lib.FileContext.is_gettable: Add property

Analogous to the is_dir() method, add an is_gettable() method: The last
commit introduces FT_COMPOUND, a file type which is a hybrid between
directory and regular file. is_dir() succeeds on it, so is_gettable()
symmetrically provides a test find out if get() also works on a file.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/FileContext.py

@@ -308,6 +308,30 @@ class FileContext(abc.ABC):
     async def is_dir(self, path: str, follow_symlinks: bool = True) -> bool:
         return await self._is_dir(self._chroot(path), follow_symlinks = follow_symlinks)
 
+    async def _is_gettable(self, path: str, follow_symlinks: bool) -> bool:
+        try:
+            return (await self._stat(path, follow_symlinks)).is_gettable
+        except NotImplementedError:
+            log(
+                DEBUG,
+                (
+                    f"{self.log_name} doesn't implement stat(), judging by "
+                    f'trailing slash if {path} is a file'
+                ),
+            )
+            return path[-1] != '/'
+        except FileNotFoundError as e:
+            log(DEBUG, f'{self.log_name}: Failed to stat({path}) ({str(e)})')
+            return False
+        except Exception as e:
+            log(ERR, f'{self.log_name}: Failed to stat({path}) ({str(e)})')
+            raise
+
+    async def is_gettable(self, path: str, follow_symlinks: bool = True) -> bool:
+        return await self._is_gettable(
+            self._chroot(path), follow_symlinks = follow_symlinks
+        )
+
     async def _readdir(self, path: str) -> Iterable[str]:
         raise NotImplementedError(
             f'{self.log_name}: readdir("{path}") is not implemented'