[wrangler] fix: don't crash wrangler dev when source-mapping a truncated error chunk by matingathani · Pull Request #14316 · cloudflare/workers-sdk

matingathani · 2026-06-16T05:02:31Z

When a worker throws errors in rapid succession, the stderr chunks received by wrangler dev can arrive mid-frame — so a call site ends up with a negative column number. The @jridgewell/trace-mapping library throws Error: \column` must be greater than or equal to 0` in that case, which was bubbling up uncaught and crashing the wrangler process.

The fix wraps the prepareStack(...) call in getSourceMappedString in a try/catch. If source mapping throws for any reason, we fall back to returning the original (un-source-mapped) string. The worker process keeps running and the user still sees the error message, just without source map translation.

I reproduced this with the snippet from the issue:

export default {
  fetch: () => {
    let obj = {};
    Error.captureStackTrace(obj);
    console.error(obj.stack.slice(0, -3)); // truncated stack
    return new Response('ok');
  },
};

Hitting the worker endpoint a few times caused wrangler dev to crash before this fix. After the fix, it logs the raw stack and keeps running.

Tests
- Additional testing not necessary because: the fix is a defensive try/catch around an existing path. The existing sourcemap tests cover the normal code path. The error path (truncated column) is hard to unit-test deterministically since it depends on OS-level chunk boundaries in stderr delivery.
Public documentation
- Documentation not necessary because: this is a crash fix with no API or behaviour change.

workers-devprod · 2026-06-16T05:03:03Z

Codeowners approval required for this PR:

✅ @cloudflare/wrangler

Show detailed file reviewers

- Move for-loop inside try block so sourceMappedStackTrace can be const - Capture caught error and log at debug level instead of silently dropping it

changeset-bot · 2026-06-16T05:08:43Z

🦋 Changeset detected

Latest commit: eee9897

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
wrangler	Patch
@cloudflare/vite-plugin	Patch
@cloudflare/vitest-pool-workers	Patch

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pkg-pr-new · 2026-06-16T05:36:09Z

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commit: eee9897

matingathani · 2026-06-16T05:46:15Z

The 'Tests (Windows, packages-and-tools)' failure is a pre-existing flake in miniflare's browser tests unrelated to this PR. The Chrome DLL gets locked between parallel test processes on the Windows runner. The same failure appears on main without our changes.

petebacondarwin

I think it would be helpful to have an automated regression test if possible.
Please can you see if you can create one?

matingathani · 2026-06-17T05:01:30Z

Addressed all the review feedback in the latest commit:

Narrowed try-catch to only wrap prepareStack() — instead of wrapping both prepareStack() and the for-loop, the try-catch now only wraps the prepareStack(placeholderError, callSites) call and early-returns the original value on failure. This means the for-loop replacements are never partially applied then silently discarded — either the mapping fully succeeds or the original string is returned unchanged.

Fixed getFileName() === null — CallSite.getFileName() returns string | null, never undefined, so the old === undefined check always evaluated false (filed by Devin). Changed to === null.

Added regression test in packages/deploy-helpers/tests/sourcemap.test.ts — verifies that getSourceMappedString returns the original value without throwing when source mapping fails, covering the truncated-chunk crash scenario.

When the cached Chrome binary exists but is corrupt, the retry path calls install() again, which fires the downloadProgressCallback and starts the spinner. Without a matching s.stop(), the spinner runs indefinitely through the subsequent launch() and waitForBrowserReady() calls, leaving the terminal in a broken state. Reset startedDownloading before the retry so the callback re-arms cleanly, then stop the spinner after install() returns (success path) or throws (failure path), mirroring the pattern on lines 163-175. Addresses Devin review comment on PR cloudflare#14316.

petebacondarwin · 2026-06-17T09:39:09Z

@matingathani - this seems to have picked up the changes from another PR too?

Wraps the prepareStack call in getSourceMappedString in a try-catch so that if the source map library throws (e.g. because a truncated stderr chunk produced a call site with an invalid column number), the original un-source-mapped string is returned instead of crashing wrangler dev.

…and fix null check - Narrow try-catch to wrap only `prepareStack()` and early-return on failure, so the for-loop replacements are never partially applied then silently dropped - Fix `getFileName() === undefined` → `=== null` (`CallSite.getFileName()` returns `string | null`, never `undefined`, so the old guard always evaluated false) - Add regression test verifying `getSourceMappedString` returns the original value when source mapping fails instead of throwing

…able let Factors the try-catch into a dedicated `tryPrepareStack` helper that returns `null` on failure instead of throwing, letting `getSourceMappedString` use `const` for the result and check `=== null` before entering the for-loop. Addresses Copilot review feedback (prefer const over let-bridging a try block) and aligns with petebacondarwin's suggestion to make prepareStack non-throwing.

matingathani · 2026-06-18T05:18:27Z

Cleaned up — the branch had picked up two miniflare/browser-rendering commits (d17f853, 964dd21) from a different in-progress PR that had been accidentally merged into this branch. I've rebuilt the branch from origin/main with only the three sourcemap-related commits cherry-picked:

fix(wrangler): don't crash when source-mapping truncated error chunks
fix(deploy-helpers): narrow sourcemap try-catch to prepareStack only and fix null check
refactor(deploy-helpers): extract tryPrepareStack helper to avoid mutable let

The diff is now clean — only .changeset/fix-sourcemap-crash-invalid-column.md, packages/deploy-helpers/src/deploy/helpers/sourcemap.ts, and packages/deploy-helpers/tests/sourcemap.test.ts are changed. Will mark ready for review once CI passes.

…eStack The catch block was silently swallowing exceptions, making it hard to diagnose unexpected source-map regressions. Now logs at debug level before returning null so the fallback is still transparent to users but visible with --log-level=debug.

…PrepareStack logger from shared/context is undefined until initDeployHelpersContext() is called. Tests that call getSourceMappedString directly never initialize the context, so logger?.debug avoids a TypeError when the logger has not been set up.

workers-devprod

Codeowners reviews satisfied

matingathani · 2026-06-18T10:24:08Z

Windows CI failure — pre-existing miniflare browser rendering flake

The Tests (Windows, packages-and-tools) failure is in miniflare/test/plugins/browser/index.spec.ts (browser rendering suite), which is outside this PR's scope — this PR only changes packages/deploy-helpers/src/deploy/helpers/sourcemap.ts and adds packages/deploy-helpers/tests/sourcemap.test.ts.

The failure is the same Chrome connectivity issue on Windows CI that appears on other PRs too (Chrome process startup timeout / DLL lock on Windows runners). @petebacondarwin already has pbd/miniflare/browser-rendering-windows-flake addressing it.

Copilot AI review requested due to automatic review settings June 16, 2026 05:02

matingathani requested a review from workers-devprod as a code owner June 16, 2026 05:02

workers-devprod requested review from a team and jamesopstad and removed request for a team June 16, 2026 05:03

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matingathani force-pushed the fix/sourcemap-crash-on-invalid-column branch from 0ee4112 to e7325f9 Compare June 16, 2026 05:24

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petebacondarwin marked this pull request as draft June 17, 2026 16:14

matingathani added 3 commits June 18, 2026 10:47

matingathani force-pushed the fix/sourcemap-crash-on-invalid-column branch from 82d628e to f179b04 Compare June 18, 2026 05:17

matingathani added 2 commits June 18, 2026 11:00

petebacondarwin approved these changes Jun 18, 2026

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petebacondarwin marked this pull request as ready for review June 18, 2026 09:48

petebacondarwin merged commit 444b75e into cloudflare:main Jun 18, 2026
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