Perf improvement to stat in jest-resolve

[markjm]

🐛 Bug Report

jest-resolve specified its own isFile and isDirectory. stat[Sync] does some weird stuff by capturing a very large stack trace on failure (see here). Based on what we need from the errors of statSync for resolving, we dont need these stack traces (as errors when resolving are much more "expected"). My proposal below should improve resolving performance (with included rough console.time numbers):

To Reproduce

Create a "simulated" resolve environment (just forcing a lot of failed stat calls)

const fs = require("fs");
function oldStat(path) {
  let stat;

  try {
    stat = fs.statSync(path);
  } catch (e) {
    if (!(e && (e.code === "ENOENT" || e.code === "ENOTDIR"))) {
      throw e;
    }
  }
}

console.time("oldStat");
for (let i = 0; i < 100000; i++) oldStat("not-real-path");
console.timeEnd("oldStat");


# Console output
oldStat: 8.336s

Expected behavior

If we prevent capturing these extended traces, we see much improved CPU time for these stat calls.

function newStat(path) {
  let stat;
  let oldTrace = Object.getOwnPropertyDescriptors(Error).stackTraceLimit;

  try {
    Object.defineProperty(Error, "stackTraceLimit", {
      value: 0,
      writable: false,
    });
    stat = fs.statSync(path);
  } catch (e) {
    if (!(e && (e.code === "ENOENT" || e.code === "ENOTDIR"))) {
      throw e;
    }
  } finally {
    Object.defineProperty(Error, "stackTraceLimit", oldTrace);
  }
}

console.time("newStat");
for (let i = 0; i < 100000; i++) newStat("not-real-path");
console.timeEnd("newStat");

# Console output
newStat: 5.014s

Is there any interest in this change? If so, I can make a simple PR to get this going. Apologies if this doesnt dall in "bug" work item type, but didnt think it was a feature either.

[markjm]

@sokra I wonder if this optimization can also be added to enhanced-resolve?

[SimenB]

Feel free to send a PR with this change, seems reasonable to me 🙂 Ideally there'd be a way to stat and automatically ignore "not found" errors, but there probably isn't

[sokra]

This only affects statSync. In very recent node.js versions there is an option to return undefined instead of throwing an error on not found

[SimenB]

#11749

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