Ticket #4149 (closed proposal: fixed)
Make Permissions type abstract
|Reported by:||igloo||Owned by:|
|Type of failure:||None/Unknown||Difficulty:|
|Test Case:||Blocked By:|
The Permissions type in System.Directory aims to be a lowest-common-denominator type. This makes it unsuitable for some tasks. For example, a copyPermissions primitive had to be implemented, as it is not possible to use the getPermissions and setPermissions functions to copy the permissions from one file to another:
$ ls -l foo* -rwxr-x-wx 1 ian ian 0 Jun 23 21:27 foo1 ---------- 1 ian ian 0 Jun 23 21:27 foo2 ---------- 1 ian ian 0 Jun 23 21:27 foo3 $ hd -e 'System.Directory.copyPermissions "foo1" "foo2"' $ hd -e 'System.Directory.getPermissions "foo1" >>= System.Directory.setPermissions "foo3"' $ ls -l foo* -rwxr-x-wx 1 ian ian 0 Jun 23 21:27 foo1 -rwxr-x-wx 1 ian ian 0 Jun 23 21:27 foo2 -rwx------ 1 ian ian 0 Jun 23 21:27 foo3
I think we would be better served by the Permissions type being abstract in System.Directory, with the unix and Win32 packages providing the real definition, and some system-specific functions on it. This would allow the generic get/set functions to implement copyPermissions.
This proposal just does the step which has most potential to cause problems for packages that use the type: It makes the type abstract in System.Directory (and adds explicit setter functions, so no functionality is lost).
The type is also exported in Haskell 98's Directory module. I think this should get its own copy of the type.
Suggested discussion deadline: 9 July 2010.