perf(core): check files before interacting with them

packages/babel-core/src/config/files/configuration.ts

@@ -1,4 +1,5 @@
 import buildDebug from "debug";
+import nodeFs from "fs";
 import path from "path";
 import json5 from "json5";
 import gensync from "gensync";
@@ -36,11 +37,11 @@ const RELATIVE_CONFIG_FILENAMES = [
 
 const BABELIGNORE_FILENAME = ".babelignore";
 
-export function* findConfigUpwards(rootDir: string): Handler<string | null> {
+export function findConfigUpwards(rootDir: string): string | null {
   let dirname = rootDir;
-  while (true) {
+  for (;;) {
     for (const filename of ROOT_CONFIG_FILENAMES) {
-      if (yield* fs.exists(path.join(dirname, filename))) {
+      if (nodeFs.existsSync(path.join(dirname, filename))) {
         return dirname;
       }
     }
@@ -165,7 +166,7 @@ const readConfigJS = makeStrongCache(function* readConfigJS(
     caller: CallerMetadata | void;
   }>,
 ): Handler<ConfigFile | null> {
-  if (!fs.exists.sync(filepath)) {
+  if (!nodeFs.existsSync(filepath)) {
     cache.never();
     return null;
   }

packages/babel-core/src/config/files/index-browser.ts

@@ -11,11 +11,10 @@ import type { CallerMetadata } from "../validation/options";
 
 export type { ConfigFile, IgnoreFile, RelativeConfig, FilePackageData };
 
-// eslint-disable-next-line require-yield
-export function* findConfigUpwards(
+export function findConfigUpwards(
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   rootDir: string,
-): Handler<string | null> {
+): string | null {
   return null;
 }
 

packages/babel-core/src/config/files/utils.ts

@@ -23,6 +23,8 @@ export function makeStaticFileCache<T>(
 }
 
 function fileMtime(filepath: string): number | null {
+  if (!nodeFs.existsSync(filepath)) return null;
+
   try {
     return +nodeFs.statSync(filepath).mtime;
   } catch (e) {

packages/babel-core/src/config/partial.ts

@@ -23,21 +23,18 @@ import {
 import type { ConfigFile, IgnoreFile } from "./files";
 import { resolveTargets } from "./resolve-targets";
 
-function* resolveRootMode(
-  rootDir: string,
-  rootMode: RootMode,
-): Handler<string> {
+function resolveRootMode(rootDir: string, rootMode: RootMode): string {
   switch (rootMode) {
     case "root":
       return rootDir;
 
     case "upward-optional": {
-      const upwardRootDir = yield* findConfigUpwards(rootDir);
+      const upwardRootDir = findConfigUpwards(rootDir);
       return upwardRootDir === null ? rootDir : upwardRootDir;
     }
 
     case "upward": {
-      const upwardRootDir = yield* findConfigUpwards(rootDir);
+      const upwardRootDir = findConfigUpwards(rootDir);
       if (upwardRootDir !== null) return upwardRootDir;
 
       throw Object.assign(
@@ -89,7 +86,7 @@ export default function* loadPrivatePartialConfig(
     cloneInputAst = true,
   } = args;
   const absoluteCwd = path.resolve(cwd);
-  const absoluteRootDir = yield* resolveRootMode(
+  const absoluteRootDir = resolveRootMode(
     path.resolve(absoluteCwd, rootDir),
     rootMode,
   );

packages/babel-core/src/gensync-utils/fs.ts

@@ -8,18 +8,6 @@ export const readFile = gensync<(filepath: string, encoding: "utf8") => string>(
   },
 );
 
-export const exists = gensync<(filepath: string) => boolean>({
-  sync(path) {
-    try {
-      fs.accessSync(path);
-      return true;
-    } catch {
-      return false;
-    }
-  },
-  errback: (path, cb) => fs.access(path, undefined, err => cb(null, !err)),
-});
-
 export const stat = gensync<typeof fs.statSync>({
   sync: fs.statSync,
   errback: fs.stat,