## Summary
We're experiencing some issues internally where the component stack is
getting into our way of fixing them as it causes the page to become
unresponsive. This adds a flag so that we can disable this feature as a
temporary workaround.
More internal context: https://fburl.com/go9yoklm
## Test Plan
I tried to default this flag to `__VARIANT__` but the variant tests
(`yarn test-www --variant`) started to fail across the board since a lot
of tests depend on the component tree, things like this:
https://user-images.githubusercontent.com/458591/100771192-6a1e1c00-33fe-11eb-9ab0-8ff46ba378a2.png
So, it seems to work :-)
Given that it's unhandy to update the hundreds of tests that are failing
I decided to hard code this to `false` like we already do for some other
options.
* Remove Blocks
* Remove Flight Server Runtime
There's no need for this now that the JSResource is part of the bundler
protocol. Might need something for Webpack plugin specifically later.
* Devtools
This could be used to do custom formatting of the stack trace in a way
that isn't compatible with how we use it. So we disable it while we use
it.
In theory we could call this ourselves with the result of our stack.
It would be a lot of extra production code though. My personal opinion
is that this should always be done server side instead of on the client.
We could expose a custom parser that converts it and passes it through
prepareStackTrace as structured data. That way it's external and doesn't
have to be built-in to React.
* Add more edge cases to fixture
Also adjust some expectations. I think the column should ideally be 1 but varies.
The Example row is one line off because it throws on the hook but should ideally be the component.
Similarly class components with constructors may have the line in the constructor.
* Account for the construct call taking a stack frame
We do this by first searching for the first different frame, then find
the same frames and then find the first different frame again.
* Throw controls
Otherwise they don't get a stack frame associated with them in IE.
* Protect against generating stacks failing
Errors while generating stacks will bubble to the root. Since this technique
is a bit sketchy, we should probably protect against it.
* Don't construct the thing that throws
Instead, we pass the prototype as the "this". It's new every time anyway.
* Implement component stack extraction hack
* Normalize errors in tests
This drops the requirement to include owner to pass the test.
* Special case tests
* Add destructuring to force toObject which throws before the side-effects
This ensures that we don't double call yieldValue or advanceTime in tests.
Ideally we could use empty destructuring but ES lint doesn't like it.
* Cache the result in DEV
In DEV it's somewhat likely that we'll see many logs that add component
stacks. This could be slow so we cache the results of previous components.
* Fixture
* Add Reflect to lint
* Log if out of range.
* Fix special case when the function call throws in V8
In V8 we need to ignore the first line. Normally we would never get there
because the stacks would differ before that, but the stacks are the same if
we end up throwing at the same place as the control.
We can't patch the row. We could give these their own "built-in" stack
frame since they're conceptually HoCs. However, from a debugging
perspective this is not very useful meta data and quite noisy. So I'm
just going to exclude them.
* Add feature flag
* Split stack from current fiber
You can get stack from any fiber, not just current.
* Refactor description of component frames
These should use fiber tags for switching. This also puts the relevant code
behind DEV flags.
* We no longer expose StrictMode in component stacks
They're not super useful and will go away later anyway.
* Update tests
Context is no longer part of SSR stacks. This was already the case on the
client.
forwardRef no longer is wrapped on the stack. It's still in getComponentName
but it's probably just noise in stacks. Eventually we'll remove the wrapper
so it'll go away anyway. If we use native stack frames they won't have this
extra wrapper.
It also doesn't pick up displayName from the outer wrapper. We could maybe
transfer it but this will also be fixed by removing the wrapper.
* Forward displayName onto the inner function for forwardRef and memo in DEV
This allows them to show up in stack traces.
I'm not doing this for lazy because lazy is supposed to be called on the
consuming side so you shouldn't assign it a name on that end. Especially
not one that mutates the inner.
* Use multiple instances of the fake component
We mutate the inner component for its name so we need multiple copies.
