Migratior up function throws error when running on Bun

[danlannz]

When running migratior.up() on bun I'm getting migration error as MigrationClass is undefined.

MigrationError: Migration Migration20240318042632 (up) failed: Original error: undefined is not a constructor (evaluating 'new (Object.values(migration))[0](this.driver, this.config)')
 info: {
  "direction": "up",
  "name": "Migration20240318042632",
  "path": "/mikro-orm-elysia/src/migrations/Migration20240318042632.ts",
  "context": {}
}

      at new ErrorWithCause (/mikro-orm-elysia/node_modules/pony-cause/lib/error-with-cause.js:4:12)
      at new MigrationError (/mikro-orm-elysia/node_modules/umzug/lib/umzug.js:45:9)
      at /mikro-orm-elysia/node_modules/umzug/lib/umzug.js:177:31

196 |     }
197 |     resolve(params) {
198 |         const createMigrationHandler = async (method) => {
199 |             const migration = await core_1.Utils.dynamicImport(params.path);
200 |             const MigrationClass = Object.values(migration)[0];
201 |             const instance = new MigrationClass(this.driver, this.config);
                                                       ^
TypeError: undefined is not a constructor (evaluating 'new (Object.values(migration))[0](this.driver, this.config)')
      at /mikro-orm-elysia/node_modules/@mikro-orm/migrations/Migrator.js:201:50

Doing some debugging it appears that the Object.values returns an empty array from the dynamic import object on Bun

mikro-orm/packages/migrations/src/Migrator.ts

Lines 250 to 251 in 8799461

	const migration = await Utils.dynamicImport(params.path!);
	const MigrationClass = Object.values(migration)[0] as Constructor<Migration>;

I'm currently using the following workaround, will open a PR if this workaround is also compatible with all supported runtimes

  const migration = await Utils.dynamicImport(params.path!); 
  const fileName = params.name.split('.')[0];
  const MigrationClass = migration[fileName];

[B4nan]

Bugs in bun should be reported to bun, they claim to be node compatible, this is their problem to solve.

The proposed workaround won't work, the file name does not have to match the class name. Technically you could get around this by using migrationsList, handling the imports yourself:

https://mikro-orm.io/docs/migrations#importing-migrations-statically

[B4nan]

I got one more idea for a workaround, you could try to use require here - what the Utils.dynamicImport helper does is configurable via dynamicImportProvider ORM config option.

dynamicImportProvider: id => require(id),

[danlannz]

thanks @B4nan, I tried your suggested workaround but initially had the same issue.

Surprisingly, replacing require(id) with import(id) on your workaround did work, which I believe is the default implementation. This makes me think the issue is due to the way bun handles import() in the compiled CJS module. I will report the issue on the Bun repo 🙏

[B4nan]

Yes, its almost certainly something to fix on their end, there are quite a few open bug reports about dynamic import (but I haven't found one that would be matching this exactly, so better to have a new repro and open a new issue).

[B4nan]

Are you on windows btw? If so, maybe its about this bit:

https://github.com/mikro-orm/mikro-orm/blob/master/packages/core/src/utils/Utils.ts#L1062-L1068

[co-sic]

I'm on ubuntu and have the same problem for some time now. I had an ugly workaround in place, but now with the dynamicImportProvider this is at least a lot cleaner :)