On Windows, patch Node's lstat to work around permissions error. Fixesaspnet#1101

Author: SteveSandersonMS

src/Microsoft.AspNetCore.NodeServices/Content/Node/entrypoint-http.js

@@ -55,10 +55,11 @@
 // Limit dependencies to core Node modules. This means the code in this file has to be very low-level and unattractive,
 // but simplifies things for the consumer of this module.
 __webpack_require__(2);
-varhttp=__webpack_require__(3);
-varpath=__webpack_require__(4);
-varArgsUtil_1=__webpack_require__(5);
-varExitWhenParentExits_1=__webpack_require__(6);
+__webpack_require__(4);
+varhttp=__webpack_require__(5);
+varpath=__webpack_require__(3);
+varArgsUtil_1=__webpack_require__(6);
+varExitWhenParentExits_1=__webpack_require__(7);
 // Webpack doesn't support dynamic requires for files not present at compile time, so grab a direct
 // reference to Node's runtime 'require' function.
 vardynamicRequire=eval('require');
@@ -142,6 +143,64 @@
 
 /***/},
 /* 2 */
+/***/function(module,exports,__webpack_require__){
+
+"use strict";
+varpath=__webpack_require__(3);
+varstartsWith=function(str,prefix){returnstr.substring(0,prefix.length)===prefix;};
+varappRootDir=process.cwd();
+functionpatchedLStat(pathToStatLong){
+try{
+// If the lstat completes without errors, we don't modify its behavior at all
+returnorigLStat.apply(this,arguments);
+}
+catch(ex){
+varshouldOverrideError=startsWith(ex.message,'EPERM')// It's a permissions error
+&&typeofappRootDirLong==='string'
+&&startsWith(appRootDirLong,pathToStatLong)// ... for an ancestor directory
+&&ex.stack.indexOf('Object.realpathSync ')>=0;// ... during symlink resolution
+if(shouldOverrideError){
+// Fake the result to give the same result as an 'lstat' on the app root dir.
+// This stops Node failing to load modules just because it doesn't know whether
+// ancestor directories are symlinks or not. If there's a genuine file
+// permissions issue, it will still surface later when Node actually
+// tries to read the file.
+returnorigLStat.call(this,appRootDir);
+}
+else{
+// In any other case, preserve the original error
+throwex;
+}
+}
+}
+;
+// It's only necessary to apply this workaround on Windows
+varappRootDirLong=null;
+varorigLStat=null;
+if(/^win/.test(process.platform)){
+try{
+// Get the app's root dir in Node's internal "long" format (e.g., \\?\C:\dir\subdir)
+appRootDirLong=path._makeLong(appRootDir);
+// Actually apply the patch, being as defensive as possible
+varbindingFs=process.binding('fs');
+origLStat=bindingFs.lstat;
+if(typeoforigLStat==='function'){
+bindingFs.lstat=patchedLStat;
+}
+}
+catch(ex){
+}
+}
+
+
+/***/},
+/* 3 */
+/***/function(module,exports){
+
+module.exports=require("path");
+
+/***/},
+/* 4 */
 /***/function(module,exports){
 
 // When Node writes to stdout/strerr, we capture that and convert the lines into calls on the
@@ -182,19 +241,13 @@
 
 
 /***/},
-/* 3 */
+/* 5 */
 /***/function(module,exports){
 
 module.exports=require("http");
 
 /***/},
-/* 4 */
-/***/function(module,exports){
-
-module.exports=require("path");
-
-/***/},
-/* 5 */
+/* 6 */
 /***/function(module,exports){
 
 "use strict";
@@ -220,7 +273,7 @@
 
 
 /***/},
-/* 6 */
+/* 7 */
 /***/function(module,exports){
 
 /*

src/Microsoft.AspNetCore.NodeServices/TypeScript/HttpNodeInstanceEntryPoint.ts

@@ -1,5 +1,6 @@
 // Limit dependencies to core Node modules. This means the code in this file has to be very low-level and unattractive,
 // but simplifies things for the consumer of this module.
+import'./Util/PatchModuleResolutionLStat';
 import'./Util/OverrideStdOutputs';
 import*ashttpfrom'http';
 import*aspathfrom'path';

src/Microsoft.AspNetCore.NodeServices/TypeScript/Util/PatchModuleResolutionLStat.ts

@@ -0,0 +1,48 @@
+import*aspathfrom'path';
+conststartsWith=(str: string,prefix: string)=>str.substring(0,prefix.length)===prefix;
+constappRootDir=process.cwd();
+
+functionpatchedLStat(pathToStatLong: string){
+try{
+// If the lstat completes without errors, we don't modify its behavior at all
+returnorigLStat.apply(this,arguments);
+}catch(ex){
+constshouldOverrideError=
+startsWith(ex.message,'EPERM')// It's a permissions error
+&&typeofappRootDirLong==='string'
+&&startsWith(appRootDirLong,pathToStatLong)// ... for an ancestor directory
+&&ex.stack.indexOf('Object.realpathSync ')>=0;// ... during symlink resolution
+
+if(shouldOverrideError){
+// Fake the result to give the same result as an 'lstat' on the app root dir.
+// This stops Node failing to load modules just because it doesn't know whether
+// ancestor directories are symlinks or not. If there's a genuine file
+// permissions issue, it will still surface later when Node actually
+// tries to read the file.
+returnorigLStat.call(this,appRootDir);
+}else{
+// In any other case, preserve the original error
+throwex;
+}
+}
+};
+
+// It's only necessary to apply this workaround on Windows
+letappRootDirLong: string=null;
+letorigLStat: Function=null;
+if(/^win/.test(process.platform)){
+try{
+// Get the app's root dir in Node's internal "long" format (e.g., \\?\C:\dir\subdir)
+appRootDirLong=(pathasany)._makeLong(appRootDir);
+
+// Actually apply the patch, being as defensive as possible
+constbindingFs=(processasany).binding('fs');
+origLStat=bindingFs.lstat;
+if(typeoforigLStat==='function'){
+bindingFs.lstat=patchedLStat;
+}
+}catch(ex){
+// If some future version of Node throws (e.g., to prevent use of process.binding()),
+// don't apply the patch, but still let the application run.
+}
+}