fix: add support for no colors mode

README.md

@@ -74,11 +74,12 @@ def __repr__(self) -> str:
 
 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-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` |
+| Option                         | Description                                                                                                                    | Default                                          |
+| ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------ |
+| `--snapshot-update`            | Snapshots will be updated to match assertions and unused snapshots will be deleted.                                            | `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.                                                                            | `syrupy.extensions.amber.AmberSnapshotExtension` |
+| `--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.          |
 
 ### Assertion Options
 

conftest.py

@@ -1,4 +1,13 @@
 import typing
 
+import pytest
+
+from syrupy.utils import env_context
+
 typing.TYPE_CHECKING = True
 pytest_plugins = "pytester"
+
+
+@pytest.fixture
+def osenv():
+    return env_context

dev_requirements.txt

@@ -9,15 +9,13 @@ attrs==20.2.0             # via flake8-bugbear, pytest, syrupy
 black==20.8b1             # via syrupy
 bleach==3.2.1             # via readme-renderer
 certifi==2020.6.20        # via requests
-cffi==1.14.2              # via cryptography
 chardet==3.0.4            # via requests
 click==7.1.2              # via black, pip-tools
 codecov==2.1.9            # via syrupy
 colorama==0.4.3           # via twine
 colored==1.4.2            # via syrupy
 configparser==5.0.0       # via py-githooks
-coverage[toml]==5.3     # via codecov, syrupy
-cryptography==3.1         # via secretstorage
+coverage[toml]==5.3       # via codecov, syrupy
 deprecated==1.2.10        # via pygithub
 docutils==0.16            # via readme-renderer
 flake8-bugbear==20.1.4    # via syrupy
@@ -29,7 +27,6 @@ idna==2.10                # via requests
 iniconfig==1.0.1          # via pytest
 invoke==1.4.1             # via syrupy
 isort==5.5.2              # via syrupy
-jeepney==0.4.3            # via keyring, secretstorage
 keyring==21.4.0           # via twine
 mccabe==0.6.1             # via flake8
 more-itertools==8.5.0     # via pytest
@@ -43,7 +40,6 @@ pluggy==0.13.1            # via pytest
 py-githooks==1.1.0        # via syrupy
 py==1.9.0                 # via pytest
 pycodestyle==2.6.0        # via flake8
-pycparser==2.20           # via cffi
 pyflakes==2.2.0           # via flake8
 pygithub==1.53            # via syrupy
 pygments==2.7.1           # via readme-renderer
@@ -56,9 +52,8 @@ regex==2020.7.14          # via black
 requests-toolbelt==0.9.1  # via twine
 requests==2.24.0          # via codecov, pygithub, requests-toolbelt, twine
 rfc3986==1.4.0            # via twine
-secretstorage==3.1.2      # via keyring
 semver==2.10.2            # via syrupy
-six==1.15.0               # via bleach, cryptography, packaging, pip-tools, readme-renderer
+six==1.15.0               # via bleach, packaging, pip-tools, readme-renderer
 toml==0.10.1              # via black, coverage, pytest
 tqdm==4.49.0              # via twine
 twine==3.2.0              # via syrupy

src/syrupy/__init__.py

@@ -1,15 +1,18 @@
 import argparse
 import glob
+import sys
 from gettext import gettext
 from typing import (
     Any,
+    ContextManager,
     List,
     Optional,
 )
 
 import pytest
 
 from .assertion import SnapshotAssertion
+from .constants import DISABLE_COLOR_ENV_VAR
 from .exceptions import FailedToLoadModuleMember
 from .extensions import DEFAULT_EXTENSION
 from .location import TestLocation
@@ -19,7 +22,10 @@
     reset,
     snapshot_style,
 )
-from .utils import import_module_member
+from .utils import (
+    env_context,
+    import_module_member,
+)
 
 
 def __default_extension_option(value: str) -> Any:
@@ -56,23 +62,41 @@ def pytest_addoption(parser: Any) -> None:
         dest="default_extension",
         help="Specify the default snapshot extension",
     )
+    group.addoption(
+        "--snapshot-no-colors",
+        action="store_true",
+        default=not sys.stdout.isatty(),
+        dest="no_colors",
+        help="Disable test results output highlighting",
+    )
+
+
+def __terminal_color(config: Any) -> "ContextManager[None]":
+    env = {}
+    if config.option.no_colors:
+        env[DISABLE_COLOR_ENV_VAR] = "true"
+
+    return env_context(**env)
 
