bpo-39950: add `pathlib.Path.hardlink_to()` method that supersedes `link_to()` (GH-18909)

The argument order of `link_to()` is reversed compared to what one may expect, so:

    a.link_to(b)

Might be expected to create *a* as a link to *b*, in fact it creates *b* as a link to *a*, making it function more like a "link from". This doesn't match `symlink_to()` nor the documentation and doesn't seem to be the original author's intent.

This PR deprecates `link_to()` and introduces `hardlink_to()`, which has the same argument order as `symlink_to()`.

2 files changed, 27 insertions, 3 deletions

diff --git a/Doc/library/pathlib.rst b/Doc/library/pathlib.rst
index 122642a..b6507eb 100644
--- a/Doc/library/pathlib.rst
+++ b/Doc/library/pathlib.rst
@@ -1140,6 +1140,15 @@ call fails (for example because the path doesn't exist).
       The order of arguments (link, target) is the reverse
       of :func:`os.symlink`'s.
 
+.. method:: Path.hardlink_to(target)
+
+   Make this path a hard link to the same file as *target*.
+
+   .. note::
+      The order of arguments (link, target) is the reverse
+      of :func:`os.link`'s.
+
+   .. versionadded:: 3.10
 
 .. method:: Path.link_to(target)
 
@@ -1149,11 +1158,17 @@ call fails (for example because the path doesn't exist).
 
       This function does not make this path a hard link to *target*, despite
       the implication of the function and argument names. The argument order
-      (target, link) is the reverse of :func:`Path.symlink_to`, but matches
-      that of :func:`os.link`.
+      (target, link) is the reverse of :func:`Path.symlink_to` and
+      :func:`Path.hardlink_to`, but matches that of :func:`os.link`.
 
    .. versionadded:: 3.8
 
+   .. deprecated:: 3.10
+
+      This method is deprecated in favor of :meth:`Path.hardlink_to`, as the
+      argument order of :meth:`Path.link_to`  does not match that of
+      :meth:`Path.symlink_to`.
+
 
 .. method:: Path.touch(mode=0o666, exist_ok=True)
 
@@ -1246,7 +1261,7 @@ Below is a table mapping various :mod:`os` functions to their corresponding
 :func:`os.path.isdir`                  :meth:`Path.is_dir`
 :func:`os.path.isfile`                 :meth:`Path.is_file`
 :func:`os.path.islink`                 :meth:`Path.is_symlink`
-:func:`os.link`                        :meth:`Path.link_to`
+:func:`os.link`                        :meth:`Path.hardlink_to`
 :func:`os.symlink`                     :meth:`Path.symlink_to`
 :func:`os.readlink`                    :meth:`Path.readlink`
 :func:`os.path.relpath`                :meth:`Path.relative_to` [#]_
diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst
index 86cf11f..247749a 100644
--- a/Doc/whatsnew/3.10.rst
+++ b/Doc/whatsnew/3.10.rst
@@ -1007,6 +1007,11 @@ Added negative indexing support to :attr:`PurePath.parents
 <pathlib.PurePath.parents>`.
 (Contributed by Yaroslav Pankovych in :issue:`21041`)
 
+Added :meth:`Path.hardlink_to <pathlib.Path.hardlink_to>` method that
+supersedes :meth:`~pathlib.Path.link_to`. The new method has the same argument
+order as :meth:`~pathlib.Path.symlink_to`.
+(Contributed by Barney Gale in :issue:`39950`.)
+
 platform
 --------
 
@@ -1363,6 +1368,10 @@ Deprecated
 
   (Contributed by Jelle Zijlstra in :issue:`21574`.)
 
+* :meth:`pathlib.Path.link_to` is deprecated and slated for removal in
+  Python 3.12. Use :meth:`pathlib.Path.hardlink_to` instead.
+  (Contributed by Barney Gale in :issue:`39950`.)
+
 
 Removed
 =======