Bug 1719598 - fix unicode handling of file extensions in nsExternalHelperAppService, r=mtigley

Differential Revision: https://phabricator.services.mozilla.com/D120218

uriloader/exthandler/nsExternalHelperAppService.cpp

@@ -2800,7 +2800,7 @@ NS_IMETHODIMP nsExternalHelperAppService::GetFromTypeAndExtension(
     // XXXzpao This should probably be localized
     nsAutoCString desc(aFileExt);
     desc.AppendLiteral(" File");
-    (*_retval)->SetDescription(NS_ConvertASCIItoUTF16(desc));
+    (*_retval)->SetDescription(NS_ConvertUTF8toUTF16(desc));
     LOG(("Falling back to 'File' file description\n"));
   }
 

uriloader/exthandler/tests/unit/test_getFromTypeAndExtension.js

@@ -0,0 +1,17 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function test_utf8_extension() {
+  const mimeService = Cc["@mozilla.org/mime;1"].getService(Ci.nsIMIMEService);
+  let someMIME = mimeService.getFromTypeAndExtension(
+    "application/x-gobbledygook",
+    ".тест"
+  );
+  Assert.stringContains(someMIME.description, "тест");
+  // primary extension isn't set on macOS, see bug 1721181
+  if (AppConstants.platform != "macosx") {
+    Assert.equal(someMIME.primaryExtension, ".тест");
+  }
+});

uriloader/exthandler/tests/unit/xpcshell.ini

@@ -7,6 +7,7 @@ firefox-appdir = browser
 # No default stored handlers on android given lack of support.
 # No default stored handlers on Thunderbird.
 skip-if = os == "android" || appname == "thunderbird"
+[test_getFromTypeAndExtension.js]
 [test_getMIMEInfo_pdf.js]
 [test_getMIMEInfo_unknown_mime_type.js]
 run-if = os == "win" # Windows only test