Implementation of --adjacent-node-modules to support module symlinking to global cache

lib/module.js

@@ -10,6 +10,8 @@ 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
+  || (process.env.NODE_ADJACENT_NODE_MODULES || '0') === '1';
 
 // If obj.hasOwnProperty has been overridden, then calling
 // obj.hasOwnProperty(prop) will break.
@@ -122,7 +124,7 @@ delete fs.realpathCacheKey;
 // 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);
@@ -174,7 +176,7 @@ Module._findPath = function(request, paths, isMain) {
     if (!trailingSlash) {
       const rc = stat(basePath);
       if (rc === 0) {  // File.
-        if (preserveSymlinks && !isMain) {
+        if (preserveSymlinks && !isMain || adjacentNodeModules) {
           filename = path.resolve(basePath);
         } else {
           filename = toRealPath(basePath);
@@ -255,9 +257,22 @@ 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 === 47/*.*/)) {
+        if (p !== nmLen) {
+          var parent = from.slice(0, last);
+          paths.push(parent + '\\node_modules');
+
+          if (adjacentNodeModules) {
+            paths.push(parent + '.node_modules');
+            if (code === 46/*.*/ && i > 0)
+              while (--i >= 0) {
+                const code = from.charCodeAt(i);
+                if (code === 92/*\*/ || code === 47/*/*/ || code === 58/*:*/)
+                  break;
+              }
+          }
+        }
         last = i;
         p = 0;
       } else if (p !== -1) {
@@ -269,6 +284,8 @@ if (process.platform === 'win32') {
       }
     }
 
+    if (adjacentNodeModules) paths.pop();
+
     return paths;
   };
 } else { // posix
@@ -289,9 +306,21 @@ 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/*.*/ && i > 0)
+              while (--i >= 0) {
+                const code = from.charCodeAt(i);
+                if (code === 47/*/*/)
+                  break;
+              }
+          }
+        }
         last = i;
         p = 0;
       } else if (p !== -1) {
@@ -303,6 +332,8 @@ if (process.platform === 'win32') {
       }
     }
 
+    if (adjacentNodeModules) paths.pop();
+
     // Append /node_modules to handle root paths.
     paths.push('/node_modules');
 

src/node.cc

@@ -185,6 +185,10 @@ 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;
+// Set in node.cc by ParseArgs when --adjacent-node-modules is used.
+// Used in node_config.cc to set a constant on process.binding('config')
+// that is used by lib/module.js
+bool config_adjacent_node_modules = false;
 
 bool v8_initialized = false;
 
@@ -3704,6 +3708,8 @@ 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;

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

@@ -41,6 +41,11 @@ extern const char* openssl_config;
 // that is used by lib/module.js
 extern bool config_preserve_symlinks;
 
+// Set in node.cc by ParseArgs when --adjacent-node-modules is used.
+// Used in node_config.cc to set a constant on process.binding('config')
+// that is used by lib/module.js
+extern bool config_adjacent_node_modules;
+
 // Tells whether it is safe to call v8::Isolate::GetCurrent().
 extern bool v8_initialized;