Add templates config option to the Mustache extension

[ppalaga]

The mustache extension requires that the application developers use quarkus.native.additional-build-args =-H:ResourceConfigurationFiles=resources-config.json https://github.com/apache/camel-quarkus/pull/866/files#diff-8dd2b01ede99ee34a76c5e27361d4825R17 to add the templates to the native image.

This solution has several drawbacks:

• It is not ergonomic
• It is not consistent with how we did similar things in other extensions so far and
• It breaks the portability of the test to quarkus-platform - one would have to copy the json file manually.

There are two ways this handled in other extensions:

1. Include/exclude patterns like in https://github.com/apache/camel-quarkus/blob/master/extensions/core/runtime/src/main/java/org/apache/camel/quarkus/core/CamelConfig.java#L75-L100

2. List of files or directories like in 161ddb1#diff-56b018479519fc93fac85a776b5c285aR38

[lburgazzoli]

Wonder if we can pre-compile the templates similar to what we have done for xslt, if the user still need to have the files then resources-config.json could be the way to go but will be user responsability

[lburgazzoli]

Maybe we could also make a little easier to include resource files with properties like:

quarkus.camel.resources.includes  = ...
quarkus.camel.resources.excludes  = ...

[ppalaga]

Or even

quarkus.resources.includes  = ...
quarkus.resources.excludes  = ...

[ppalaga]

... which is to say that I like the general idea and that we should try to contribute it to Quarkus.

[lburgazzoli]

Wonder if we can pre-compile the templates similar to what we have done for xslt, if the user still need to have the files then resources-config.json could be the way to go but will be user responsability

@aldettinger mind to check if this ^^^ would be possible ?

[aldettinger]

As far as I could drill, I've found no way to pre-compile templates on top of camel 3.1.

I'm thinking about complementing the mustache component with a kind of "mustache registry" (resourceUri -> pre-compiled-mustache-template). At endpoint creation time, the mustache component could then try to provide a pre-compiled mustache template according to the resource uri. OnExchange processing, the template is resolved with priority from header, then pre-compiled, then as usual.

On camel-quarkus side, I guess we would just need to record the "registry" / component initialization.

Maybe there is a way to skip the component level and make camel-quarkus store the "mustache registry" in the camel-registry... I don't know.

Any advices, inputs, pointers are welcome :)

[aldettinger]

I may step back from the fully pre-compiled approach as I'm stuck on mustache object serialization to runtime init phase. I'll check other options.

[aldettinger]

Mustache integration tests are now using include-patterns/exclude-patterns for resource inclusion.