### Problem
- Users encounter “Failed to construct 'URL': Invalid base URL” when
clicking the “View source” action in DevTools if the underlying base URL
is invalid.
- This exception originates from `new URL(relative, base)` and bubbles
up, interrupting the DevTools UI.
- Fixes GitHub issue
[#34317](https://github.com/facebook/react/issues/34317)
### Solution
- Wrap URL construction to:
- First try `new URL(sourceMapAt, sourceURL)`.
- If that fails, try `new URL(sourceMapAt)` as an absolute URL.
- If both fail, return `null` (no symbolication) rather than throwing.
- This preserves normal behavior for valid bases and absolute URLs,
while avoiding crashes for invalid bases.
### Implementation details
- Updated `symbolicateSource` in
`packages/react-devtools-shared/src/symbolicateSource.js` to handle
invalid base URL scenarios without throwing.
- Added/verified tests in
`packages/react-devtools-shared/src/__tests__/utils-test.js`:
- “should not throw for invalid base URL with relative source map” →
resolves to `null`.
- “should resolve absolute source map even if base URL is invalid” →
still resolves correctly.
### Test plan
- Lint/format:
- `yarn prettier-check`
- `yarn linc`
- Type checking:
- `yarn flow dom-node`
- Unit tests:
- `yarn test --watchAll=false utils-test`
- Optionally: `yarn test --watchAll=false utils-test inspectedElement`
- All of the above pass locally for experimental channel.
### Risks and rollout
- Risk: Low. Only affects cases where the base URL is invalid.
- Normal cases (valid base or absolute `sourceMappingURL`) are
unchanged.
- No user-facing API changes; DevTools UX becomes more resilient.
### Affected packages
- `react-devtools-shared`
### Related
- Fixes GitHub issue
[#34317](https://github.com/facebook/react/issues/34317)
### Checklist
- [x] Ran `yarn prettier-check`
- [x] Ran `yarn linc`
- [x] Ran `yarn flow dom-node`
- [x] Relevant unit tests passing
- [x] Linked issue and added a concise summary
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## How did you test this change?
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Stacked on #34093.
Instead of using the original `ReactStackTrace` that has the call sites
on the server, this parses the `Error` object which has the virtual call
sites on the client. We'll need this technique for things stack traces
suspending on the client anyway like `use()`.
We can then use these callsites to source map in the front end.
We currently don't source map function names but might be useful for
this use case as well as getting original component names from prod.
One thing this doesn't do yet is that it doesn't ignore list the stack
traces on the client using the source map's ignore list setting. It's
not super important since we expect to have already ignore listed on the
server but this will become important for client stack traces like
`use()`.
Stacked on #34094.
This shows the I/O stack if available. If it's not available or if it
has a different owner (like if it was passed in) then we show the
`"awaited at:"` stack below it so you can see where it started and where
it was awaited. If it's the same owner this tends to be unnecessary
noise. We could maybe be smarter if the stacks are very different then
you might want to show both even with the same owner.
<img width="517" height="478" alt="Screenshot 2025-08-04 at 11 57 28 AM"
src="https://github.com/user-attachments/assets/2dbfbed4-4671-4a5f-8e6e-ebec6fe8a1b7"
/>
Additionally, this adds an inferred await if there's no owner and no
stack for the await. The inferred await of a function/class component is
just the owner. No stack. Because the stack trace would be the return
value. This will also be the case if you use throw-a-Promise. The
inferred await in the child position of a built-in is the JSX location
of that await like if you pass a promise to a child. This inference
already happens when you pass a Promise from RSC so in this case it
already has an await - so this is mainly for client promises.
In RSC and other stacks now we use a lot of `ReactFunctionLocation` type
to represent the location of a function. I.e. the location of the
beginning of the function (the enclosing line/col) that is represented
by the "Source" of the function. This is also what the parent Component
Stacks represents.
As opposed to `ReactCallSite` which is what normal stack traces and
owner stacks represent. I.e. the line/column number of the callsite into
the next function.
We can start sharing more code by using the `ReactFunctionLocation` type
to represent the component source location and it also helps clarify
which ones are function locations and which ones are callsites as we
start adding more stack traces (e.g. for async debug info and owner
stack traces).
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TestName` is helpful in development.
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open `chrome://inspect`, and press "Inspect".
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[prettier](https://github.com/prettier/prettier) (`yarn prettier`).
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## Summary
Fix how devtools handles URLs. It
- cannot handle relative source map URLs `//# sourceMappingURL=x.map`
- cannot recognize Windows style URLs
## How did you test this change?
works on my side
Stacked on https://github.com/facebook/react/pull/28351, please review
only the last commit.
Top-level description of the approach:
1. Once user selects an element from the tree, frontend asks backend to
return the inspected element, this is where we simulate an error
happening in `render` function of the component and then we parse the
error stack. As an improvement, we should probably migrate from custom
implementation of error stack parser to `error-stack-parser` from npm.
2. When frontend receives the inspected element and this object is being
propagated, we create a Promise for symbolicated source, which is then
passed down to all components, which are using `source`.
3. These components use `use` hook for this promise and are wrapped in
Suspense.
Caching:
1. For browser extension, we cache Promises based on requested resource
+ key + column, also added use of
`chrome.devtools.inspectedWindow.getResource` API.
2. For standalone case (RN), we cache based on requested resource url,
we cache the content of it.
