Better method of unsetting and restoring Mozilla environment variables

Hopefully a better fix for #4981, which wasn't working properly on at
least some Linux systems because the variables were getting restored
before the subprocess launched. This delays a (debounced) second, to
give the subprocess time to start, and then automatically restores the
variables.

An explicit restart via app code also immediately restores the
variables, since restarts on Linux inherent the environment and don't
use our startup script. (An upgrade restart could still happen when the
variables were cleared, but you'd have to be extremely unlucky --
launching URLs or files while also performing a manual restart the same
second.)

chrome/content/zotero/xpcom/fileHandlers.js

@@ -157,9 +157,6 @@ Zotero.FileHandlers = {
 				catch (e) {
 					Zotero.logError(e);
 				}
-				finally {
-					Zotero.Utilities.Internal.Environment.restoreMozillaVariables();
-				}
 			}
 			
 			try {
@@ -508,9 +505,7 @@ Zotero.FileHandlers = {
 		Zotero.Utilities.Internal.Environment.clearMozillaVariables();
 		
 		// Do not await
-		var promise = Zotero.Utilities.Internal.exec(command, args);
-		
-		promise.finally(() => Zotero.Utilities.Internal.Environment.restoreMozillaVariables());
+		Zotero.Utilities.Internal.exec(command, args);
 	},
 };
 

chrome/content/zotero/xpcom/utilities_internal.js

@@ -1897,6 +1897,7 @@ Zotero.Utilities.Internal = {
 		var startup = Services.startup;
 		if (restart) {
 			Zotero.restarting = true;
+			this.Environment.restoreMozillaVariables();
 		}
 		startup.quit(startup.eAttemptQuit | (restart ? startup.eRestart : 0));
 	},
@@ -2999,21 +3000,44 @@ Zotero.Utilities.Internal.Environment = {
 	 * using the wrong Firefox profile when launching URLs or PDFs. On Windows, it's not necessary
 	 * to call this when launching URLs, only processes.
 	 *
+	 * The variables are restored a (debounced) second after this is called. Restoring mostly isn't
+	 * necessary, since most new launches of Zotero would use the modified launcher, but a restart
+	 * on Linux (e.g., during an upgrade) skips our shell script where we set these variables.
+	 *
 	 * https://github.com/zotero/zotero/issues/4981
 	 */
 	clearMozillaVariables: function () {
+		const RESTORE_DEBOUNCE_DELAY = 1000;
+		
 		this.unset("MOZ_ALLOW_DOWNGRADE");
 		this.unset("MOZ_LEGACY_PROFILES");
+		
+		if (this._restoreTimeout) {
+			clearTimeout(this._restoreTimeout);
+			delete this._restoreTimeout;
+		}
+		
+		this._restoreTimeout = setTimeout(() => {
+			delete this._restoreTimeout;
+			this._restoreMozillaVariables();
+		}, RESTORE_DEBOUNCE_DELAY);
 	},
 	
 	/**
-	 * Re-set the Mozilla environment variables that we changed in the launcher
+	 * Immediately restore the Mozilla environment variables
 	 *
-	 * Call this in a finally() after using unsetMozillaVariables(). This mostly isn't necessary,
-	 * since most new launches of Zotero would use the modified launcher, but a restart on Linux
-	 * skips our shell script where we set these variables.
+	 * The variables are automatically restored shortly after they're cleared, but this can be
+	 * called before explicit restarts.
 	 */
 	restoreMozillaVariables: function () {
+		if (this._restoreTimeout) {
+			clearTimeout(this._restoreTimeout);
+			delete this._restoreTimeout;
+		}
+		this._restoreMozillaVariables();
+	},
+	
+	_restoreMozillaVariables: function () {
 		var env = Cc["@mozilla.org/process/environment;1"].getService(Ci.nsIEnvironment);
 		env.set("MOZ_ALLOW_DOWNGRADE", "1");
 		env.set("MOZ_LEGACY_PROFILES", "1");

chrome/content/zotero/xpcom/zotero.js

@@ -1042,9 +1042,6 @@ Services.scriptloader.loadSubScript("resource://zotero/polyfill.js");
 				);
 			}
 		}
-		finally {
-			Zotero.Utilities.Internal.Environment.restoreMozillaVariables();
-		}
 	};
 	
 	
@@ -1072,9 +1069,7 @@ Services.scriptloader.loadSubScript("resource://zotero/polyfill.js");
 		Zotero.Utilities.Internal.Environment.clearMozillaVariables();
 		
 		// Async, but we don't want to block
-		var promise = Zotero.Utilities.Internal.exec(applicationPath, args);
-		
-		promise.finally(() => Zotero.Utilities.Internal.Environment.restoreMozillaVariables());
+		Zotero.Utilities.Internal.exec(applicationPath, args);
 	};
 	
 	
@@ -1104,27 +1099,18 @@ Services.scriptloader.loadSubScript("resource://zotero/polyfill.js");
 				if (!found.value) {
 					throw new Error(`Handler not found for '${scheme}' URLs`);
 				}
-				try {
-					if (!Zotero.isWin) {
-						Zotero.Utilities.Internal.Environment.clearMozillaVariables();
-					}
-					
-					svc.loadURI(Services.io.newURI(url, null, null));
-				}
-				finally {
-					if (!Zotero.isWin) {
-						Zotero.Utilities.Internal.Environment.restoreMozillaVariables();
-					}
+				if (!Zotero.isWin) {
+					Zotero.Utilities.Internal.Environment.clearMozillaVariables();
 				}
+				
+				svc.loadURI(Services.io.newURI(url, null, null));
 				return;
 			}
 		}
 		
-		var mozCleared = false;
 		try {
 			if (!Zotero.isWin) {
 				Zotero.Utilities.Internal.Environment.clearMozillaVariables();
-				mozCleared = true;
 			}
 			
 			var uri = Services.io.newURI(url, null, null);
@@ -1151,10 +1137,7 @@ Services.scriptloader.loadSubScript("resource://zotero/polyfill.js");
 					+ "check extensions.zotero." + pref + " in about:config");
 			}
 			
-			if (!mozCleared) {
-				Zotero.Utilities.Internal.Environment.clearMozillaVariables();
-				mozCleared = true;
-			}
+			Zotero.Utilities.Internal.Environment.clearMozillaVariables();
 			
 			var proc = Components.classes["@mozilla.org/process/util;1"]
 							.createInstance(Components.interfaces.nsIProcess);
@@ -1163,11 +1146,6 @@ Services.scriptloader.loadSubScript("resource://zotero/polyfill.js");
 			var args = [url];
 			proc.runw(false, args, args.length);
 		}
-		finally {
-			if (mozCleared) {
-				Zotero.Utilities.Internal.Environment.restoreMozillaVariables();
-			}
-		}
 	}