Allow response.render to also work with .njk files

[frankieroberto]

We have enable the auto-routing to work with both .html and .njk files.

However if you do a custom route and call res.render('my-page') then it currently only works with a my-page.html file, not my-page.njk.

Ideally we should let it work with both.

[paulrobertlloyd]

In this function:

export function setViewEngine(app) {
  app.set('view engine', 'html')
}

you could pass a config value, either as a second param, or maybe even as an option somewhere on app?

[frankieroberto]

Looks like this might be tricky: expressjs/express#3485

[paulrobertlloyd]

export function setViewEngine(app, extension) {
  app.set('view engine', extension || 'html')
}

[frankieroberto]

This seems to work: NHSDigital/manage-vaccinations-in-schools-prototype@11ba67e

calling this in app.js after the init function:

prototype.app.set('view engine', 'njk')

possibly that could be set as an option in the init function to make it a tad easier.

However that just switches the default extension for render(). There doesn't seem to be an easy way (yet) in Express to have multiple extensions which automatically get tried.

[colinrotherham]

Looks like there's an alternative to call app.engine() multiple times?

We might as well add the same Nunjucks renderer to both html and njk out of the box?

[colinrotherham]

Fixed by #260