cask/artifact/symlinked: allow --force to overwrite symbolic links

[miccal]

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In a previous PR I changed how binary and manpage links were handled for casks to ensure that neither an existing file nor an existing symbolic link would be overwritten.

This change allows the --force flag to override this check, essentially using the same logic as in cask/artifact/moved.

I have tested this locally, and running brew cask install {something with a conflicting binary name} outputs the error:

Error: It seems there already exists a Binary at '/usr/local/bin/{conflicting name}'; not overwriting.

and hence the install fails, while running brew cask install --force {something with a conflicting binary name} outputs the warning:

Warning: It seems there already exists a Binary at '/usr/local/bin/{conflicting name}'; overwriting.

and the install succeeds.

This should (hopefully) resolve Homebrew/homebrew-cask#88401.

Ping @reitermarkus and @vitorgalvao for thoughts and review.

Thank you.

[reitermarkus]

As mentioned in Homebrew/homebrew-cask#88401 (comment), we should only override if the symlink point to the same cask.

So we need some method like Caskroom.cask_for_path which returns the cask token if the given path points to the Caskroom.

[miccal]

As mentioned in Homebrew/homebrew-cask#88401 (comment), we should only override if the symlink point to the same cask.

So we need some method like Caskroom.cask_for_path which returns the cask token if the given path points to the Caskroom.

This will take me some time; please feel free to take over in this PR (or a new one if you prefer) if you wish.

[miccal]

Ok, I have made some changes that get part of the way there. Running brew cask install {something with a conflicting name} outputs the error:

Error: It seems there already exists a Binary at '/usr/local/bin/{conflicting name}'; not overwriting.

regardless of wether {conflicting name} is a file or a symbolic link.

Running brew cask install --force {something with a conflicting name} outputs the error:

Error: It seems there already exists a Binary at '/usr/local/bin/{conflicting name}'; not overwriting.

if {conflicting name} is a file.

Running brew cask install --force {something with a conflicting name} outputs the warning:

Warning: It seems there already exists a Binary at '/usr/local/bin/{conflicting name}'; overwriting.

if {conflicting name} is a symbolic link.

@reitermarkus I will probably need some help with the last bit, namely checking if the symbolic link being over-written points to the same cask.

[miccal]

@reitermarkus I have an idea on how to achieve the desired result, but I am not sure if it will work, nor am I sure on how to do it exactly.

Let me try and explain ...

Before the create_filesystem_link step, source is pointing to:

/usr/local/Caskroom/{new cask name}/{new cask version}/{path to binary}/{new binary}

while target is pointing to:

/usr/local/bin/{old binary}

and I assume that target.readlink is pointing to:

/usr/local/Caskroom/{old cask name}/{old cask version}/{path to binary}/{old binary}

Now, if I have this correct, is there a way to extract {new cask name} from source and {old cask name} from target.readlink?

And if so, can we compare them and allow the overwrite if and only if {new cask name} = {old cask name}?

[reitermarkus]

is there a way to extract {new cask name} from source and {old cask name} from target.readlink?

Not yet, that's why we need a helper function for that as I mentioned.

[miccal]

@reitermarkus and @vitorgalvao I have come up with a way to achieve the desired results for this -- explanation and testing results are given below. Apologies in advance for the long read!

Installing a test-cask both without --force and with --force when there exists a conflicting file in /usr/local/bin/ results in the error:

Error: It seems there is already a Binary at '/usr/local/bin/{file}'.

and the install fails.

Installing a test-cask both without --force and with --force when there exists a conflicting symbolic link in /usr/local/bin/ that is not related in any way to the test-cask results in the error:

Error: It seems there is already a Binary at '/usr/local/bin/{symlink}'.

and the install fails.

Installing a test-cask without --force when there exists a conflicting symbolic link in /usr/local/bin/ that is related to the test-cask results in the error:

Error: It seems there is already a Binary at '/usr/local/bin/{symlink}'.

and the install fails.

Installing a test-cask with --force when there exists a conflicting symbolic link in /usr/local/bin/ that is related to the test-cask in the warning:

Warning: It seems there is already a Binary at '/usr/local/bin/{symlink}'; overwriting.

and the install succeeds.

The main reason why I decided to implement the check via:

raise CaskError, "#{message}." unless cask.artifacts.to_s.include? target.readlink.to_s

is because the symbolic link that we want to be overwritten may not necessarily point to the Caskroom.

Let me illustrate this with two more examples:

For the cask chromium that includes a shimscript, there is a symbolic link:

/usr/local/bin/chromium

pointing to:

/usr/local/Caskroom/chromium/802933/chromium.wrapper.sh

and installing with --force results in the warning:

Warning: It seems there is already a Binary at '/usr/local/bin/chromium'; overwriting.

and the install succeeds. Note that in this case target.readlink points to the Caskroom.

For the cask suspicious-package that includes a binary, there is a symbolic link:

/usr/local/bin/spkg

pointing to:

/Applications/Suspicious Package.app/Contents/SharedSupport/spkg

and installing with --force results in the warning:

Warning: It seems there is already a Binary at '/usr/local/bin/spkg'; overwriting.

and the install succeeds. Note that in this case target.readlink does not point to the Caskroom.

Thank you.

[reitermarkus]

Thanks, @miccal!

[miccal]

No problem, and thank you for all your help @reitermarkus.