you can make whitespace significant, so that `<@foo x -1 />` and `<@foo x - 1 />` has different meaning, but its a quite extreme syntax design, and when you writing templates, I doubt many users will even realize that such subtle rules exist. With comma, it's obvious to do (`<@foo x - 1 />` VS `<@foo x, -1 />`, or even `<@foo x, - 1 />`). It looks a bit odd next to named parameters, but certainly by far the most common application of mixed positional and named parameters is when you have only one positional parameters (<@launch rocket1 delay=3 />), in which case the comma doesn't appear anyway. For function calls, which follow typical C-ish expression syntax, using commas even between named parameters is the natural thing (as in `f(1, 2, foo=3, bar=4)`), so I would stick to that. [snip] > parameters is `<#ftl outputFormat='RTF'>`. So far it's the same as in > FM2. But now we could have both in once call, such as > `<#visit node handlers=myNamespace>` (regular syntax), which was > `<#visit node using myNamespace>` in FM2 (irregular syntax hard coded > into the parser). [snip] For completeness, let's see what other non-regular core directives we have. - For #import I would switch to assignment-like approach: FM2: <#import "foo.ftl" as f> <#import "bar.ftl" as b> FM3: <#import f="foo.ftl" b="bar.ftl"> - #escape doesn't mater, as it will be removed (in favor of output formats introduced in 2.3.24). - #assign has this `in` thing, like `<#assign x = 1 in ns>`. We will want to allow <#assign ns.x = 1> (actually, #set) anyway, so that won't mater either. -- Thanks, Daniel Dekany
