Support for `deno.json`

[l0uisgrange]

Describe the problem

Hi 👋,

Would it be possible to support deno.json?
I tried running deno task dev and everything works perfectly 😲, but when running deno task build the adapter-node adapter gives me an error before shutting down (see logs below).

Describe the proposed solution

I know everyone still uses Node.js these days, but I have migrated my codebase to Deno to try something more cool, modern, performant and secure. I think either a native support for the deno.json file (without package.json) or a dedicated adapter would be very nice.

Alternatives considered

I've tried using package.json and it works out of the box, but I think supporting deno.json would be very nice 🤩 because it would allow me to only have deno.json and not both package.json and deno.json.

Moreover, the package.json currently does not allow me to install dependencies using other registries than npm, such as jsr, GitHub or classic https.

Importance

would make my life easier

Additional Information

Task build vite build
vite v7.1.7 building SSR bundle for production...
✓ 196 modules transformed.
vite v7.1.7 building for production...
✓ 146 modules transformed.
.svelte-kit/output/client/_app/version.json                        0.03 kB │ gzip:  0.05 kB
.svelte-kit/output/client/.vite/manifest.json                      2.80 kB │ gzip:  0.58 kB
.svelte-kit/output/client/_app/immutable/assets/0.5WzQQzpg.css     8.77 kB │ gzip:  2.33 kB
.svelte-kit/output/client/_app/immutable/chunks/mayyaSW0.js        0.03 kB │ gzip:  0.05 kB
.svelte-kit/output/client/_app/immutable/chunks/DsnmJJEf.js        0.07 kB │ gzip:  0.08 kB
.svelte-kit/output/client/_app/immutable/entry/start.C74wFzzr.js   0.08 kB │ gzip:  0.09 kB
.svelte-kit/output/client/_app/immutable/nodes/2.CdLSh2Pz.js       0.32 kB │ gzip:  0.24 kB
.svelte-kit/output/client/_app/immutable/chunks/C4j6WD8h.js        0.74 kB │ gzip:  0.47 kB
.svelte-kit/output/client/_app/immutable/nodes/1.zGpPfBzx.js       1.01 kB │ gzip:  0.58 kB
.svelte-kit/output/client/_app/immutable/nodes/0.C_6q7sZ_.js       2.73 kB │ gzip:  1.19 kB
.svelte-kit/output/client/_app/immutable/chunks/D13MIZDl.js        6.50 kB │ gzip:  3.02 kB
.svelte-kit/output/client/_app/immutable/entry/app.DUoBPkWT.js     7.33 kB │ gzip:  3.49 kB
.svelte-kit/output/client/_app/immutable/chunks/CjWXeMaj.js       20.57 kB │ gzip:  8.26 kB
.svelte-kit/output/client/_app/immutable/chunks/Ra-NgKqZ.js       32.12 kB │ gzip: 12.65 kB
✓ built in 218ms
.svelte-kit/output/server/.vite/manifest.json                           2.90 kB
.svelte-kit/output/server/_app/immutable/assets/_layout.5WzQQzpg.css    8.77 kB
.svelte-kit/output/server/entries/pages/_page.svelte.js                 0.22 kB
.svelte-kit/output/server/internal.js                                   0.33 kB
.svelte-kit/output/server/chunks/environment.js                         0.66 kB
.svelte-kit/output/server/chunks/equality.js                            1.23 kB
.svelte-kit/output/server/entries/fallbacks/error.svelte.js             1.35 kB
.svelte-kit/output/server/chunks/context.js                             1.70 kB
.svelte-kit/output/server/entries/pages/_layout.svelte.js               2.47 kB
.svelte-kit/output/server/chunks/utils.js                               3.48 kB
.svelte-kit/output/server/chunks/exports.js                             6.92 kB
.svelte-kit/output/server/remote-entry.js                              16.24 kB
.svelte-kit/output/server/chunks/shared.js                             16.46 kB
.svelte-kit/output/server/chunks/index.js                              24.50 kB
.svelte-kit/output/server/chunks/internal.js                           71.82 kB
.svelte-kit/output/server/index.js                                    145.17 kB
✓ built in 859ms

Run npm run preview to preview your production build locally.

