How to test legacy version performance during development

help
1

Currently, it seems that legacy JavaScript files only load in older browsers when using modern: false and running meteor run --production . However, the JavaScript files are minified and obfuscated in this mode, making debugging difficult.

Is there a way to build the legacy version with meteor run during normal development, so we can properly test and debug the legacy version behavior?

2

You don’t need to disable modern entirely. You can just disable modern webArchs.

"meteor": {
  "modern": {
    "webArchOnly": false
  }
}

I assume after doing this you should be able to test similarly with meteor run as done with the Meteor bundler. To trigger the legacy builder you should probably use a legacy browser context for it to properly get loaded.

3

I tried, but under the dev environment, there is still no build for legacy.

modern browser
image
image

legacy browser
image
image

4

I compared modern browsers and legacy browsers, and there is no difference in the output files from Meteor. I have opened an issue on GitHub.

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5

Does it happen in Meteor 3.3 or before as well? Or only as part of Meteor 3.4 and the Rspack integration?

Update: I’ve reproduced this issue. Verified that it comes as part of the Rspack integration. I’ll take a look to find the fix and ensure same behavior on adopting the new bundler.

2 Likes