await import(pathToJSONFile, { with: { type: 'json' } }) transpiles to { assert: { type: 'json' }} in 6.1.x

[johnnybenson]

Describe the bug

Looking at the compiled output, it looks like 6.1.x reverted back to the old keyword assert for dynamic imports instead of with -- is this expected?

6.1.x

const outputFilePath = path.join(PATHS.source, outputFile);
const outputData = await import(outputFilePath, { assert: { type: 'json' } });

6.0.1

const outputFilePath = path.join(PATHS.source, outputFile);
const outputData = await import(outputFilePath, { with: { type: 'json' } });

node:internal/modules/esm/assert:88
        throw new ERR_IMPORT_ATTRIBUTE_MISSING(url, 'type', validType);
              ^

TypeError [ERR_IMPORT_ATTRIBUTE_MISSING]: Module "file:///Users/johnny/path/to/my/data.json" needs an import attribute of "type: json"
    at validateAttributes (node:internal/modules/esm/assert:88:15)
    at defaultLoad (node:internal/modules/esm/load:129:3)
    at async ModuleLoader.loadAndTranslate (node:internal/modules/esm/loader:516:32)
    at async ModuleJob._link (node:internal/modules/esm/module_job:115:19) {
  code: 'ERR_IMPORT_ATTRIBUTE_MISSING'
}

Node.js v23.6.0
error Command failed

The compiled CJS code like the above started emitting errors for me in 6.1.0, 6.1.1.
Downgrading to 6.0.11, the error seems to go away.

Experimented with build target a bit esnext, modules, node23, chrome123
None of these transpile to the syntax { with: { type: 'json' } }

Checked MDN to make sure with is still the thing 😅

Checked MDN again to make sure variables are OK to use. Vite Docs give mixed signals about variables in dynamic imports, despite this working prior to upgrading.

Checked esbuild and everything seems good

Note: This particular project targets 'esnext' everywhere, I understand that's a moving target. If I just need to update configuration to achieve the expected output, that sounds good to me! Thanks for any insights.

Reproduction

https://github.com/johnnybenson/vite-await-import-with-type-json-bug

Steps to reproduce

Steps

git clone git@github.com:johnnybenson/vite-await-import-with-type-json-bug.git .
yarn install
yarn build
yarn start_cjs 
# yarn start_es

Source

cat ./src/index.ts | grep with   
#  return await import(pathToJSONFile, { with: { type: 'json' } });

Build

cat ./dist/index.js | grep assert                                             
#  return await import(pathToJSONFile, { assert: { type: "json" } });

System Info

System:
    OS: macOS 15.3.1
    CPU: (12) arm64 Apple M2 Max
    Memory: 22.34 GB / 96.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 23.6.0 - ~/.nvm/versions/node/v23.6.0/bin/node
    Yarn: 1.22.22 - ~/.nvm/versions/node/v23.6.0/bin/yarn
    npm: 10.9.2 - ~/.nvm/versions/node/v23.6.0/bin/npm
    pnpm: 9.15.4 - ~/.nvm/versions/node/v23.6.0/bin/pnpm
  Browsers:
    Chrome: 133.0.6943.127
    Safari: 18.3
  npmPackages:
    vite: 6.1.1 => 6.1.1

Used Package Manager

yarn

Logs

No response

Validations

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• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
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• The provided reproduction is a minimal reproducible example of the bug.

[johnnybenson]

May be related to this: rollup/rollup#5814 https://github.com/rollup/rollup/pull/5818/files

[hi-ogawa]

It looks like this needs to be configured by rollup's output.importAttributesKey: "with" since the default is "assert". Here is an updated repro https://stackblitz.com/edit/github-492ifbmg?file=vite.config.ts%3AL19

Probably older rollup was ignoring this config and outputting with, but it was fixed to respect the config rollup/rollup#5814 You need to manually configure output.importAttributesKey from now on.

(Maybe the default should be changed, but I think this is an upstream issue, so let me close this for now.)

[johnnybenson]

thanks so much, agree about the default behavior too. cheers!