Added support for "last modified time" in getinfo.

A new namespace "modified" was introduced to the `getinfo` function to potentially use cheaper commands compared to the general "details" namespace. In particular, `FTPFS` now uses the MDTM command if supported by the server.

Author: atollk

CHANGELOG.md

@@ -13,6 +13,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added `fs.copy.copy_file_if`, `fs.copy.copy_dir_if`, and `fs.copy.copy_fs_if`. 
   Closes [#458](https://github.com/PyFilesystem/pyfilesystem2/issues/458).
 
+### Changed
+
+- FTP servers that do not support the MLST command now try to use the MDTM command to
+  retrieve the last modification timestamp of a resource. 
+  Closes [#456](https://github.com/PyFilesystem/pyfilesystem2/pull/456).
+  
 ### Fixed
 
 - Fixed performance bugs in `fs.copy.copy_dir_if_newer`. Test cases were adapted to catch those bugs in the future.

fs/base.py

@@ -697,6 +697,25 @@ def readtext(
 
     gettext = _new_name(readtext, "gettext")
 
+    def getmodified(self, path):
+        # type: (Text) -> Optional[datetime]
+        """Get the timestamp of the last modifying access of a resource.
+
+        Arguments:
+            path (str): A path to a resource.
+
+        Returns:
+            datetime: The timestamp of the last modification.
+
+        The *modified timestamp* of a file is the point in time
+        that the file was last changed. Depending on the file system,
+        it might only have limited accuracy.
+
+        """
+        if self.getmeta().get("supports_mtime", False):
+            return self.getinfo(path, namespaces=["modified"]).modified
+        return self.getinfo(path, namespaces=["details"]).modified
+
     def getmeta(self, namespace="standard"):
         # type: (Text) -> Mapping[Text, object]
         """Get meta information regarding a filesystem.
@@ -734,6 +753,8 @@ def getmeta(self, namespace="standard"):
         read_only           `True` if this filesystem is read only.
         supports_rename     `True` if this filesystem supports an
                             `os.rename` operation.
+        supports_mtime      `True` if this filesystem supports a native
+                            operation to retreive the "last modified" time.
         =================== ============================================
 
         Most builtin filesystems will provide all these keys, and third-

fs/copy.py

@@ -463,9 +463,8 @@ def _copy_is_necessary(
 
     elif condition == "newer":
         try:
-            namespace = ("details",)
-            src_modified = src_fs.getinfo(src_path, namespace).modified
-            dst_modified = dst_fs.getinfo(dst_path, namespace).modified
+            src_modified = src_fs.getmodified(src_path)
+            dst_modified = dst_fs.getmodified(dst_path)
         except ResourceNotFound:
             return True
         else:
@@ -477,9 +476,8 @@ def _copy_is_necessary(
 
     elif condition == "older":
         try:
-            namespace = ("details",)
-            src_modified = src_fs.getinfo(src_path, namespace).modified
-            dst_modified = dst_fs.getinfo(dst_path, namespace).modified
+            src_modified = src_fs.getmodified(src_path)
+            dst_modified = dst_fs.getmodified(dst_path)
         except ResourceNotFound:
             return True
         else:

fs/ftpfs.py

@@ -16,6 +16,7 @@
 from contextlib import contextmanager
 from ftplib import FTP
 
+
 try:
     from ftplib import FTP_TLS
 except ImportError as err:
@@ -667,6 +668,18 @@ def getinfo(self, path, namespaces=None):
                 }
             )
 
+        if "modified" in namespaces:
+            if "basic" in namespaces or "details" in namespaces:
+                raise ValueError(
+                    'Cannot use the "modified" namespace in combination with others.'
+                )
+            with self._lock:
+                with ftp_errors(self, path=path):
+                    cmd = "MDTM " + _encode(self.validatepath(path), self.ftp.encoding)
+                    response = self.ftp.sendcmd(cmd)
+                modified_info = {"modified": self._parse_ftp_time(response.split()[1])}
+                return Info({"modified": modified_info})
+
         if self.supports_mlst:
             with self._lock:
                 with ftp_errors(self, path=path):
@@ -692,6 +705,7 @@ def getmeta(self, namespace="standard"):
         if namespace == "standard":
             _meta = self._meta.copy()
             _meta["unicode_paths"] = "UTF8" in self.features
+            _meta["supports_mtime"] = "MDTM" in self.features
         return _meta
 
     def listdir(self, path):

fs/info.py

@@ -317,9 +317,12 @@ def modified(self):
                 namespace is not in the Info.
 
         """
-        self._require_namespace("details")
-        _time = self._make_datetime(self.get("details", "modified"))
-        return _time
+        try:
+            self._require_namespace("details")
+            return self._make_datetime(self.get("details", "modified"))
+        except MissingInfoNamespace:
+            self._require_namespace("modified")
+            return self._make_datetime(self.get("modified", "modified"))
 
     @property
     def created(self):

fs/osfs.py

@@ -145,6 +145,7 @@ def __init__(
             "network": False,
             "read_only": False,
             "supports_rename": True,
+            "supports_mtime": False,
             "thread_safe": True,
             "unicode_paths": os.path.supports_unicode_filenames,
             "virtual": False,

tests/test_ftpfs.py

@@ -261,6 +261,23 @@ def test_getmeta_unicode_path(self):
         del self.fs.features["UTF8"]
         self.assertFalse(self.fs.getmeta().get("unicode_paths"))
 
+    def test_getinfo_modified(self):
+        self.assertIn("MDTM", self.fs.features)
+        self.fs.create("bar")
+        mtime_detail = self.fs.getinfo("bar", ("basic", "details")).modified
+        mtime_modified = self.fs.getinfo("bar", ("modified",)).modified
+        # Microsecond and seconds might not actually be supported by all
+        # FTP commands, so we strip them before comparing if it looks
+        # like at least one of the two values does not contain them.
+        replacement = {}
+        if mtime_detail.microsecond == 0 or mtime_modified.microsecond == 0:
+            replacement["microsecond"] = 0
+        if mtime_detail.second == 0 or mtime_modified.second == 0:
+            replacement["second"] = 0
+        self.assertEqual(
+            mtime_detail.replace(**replacement), mtime_modified.replace(**replacement)
+        )
+
     def test_opener_path(self):
         self.fs.makedir("foo")
         self.fs.writetext("foo/bar", "baz")

tests/test_memoryfs.py

@@ -72,14 +72,13 @@ def test_copy_preserve_time(self):
         self.fs.makedir("bar")
         self.fs.touch("foo/file.txt")
 
-        namespaces = ("details", "modified")
-        src_info = self.fs.getinfo("foo/file.txt", namespaces)
+        src_info = self.fs.getmodified("foo/file.txt")
 
         self.fs.copy("foo/file.txt", "bar/file.txt", preserve_time=True)
         self.assertTrue(self.fs.exists("bar/file.txt"))
 
-        dst_info = self.fs.getinfo("bar/file.txt", namespaces)
-        self.assertEqual(dst_info.modified, src_info.modified)
+        dst_info = self.fs.getmodified("bar/file.txt")
+        self.assertEqual(dst_info, src_info)
 
 
 class TestMemoryFile(unittest.TestCase):