feat: resolve svelte to svelte/ssr when building for ssr (fixes #74)

[dominikg]

implementation is here:
https://github.com/sveltejs/vite-plugin-svelte/compare/feat/svelte-ssr?expand=1#diff-71fd6d8bccf1f224607bb27c94b502d32abf70103f0a2a59ad3acb5d229c443bR113

the kit demo app has been added to the playground to try it.
@dummdidumm @tanhauhau please have a look

[dummdidumm]

I don't know when that ssr parameter in the enhanced function is true (I guess when Vite builds the stuff for the Server output). Assuming it does what I think it does this looks good to me.

[dominikg]

turns out you have to add svelte to ssr.noExternal in vite config for it to get passed through resolveId.

Adding it to the playground config results in the expected warning for a missing svelte/ssr export.

vite v2.3.8 building SSR bundle for production...
transforming (1) .svelte-kit/build/app.js[vite-plugin-svelte] failed to resolve svelte  to svelte/ssr
Error: Missing "./ssr" export in "svelte" package
    at bail (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/vite@2.3.8/node_modules/vite/dist/node/chunks/dep-0ed4fbc0.js:32135:8)
    at resolve$1 (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/vite@2.3.8/node_modules/vite/dist/node/chunks/dep-0ed4fbc0.js:32211:10)
    at resolveExports (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/vite@2.3.8/node_modules/vite/dist/node/chunks/dep-0ed4fbc0.js:32640:12)
    at resolveDeepImport (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/vite@2.3.8/node_modules/vite/dist/node/chunks/dep-0ed4fbc0.js:32657:26)
    at tryNodeResolve (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/vite@2.3.8/node_modules/vite/dist/node/chunks/dep-0ed4fbc0.js:32446:11)
    at Object.resolveId (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/vite@2.3.8/node_modules/vite/dist/node/chunks/dep-0ed4fbc0.js:32330:28)
    at Object.<anonymous> (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/vite@2.3.8/node_modules/vite/dist/node/chunks/dep-0ed4fbc0.js:45595:33)
    at /home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/rollup@2.52.4/node_modules/rollup/dist/shared/rollup.js:20008:25 {
  code: 'PLUGIN_ERROR',
  plugin: 'vite:resolve',
  hook: 'resolveId'
}

Question is, is that actually what kit wants to do? Or are there other ways to achieve this by using import.meta.env.SSR or $app/env ?

[dominikg]

Cleaned it up a bit:

• automatically add svelte to ssr.noExternal
• less logging, inform user to update svelte (needed?)
• testwith clientside dynamic import

To start the tests without all the others use
pnpm test:ci:build -- --testNamePattern=kit-node