refactor: pure intersection and union of compound paths

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Version 0.9.0 (unreleased)
 
+**Breaking Changes**
+
+- `CompoundJSONPath` instances are no longer updated in-place when using `.union()` and `.intersection()`. Instead, a new `CompoundJSONPath` is returned. `CompoundJSONPath.paths` is now a tuple instead of a list.
+
 **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. We now raise a `JSONPointerError` in such cases. See [#27](https://github.com/jg-rp/python-jsonpath/issues/27).

jsonpath/env.py

@@ -161,15 +161,15 @@ def compile(self, path: str) -> Union[JSONPath, CompoundJSONPath]: # noqa: A003
 
  if stream.current.kind == TOKEN_UNION:
  stream.next_token()
- _path.union(
+ _path = _path.union(
  JSONPath(
  env=self,
  selectors=self.parser.parse(stream),
  )
  )
  elif stream.current.kind == TOKEN_INTERSECTION:
  stream.next_token()
- _path.intersection(
+ _path = _path.intersection(
  JSONPath(
  env=self,
  selectors=self.parser.parse(stream),

jsonpath/path.py

@@ -223,10 +223,11 @@ def __init__(
  *,
  env: JSONPathEnvironment,
  path: Union[JSONPath, CompoundJSONPath],
+ paths: Iterable[Tuple[str, JSONPath]] = (),
  ) -> None:
  self.env = env
  self.path = path
- self.paths: List[Tuple[(str, JSONPath)]] = []
+ self.paths = tuple(paths)
 
  def __str__(self) -> str:
  buf: List[str] = [str(self.path)]
@@ -381,14 +382,20 @@ async def finditer_async(
  return matches
 
  def union(self, path: JSONPath) -> CompoundJSONPath:
- """In-place union of this path and another path."""
- self.paths.append((self.env.union_token, path))
- return self
+ """Union of this path and another path."""
+ return self.__class__(
+ env=self.env,
+ path=self.path,
+ paths=self.paths + ((self.env.union_token, path),),
+ )
 
  def intersection(self, path: JSONPath) -> CompoundJSONPath:
- """In-place intersection of this path and another path."""
- self.paths.append((self.env.intersection_token, path))
- return self
+ """Intersection of this path and another path."""
+ return self.__class__(
+ env=self.env,
+ path=self.path,
+ paths=self.paths + ((self.env.intersection_token, path),),
+ )
 
 
 T = TypeVar("T")