Allow override for ENVIRONMENT_IS*

AUTHORS

@@ -209,4 +209,5 @@ a license to everyone to use it as detailed in LICENSE.)
 * Louis Lagrange <lagrange.louis@gmail.com>
 * Ying-Ruei Liang <thumbd03803@gmail.com>
 * Stuart Geipel <lapimlu@gmail.com>
+* Vincenzo Chianese <vincenz.chianese@icloud.com>
 

site/source/docs/api_reference/module.rst

@@ -103,3 +103,21 @@ Other methods
 
 	:param obj: The JavaScript-wrapped C++ object to be destroyed.
 	
+Overriding execution environment
+================================
+
+The generated program is able to detect its execution environment by checking the presence of some typical objects of the environment itself (such as ``window`` for browsers).
+
+However, sometimes it may be needed to override the detected environment: a typical use case would be module bundlers (like webpack): they are executed by nodejs but the final output is for browser.
+
+In order to do that, you can dictate your preferred execution environment by setting the ``Module.ENVIRONMENT`` variable to one of those allowed values: 
+
+``WEB``
+
+``WORKER``
+
+``NODE``
+
+``SHELL``
+
+In that case, ``Module`` will honor your preference and skip auto detection.

src/shell.js

@@ -34,13 +34,35 @@ for (var key in Module) {
 
 // The environment setup code below is customized to use Module.
 // *** Environment setup code ***
-var ENVIRONMENT_IS_WEB = typeof window === 'object';
+var ENVIRONMENT_IS_WEB = false;
+var ENVIRONMENT_IS_WORKER = false;
+var ENVIRONMENT_IS_NODE = false;
+var ENVIRONMENT_IS_SHELL = false;
+
 // Three configurations we can be running in:
 // 1) We could be the application main() thread running in the main JS UI thread. (ENVIRONMENT_IS_WORKER == false and ENVIRONMENT_IS_PTHREAD == false)
 // 2) We could be the application main() thread proxied to worker. (with Emscripten -s PROXY_TO_WORKER=1) (ENVIRONMENT_IS_WORKER == true, ENVIRONMENT_IS_PTHREAD == false)
 // 3) We could be an application pthread running in a worker. (ENVIRONMENT_IS_WORKER == true and ENVIRONMENT_IS_PTHREAD == true)
-var ENVIRONMENT_IS_WORKER = typeof importScripts === 'function';
-var ENVIRONMENT_IS_NODE = typeof process === 'object' && typeof require === 'function' && !ENVIRONMENT_IS_WEB && !ENVIRONMENT_IS_WORKER;
+
+if (Module['ENVIRONMENT']) {
+  if (Module['ENVIRONMENT'] === 'WEB') {
+    ENVIRONMENT_IS_WEB = true;
+  } else if (Module['ENVIRONMENT'] === 'WORKER') {
+    ENVIRONMENT_IS_WORKER = true;
+  } else if (Module['ENVIRONMENT'] === 'NODE') {
+    ENVIRONMENT_IS_NODE = true;
+  } else if (Module['ENVIRONMENT'] === 'SHELL') {
+    ENVIRONMENT_IS_SHELL = true;
+  } else {
+    throw new Error('The provided Module[\'ENVIRONMENT\'] value is not valid. It must be one of: WEB|WORKER|NODE|SHELL.');
+  }
+} else {
+  ENVIRONMENT_IS_WEB = typeof window === 'object';
+  ENVIRONMENT_IS_WORKER = typeof importScripts === 'function';
+  ENVIRONMENT_IS_NODE = typeof process === 'object' && typeof require === 'function' && !ENVIRONMENT_IS_WEB && !ENVIRONMENT_IS_WORKER;
+  ENVIRONMENT_IS_SHELL = !ENVIRONMENT_IS_WEB && !ENVIRONMENT_IS_NODE && !ENVIRONMENT_IS_WORKER;  
+}
+
 #if USE_PTHREADS
 var ENVIRONMENT_IS_PTHREAD;
 if (!ENVIRONMENT_IS_PTHREAD) ENVIRONMENT_IS_PTHREAD = false; // ENVIRONMENT_IS_PTHREAD=true will have been preset in pthread-main.js. Make it false in the main runtime thread.
@@ -48,7 +70,6 @@ var PthreadWorkerInit; // Collects together variables that are needed at initial
 if (!ENVIRONMENT_IS_PTHREAD) PthreadWorkerInit = {};
 var currentScriptUrl = ENVIRONMENT_IS_WORKER ? undefined : document.currentScript.src;
 #endif
-var ENVIRONMENT_IS_SHELL = !ENVIRONMENT_IS_WEB && !ENVIRONMENT_IS_NODE && !ENVIRONMENT_IS_WORKER;
 
 if (ENVIRONMENT_IS_NODE) {
   // Expose functionality in the same simple way that the shells work