fix(ssr): use optional chaining to prevent "undefined is not an object" happening in ssrRewriteStacktrace

[saintnoodle]

Description

This PR handles a case where varName passed from a RegExp match on stacktrace lines is undefined and causes ssrRewriteStacktrace to fail on varName.trim().

This bug was encounted in the Vite dev server running with Bun via the command bunx --bun vite.

I have a reproduction which demonstrates the error in a simple manner. There is also a patch for Vite on the branch "fix-patch" which demonstrates the fixed behaviour.

I'm not the first to encounter this according to this issue over at Bun.

Explaination

Upon inspecting the stack traces and comparing them between Node and Bun, the first line of the stack trace tends to contain "eval", which means the function safely accesses varName.trim() and continues to completion. However, in Bun, varName is undefined which causes the function to fail when it tries to access .trim() where it doesn't exist.

If it weren't for modules outside of the module graph being skipped after moduleGraph.getModuleById(), is undefined failure would be common as anonymous entries in the stacktrace usually occur.

The existance of if (!trimmedVarName ... indicates to me that this was expected, but trimmedVarName can't be undefined because of the lack of optional chaining since the function fails if the value is not a string before undefined can be assigned.

Bun stacktrace:

Error: Anonymous Error
    at C:/Users/{username}/Projects/vite-ssr-repro/app/routes/anonymous-error.tsx:7:10
    at loader (C:/Users/{username}/Projects/vite-ssr-repro/app/routes/anonymous-error.tsx:8:4)
    at C:\Users\{username}\Projects\vite-ssr-repro\node_modules\react-router\dist\development\index.js:9174:21
    at callRouteHandler (C:\Users\{username}\Projects\vite-ssr-repro\node_modules\react-router\dist\development\index.js:9173:32)
    at C:\Users\{username}\Projects\vite-ssr-repro\node_modules\react-router\dist\development\index.js:9287:24
    at C:\Users\{username}\Projects\vite-ssr-repro\node_modules\react-router\dist\development\index.js:9263:43
    at C:\Users\{username}\Projects\vite-ssr-repro\node_modules\react-router\dist\development\index.js:3893:90
    at C:\Users\{username}\Projects\vite-ssr-repro\node_modules\react-router\dist\development\index.js:3891:38
    at runHandler (C:\Users\{username}\Projects\vite-ssr-repro\node_modules\react-router\dist\development\index.js:3896:42)
    at C:\Users\{username}\Projects\vite-ssr-repro\node_modules\react-router\dist\development\index.js:3943:21

Node stacktrace:

Error: Anonymous Error
    at eval (C:/Users/{username}/Projects/vite-ssr-node/app/routes/anonymous-error.tsx:7:11)
    at loader (C:/Users/{username}/Projects/vite-ssr-node/app/routes/anonymous-error.tsx:8:5)
    at callRouteHandler (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:9026:22)
    at commonRoute.loader (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:9139:25)
    at actualHandler (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:3734:14)
    at file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:3745:91
    at runHandler (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:3750:7)
    at callLoaderOrAction (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:3795:22)
    at Object.resolve (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:3690:27)
    at file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:3565:62
    at Array.map (<anonymous>)
    at defaultDataStrategy (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:3565:49)
    at callDataStrategyImpl (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:3705:23)
    at callDataStrategy (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:3117:25)
    at loadRouteData (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:3084:25)
    at queryImpl (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:2900:26)
    at Object.query (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:2764:24)
    at handleDocumentRequest (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:9758:40)
    at requestHandler (file:///C:/Users/{username}/Projects/vite-ssr-node/node_modules/react-router/dist/development/chunk-K6CSEXPM.mjs:9684:24)
    at processTicksAndRejections (node:internal/process/task_queues:105:5)
    at nodeHandler (C:\Users\{username}\Projects\vite-ssr-node\node_modules\@react-router\dev\dist\vite.js:2932:30)
    at C:\Users\{username}\Projects\vite-ssr-node\node_modules\@react-router\dev\dist\vite.js:2938:17

[hi-ogawa]

I think adding this small safety measure is okay, but the reproduction might be somewhat specific to react-router, which is using vite-node's source map support at the same time. https://github.com/remix-run/react-router/blob/796e9ae10f74ba453b738f9d80049885f24caccf/packages/react-router-dev/vite/vite-node.ts#L47-L49

Normally bun's error seems to have <anonymous> in the stack like below, but vite-node's Error.prepareStackTrace probably strips it out somehow, which might be the actual part of bun's node incompatibility.

Error: __TEST_ERROR__
    at <anonymous> (/xxx/src/test.tsx:5:20)
    at test (/xxx/src/test.tsx:6:5)
    at <anonymous> (/xxx/repro.js:8:9)
    at processTicksAndRejections (native:7:39)

[saintnoodle]

I knew there was something going on further up the chain, but I couldn't quite figure it out. This makes things a lot clearer, thanks for pointing that out.

[hi-ogawa]

My best guess is that bun might have a different behavior in CallSite.getFunctionName https://github.com/vitest-dev/vitest/blob/0c2924b7aeb7eaf1b1fa0e78d2da76a7f3197b50/packages/vite-node/src/source-map-handler.ts#L404-L411 If someone can debug this, it would be better to be reported on bun, but adding optional chain looks fine for me.

---

Or maybe that's not it. Node has eval but Bun has <anonymous>, which probably makes vite-node to do a different thing 🤔

[saintnoodle]

<anonymous> only appears to display in the console and on CallSite.toString(). On anonymous stack entries, CallSite.getFunctionName() returns undefined. I don't think I'm smart enough to understand the why of all this, but these are observations I've made poking around. The main thing I'm confused about is why eval is reported in Node and not in Bun.

[sapphi-red]

Putting Bun's Node compat bug aside, I think we should merge this PR as the regex allows varName to be undefined and the code should have been written like this.