[Flight] Source Map Actions in Reference Node Loader Transforms

[sebmarkbage]

Follow up to #30741.

This is just for the reference Webpack implementation.

If there is a source map associated with a Node ESM loader, we generate new source map entries for every registerServerReference call.

To avoid messing too much with it, this doesn't rewrite the original mappings. It just reads them while finding each of the exports in the original mappings. We need to read all since whatever we append at the end is relative. Then we just generate new appended entries at the end.

For the location I picked the location of the local name identifier. Since that's the name of the function and that gives us a source map name index. It means it jumps to the name rather than the beginning of the function declaration. It could be made more clever like finding a local function definition if it is reexported. We could also point to the line/column of the function declaration rather than the identifier but point to the name index of the identifier name.

Now jumping to definition works in the fixture.

Unfortunately this technique doesn't seem to work in Firefox nor Safari. They don't apply the source map for jumping to the definition.

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
react-compiler-playground	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Aug 20, 2024 9:46pm

[react-sizebot]

Comparing: e831c23...ca1ea70

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
oss-stable/react-dom/cjs/react-dom.production.js	=	6.68 kB	6.68 kB	=	1.82 kB	1.82 kB
oss-stable/react-dom/cjs/react-dom-client.production.js	=	500.37 kB	500.37 kB	=	89.80 kB	89.80 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	6.69 kB	6.69 kB	=	1.83 kB	1.83 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	507.50 kB	507.50 kB	=	90.96 kB	90.96 kB
facebook-www/ReactDOM-prod.classic.js	=	595.24 kB	595.24 kB	=	105.55 kB	105.55 kB
facebook-www/ReactDOM-prod.modern.js	=	571.54 kB	571.54 kB	=	101.75 kB	101.75 kB
oss-experimental/react-server-dom-webpack/esm/react-server-dom-webpack-node-loader.production.js	+60.66%	12.53 kB	20.14 kB	+60.72%	3.09 kB	4.97 kB
oss-stable-rc/react-server-dom-webpack/esm/react-server-dom-webpack-node-loader.production.js	+60.66%	12.53 kB	20.14 kB	+60.72%	3.09 kB	4.97 kB
oss-stable-semver/react-server-dom-webpack/esm/react-server-dom-webpack-node-loader.production.js	+60.66%	12.53 kB	20.14 kB	+60.72%	3.09 kB	4.97 kB
oss-stable/react-server-dom-webpack/esm/react-server-dom-webpack-node-loader.production.js	+60.66%	12.53 kB	20.14 kB	+60.72%	3.09 kB	4.97 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
oss-experimental/react-server-dom-webpack/esm/react-server-dom-webpack-node-loader.production.js	+60.66%	12.53 kB	20.14 kB	+60.72%	3.09 kB	4.97 kB
oss-stable-rc/react-server-dom-webpack/esm/react-server-dom-webpack-node-loader.production.js	+60.66%	12.53 kB	20.14 kB	+60.72%	3.09 kB	4.97 kB
oss-stable-semver/react-server-dom-webpack/esm/react-server-dom-webpack-node-loader.production.js	+60.66%	12.53 kB	20.14 kB	+60.72%	3.09 kB	4.97 kB
oss-stable/react-server-dom-webpack/esm/react-server-dom-webpack-node-loader.production.js	+60.66%	12.53 kB	20.14 kB	+60.72%	3.09 kB	4.97 kB

Generated by 🚫 dangerJS against b3da2c2

[eps1lon]

Was wondering if we need to update the build-for-flight-dev command but that already builds react-server-dom-webpack

[sebmarkbage]

This was previously just copied into the folder but that didn't make yarn consider its dependencies when resolving dependencies.