Follow file symlinks too

[lukaslihotzki]

Currently, pub publish follows directory symlinks, but not file symlinks. With this PR, file symlinks are followed too. This fixes broken symlinks if they point outside the package root and should not break anything, although it could increase package size.

The dry-run shows the directory tree with directory symlinks resolved, and without indicating symlinks for file symlinks, so it is very confusing currently.

Ideally, symlinks would only be resolved if they point outside the package root. However, that would need two or three tar runs (one with, one without --dereference) and using tar --concatenate (in the second or the final, third run). It would make the code significantly more complex.

Related issues:

• pub publish doesn't follow file symlinks #2193 (Why is this closed?)
• pub publish is not picking symbolic links #2699

[sigurdm]

I think I agree this is the right behavior.

One issue here is that we don't have the same tar process for windows and linux/macos. On windows we use 7zip. On the other hand symlinks are probably much less used on windows.

Could you write a test that shows this as being fixed?

We are working on migrating to a tar implementation in dart (#2817). But it is not clear how long it will take to land. It would be great to have the test for ensuring that the behavior stays consistent when we do the switch.

[lukaslihotzki]

On Windows, 7-Zip has no option to follow file symlinks. There are just these options about links:

  -snh : store hard links as links
  -snl : store symbolic links as links

Windows 10 seems to have a system tar.exe included since v1803 (bsdtar 3.3.2). This one could support -L to dereference symlinks on create. However, I would prefer to disable the test on Windows until #2817.

[jonasfj]

Currently, pub publish follows directory symlinks, but not file symlinks.

It does follow directory symlinks? doesn't it just package the actual symlink?

[lukaslihotzki]

It does follow directory symlinks? doesn't it just package the actual symlink?

It does follow directory symlinks, as shown by the 'publish follows directory symlinks' test in this PR. At least for symlinks pointing to excluded or out-of-package-root targets, this is the only sensible behavior.

[sigurdm]

We have merged #2817 . If you want we can land the test. I believe our implementation follows links.

[sigurdm]

Closing for lack of activity.

Feel welcome to open a new PR with the test if you would like ensuring the desired behavior does not regress.