module: preserve symlinks when requiring

lib/module.js

@@ -97,27 +97,32 @@ function readPackage(requestPath) {
   return pkg;
 }
 
-function tryPackage(requestPath, exts) {
+function tryPackage(requestPath, exts, isMain) {
   var pkg = readPackage(requestPath);
 
   if (!pkg) return false;
 
   var filename = path.resolve(requestPath, pkg);
-  return tryFile(filename) ||
-         tryExtensions(filename, exts) ||
-         tryExtensions(path.resolve(filename, 'index'), exts);
+  return tryFile(filename, isMain) ||
+         tryExtensions(filename, exts, isMain) ||
+         tryExtensions(path.resolve(filename, 'index'), exts, isMain);
 }
 
 // check if the file exists and is not a directory
-function tryFile(requestPath) {
+// resolve to the absolute realpath if running main module,
+// otherwise resolve to absolute while keeping symlinks intact.
+function tryFile(requestPath, isMain) {
   const rc = stat(requestPath);
-  return rc === 0 && fs.realpathSync(requestPath);
+  if (isMain) {
+    return rc === 0 && fs.realpathSync(requestPath);
+  }
+  return rc === 0 && path.resolve(requestPath);
 }
 
 // given a path check a the file exists with any of the set extensions
-function tryExtensions(p, exts) {
+function tryExtensions(p, exts, isMain) {
   for (var i = 0; i < exts.length; i++) {
-    const filename = tryFile(p + exts[i]);
+    const filename = tryFile(p + exts[i], isMain);
 
     if (filename) {
       return filename;
@@ -127,7 +132,7 @@ function tryExtensions(p, exts) {
 }
 
 var warned = false;
-Module._findPath = function(request, paths) {
+Module._findPath = function(request, paths, isMain) {
   if (path.isAbsolute(request)) {
     paths = [''];
   } else if (!paths || paths.length === 0) {
@@ -154,32 +159,36 @@ Module._findPath = function(request, paths) {
     if (!trailingSlash) {
       const rc = stat(basePath);
       if (rc === 0) {  // File.
-        filename = fs.realpathSync(basePath);
+        if (!isMain) {
+          filename = path.resolve(basePath);
+        } else {
+          filename = fs.realpathSync(basePath);
+        }
       } else if (rc === 1) {  // Directory.
         if (exts === undefined)
           exts = Object.keys(Module._extensions);
-        filename = tryPackage(basePath, exts);
+        filename = tryPackage(basePath, exts, isMain);
       }
 
       if (!filename) {
         // try it with each of the extensions
         if (exts === undefined)
           exts = Object.keys(Module._extensions);
-        filename = tryExtensions(basePath, exts);
+        filename = tryExtensions(basePath, exts, isMain);
       }
     }
 
     if (!filename) {
       if (exts === undefined)
         exts = Object.keys(Module._extensions);
-      filename = tryPackage(basePath, exts);
+      filename = tryPackage(basePath, exts, isMain);
     }
 
     if (!filename) {
       // try it with each of the extensions at "index"
       if (exts === undefined)
         exts = Object.keys(Module._extensions);
-      filename = tryExtensions(path.resolve(basePath, 'index'), exts);
+      filename = tryExtensions(path.resolve(basePath, 'index'), exts, isMain);
     }
 
     if (filename) {
@@ -374,7 +383,7 @@ Module._load = function(request, parent, isMain) {
     debug('Module._load REQUEST %s parent: %s', request, parent.id);
   }
 
-  var filename = Module._resolveFilename(request, parent);
+  var filename = Module._resolveFilename(request, parent, isMain);
 
   var cachedModule = Module._cache[filename];
   if (cachedModule) {
@@ -412,7 +421,7 @@ function tryModuleLoad(module, filename) {
   }
 }
 
-Module._resolveFilename = function(request, parent) {
+Module._resolveFilename = function(request, parent, isMain) {
   if (NativeModule.nonInternalExists(request)) {
     return request;
   }
@@ -424,7 +433,7 @@ Module._resolveFilename = function(request, parent) {
   // look up the filename first, since that's the cache key.
   debug('looking for %j in %j', id, paths);
 
-  var filename = Module._findPath(request, paths);
+  var filename = Module._findPath(request, paths, isMain);
   if (!filename) {
     var err = new Error("Cannot find module '" + request + "'");
     err.code = 'MODULE_NOT_FOUND';

test/fixtures/module-require-symlink/foo.js

@@ -0,0 +1,2 @@
+exports.dep1 = require('dep1');
+exports.dep2 = exports.dep1.dep2;

test/fixtures/module-require-symlink/symlinked.js

@@ -0,0 +1,13 @@
+'use strict';
+const assert = require('assert');
+const common = require('../../common');
+const path = require('path');
+
+const linkScriptTarget = path.join(common.fixturesDir,
+  '/module-require-symlink/symlinked.js');
+
+var foo = require('./foo');
+assert.equal(foo.dep1.bar.version, 'CORRECT_VERSION');
+assert.equal(foo.dep2.bar.version, 'CORRECT_VERSION');
+assert.equal(__filename, linkScriptTarget);
+assert(__filename in require.cache);

test/parallel/test-require-symlink.js

@@ -0,0 +1,57 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const path = require('path');
+const fs = require('fs');
+const exec = require('child_process').exec;
+const spawn = require('child_process').spawn;
+
+const linkTarget = path.join(common.fixturesDir,
+  '/module-require-symlink/node_modules/dep2/');
+
+const linkDir = path.join(common.fixturesDir,
+  '/module-require-symlink/node_modules/dep1/node_modules/dep2');
+
+const linkScriptTarget = path.join(common.fixturesDir,
+  '/module-require-symlink/symlinked.js');
+
+const linkScript = path.join(common.tmpDir, 'module-require-symlink.js');
+
+if (common.isWindows) {
+  // On Windows, creating symlinks requires admin privileges.
+  // We'll only try to run symlink test if we have enough privileges.
+  exec('whoami /priv', function(err, o) {
+    if (err || o.indexOf('SeCreateSymbolicLinkPrivilege') == -1) {
+      console.log('Skipped: insufficient privileges');
+      return;
+    } else {
+      test();
+    }
+  });
+} else {
+  test();
+}
+
+function test() {
+  process.on('exit', function() {
+    fs.unlinkSync(linkDir);
+    fs.unlinkSync(linkScript);
+  });
+
+  fs.symlinkSync(linkTarget, linkDir);
+  fs.symlinkSync(linkScriptTarget, linkScript);
+
+  // load symlinked-module
+  var fooModule =
+    require(path.join(common.fixturesDir, '/module-require-symlink/foo.js'));
+  assert.equal(fooModule.dep1.bar.version, 'CORRECT_VERSION');
+  assert.equal(fooModule.dep2.bar.version, 'CORRECT_VERSION');
+
+  // load symlinked-script as main
+  var node = process.execPath;
+  var child = spawn(node, [linkScript]);
+  child.on('close', function(code, signal) {
+    assert(!code);
+    assert(!signal);
+  });
+}