Also forward error requests to the proxy

[OliverJAsh]

Fixes#2380

• This is a bugfix
• This is a feature
• This is a code refactor
• This is a test update
• This is a docs update
• This is a metadata update

For Bugs and Features; did you add new tests?

Yes

Motivation / Use-Case

See #2380 and #2380 (comment).

Breaking Changes

Additional Info

[codecov]

Codecov Report

Merging #2425 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@ Coverage Diff @@## master #2425 +/- ##
==========================================
+ Coverage 93.8% 93.81% +<.01% 
==========================================
Files 34 34 Lines 1307 1309 +2 Branches 371 371 ==========================================
+ Hits 1226 1228 +2 
Misses 79 79 Partials 2 2

Impacted Files	Coverage Δ
lib/Server.js	96.73% <100%> (+0.01%)	⬆️

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[alexander-akait]

It is create two instances of proxy that was reduce performance

[OliverJAsh]

The proxy middleware is created once, outside of handle:

proxyMiddleware=getProxyMiddleware(proxyConfig);

… and the result is used in handle on each request, be it a non-error or error request. So I don't think this change will hurt performance in any way.

If you really think this will hurt performance, are you able to provide an example to demonstrate that's the case?

[alexander-akait]

Each request now run handle (

webpack-dev-server/lib/Server.js

Line 291 in 29a822e

consthandle=(req,res,next)=>{

) twice so we potentially send require to middleware twice

webpack-dev-server/lib/Server.js

Line 318 in 29a822e

returnproxyMiddleware(req,res,next);

[OliverJAsh]

I don't believe that's true. handle will only run once:

• If the request has not errored, handle will be called via app.use(handle).
• If the request has errored, handle will be called via app.use((error, req, res, next) => handle(req, res, next)).

You can see this for yourself if you add some logging to handle.

[alexander-akait]

Hm, looks you are right https://expressjs.com/en/guide/error-handling.html

[alexander-akait]

Something broken on CI, I rerun tests

[alexander-akait]

/cc @hiroppy@Loonride need review and I will do patch release

[alexander-akait]

/cc @hiroppy@Loonride Feel free to leave feedback, I will make a patch release after merge

[alexander-akait]

Bit thanks, sometimes I get too much error flow, and do not have time to investigate them in detail, I apologize for the situation and am very glad that you yourself could find the problem and fix it

[OliverJAsh]

@evilebottnawi No problem, thanks for reviewing my PR! 😄