Fix DataPath error handling for unsupported methods (#517)

* upath._flavours: adjust flavour for DataPath

* upath.implementations.data: adjust DataPath to fix error handling

Author: ap--

dev/fsspec_inspector/generate_flavours.py

@@ -142,6 +142,15 @@ def _fix_azure_blob_file_system(x: str) -> str:
     return x
 
 
+def _fix_data_file_system(x: str) -> str:
+    return re.sub(
+        "sep = '/'",
+        "sep = ''  # type: ignore[assignment]\n    "
+        "altsep = ' '  # type: ignore[assignment]",
+        x,
+    )
+
+
 def _fix_memfs_file_system(x: str) -> str:
     return re.sub(
         "_MemFS",
@@ -184,6 +193,7 @@ def _fix_xrootd_file_system(x: str) -> str:
 FIX_SOURCE = {
     "AbstractFileSystem": _fix_abstract_file_system,
     "AzureBlobFileSystem": _fix_azure_blob_file_system,
+    "DataFileSystem": _fix_data_file_system,
     "MemFS": _fix_memfs_file_system,
     "MemoryFileSystem": _fix_memory_file_system,
     "OSSFileSystem": _fix_oss_file_system,

upath/_flavour.py

@@ -274,7 +274,7 @@ def sep(self) -> str:  # type: ignore[override]
 
     @property
     def altsep(self) -> str | None:  # type: ignore[override]
-        return None
+        return getattr(self._spec, "altsep", None)
 
     def isabs(self, path: JoinablePathLike) -> bool:
         path = self.strip_protocol(path)

upath/_flavour_sources.py

@@ -341,7 +341,8 @@ class DataFileSystemFlavour(AbstractFileSystemFlavour):
     __orig_version__ = '2025.10.0'
     protocol = ('data',)
     root_marker = ''
-    sep = '/'
+    sep = ""  # type: ignore[assignment]
+    altsep = " "  # type: ignore[assignment]
 
 
 class DatabricksFileSystemFlavour(AbstractFileSystemFlavour):

upath/implementations/data.py

@@ -1,9 +1,12 @@
 from __future__ import annotations
 
 import sys
+from collections.abc import Iterator
 from collections.abc import Sequence
 from typing import TYPE_CHECKING
+from urllib.parse import quote_plus
 
+from upath._protocol import get_upath_protocol
 from upath.core import UnsupportedOperation
 from upath.core import UPath
 from upath.types import JoinablePathLike
@@ -45,10 +48,49 @@ def __str__(self) -> str:
         return self.parser.join(*self._raw_urlpaths)
 
     def with_segments(self, *pathsegments: JoinablePathLike) -> Self:
-        raise UnsupportedOperation("path operation not supported by DataPath")
+        try:
+            (segment,) = pathsegments
+        except ValueError:
+            raise UnsupportedOperation("join not supported by DataPath")
+        if get_upath_protocol(segment) != "data":
+            raise ValueError(f"requires a data URI, got: {segment!r}")
+        return type(self)(segment, protocol="data", **self.storage_options)
+
+    @property
+    def name(self) -> str:
+        return quote_plus(self.path)
+
+    @property
+    def stem(self) -> str:
+        return quote_plus(self.path)
+
+    @property
+    def suffix(self) -> str:
+        return ""
+
+    @property
+    def suffixes(self) -> list[str]:
+        return []
+
+    def with_name(self, name: str) -> Self:
+        raise UnsupportedOperation("with_name not supported by DataPath")
 
     def with_suffix(self, suffix: str) -> Self:
-        raise UnsupportedOperation("path operation not supported by DataPath")
+        raise UnsupportedOperation("with_suffix not supported by DataPath")
+
+    def with_stem(self, stem: str) -> Self:
+        raise UnsupportedOperation("with_stem not supported by DataPath")
+
+    @property
+    def parent(self) -> Self:
+        return self
+
+    @property
+    def parents(self) -> Sequence[Self]:
+        return []
+
+    def full_match(self, pattern, *, case_sensitive: bool | None = None) -> bool:
+        return super().full_match(pattern, case_sensitive=case_sensitive)
 
     def mkdir(
         self, mode: int = 0o777, parents: bool = False, exist_ok: bool = False
@@ -66,3 +108,19 @@ def write_text(
         newline: str | None = None,
     ) -> int:
         raise UnsupportedOperation("DataPath does not support writing")
+
+    def iterdir(self) -> Iterator[Self]:
+        raise NotADirectoryError
+
+    def glob(
+        self, pattern, *, case_sensitive=None, recurse_symlinks=False
+    ) -> Iterator[Self]:
+        return iter([])
+
+    def rglob(
+        self, pattern, *, case_sensitive=None, recurse_symlinks=False
+    ) -> Iterator[Self]:
+        return iter([])
+
+    def unlink(self, missing_ok: bool = False) -> None:
+        raise UnsupportedOperation