feat(amber): add property matcher support

.prettierrc.toml

@@ -0,0 +1 @@
+tabWidth = 2

README.md

@@ -70,7 +70,7 @@ def __repr__(self) -> str:
     return "MyCustomClass(...)"
 ```
 
-### Options
+### CLI Options
 
 These are the cli options exposed to `pytest` by the plugin.
 
@@ -80,7 +80,74 @@ These are the cli options exposed to `pytest` by the plugin.
 | `--snapshot-warn-unused`       | Prints a warning on unused snapshots rather than fail the test suite.               | `False`                                          |
 | `--snapshot-default-extension` | Use to change the default snapshot extension class.                                 | `syrupy.extensions.amber.AmberSnapshotExtension` |
 
-### Built-In Extensions
+### Assertion Options
+
+These are the options available on the `snapshot` assertion fixture.
+Use of these options are one shot and do not persist across assertions.
+For more persitent options see the [advanced usage](#advanced-usage).
+
+#### `matcher`
+
+This allows you to match on a property path and value to control how specific object shapes are serialized.
+
+The matcher is a function that takes two keyword arguments:
+
+| Argument | Description                                                                   |
+| -------- | ----------------------------------------------------------------------------- |
+| `data`   | Current serializable value being matched on                                   |
+| `path`   | Ordered path traversed to the current value e.g. `(("a", dict), ("b", dict))` |
+
+**NOTE:** Do not mutate the value received as it could cause unintended side effects.
+
+##### Built-In Matchers
+
+Syrupy comes with a few built-in matcher presets that can be used to make easy work of using property matchers.
+
+###### `path_type(mapping=None, *, types=(), strict=True)`
+
+Easy way to build a matcher that uses the path and value type to replace serialized data.
+When strict, this will raise a `ValueError` if the types specified are not matched.
+
+| Argument  | Description                                                                                                                        |
+| --------- | ---------------------------------------------------------------------------------------------------------------------------------- |
+| `mapping` | Dict of path string to tuples of class types                                                                                       |
+| `types`   | Tuple of class types used if none of the path strings from the mapping are matched                                                 |
+| `strict`  | If a path is matched but the value at the path does not match one of the class types in the tuple then a `PathTypeError` is raised |
+
+```py
+from syrupy.matchers import path_type
+
+def test_bar(snapshot):
+    actual = {
+      "date_created": datetime.now(),
+      "value": "Some computed value!",
+    }
+    assert actual == snapshot(matcher=path_type({
+      "date_created": (datetime,),
+      "nested.path.id": (int,),
+    }))
+```
+
+```ambr
+# name: test_bar
+  <class 'dict'> {
+    'date_created': <class 'datetime'>,
+    'value': 'Some computed value!',
+  }
+---
+```
+
+#### `extension_class`
+
+This is a way to modify how the snapshot matches and serializes your data in a single assertion.
+
+```py
+def test_foo(snapshot):
+    actual_svg = "<svg></svg>"
+    assert actual_svg = snapshot(extension_class=SVGImageSnapshotExtension)
+```
+
+##### Built-In Extensions
 
 Syrupy comes with a few built-in preset configurations for you to choose from. You should also feel free to extend the `AbstractSyrupyExtension` if your project has a need not captured by one our built-ins.
 
@@ -141,7 +208,9 @@ To develop locally, clone this repository and run `. script/bootstrap` to instal
 
 <!-- markdownlint-enable -->
 <!-- prettier-ignore-end -->
+
 <!-- ALL-CONTRIBUTORS-LIST:END -->
+
 This section is automatically generated via tagging the all-contributors bot in a PR:
 
 ```text

src/syrupy/__init__.py

@@ -67,12 +67,12 @@ def pytest_assertrepr_compare(op: str, left: Any, right: Any) -> Optional[List[s
         assert_msg = reset(
             f"{snapshot_style(left.name)} {op} {received_style('received')}"
         )
-        return [assert_msg] + left.get_assert_diff(right)
+        return [assert_msg] + left.get_assert_diff()
     elif isinstance(right, SnapshotAssertion):
         assert_msg = reset(
             f"{received_style('received')} {op} {snapshot_style(right.name)}"
         )
-        return [assert_msg] + right.get_assert_diff(left)
+        return [assert_msg] + right.get_assert_diff()
     return None
 
 

src/syrupy/assertion.py

@@ -17,7 +17,7 @@
     from .location import TestLocation
     from .extensions.base import AbstractSyrupyExtension
     from .session import SnapshotSession
-    from .types import SerializableData, SerializedData  # noqa: F401
+    from .types import PropertyMatcher, SerializableData, SerializedData
 
 
 @attr.s
@@ -45,6 +45,7 @@ class SnapshotAssertion:
     _test_location: "TestLocation" = attr.ib(kw_only=True)
     _update_snapshots: bool = attr.ib(kw_only=True)
     _extension: Optional["AbstractSyrupyExtension"] = attr.ib(init=False, default=None)
+    _matcher: Optional["PropertyMatcher"] = attr.ib(init=False, default=None)
     _executions: int = attr.ib(init=False, default=0)
     _execution_results: Dict[int, "AssertionResult"] = attr.ib(init=False, factory=dict)
     _post_assert_actions: List[Callable[..., None]] = attr.ib(init=False, factory=list)
@@ -88,10 +89,13 @@ def use_extension(
     def assert_match(self, data: "SerializableData") -> None:
         assert self == data
 
-    def get_assert_diff(self, data: "SerializableData") -> List[str]:
+    def _serialize(self, data: "SerializableData") -> "SerializedData":
+        return self.extension.serialize(data, matcher=self._matcher)
+
+    def get_assert_diff(self) -> List[str]:
         assertion_result = self._execution_results[self.num_executions - 1]
         snapshot_data = assertion_result.recalled_data
-        serialized_data = self.extension.serialize(data)
+        serialized_data = assertion_result.asserted_data or ""
         diff: List[str] = []
         if snapshot_data is None:
             diff.append(gettext("Snapshot does not exist!"))
@@ -100,7 +104,10 @@ def get_assert_diff(self, data: "SerializableData") -> List[str]:
         return diff
 
     def __call__(
-        self, *, extension_class: Optional[Type["AbstractSyrupyExtension"]]
+        self,
+        *,
+        extension_class: Optional[Type["AbstractSyrupyExtension"]] = None,
+        matcher: Optional["PropertyMatcher"] = None,
     ) -> "SnapshotAssertion":
         """
         Modifies assertion instance options
@@ -112,6 +119,13 @@ def clear_extension() -> None:
                 self._extension = None
 
             self._post_assert_actions.append(clear_extension)
+        if matcher:
+            self._matcher = matcher
+
+            def clear_matcher() -> None:
+                self._matcher = None
+
+            self._post_assert_actions.append(clear_matcher)
         return self
 
     def __repr__(self) -> str:
@@ -131,7 +145,7 @@ def _assert(self, data: "SerializableData") -> bool:
         assertion_success = False
         try:
             snapshot_data = self._recall_data(index=self.num_executions)
-            serialized_data = self.extension.serialize(data)
+            serialized_data = self._serialize(data)
             matches = snapshot_data is not None and serialized_data == snapshot_data
             assertion_success = matches
             if not matches and self._update_snapshots:

src/syrupy/data.py

@@ -16,7 +16,7 @@
 
 
 if TYPE_CHECKING:
-    from .types import SerializedData  # noqa: F401
+    from .types import SerializedData
 
 
 @attr.s(frozen=True)