bpo-33123: pathlib: Add missing_ok parameter to Path.unlink (pythonGH-6191)

Similarly to how several pathlib file creation functions have an "exists_ok" parameter, we should introduce "missing_ok" that makes removal functions not raise an exception when a file or directory is already absent.  IMHO, this should cover Path.unlink and Path.rmdir.  Note, Path.resolve() has a "strict" parameter since 3.6 that does the same thing. Naming this of this new parameter tries to be consistent with the "exists_ok" parameter as that is more explicit about what it does (as opposed to "strict").


https://bugs.python.org/issue33123

Author: rbu

Doc/library/pathlib.rst

@@ -1048,11 +1048,20 @@ call fails (for example because the path doesn't exist).
    otherwise :exc:`FileExistsError` is raised.
 
 
-.. method:: Path.unlink()
+.. method:: Path.unlink(missing_ok=False)
 
    Remove this file or symbolic link.  If the path points to a directory,
    use :func:`Path.rmdir` instead.
 
+   If *missing_ok* is false (the default), :exc:`FileNotFoundError` is
+   raised if the path does not exist.
+
+   If *missing_ok* is true, :exc:`FileNotFoundError` exceptions will be
+   ignored (same behavior as the POSIX ``rm -f`` command).
+
+   .. versionchanged:: 3.8
+      The *missing_ok* parameter was added.
+
 
 .. method:: Path.link_to(target)
 

Lib/pathlib.py

@@ -1279,14 +1279,18 @@ def lchmod(self, mode):
             self._raise_closed()
         self._accessor.lchmod(self, mode)
 
-    def unlink(self):
+    def unlink(self, missing_ok=False):
         """
         Remove this file or link.
         If the path is a directory, use rmdir() instead.
         """
         if self._closed:
             self._raise_closed()
-        self._accessor.unlink(self)
+        try:
+            self._accessor.unlink(self)
+        except FileNotFoundError:
+            if not missing_ok:
+                raise
 
     def rmdir(self):
         """

Lib/test/test_pathlib.py

@@ -1635,6 +1635,11 @@ def test_unlink(self):
         self.assertFileNotFound(p.stat)
         self.assertFileNotFound(p.unlink)
 
+    def test_unlink_missing_ok(self):
+        p = self.cls(BASE) / 'fileAAA'
+        self.assertFileNotFound(p.unlink)
+        p.unlink(missing_ok=True)
+
     def test_rmdir(self):
         p = self.cls(BASE) / 'dirA'
         for q in p.iterdir():

Misc/NEWS.d/next/Library/2018-03-22-19-13-19.bpo-33123._Y5ooE.rst

@@ -0,0 +1,2 @@
+:class:`pathlib.Path.unlink` now accepts a *missing_ok* parameter to avoid a
+:exc:`FileNotFoundError` from being raised. Patch by Robert Buchholz.