[Fix] preserveSymlinks: false ensure that files are realpathed

Fixes #196.

Author: ljharb

.eslintrc

@@ -27,5 +27,13 @@
         "object-curly-newline": 0,
         "operator-linebreak": [2, "before"],
         "sort-keys": 0,
-    }
+    },
+    "overrides": [
+        {
+            "files": "test/resolver/nested_symlinks/mylib/*.js",
+            "rules": {
+                "no-throw-literal": 0,
+            },
+        },
+    ],
 }

lib/async.js

@@ -85,8 +85,15 @@ module.exports = function resolve(x, options, callback) {
         } else loadNodeModules(x, basedir, function (err, n, pkg) {
             if (err) cb(err);
             else if (core[x]) return cb(null, x);
-            else if (n) cb(null, n, pkg);
-            else {
+            else if (n) {
+                return maybeUnwrapSymlink(n, opts, function (err, realN) {
+                    if (err) {
+                        cb(err);
+                    } else {
+                        cb(null, realN, pkg);
+                    }
+                });
+            } else {
                 var moduleError = new Error("Cannot find module '" + x + "' from '" + parent + "'");
                 moduleError.code = 'MODULE_NOT_FOUND';
                 cb(moduleError);
@@ -99,8 +106,15 @@ module.exports = function resolve(x, options, callback) {
         else if (m) cb(null, m, pkg);
         else loadAsDirectory(res, function (err, d, pkg) {
             if (err) cb(err);
-            else if (d) cb(null, d, pkg);
-            else {
+            else if (d) {
+                maybeUnwrapSymlink(d, opts, function (err, realD) {
+                    if (err) {
+                        cb(err);
+                    } else {
+                        cb(null, realD, pkg);
+                    }
+                });
+            } else {
                 var moduleError = new Error("Cannot find module '" + x + "' from '" + parent + "'");
                 moduleError.code = 'MODULE_NOT_FOUND';
                 cb(moduleError);

lib/sync.js

@@ -61,12 +61,12 @@ module.exports = function (x, options) {
         var res = path.resolve(absoluteStart, x);
         if (x === '..' || x.slice(-1) === '/') res += '/';
         var m = loadAsFileSync(res) || loadAsDirectorySync(res);
-        if (m) return m;
+        if (m) return maybeUnwrapSymlink(m, opts);
     } else if (core[x]) {
         return x;
     } else {
         var n = loadNodeModulesSync(x, absoluteStart);
-        if (n) return n;
+        if (n) return maybeUnwrapSymlink(n, opts);
     }
 
     if (core[x]) return x;

package.json

@@ -16,6 +16,7 @@
   "scripts": {
     "prepublish": "safe-publish-latest",
     "lint": "eslint .",
+    "pretests-only": "cd ./test/resolver/nested_symlinks && node mylib/sync && node mylib/async",
     "tests-only": "tape test/*.js",
     "pretest": "npm run lint",
     "test": "npm run --silent tests-only",

test/resolver/nested_symlinks/common/node_modules/buffer/index.js

@@ -0,0 +1,26 @@
+var a = require.resolve('buffer/').replace(process.cwd(), '$CWD');
+var b;
+var c;
+
+var test = function test() {
+    console.log(a, ': require.resolve, preserveSymlinks ' + (process.execArgv.indexOf('preserve-symlinks') > -1 ? 'true' : 'false'));
+    console.log(b, ': preserveSymlinks true');
+    console.log(c, ': preserveSymlinks false');
+
+    if (a !== b && a !== c) {
+        throw 'async: no match';
+    }
+    console.log('async: success! a matched either b or c\n');
+};
+
+require('resolve')('buffer/', { preserveSymlinks: true }, function (err, result) {
+    if (err) { throw err; }
+    b = result.replace(process.cwd(), '$CWD');
+    if (b && c) { test(); }
+});
+require('resolve')('buffer/', { preserveSymlinks: false }, function (err, result) {
+    if (err) { throw err; }
+    c = result.replace(process.cwd(), '$CWD');
+    if (b && c) { test(); }
+});
+

test/resolver/nested_symlinks/common/node_modules/buffer/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "mylib",
+  "version": "0.0.0",
+  "description": "",
+  "private": true,
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "buffer": "*"
+  }
+}