feat: pretty diff of failed snapshot assertions (#86)

* refactor: move diff generation into serializer

* wip: python difflib

* wip: use colored library and show some diff context

* wip: fix setup py

* wip: simplify diff lines

* wip: highlight deleted snapshots

* wip: highlight changed snapshot lines

* refactor: streamline some logic

* refactor: fix single line

* test: snapshot test diff output

* test: snapshot color changing diff

* test: make more robust

Co-authored-by: Noah <[email protected]>

Author: iamogbz

requirements.txt

@@ -2,29 +2,33 @@
 # This file is autogenerated by pip-compile
 # To update, run:
 #
-#    pip-compile --allow-unsafe --no-emit-find-links --no-index requirements.in
+#    pip-compile --allow-unsafe --no-emit-find-links --no-index --output-file=- -
 #
 appdirs==1.4.3            # via black
 attrs==19.3.0             # via black, flake8-bugbear, pytest
 black==19.10b0
 bleach==3.1.0             # via readme-renderer
 certifi==2019.11.28       # via requests
+cffi==1.13.2              # via cryptography
 chardet==3.0.4            # via requests
 click==7.0                # via black, pip-tools
 codecov==2.0.15
+colored==1.4.2
 configparser==4.0.2       # via py-githooks
-coverage[toml]==5.0.1
+coverage[toml]==5.0.1     # via codecov
+cryptography==2.8         # via secretstorage
 docutils==0.15.2          # via readme-renderer
 entrypoints==0.3          # via flake8
-flake8-bugbear==19.8.0
+flake8-bugbear==20.1.0
 flake8-builtins==1.4.2
 flake8-comprehensions==3.1.4
 flake8-i18n==0.1.0
-flake8==3.7.9
+flake8==3.7.9             # via flake8-bugbear, flake8-builtins, flake8-comprehensions, flake8-i18n
 idna==2.8                 # via requests
 importlib-metadata==1.3.0  # via flake8-comprehensions, keyring, pluggy, pytest, twine
-invoke==1.3.0
+invoke==1.4.0
 isort==4.3.21
+jeepney==0.4.2            # via secretstorage
 keyring==21.0.0           # via twine
 mccabe==0.6.1             # via flake8
 more-itertools==8.0.2     # via pytest, zipp
@@ -38,6 +42,7 @@ pluggy==0.13.1            # via pytest
 py-githooks==1.1.0
 py==1.8.1                 # via pytest
 pycodestyle==2.5.0        # via flake8
+pycparser==2.19           # via cffi
 pyflakes==2.1.1           # via flake8
 pygments==2.5.2           # via readme-renderer
 pyparsing==2.4.6          # via packaging
@@ -46,18 +51,19 @@ readme-renderer==24.0     # via twine
 regex==2019.12.20         # via black
 requests-toolbelt==0.9.1  # via twine
 requests==2.22.0          # via codecov, requests-toolbelt, twine
+secretstorage==3.1.1      # via keyring
 semver==2.9.0
-six==1.13.0               # via bleach, packaging, pip-tools, readme-renderer
+six==1.13.0               # via bleach, cryptography, packaging, pip-tools, readme-renderer
 toml==0.10.0              # via black, coverage
-tqdm==4.41.0              # via twine
+tqdm==4.41.1              # via twine
 twine==3.1.1
 typed-ast==1.4.0          # via black, mypy
-typing-extensions==3.7.4.1
+typing-extensions==3.7.4.1  # via mypy
 urllib3==1.25.7           # via requests
-wcwidth==0.1.7            # via pytest
+wcwidth==0.1.8            # via pytest
 webencodings==0.5.1       # via bleach
 wheel==0.33.6
 zipp==0.6.0               # via importlib-metadata
 
 # The following packages are considered to be unsafe in a requirements file:
-setuptools==42.0.2        # via twine
+setuptools==44.0.0        # via twine

setup.py

@@ -9,7 +9,7 @@
 
 python_requires = "~=3.6"
 setup_requires = ["setuptools_scm"]
-install_requires = ["typing_extensions>=3.6"]
+install_requires = ["colored", "typing_extensions>=3.6"]
 dev_requires = [
     "black",
     "codecov",

src/syrupy/__init__.py

@@ -10,6 +10,11 @@
 from .location import TestLocation
 from .serializers import DEFAULT_SERIALIZER
 from .session import SnapshotSession
+from .terminal import (
+    green,
+    red,
+    reset,
+)
 
