How to extract zip file with lightroom sdk?

Question

I am developing a lightroom plugin and have a requirement to update the plugin with the plugin manager. I am storing all the plugin versions on the server in a zip file. Now I wanted to download and extract that file to the plugin directory. I can download that zip file on the plugin directory but don't have an idea to extract that zip file. The plugin is compatible with windows and mac so I need some solution that can extract that plugin file into the plugin directory. Below is the code for downloading the zip file.

local downloadButton = f:push_button { -- create button
    enabled = bind 'downloadButton',
    visible = false,
    title = "Download",
    bind_to_object = prefs,
    action = function( button )
        local headers = {
            { field = 'Content-Type', value = "application/json" }
        }
        LrTasks.startAsyncTask(
            function()
                local url = "https://WEBSITEPATH/assets/plugins/staging/1.3.5/BatchAI.lrdevplugin.zip"
                local response, hdrs = LrHttp.get(url,headers)
                local saveFile = assert(io.open(downloadPath .. "BatchAI.lrdevplugin", 'wb'))
                saveFile:write(response)
                saveFile:close()
                LrDialogs.message('Plugin updated')
            end
        )
    end
}

If anyone has a solution on how to extract the zip file or any other solution to update the plugin withing the plugin manager, please share your thoughts here. Thank you.

Answer 1

Have you considered doing it via a shell command using LrTasks.execute(cmd)? You can then use LrPathUtils and LrFileUtils namespaces of the Lightroom API for copying/moving/deleting files as needed.

MacOS has native unzip support:

unzip plugin.zip - d ~/another/foo

In Windows 10, PowerShell can do it using "Expand-Archive" cmdlet, available in PowerShell version V5+, which is installed by default in Windows 10.

Windows 10 using PowerShell v5+:

Expand-Archive C:\foo\plugin.zip C:\somefolder

or if you want to be more precise:

Expand-Archive -Path "C:\my foo\plugin.zip" -DestinationPath "C:\My Docs"

or when called through LrTasks.execute(cmd):

local cmd = 'powershell -Command "Expand-Archive C:\foo\plugin.zip C:\somewhere"' 
local status = LrTasks.execute(cmd)

But, since April 2018, Windows 10 has tar support, available in both the Command Prompt and PowerShell, bringing Windows 10 in line with MacOS and Linux, making everything more convenient:

tar -xf foo.zip -C c:\somefolder

or the (more clear) long form:

tar --extract --file foo.zip --directory c:\somefolder

That said, a good practice is to check for the existence of a command in Windows and take further steps accordingly.

In the Command Prompt, you can check if a command exists using WHERE:

WHERE tar

If command exists, it will return the path of the executable, if it doesn't, it will return a message to that effect.

WHERE tar
C:\Windows\System32\tar.exe

WHERE foo
INFO: Could not find files for the given pattern(s).

In PowerShell, you can check if a command exists using Get-Command:

Get-Command Expand-Archive
Get-Command Extract-Archive

If command exists, PowerShell will display the version of it, or an error otherwise:

Get-Command Expand-Archive
Function  Expand-Archive 1.0.1.0  Microsoft.PowerShell.Archive

Get-Command Extract-Archive
Get-Command : The term 'Extract-Archive' is not recognized as the name of a cmdlet...

In any cases, Lightroom's LrTasks.execute(cmd) will return the exit status of the OS shell command, which is 0 for success or 1 (or some other numbers) if erros or not found:

local status = LrTasks.execute('cmd /c "WHERE tar"')

Here's a sample gist I made for this, for checking for a command support using Lua and the Lightroom SDK: https://gist.github.com/27shutterclicks/6fb07c58d3bc5477612c6e0257d20e6f

My own preference is to stick with tar since it allows for the same command across operating systems, with the added benefit of a special feature that allows for the removal of the root folder of an archive:

tar --strip-components=1 -xf foo.zip -C c:\somefolder

This is useful when downloading release packages from GitHub which creates archives that include the repo name and version as the root folder.