feat: Added a new CLI flag: --snapshot-patch-pycharm-diff

README.md

@@ -132,12 +132,13 @@ Both options will generate equivalent snapshots but the latter is only viable wh
 These are the cli options exposed to `pytest` by the plugin.
 
 | Option                         | Description                                                                                                                    | Default                                                                                                      |
-| ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------ |
+| ------------------------------ |--------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------|
 | `--snapshot-update`            | Snapshots will be updated to match assertions and unused snapshots will be deleted.                                            | `False`                                                                                                      |
 | `--snapshot-details`           | Includes details of unused snapshots (test name and snapshot location) in the final report.                                    | `False`                                                                                                      |
 | `--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.                                                                            | [AmberSnapshotExtension](https://github.com/syrupy-project/syrupy/blob/main/src/syrupy/extensions/amber/__init__.py) |
 | `--snapshot-no-colors`         | Disable test results output highlighting. Equivalent to setting the environment variables `ANSI_COLORS_DISABLED` or `NO_COLOR` | Disabled by default if not in terminal.                                                                      |
+| `--snapshot-patch-pycharm-diff`| Override PyCharm's default diffs viewer when looking at snapshot diffs. See [IDE Integrations](#ide-integrations)        | `False`                                                                                                      |
 
 ### Assertion Options
 
@@ -470,6 +471,21 @@ The generated snapshot:
 - [JPEG image extension](https://github.com/syrupy-project/syrupy/tree/main/tests/examples/test_custom_image_extension.py)
 - [Built-in image extensions](https://github.com/syrupy-project/syrupy/blob/main/tests/syrupy/extensions/image/test_image_svg.py)
 
+## IDE Integrations
+
+### PyCharm
+
+The [PyCharm](https://www.jetbrains.com/pycharm/) IDE comes with a built-in tool for visualizing differences between expected and actual results in a test. To properly render Syrupy snapshots in the PyCharm diff viewer, we need to apply a patch to the diff viewer library. To do this, use the `--snapshot-patch-pycharm-diff` flag, e.g.:
+
+In your `pytest.ini`:
+
+```ini
+[pytest]
+addopts = --snapshot-patch-pycharm-diff
+```
+
+See [#675](https://github.com/syrupy-project/syrupy/issues/675) for the original issue.
+
 ## Uninstalling
 
 ```python

src/syrupy/__init__.py

@@ -5,6 +5,7 @@
 from typing import (
     Any,
     ContextManager,
+    Iterator,
     List,
     Optional,
 )
@@ -16,6 +17,7 @@
 from .exceptions import FailedToLoadModuleMember
 from .extensions import DEFAULT_EXTENSION
 from .location import PyTestLocation
+from .patches.pycharm_diff import patch_pycharm_diff
 from .session import SnapshotSession
 from .terminal import (
     received_style,
@@ -85,6 +87,13 @@ def pytest_addoption(parser: Any) -> None:
         dest="no_colors",
         help="Disable test results output highlighting",
     )
+    group.addoption(
+        "--snapshot-patch-pycharm-diff",
+        action="store_true",
+        default=False,
+        dest="patch_pycharm_diff",
+        help="Patch PyCharm diff",
+    )
 
 
 def __terminal_color(config: Any) -> "ContextManager[None]":
@@ -185,10 +194,19 @@ def pytest_terminal_summary(
 
 
 @pytest.fixture
-def snapshot(request: Any) -> "SnapshotAssertion":
+def snapshot(request: "pytest.FixtureRequest") -> "SnapshotAssertion":
     return SnapshotAssertion(
         update_snapshots=request.config.option.update_snapshots,
         extension_class=__import_extension(request.config.option.default_extension),
         test_location=PyTestLocation(request.node),
-        session=request.session.config._syrupy,
+        session=request.session.config._syrupy,  # type: ignore
     )
+
+
+@pytest.fixture(scope="session", autouse=True)
+def _syrupy_apply_ide_patches(request: "pytest.FixtureRequest") -> Iterator[None]:
+    if request.config.option.patch_pycharm_diff:
+        with patch_pycharm_diff():
+            yield
+    else:
+        yield

src/syrupy/patches/pycharm_diff.py

@@ -0,0 +1,76 @@
+import warnings
+from contextlib import contextmanager
+from functools import wraps
+from inspect import signature
+from typing import (
+    Any,
+    Iterator,
+)
+
+from syrupy.assertion import SnapshotAssertion
+
+
+@contextmanager
+def patch_pycharm_diff() -> Iterator[None]:
+    """
+    Applies PyCharm diff patch to add Syrupy snapshot support.
+    See: https://github.com/syrupy-project/syrupy/issues/675
+    """
+
+    try:
+        from teamcity.diff_tools import EqualsAssertionError  # type: ignore
+    except ImportError:
+        warnings.warn(
+            "Failed to patch PyCharm's diff tools. Skipping patch.",
+            stacklevel=2,
+        )
+        yield
+        return
+
+    old_init = EqualsAssertionError.__init__
+    old_init_signature = signature(old_init)
+
+    @wraps(old_init)
+    def new_init(self: "EqualsAssertionError", *args: Any, **kwargs: Any) -> None:
+
+        # Extract the __init__ arguments as originally passed in order to
+        # process them later
+        parameters = old_init_signature.bind(self, *args, **kwargs)
+        parameters.apply_defaults()
+
+        expected = parameters.arguments["expected"]
+        actual = parameters.arguments["actual"]
+        real_exception = parameters.arguments["real_exception"]
+
+        if isinstance(expected, SnapshotAssertion):
+            snapshot = expected
+        elif isinstance(actual, SnapshotAssertion):
+            snapshot = actual
+        else:
+            snapshot = None
+
+        old_init(self, *args, **kwargs)
+
+        # No snapshot was involved in the assertion. Let the old logic do its
+        # thing.
+        if snapshot is None:
+            return
+
+        # Although a snapshot was involved in the assertion, it seems the error
+        # was a result of a non-assertion exception (Ex. `assert 1/0`).
+        # Therefore, We will not do anything here either.
+        if real_exception is not None:
+            return
+
+        assertion_result = snapshot.executions[snapshot.num_executions - 1]
+        if assertion_result.exception is not None:
+            return
+
+        self.expected = str(assertion_result.recalled_data)
+        self.actual = str(assertion_result.asserted_data)
+
+    try:
+        EqualsAssertionError.__init__ = new_init
+        yield
+    finally:
+        EqualsAssertionError.__init__ = old_init