 
 def pytest_addoption(parser: Any) -> None:
@@ -40,10 +45,10 @@ def pytest_assertrepr_compare(op: str, left: Any, right: Any) -> Optional[List[s
     https://docs.pytest.org/en/latest/reference.html#_pytest.hookspec.pytest_assertrepr_compare
     """
     if isinstance(left, SnapshotAssertion):
-        assert_msg = f"{left.name} {op} {right}"
+        assert_msg = reset(f"{green(left.name)} {op} {red('received')}")
         return [assert_msg] + left.get_assert_diff(right)
     elif isinstance(right, SnapshotAssertion):
-        assert_msg = f"{left} {op} {right.name}"
+        assert_msg = reset(f"{red('received')} {op} {green(right.name)}")
         return [assert_msg] + right.get_assert_diff(left)
     return None
 

src/syrupy/assertion.py

@@ -1,5 +1,4 @@
 from gettext import gettext
-from itertools import zip_longest
 from typing import (
     TYPE_CHECKING,
     Dict,
@@ -16,12 +15,6 @@
     SnapshotFiles,
 )
 from .exceptions import SnapshotDoesNotExist
-from .terminal import (
-    error_style,
-    green,
-    red,
-    success_style,
-)
 from .utils import walk_snapshot_dir
 
 
@@ -111,27 +104,9 @@ def get_assert_diff(self, data: "SerializableData") -> List[str]:
         if snapshot_data is None:
             return [gettext("Snapshot does not exist!")]
 
-        diff = []
+        diff: List[str] = []
         if not assertion_result.success:
-            received = serialized_data.splitlines()
-            stored = snapshot_data.splitlines()
-
-            marker_stored = success_style("-")
-            marker_received = error_style("+")
-
-            for received_line, stored_line in zip_longest(received, stored):
-                if received_line is None:
-                    diff.append(f"{marker_stored} {green(stored_line)}")
-                elif stored_line is None:
-                    diff.append(f"{marker_received} {red(received_line)}")
-                elif received_line != stored_line:
-                    diff.extend(
-                        [
-                            f"{marker_stored} {green(stored_line)}",
-                            f"{marker_received} {red(received_line)}",
-                        ]
-                    )
-
+            diff.extend(self.serializer.diff_lines(serialized_data, snapshot_data))
         return diff
 
     def __repr__(self) -> str:

src/syrupy/report.py

@@ -175,7 +175,7 @@ def lines(self) -> Generator[str, None, None]:
                     snapshots = (snapshot.name for snapshot in snapshot_file)
                     path_to_file = os.path.relpath(filepath, self.base_dir)
                     deleted_snapshots = ", ".join(map(bold, sorted(snapshots)))
-                    yield gettext("Deleted {} ({})").format(
+                    yield warning_style(gettext("Deleted {} ({})")).format(
                         deleted_snapshots, path_to_file
                     )
             else:

src/syrupy/serializers/base.py

@@ -4,10 +4,15 @@
     ABC,
     abstractmethod,
 )
+from difflib import ndiff
+from itertools import zip_longest
 from typing import (
     TYPE_CHECKING,
+    Callable,
+    Generator,
     Optional,
     Set,
+    Union,
 )
 
 from typing_extensions import final
@@ -18,6 +23,13 @@
     SnapshotFile,
 )
 from syrupy.exceptions import SnapshotDoesNotExist
+from syrupy.terminal import (
+    emphasize,
+    green,
+    mute,
+    red,
+    reset,
+)
 
 
 if TYPE_CHECKING:
@@ -182,3 +194,35 @@ def _write_snapshot_to_file(self, snapshot_file: "SnapshotFile") -> None:
         Adds the snapshot data to the snapshots read from the file
         """
         raise NotImplementedError
+
+    def diff_lines(
+        self, serialized_data: "SerializedData", snapshot_data: "SerializedData"
+    ) -> Generator[str, None, None]:
+        for line in self.__diff_lines(str(snapshot_data), str(serialized_data)):
+            yield reset(line)
+
+    def __diff_lines(self, a: str, b: str) -> Generator[str, None, None]:
+        line_styler = {"-": green, "+": red}
+        staged_line, skip = "", False
+        for line in ndiff(a.splitlines(), b.splitlines()):
+            if staged_line and line[:1] != "?":
+                yield line_styler[staged_line[:1]](staged_line)
+                staged_line, skip = "", False
+            if line[:1] in "-+":
+                staged_line = line
+            elif line[:1] == "?":
+                yield self.__diff_line(line, staged_line, line_styler[staged_line[:1]])
+                staged_line, skip = "", False
+            elif not skip:
+                yield mute("  ...")
+                skip = True
+        if staged_line:
+            yield line_styler[staged_line[:1]](staged_line)
+
+    def __diff_line(
+        self, marker_line: str, line: str, line_style: Callable[[Union[str, int]], str]
+    ) -> str:
+        return "".join(
+            emphasize(line_style(char)) if str(marker) in "-+^" else line_style(char)
+            for marker, char in zip_longest(marker_line.strip(), line)
+        )