> Using @sveltejs/adapter-node                                                                                                                                                     
error during build:
Error: ENOENT: no such file or directory, open 'package.json'                                                                                                                      
    at __node_internal_captureLargerStackTrace (ext:deno_node/internal/errors.ts:90:3)                                                                                             
    at __node_internal_uvException (ext:deno_node/internal/errors.ts:183:10)                                                                                                       
    at denoErrorToNodeError (ext:deno_node/internal/errors.ts:1913:14)                                                                                                             
    at readFileSync (ext:deno_node/_fs/_fs_readFile.ts:70:13)                                                                                                                      
    at adapt (file:///Users/louis/WebstormProjects/test2/node_modules/.deno/@sveltejs+adapter-node@5.3.2/node_modules/@sveltejs/adapter-node/index.js:60:27)                       
    at Object.runMicrotasks (ext:core/01_core.js:693:26)                                                                                                                           
    at Array.processTicksAndRejections (ext:deno_node/_next_tick.ts:59:10)                                                                                                         
    at eventLoopTick (ext:core/01_core.js:176:29)                                                                                                                                  
    at async adapt (file:///Users/louis/WebstormProjects/test2/node_modules/.deno/@sveltejs+kit@2.43.5/node_modules/@sveltejs/kit/src/core/adapt/index.js:41:2)                    
    at async finalise (file:///Users/louis/WebstormProjects/test2/node_modules/.deno/@sveltejs+kit@2.43.5/node_modules/@sveltejs/kit/src/exports/vite/index.js:1312:7) 

[brunnerh]

For JSR, I currently use the NPM compatibility layer as a workaround.

[benmccann]

It looks like we read it to get the dependencies field. Does Deno specify dependencies in the same manner as npm?

kit/packages/adapter-node/index.js

Line 60 in d4dd214

const pkg = JSON.parse(readFileSync('package.json', 'utf8'));

[l0uisgrange]

Yes, deno.json also has dependencies like npm in its imports property.

See the online example below:

{
  "imports": {
    "@sveltejs/adapter-node": "npm:@sveltejs/adapter-node@^4.0.0",
    "vite": "npm:vite@7"
  }
}
 

In the code you cited, we would just have to check if package.json exists, then try deno.json and parse using regex (same as package.json but with a different expression).

We should also be aware that deno supports different imports (jsr, https, etc.)... I don't know if this could create problems?

[Conduitry]

Do those distinguish between prod and dev dependencies? That's an important distinction for the Node adapter, because it determines whether they are bundled in the generated app.

[brunnerh]

I do not think there currently is such a distinction.
imports is also used for aliasing. E.g. I also have this in there to make $lib work properly:

"$lib/": "./src/lib/"

[l0uisgrange]

In Deno, there is no distinction between development and classic dependencies, because the runtime only installs and loads dependencies used by the code executed (either compiled for prod or directly on the dev server).

However, if needed, the official convention to mark development dependencies is by commenting the line like this:

{
  "imports": {
    "@std/fs": "jsr:@std/fs@1",
    "@std/testing": "jsr:@std/testing@1" // dev
  }
}

See the documentation for more informations on this matter.

But maybe we can use Deno's magic here and let Deno decide whether the dependency will be bundled or not?

[Conduitry]

If we do something like that (using Deno's magic) that's starting to sound much more like a separate adapter. I believe there actually already are unofficial Deno adapters, but I have no idea how well maintained they are.

[l0uisgrange]

I've done some research before opening this issue, and there exists only one, but it's not maintained since deno 1.0 (2 years ago, we're at 2.5, 1.0 didn't even have deno.json).

I think it would be nice for svelte to fully support Deno, as it will become more and more popular throughout the coming months/years, maybe even replace Node in the future?

Of course, this would be awesome but I'd understand if this would create too much maintainable codebase for @sveltejs.

[benmccann]

It seems the reason that adapter has not been maintained is because they said adapter-node works out-of-the-box: pluvial/svelte-adapter-deno#45 (comment)

I'm not sure whether something changed on our side to make that no longer true, or if they were referring to the compatibility layer, or just aren't aware of the issue you shared here. It might be helpful if you're able to share this issue over in that repo to see if it might spur any rethinking on that topic.

[l0uisgrange]

I think they meant it is possible to use Deno with package.json out of the box, but deno.json support has never been implemented either on their side or on adapter-node as it's been released in Deno 2.0, just a few months ago.

Also, they don't seem to answer issues or PRs and the repo is no longer maintained.

[dominikg]

agree with Conduitry that this reads more like a separate adapter than making adapter-node fit both. While it may work today, it can put us in a bind later if deno and node diverge.

There is @deno/svelte-adapter https://github.com/denoland/svelte-adapter/blob/main/src/index.ts but i think that is specific for deploying deno.land.

[l0uisgrange]

Unfortunately, the adapter you provided @dominikg works only with Deno Deploy (their proprietary hosting services).

Does this mean I can hope for a dedicated @sveltejs/adapter-deno one day?