Allow String concat in Qute when used as parameters

[ia3andy]

Description

Currently, this doesn't work:
{page.image('partenaires/' + partenaire.image) }

or

{page.image('partenaires/%s'.fmt(partenaire.image)}

It would be a very nice feature to make it intuitive for Java devs.

As discussed with @mkouba we could also introduce eval: to allow doing:
{page.image(eval:'partenaires/{partenaire.image}'} (which is pretty cool also)

Implementation ideas

No response

[quarkus-bot]

/cc @mkouba (qute)

[mkouba]

Just a bit of context.

The "'partenaires/' + partenaire.image" part from the {page.image('partenaires/' + partenaire.image) } output expression is parsed as a separate expression. There is a rule that a qute tag must start with a curly bracket the content of a tag must start with a digit, an alphabet character, underscore, or a built-in command: #, !, |, @, /. Thefore, an output expression may not start with a string literal. One practical implication is that we can safely ignore JSON, e.g. {"foo": true}.

We might try to relax this requirement for virtual method params but even then {'foo' + bar} will not work whilst {someString.concat('foo' + bar)} would work. Which is a bit weird and maybe even more confusing.

Now, I do understand that the current situation is not ideal at all and we need to find a better way to handle this. So far we have {page.image(str:fmt('partenaires/%s',partenaire.image))} which is not very nice.

I can imagine that something like {str:concat('partenaires/', partenaire.image)} works better.

Maybe a StringBuilder-like construct: {str:builder('partenaires/').append(partenaire.image)} or even {str:builder('partenaires/') + partenaire.image}.

I know that all these are just workarounds but I'm trying to find an acceptable solution without breaking existing stuff 🤷.

As discussed with @mkouba we could also introduce eval: to allow doing:
{page.image(eval:'partenaires/{partenaire.image}'} (which is pretty cool also)

I like the idea but it would have to be {page.image(eval:['partenaires/{partenaire.image}']} otherwise we're in the same troubles as with ^.

[ia3andy]

Just a bit of context.

The "'partenaires/' + partenaire.image" part from the {page.image('partenaires/' + partenaire.image) } output expression is parsed as a separate expression. There is a rule that a qute tag must start with a curly bracket the content of a tag must start with a digit, an alphabet character, underscore, or a built-in command: #, !, |, @, /. Thefore, an output expression may not start with a string literal. One practical implication is that we can safely ignore JSON, e.g. {"foo": true}.

We might try to relax this requirement for virtual method params but even then {'foo' + bar} will not work whilst {someString.concat('foo' + bar)} would work. Which is a bit weird and maybe even more confusing.

I think it's fine because you can do:
foo{bar} while you can't do it for virtual methods.

[mkouba]

I think it's fine because you can do:
foo{bar} while you can't do it for virtual methods.

It's not fine because it's inconsistent. You would be able to do {page.image('partenaires/%s'.format(partenaire.image))} but not {'partenaires/%s'.format(partenaire.image))}.

[ia3andy]

@mkouba what's the point of doing: {'partenaires/%s'.format(partenaire.image))} ?

[mkouba]

@mkouba what's the point of doing: {'partenaires/%s'.format(partenaire.image))} ?

That's just an example. It could be some more complex formatting or whatever.

[ia3andy]

What do you think about this consistent rule, make it works when you have parenthesis:
{('paternaire/' + foo)} or {page.image('paternaire/' + foo)} or {#let foo = ('hello/' + b)}

and explain in the doc that we have this limitation/rule to limit conflicts with underlying syntaxes..