src/syrupy/terminal.py

@@ -1,20 +1,34 @@
 from typing import Union
 
+import colored
+
+
+def reset(text: Union[str, int]) -> str:
+    return colored.stylize(text, colored.attr("reset"))
+
 
 def red(text: Union[str, int]) -> str:
-    return f"\033[31m{text}\033[0m"
+    return colored.stylize(text, colored.fg("red"))
 
 
 def yellow(text: Union[str, int]) -> str:
-    return f"\033[33m{text}\033[0m"
+    return colored.stylize(text, colored.fg("yellow"))
 
 
 def green(text: Union[str, int]) -> str:
-    return f"\033[32m{text}\033[0m"
+    return colored.stylize(text, colored.fg("green"))
 
 
 def bold(text: Union[str, int]) -> str:
-    return f"\033[1m{text}\033[0m"
+    return colored.stylize(text, colored.attr("bold"))
+
+
+def mute(text: Union[str, int]) -> str:
+    return colored.stylize(text, colored.attr("dim"))
+
+
+def emphasize(text: Union[str, int]) -> str:
+    return colored.stylize(bold(text), colored.attr("underlined"))
 
 
 def error_style(text: Union[str, int]) -> str:

stubs/colored.pyi

@@ -0,0 +1,6 @@
+from typing import Union
+
+def attr(color: Union[str, int]) -> str: ...
+def bg(color: Union[str, int]) -> str: ...
+def fg(color: Union[str, int]) -> str: ...
+def stylize(text: Union[str, int], style: str, reset: bool = True) -> str: ...

tests/__snapshots__/test_integration.ambr

@@ -0,0 +1,83 @@
+# name: test_failing_snapshots_diff
+  '
+  
+  snapshot = SnapshotAssertion(name='snapshot', num_executions=1)
+  
+      def test_updated_1(snapshot):
+  >       assert snapshot == ['this', 'will', 'not', 'match']
+  E       AssertionError: assert snapshot == received
+  E           ...
+  E         -   'be',
+  E         -   'updated',
+  E         +   'not',
+  E         +   'match',
+  E           ...
+  
+  test_file.py:17: AssertionError
+  
+  snapshot = SnapshotAssertion(name='snapshot', num_executions=1)
+  
+      def test_updated_2(snapshot):
+  >       assert ['this', 'will', 'fail'] == snapshot
+  E       AssertionError: assert received == snapshot
+  E           ...
+  E         +   'fail',
+  E         -   'be',
+  E         -   'updated',
+  E           ...
+  
+  test_file.py:22: AssertionError
+  
+  snapshot = SnapshotAssertion(name='snapshot', num_executions=1)
+  
+      def test_updated_3(snapshot):
+  >       assert snapshot == ['this', 'will', 'be', 'too', 'much']
+  E       AssertionError: assert snapshot == received
+  E           ...
+  E         -   'updated',
+  E         +   'too',
+  E         +   'much',
+  E           ...
+  
+  test_file.py:27: AssertionError
+  
+  snapshot = SnapshotAssertion(name='snapshot', num_executions=1)
+  
+      def test_updated_4(snapshot):
+  >       assert snapshot == "sing line changeling"
+  E       AssertionError: assert snapshot == received
+  E         - 'single line change'
+  E         + 'sing line changeling'
+  
+  test_file.py:32: AssertionError
+  
+  snapshot = SnapshotAssertion(name='snapshot', num_executions=1)
+  
+      def test_updated_5(snapshot):
+  >       assert snapshot == '''
+          multiple line changes
+          with some lines not staying the same
+          intermittent changes so unchanged lines have to be ignored by the differ
+          cause when there are a lot of changes you only want to see what changed
+          you do not want to see this line
+          or this line
+          this line should show up because it changes color
+          and this line does not exist in the first one
+          '''
+  E       assert snapshot == received
+  E           ...
+  E         -     with some lines staying the same
+  E         +     with some lines not staying the same
+  E         -     intermittent changes that have to be ignore by the differ output
+  E         +     intermittent changes so unchanged lines have to be ignored by the differ
+  E         -     because when there are a lot of changes you only want to see changes
+  E         +     cause when there are a lot of changes you only want to see what changed
+  E           ...
+  E         -     this line should show up because it changes color
+  E         +     this line should show up because it changes color
+  E         +     and this line does not exist in the first one
+  E           ...
+  
+  test_file.py:37: AssertionError
+  '
+---