fix: safeguard against undefined entry

[rigor789]

The fix for #14028 added in #14030 does not catch cases where entry may be undefined.

Starting with 5.51.0 we're seeing errors like this one (even with 5.51.1):

/test/node_modules/webpack/lib/FileSystemInfo.js:817
if (entry.resolved !== undefined) return entry.resolved;
^

TypeError: Cannot read property 'resolved' of undefined
at getResolvedTimestamp (/test/node_modules/webpack/lib/FileSystemInfo.js:817:12)
at /test/node_modules/webpack/lib/FileSystemInfo.js:1167:21
at /test/node_modules/webpack/lib/util/AsyncQueue.js:352:5
at Hook.eval [as callAsync] (eval at create (/test/node_modules/webpack/node_modules/tapable/lib/HookCodeFactory.js:33:10), :4:1)
at Hook.CALL_ASYNC_DELEGATE [as _callAsync] (/test/node_modules/webpack/node_modules/tapable/lib/Hook.js:18:14)
at AsyncQueue._handleResult (/test/node_modules/webpack/lib/util/AsyncQueue.js:322:21)
at /test/node_modules/webpack/lib/util/AsyncQueue.js:305:11
at /test/node_modules/webpack/lib/FileSystemInfo.js:3098:21
at /test/node_modules/webpack/lib/FileSystemInfo.js:3010:22
at /test/node_modules/neo-async/async.js:2830:7
at done (/test/node_modules/neo-async/async.js:2925:13)
at /test/node_modules/webpack/lib/FileSystemInfo.js:2994:23
at Array. (/test/node_modules/webpack/lib/util/fs.js:311:21)
at runCallbacks (/test/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:27:15)
at /test/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:200:4
at callback (/test/node_modules/graceful-fs/polyfills.js:299:20)

What kind of change does this PR introduce?

bugfix

Did you add tests for your changes?

N/A

Does this PR introduce a breaking change?

No

What needs to be documented once your changes are merged?

N/A

[webpack-bot]

For maintainers only:

• This needs to be documented (issue in webpack/webpack.js.org will be filed when merged)
• This needs to be backported to webpack 4 (issue will be created when merged)

[alexander-akait]

Please add tests

[alexander-akait]

We should found a place/situation where we return undefined to avoid monkey patching without tests

[rigor789]

I'm sorry, but not familiar with how exactly this is used, or when this case is called to add a test or figure out why/when it may end up being undefined. Perhaps @sokra would know best, since he added the getResolvedTimestamp and getResolvedHash functions.

Willing to help, just not sure how.

[alexander-akait]

@rigor789 Can you show arguments here

webpack/lib/FileSystemInfo.js

Line 1167 in 99585d8

const resolved = getResolvedTimestamp(entry);

[alexander-akait]

For this.contextTimestampQueue.add(path, (err, entry) => {

[rigor789]

Ok that does give a clue what's going on. There's an err and entry is undefined.

We are using a virtual entry file, ie. it doesn't exist on the filesystem using https://github.com/sysgears/webpack-virtual-modules.

[alexander-akait]

To be honestly webpack never supports Webpack Virtual Modules, it is always have problems...

[alexander-akait]

Cache will be broken too

[sokra]

entry should never be undefined. Here err is not handled correctly, which is causing this problem.

[webpack-bot]

Thank you for your pull request! The most important CI builds succeeded, we’ll review the pull request soon.

[Akryum]

Hi, thanks for the fix! Do you have an estimate for a release?

[alexander-akait]

Near future, we need fix one critical bug