Electron-builder: [electron-updater] Expose location of cacheDir

[MartynasZilinskas]

Use case:
When installing an update is unsuccessful, it would be possible to provide user where to save the latest downloaded installer to install it manually.

So it would be nice to have the full path to the downloaded installer, or at least a location where updates are downloaded.

Workaround:

// @ts-ignore
const cacheDir: string = autoUpdater.downloadedUpdateHelper.cacheDir);

[develar]

Related #2709

[develar]

I don't fully understand you. Will be API soon to check _only_ cached update and install it if need.

[develar]

I don't like idea to expose internals. Instead, API to solve some task should be provided.

[MartynasZilinskas]

I don't like idea to expose internals.

Yeah, I understand that. Having full download URL and saved location, would be a big plus. To create better user experience when downloading/installing updates, in case of failure of downloading/installing an update.

[develar]

@MartynasZilinskas Please describe your use case. I don't see any reason why app can show stupid message like "Sorry, install by hand this file". We are not Microsoft. That's why I linked #2709 — in most cases "installing an update is unsuccessful" because user hard reset PC or quickly shutdown/sleep PC. New API will allow you to implement scenario like "install not on quit, but on first run after downloading".

[DovydasNavickas]

The use case is quite simple: The auto updater fails (for Ubuntu in this case), because it lacks permissions or some other reason. We want to give user exactly that: "An aut-update has failed. Please try again or download here and install it manually."

Saying that auto-updater fails only when users quickly shut down or sleep their PCs is more than optimistic, cause' there might be gazillion of errors with permissions, network and many more.

Thus, it'd be nice to have the API to get:

• full download URL
• location where file was saved

This way we can solve the problem without digging into internal stuff by going around TypeScript with // @ts-ignore 👍

[develar]

update-downloaded event now has property downloadedFile.