perf: avoid unnecessary fs.statSync calls

[marvinhagemeister]

Only resolve a module dir when we now that the mapped path is a directory. This improves linting time by about 18% in projects with lots of files.

The reason for the speedup is an accidental overhead in the callback of the filter function.

eslint-import-resolver-typescript/src/index.ts

Line 290 in 46de0e8

.filter(mappedPath => isFile(mappedPath) || isModule(mappedPath))

There we check if something resolves to file, and if not we'll check if it is a module directory. But in 99% of cases we'll be resolving file extensions in this callback. If /foo/bar/package.json is not a file, then it's very unlikely that /foo/bar.ts/package.json will be, unless /foo/bar.ts is a directory. Before this PR we'd check for the latter regardless which lead to an ENOTDIR error being thrown. The mere overhead of constantly throwing this error is where most of the time was spent in the traces I looked at.

Overall the logic can be improved further, but I think for now this PR reduces most of the overhead of calling into fs.statSync.

Before:

After:

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Latest commit: a89bdbd

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eslint-import-resolver-typescript	Patch

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