Disable HMR in SSR mode?

[Rich-Harris]

In the process of testing import.meta.env.SSR, I found that Snowpack injects code like the following if it sees import.meta:

import * as  __SNOWPACK_HMR__ from '../../__snowpack__/hmr-client.js';
import.meta.hot = __SNOWPACK_HMR__.createHotContext(import.meta.url);
import __SNOWPACK_ENV__ from '../../__snowpack__/env.js';
import.meta.env = __SNOWPACK_ENV__;

After patching our SSR module loader to accommodate import.meta, I realised that this doesn't work in the SSR context because hmr-client.js assumes that it's running in the DOM.

I see two possible solutions:

• Add an isHMR option to loadUrl so it can be explicitly disabled
• Automatically disable HMR if isSSR, by tweaking this line:

-code = wrapImportMeta({code: code as string, env: true, hmr: isHmr, config});
+code = wrapImportMeta({code: code as string, env: true, hmr: isHmr && !isSSR, config});

[Rich-Harris]

Oh — I also noticed that wrapImportMeta is testing using code.includes('import.meta'). It's valid to have whitespace inside this expression (unconventional, but it's the sort of thing Prettier might do), so it should probably be something like this:

/import\s*\.\s*meta/.test(code)

PR inbound

[FredKSchott]

both suggestions seem valuable, added in a quick PR: #1372