feat: JSONPointer.parent

CHANGELOG.md

@@ -4,11 +4,12 @@
 
 **Fixes**
 
-- Fixed a bug with the parsing of JSON Pointers. When given an arbitrary string without slashes, `JSONPointer` would resolve to the document root. The empty string is the only valid pointer that should resolve to the document root. See [#27](https://github.com/jg-rp/python-jsonpath/issues/27).
+- Fixed a bug with the parsing of JSON Pointers. When given an arbitrary string without slashes, `JSONPointer` would resolve to the document root. The empty string is the only valid pointer that should resolve to the document root. We now raise a `JSONPointerError` in such cases. See [#27](https://github.com/jg-rp/python-jsonpath/issues/27).
 
 **Features**
 
 - Added a command line interface, exposing JSONPath, JSON Pointer and JSON Patch features.
+- Added `JSONPointer.parent()`, a method that returns a the parent of the pointer, as a new `JSONPointer`.
 
 ## Version 0.8.1
 

jsonpath/pointer.py

@@ -69,7 +69,7 @@ def __init__(
  unicode_escape=unicode_escape,
  uri_decode=uri_decode,
  )
- self._s = pointer
+ self._s = self._encode(self.parts)
 
  def __str__(self) -> str:
  return self._s
@@ -215,7 +215,7 @@ def resolve_parent(
  JSONPointerTypeError: When attempting to resolve a non-index string
  path part against a sequence.
  """
- if not len(self.parts):
+ if not self.parts:
  return (None, self.resolve(data))
 
  if isinstance(data, str):
@@ -232,20 +232,26 @@ def resolve_parent(
  except (JSONPointerIndexError, JSONPointerKeyError):
  return (parent, UNDEFINED)
 
+ @staticmethod
+ def _encode(parts: Iterable[Union[int, str]]) -> str:
+ if parts:
+ return "/" + "/".join(
+ str(p).replace("~", "~0").replace("/", "~1") for p in parts
+ )
+ return ""
+
  @classmethod
  def from_match(
  cls,
  match: JSONPathMatch,
  ) -> JSONPointer:
  """Return a JSON Pointer for the path from a JSONPathMatch instance."""
  # A rfc6901 string representation of match.parts.
- if not match.parts:
+ if match.parts:
+ pointer = cls._encode(match.parts)
+ else:
  # This should not happen, unless the JSONPathMatch has been tampered with.
  pointer = ""
- else:
- pointer = "/" + "/".join(
- str(p).replace("~", "~0").replace("/", "~1") for p in match.parts
- )
 
  return cls(
  pointer,
@@ -285,9 +291,7 @@ def from_parts(
  __parts = tuple(_parts)
 
  if __parts:
- pointer = "/" + "/".join(
- p.replace("~", "~0").replace("/", "~1") for p in __parts
- )
+ pointer = cls._encode(__parts)
  else:
  pointer = ""
 
@@ -308,6 +312,21 @@ def is_relative_to(self, other: JSONPointer) -> bool:
  def __eq__(self, other: object) -> bool:
  return isinstance(other, JSONPointer) and self.parts == other.parts
 
+ def parent(self) -> JSONPointer:
+ """Return this pointer's parent, as a new `JSONPointer`.
+
+ If this pointer points to the document root, self is returned.
+ """
+ if not self.parts:
+ return self
+ parent_parts = self.parts[:-1]
+ return JSONPointer(
+ self._encode(parent_parts),
+ parts=parent_parts,
+ unicode_escape=False,
+ uri_decode=False,
+ )
+
 
 def resolve(
  pointer: Union[str, Iterable[Union[str, int]]],

tests/test_json_pointer.py

@@ -219,3 +219,26 @@ def test_pointer_with_leading_whitespace() -> None:
  data = {"some": {"thing": [1, 2, 3]}}
  pointer = JSONPointer(" /some/thing/0")
  assert pointer.resolve(data) == 1
+ assert str(pointer) == "/some/thing/0"
+
+
+def test_pointer_parent() -> None:
+ data = {"some": {"thing": [1, 2, 3]}}
+ pointer = JSONPointer("/some/thing/0")
+ assert pointer.resolve(data) == 1
+
+ parent = pointer.parent()
+ assert str(parent) == "/some/thing"
+ assert parent.resolve(data) == [1, 2, 3]
+
+ parent = parent.parent()
+ assert str(parent) == "/some"
+ assert parent.resolve(data) == {"thing": [1, 2, 3]}
+
+ parent = parent.parent()
+ assert str(parent) == ""
+ assert parent.resolve(data) == {"some": {"thing": [1, 2, 3]}}
+
+ parent = parent.parent()
+ assert str(parent) == ""
+ assert parent.resolve(data) == {"some": {"thing": [1, 2, 3]}}