[mojosetup] Patch: Fix handling of dead symbolic links on upgrades.

[Francois Gouget]

Any news on this?
Does the patch need improvement?

On Fri, 6 Mar 2015, Francois Gouget wrote:

> 
> MojoSetup.platform.exists() will return false for dead symbolic links. 
> Yet they still have to be moved out of the way on upgrade, or deleted if 
> they are no longer relevant.
> 
> There are two scenarios where symbolic links are mishandled.
> The first scenario typically happens for regular release -> 
> nightly -> regular release roundtrips.
>  * Initially the install has a valid lib/libfoo.so.8 symbolic link to 
>    libfoo.so.8.1.0.
> 
>  * During the upgrade libfoo.so.8.1.0 is replaced with libfoo.so.9.0.0. 
>    So libfoo.so.8.1.0 gets deleted by the 'Move away obsolete files' 
>    loop.
> 
>  * That loop then considers the 'lib/libfoo.so.8' symbolic link. However 
>    it is now broken so MojoSetup.platform.exists() returns false, so 
>    backup_file() is not called and lib/libfoo.so.8 is left intact except 
>    now it's not tracked by MojoSetup anymore.
> 
>  * If the user then downgrades, MojoSetup will think this was a user 
>    created file and ask whether it is ok to overwrite it. The user does 
>    not know anything about this file and is confused.
> 
> The second scenario is as follows:
>  * For whatever reason the file the lib/libfoo.so.8 symbolic link points 
>    to was deleted. Maybe the user messed with his install or whatever.
> 
>  * The user then tries to reinstall/upgrade the product to fix things.
> 
>  * install_archive_entry() is called to (re)create the lib/libfoo.so.8 
>    symbolic link.
> 
>  * In turn it calls permit_write() which return true without doing 
>    anything because MojoSetup.platform.exists() returns false on broken 
>    symbolic links.
> 
>  * install_archive_entry() then calls install_archive_entity() which 
>    calls install_symlink() which calls MojoSetup.platform.symlink() 
>    which fails because the symbolic link already exists.
> 
>  * This causes the reinstall/upgrade to fail and roll things back.
> 
> The patch below prevents both scenarios from happening.
> 
> 
> diff --git a/scripts/mojosetup_mainline.lua b/scripts/mojosetup_mainline.lua
> index 4602220..b151627 100644
> --- a/scripts/mojosetup_mainline.lua
> +++ b/scripts/mojosetup_mainline.lua
> @@ -551,7 +551,7 @@ end
>  
>  local function permit_write(dest, filename, type, file)
>      local allowoverwrite = true
> -    if MojoSetup.platform.exists(dest) then
> +    if MojoSetup.platform.exists(dest) or MojoSetup.platform.issymlink(dest) then
>          if type == "dir" then
>              allowoverwrite = true
>          else
> @@ -1908,10 +1908,10 @@ local function do_install(install)
>          --  that's ok because we will recreate them if the installation
>          --  succeeds, and restore them if it fails.
>          for path,file in pairs(MojoSetup.oldfiles) do
> -            if file.seen == nil and file.type == 'file' then
> +            if file.seen == nil and (file.type == 'file' or file.type == 'symlink') then
>                  local fullpath = MojoSetup.destination .. "/" .. path
> -                if MojoSetup.platform.exists(fullpath) then
> -                    MojoSetup.loginfo("Obsoleting file '" .. path .. "'")
> +                if MojoSetup.platform.exists(fullpath) or MojoSetup.platform.issymlink(fullpath) then
> +                    MojoSetup.loginfo("Obsoleting " .. file.type .. " '" .. path .. "'")
>                      backup_file(fullpath)
>                  end
>              end
> 
> 
> -- 
> Francois Gouget <fgouget at codeweavers.com>
> _______________________________________________
> mojosetup mailing list
> mojosetup at icculus.org
> http://icculus.org/mailman/listinfo/mojosetup
> 


-- 
Francois Gouget <fgouget at free.fr>              http://fgouget.free.fr/
             Research is the transformation of money to knowledge.
            Innovation is the transformation of knowledge to money.
                              -- Dr. Hans Meixner