From 5bec21e88aa25903bf995efb2852eb9c2504aeae Mon Sep 17 00:00:00 2001
From: Simen Bekkhus <sbekkhus91@gmail.com>
Date: Tue, 15 Feb 2022 23:05:42 +0100
Subject: [PATCH] --wip-- [skip ci]

---
 .../src/__tests__/resolve.test.ts             |  2 +-
 packages/jest-resolve/src/defaultResolver.ts  | 89 +++++++++++--------
 2 files changed, 55 insertions(+), 36 deletions(-)

diff --git a/packages/jest-resolve/src/__tests__/resolve.test.ts b/packages/jest-resolve/src/__tests__/resolve.test.ts
index 4d0b1af072a6..9bfa7468413f 100644
--- a/packages/jest-resolve/src/__tests__/resolve.test.ts
+++ b/packages/jest-resolve/src/__tests__/resolve.test.ts
@@ -298,7 +298,7 @@ describe('resolveModule', () => {
     );
   });
 
-  it('is possible to resolve node modules by resolving their realpath', () => {
+  it.only('is possible to resolve node modules by resolving their realpath', () => {
     const resolver = new Resolver(moduleMap, {
       extensions: ['.js'],
     } as ResolverConfig);
diff --git a/packages/jest-resolve/src/defaultResolver.ts b/packages/jest-resolve/src/defaultResolver.ts
index 758117214744..1997ac4f6ada 100644
--- a/packages/jest-resolve/src/defaultResolver.ts
+++ b/packages/jest-resolve/src/defaultResolver.ts
@@ -5,14 +5,13 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {isAbsolute} from 'path';
+import {dirname, isAbsolute, resolve as pathResolve} from 'path';
 import pnpResolver from 'jest-pnp-resolver';
 import {sync as resolveSync} from 'resolve';
 import {
   Options as ResolveExportsOptions,
   resolve as resolveExports,
 } from 'resolve.exports';
-import slash = require('slash');
 import type {Config} from '@jest/types';
 import {
   PkgJson,
@@ -56,12 +55,58 @@ export default function defaultResolver(
     return pnpResolver(path, options);
   }
 
-  const result = resolveSync(path, {
+  let pathToResolve = path;
+
+  if (!isAbsolute(pathToResolve) && !pathToResolve.startsWith('.')) {
+    const segments = pathToResolve.split('/');
+
+    let moduleName = segments.shift();
+
+    if (moduleName) {
+      if (moduleName.startsWith('@')) {
+        moduleName = `${moduleName}/${segments.shift()}`;
+      }
+
+      const packageJsonPath = resolveSync(`${moduleName}/package.json`, {
+        ...options,
+        isDirectory,
+        isFile,
+        preserveSymlinks: false,
+        readPackageSync,
+        realpathSync,
+      });
+
+      if (isFile(packageJsonPath)) {
+        const pkg = readPackageCached(packageJsonPath);
+
+        if (pkg.exports) {
+          // we need to make sure resolve ignores `main`
+          delete pkg.main;
+
+          const subpath = segments.join('/') || '.';
+
+          const resolved = resolveExports(
+            pkg,
+            subpath,
+            createResolveOptions(options.conditions),
+          );
+
+          // TODO: should we throw if not?
+          if (resolved) {
+            pathToResolve = pathResolve(dirname(packageJsonPath), resolved);
+          }
+        }
+      }
+    }
+  }
+
+  console.log(pathToResolve);
+
+  const result = resolveSync(pathToResolve, {
     ...options,
     isDirectory,
     isFile,
-    packageFilter: createPackageFilter(path, options.packageFilter),
-    pathFilter: createPathFilter(path, options.conditions, options.pathFilter),
+    packageFilter: createPackageFilter(pathToResolve, options.packageFilter),
     preserveSymlinks: false,
     readPackageSync,
     realpathSync,
@@ -108,39 +153,13 @@ function createPackageFilter(
   };
 }
 
-function createPathFilter(
-  originalPath: Config.Path,
-  conditions?: Array<string>,
-  userFilter?: ResolverOptions['pathFilter'],
-): ResolverOptions['pathFilter'] {
-  if (shouldIgnoreRequestForExports(originalPath)) {
-    return userFilter;
-  }
-
-  const options: ResolveExportsOptions = conditions
+function createResolveOptions(
+  conditions: Array<string> | undefined,
+): ResolveExportsOptions {
+  return conditions
     ? {conditions, unsafe: true}
     : // no conditions were passed - let's assume this is Jest internal and it should be `require`
       {browser: false, require: true};
-
-  return function pathFilter(pkg, path, relativePath, ...rest) {
-    let pathToUse = relativePath;
-
-    if (userFilter) {
-      pathToUse = userFilter(pkg, path, relativePath, ...rest);
-    }
-
-    if (pkg.exports == null) {
-      return pathToUse;
-    }
-
-    // this `index` thing can backfire, but `resolve` adds it: https://github.com/browserify/resolve/blob/f1b51848ecb7f56f77bfb823511d032489a13eab/lib/sync.js#L192
-    const isRootRequire =
-      pathToUse === 'index' && !originalPath.endsWith('/index');
-
-    const newPath = isRootRequire ? '.' : slash(pathToUse);
-
-    return resolveExports(pkg, newPath, options) || pathToUse;
-  };
 }
 
 // if it's a relative import or an absolute path, exports are ignored