Experimental: Symlinks Just Work

lib/module.js

@@ -11,6 +11,7 @@ const path = require('path');
 const internalModuleReadFile = process.binding('fs').internalModuleReadFile;
 const internalModuleStat = process.binding('fs').internalModuleStat;
 const preserveSymlinks = !!process.binding('config').preserveSymlinks;
+const adjacentNodeModules = !!process.binding('config').adjacentNodeModules;
 
 // If obj.hasOwnProperty has been overridden, then calling
 // obj.hasOwnProperty(prop) will break.
@@ -120,7 +121,7 @@ const realpathCache = new Map();
 // absolute realpath.
 function tryFile(requestPath, isMain) {
   const rc = stat(requestPath);
-  if (preserveSymlinks && !isMain) {
+  if (preserveSymlinks && !isMain || adjacentNodeModules) {
     return rc === 0 && path.resolve(requestPath);
   }
   return rc === 0 && toRealPath(requestPath);
@@ -172,7 +173,7 @@ Module._findPath = function(request, paths, isMain) {
     const rc = stat(basePath);
     if (!trailingSlash) {
       if (rc === 0) {  // File.
-        if (preserveSymlinks && !isMain) {
+        if (preserveSymlinks && !isMain || adjacentNodeModules) {
           filename = path.resolve(basePath);
         } else {
           filename = toRealPath(basePath);
@@ -253,9 +254,22 @@ if (process.platform === 'win32') {
       // Use colon as an extra condition since we can get node_modules
       // path for dirver root like 'C:\node_modules' and don't need to
       // parse driver name.
-      if (code === 92/*\*/ || code === 47/*/*/ || code === 58/*:*/) {
-        if (p !== nmLen)
-          paths.push(from.slice(0, last) + '\\node_modules');
+      if (code === 92/*\*/ || code === 47/*/*/ || code === 58/*:*/
+        || (adjacentNodeModules && code === 46/*.*/)) {
+        if (p !== nmLen) {
+          var parent = from.slice(0, last);
+          paths.push(parent + '\\node_modules');
+
+          if (adjacentNodeModules) {
+            paths.push(parent + '.node_modules');
+            if (code === 46/*.*/)
+              while (i > 1) {
+                const code = from.charCodeAt(--i);
+                if (code === 92/*\*/ || code === 47/*/*/ || code === 58/*:*/)
+                  break;
+              }
+          }
+        }
         last = i;
         p = 0;
       } else if (p !== -1) {
@@ -267,6 +281,9 @@ if (process.platform === 'win32') {
       }
     }
 
+    // superfluous "/.node_modules"
+    if (adjacentNodeModules) paths.pop();
+
     return paths;
   };
 } else { // posix
@@ -287,9 +304,17 @@ if (process.platform === 'win32') {
     var last = from.length;
     for (var i = from.length - 1; i >= 0; --i) {
       const code = from.charCodeAt(i);
-      if (code === 47/*/*/) {
-        if (p !== nmLen)
-          paths.push(from.slice(0, last) + '/node_modules');
+      if (code === 47/*/*/ || (adjacentNodeModules && code === 46/*.*/)) {
+        if (p !== nmLen) {
+          var parent = from.slice(0, last);
+          paths.push(parent + '/node_modules');
+
+          if (adjacentNodeModules) {
+            paths.push(parent + '.node_modules');
+            if (code === 46/*.*/)
+              while (i > 1 && from.charCodeAt(--i) !== 47/*/*/);
+          }
+        }
         last = i;
         p = 0;
       } else if (p !== -1) {
@@ -301,6 +326,9 @@ if (process.platform === 'win32') {
       }
     }
 
+    // superfluous "/.node_modules"
+    if (adjacentNodeModules) paths.pop();
+
     // Append /node_modules to handle root paths.
     paths.push('/node_modules');
 
@@ -416,13 +444,16 @@ Module._load = function(request, parent, isMain) {
   }
 
   var filename = Module._resolveFilename(request, parent, isMain);
+  var doesNonInternalExist = NativeModule.nonInternalExists(filename);
+  var cachePath = adjacentNodeModules && !doesNonInternalExist
+    ? toRealPath(filename) : filename;
 
-  var cachedModule = Module._cache[filename];
+  var cachedModule = Module._cache[cachePath];
   if (cachedModule) {
     return cachedModule.exports;
   }
 
-  if (NativeModule.nonInternalExists(filename)) {
+  if (doesNonInternalExist) {
     debug('load native module %s', request);
     return NativeModule.require(filename);
   }
@@ -434,21 +465,21 @@ Module._load = function(request, parent, isMain) {
     module.id = '.';
   }
 
-  Module._cache[filename] = module;
+  Module._cache[cachePath] = module;
 
-  tryModuleLoad(module, filename);
+  tryModuleLoad(module, filename, cachePath);
 
   return module.exports;
 };
 
-function tryModuleLoad(module, filename) {
+function tryModuleLoad(module, filename, cachePath) {
   var threw = true;
   try {
     module.load(filename);
     threw = false;
   } finally {
     if (threw) {
-      delete Module._cache[filename];
+      delete Module._cache[cachePath];
     }
   }
 }

src/node.cc

@@ -186,7 +186,7 @@ bool trace_warnings = false;
 // Used in node_config.cc to set a constant on process.binding('config')
 // that is used by lib/module.js
 bool config_preserve_symlinks = false;
-
+bool config_adjacent_node_modules = false;
 bool v8_initialized = false;
 
 // process-relative uptime base, initialized at start-up
@@ -3702,6 +3702,8 @@ static void ParseArgs(int* argc,
       Revert(cve);
     } else if (strcmp(arg, "--preserve-symlinks") == 0) {
       config_preserve_symlinks = true;
+    } else if (strcmp(arg, "--adjacent-node-modules") == 0) {
+      config_adjacent_node_modules = true;
     } else if (strcmp(arg, "--prof-process") == 0) {
       prof_process = true;
       short_circuit = true;
@@ -4213,6 +4215,12 @@ void Init(int* argc,
     config_preserve_symlinks = (*preserve_symlinks == '1');
   }
 
+  if (auto adjacent_node_modules
+    = secure_getenv("NODE_ADJACENT_NODE_MODULES")) {
+
+    config_adjacent_node_modules = (*adjacent_node_modules == '1');
+  }
+
   // Parse a few arguments which are specific to Node.
   int v8_argc;
   const char** v8_argv;

src/node_config.cc

@@ -44,6 +44,9 @@ void InitConfig(Local<Object> target,
 
   if (config_preserve_symlinks)
     READONLY_BOOLEAN_PROPERTY("preserveSymlinks");
+
+  if (config_adjacent_node_modules)
+    READONLY_BOOLEAN_PROPERTY("adjacentNodeModules");
 }  // InitConfig
 
 }  // namespace node

src/node_internals.h

@@ -40,6 +40,7 @@ extern const char* openssl_config;
 // Used in node_config.cc to set a constant on process.binding('config')
 // that is used by lib/module.js
 extern bool config_preserve_symlinks;
+extern bool config_adjacent_node_modules;
 
 // Tells whether it is safe to call v8::Isolate::GetCurrent().
 extern bool v8_initialized;