detect project save based on content type

Also, if saving a file is canceled, only try to cancel project save
telemetry if the save was a project save.

Also also, don't skip showing the save dialog just because a file
doesn't have an extension. Instead, just skip trying to determine
filters for the extension in this case.

Author: Christopher Willis-Ford

src/main/index.js

@@ -73,6 +73,14 @@ const createAboutWindow = () => {
     return window;
 };
 
+const getIsProjectSave = downloadItem => {
+    switch (downloadItem.getMimeType()) {
+    case 'application/x.scratch.sb3':
+        return true;
+    }
+    return false;
+};
+
 const createMainWindow = () => {
     const window = createWindow({
         width: defaultSize.width,
@@ -82,29 +90,32 @@ const createMainWindow = () => {
     const webContents = window.webContents;
 
     webContents.session.on('will-download', (ev, item) => {
+        const isProjectSave = getIsProjectSave(item);
         const itemPath = item.getFilename();
         const baseName = path.basename(itemPath);
         const extName = path.extname(baseName);
+        const options = {
+            defaultPath: baseName
+        };
         if (extName) {
             const extNameNoDot = extName.replace(/^\./, '');
-            const options = {
-                defaultPath: baseName,
-                filters: [getFilterForExtension(extNameNoDot)]
-            };
-            const userChosenPath = dialog.showSaveDialog(window, options);
-            if (userChosenPath) {
-                item.setSavePath(userChosenPath);
-                if (extNameNoDot.toUpperCase() == "SB3") { // when a project is downloaded, not an asset
-                    const newProjectTitle = path.basename(userChosenPath, extName);
-                    webContents.send('setTitleFromSave', {title: newProjectTitle});
-
-                    // "setTitleFromSave" will set the project title but GUI has already reported the telemetry event
-                    // using the old title. This call lets the telemetry client know that the save was actually completed
-                    // and the event should be committed to the event queue with this new title.
-                    telemetry.projectSaveCompleted(newProjectTitle);
-                }
-            } else {
-                item.cancel();
+            options.filters = [getFilterForExtension(extNameNoDot)];
+        }
+        const userChosenPath = dialog.showSaveDialog(window, options);
+        if (userChosenPath) {
+            item.setSavePath(userChosenPath);
+            if (isProjectSave) {
+                const newProjectTitle = path.basename(userChosenPath, extName);
+                webContents.send('setTitleFromSave', {title: newProjectTitle});
+
+                // "setTitleFromSave" will set the project title but GUI has already reported the telemetry event
+                // using the old title. This call lets the telemetry client know that the save was actually completed
+                // and the event should be committed to the event queue with this new title.
+                telemetry.projectSaveCompleted(newProjectTitle);
+            }
+        } else {
+            item.cancel();
+            if (isProjectSave) {
                 telemetry.projectSaveCanceled();
             }
         }