 
-def pytest_assertrepr_compare(op: str, left: Any, right: Any) -> Optional[List[str]]:
+def pytest_assertrepr_compare(
+    config: Any, op: str, left: Any, right: Any
+) -> Optional[List[str]]:
     """
     Return explanation for comparisons in failing assert expressions.
     https://docs.pytest.org/en/latest/reference.html#_pytest.hookspec.pytest_assertrepr_compare
     """
-    if isinstance(left, SnapshotAssertion):
-        assert_msg = reset(
-            f"{snapshot_style(left.name)} {op} {received_style('received')}"
-        )
-        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()
+    with __terminal_color(config):
+        if isinstance(left, SnapshotAssertion):
+            assert_msg = reset(
+                f"{snapshot_style(left.name)} {op} {received_style('received')}"
+            )
+            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()
     return None
 
 
@@ -144,9 +168,10 @@ def pytest_terminal_summary(
     Add syrupy report to pytest.
     https://docs.pytest.org/en/latest/reference.html#_pytest.hookspec.pytest_terminal_summary
     """
-    terminalreporter.write_sep("-", gettext("snapshot report summary"))
-    for line in terminalreporter.config._syrupy.report.lines:
-        terminalreporter.write_line(line)
+    with __terminal_color(config):
+        terminalreporter.write_sep("-", gettext("snapshot report summary"))
+        for line in terminalreporter.config._syrupy.report.lines:
+            terminalreporter.write_line(line)
 
 
 @pytest.fixture

src/syrupy/constants.py

@@ -7,3 +7,6 @@
 SYMBOL_ELLIPSIS = "..."  # U+2026
 SYMBOL_NEW_LINE = "␤"  # U+2424
 SYMBOL_CARRIAGE = "␍"  # U+240D
+
+DISABLE_COLOR_ENV_VAR = "ANSI_COLORS_DISABLED"
+DISABLE_COLOR_ENV_VARS = {DISABLE_COLOR_ENV_VAR, "NO_COLOR"}

src/syrupy/terminal.py

@@ -1,26 +1,42 @@
-from typing import Union
+from typing import (
+    Any,
+    Union,
+)
 
 import colored
 
+from .constants import DISABLE_COLOR_ENV_VARS
+from .utils import get_env_value
+
+
+def _is_color_disabled() -> bool:
+    return any(map(get_env_value, DISABLE_COLOR_ENV_VARS))
+
+
+def _stylize(text: Union[str, int], *args: Any) -> str:
+    if _is_color_disabled():
+        return str(text)
+    return colored.stylize(text, *args)
+
 
 def reset(text: Union[str, int]) -> str:
-    return colored.stylize(text, colored.attr("reset"))
+    return _stylize(text, colored.attr("reset"))
 
 
 def red(text: Union[str, int]) -> str:
-    return colored.stylize(text, colored.fg("red"))
+    return _stylize(text, colored.fg("red"))
 
 
 def yellow(text: Union[str, int]) -> str:
-    return colored.stylize(text, colored.fg("yellow"))
+    return _stylize(text, colored.fg("yellow"))
 
 
 def green(text: Union[str, int]) -> str:
-    return colored.stylize(text, colored.fg("green"))
+    return _stylize(text, colored.fg("green"))
 
 
 def bold(text: Union[str, int]) -> str:
-    return colored.stylize(text, colored.attr("bold"))
+    return _stylize(text, colored.attr("bold"))
 
 
 def error_style(text: Union[str, int]) -> str:
@@ -36,20 +52,20 @@ def success_style(text: Union[str, int]) -> str:
 
 
 def snapshot_style(text: Union[str, int]) -> str:
-    return colored.stylize(text, colored.bg(225) + colored.fg(90))
+    return _stylize(text, colored.bg(225) + colored.fg(90))
 
 
 def snapshot_diff_style(text: Union[str, int]) -> str:
-    return colored.stylize(text, colored.bg(90) + colored.fg(225))
+    return _stylize(text, colored.bg(90) + colored.fg(225))
 
 
 def received_style(text: Union[str, int]) -> str:
-    return colored.stylize(text, colored.bg(195) + colored.fg(23))
+    return _stylize(text, colored.bg(195) + colored.fg(23))
 
 
 def received_diff_style(text: Union[str, int]) -> str:
-    return colored.stylize(text, colored.bg(23) + colored.fg(195))
+    return _stylize(text, colored.bg(23) + colored.fg(195))
 
 
 def context_style(text: Union[str, int]) -> str:
-    return colored.stylize(text, colored.attr("dim"))
+    return _stylize(text, colored.attr("dim"))

src/syrupy/utils.py

@@ -1,3 +1,6 @@
+import json
+import os
+from contextlib import contextmanager
 from gettext import gettext
 from importlib import import_module
 from pathlib import Path
@@ -46,3 +49,20 @@ def import_module_member(path: str) -> Any:
                 module_name,
             )
         )
+
+
+def get_env_value(env_var_name: str) -> object:
+    try:
+        return json.loads(os.environ[env_var_name])
+    except (KeyError, TypeError, json.decoder.JSONDecodeError):
+        return os.environ.get(env_var_name)
+
+
+@contextmanager
+def env_context(**kwargs: str) -> Iterator[None]:
+    prev_env = {**os.environ}
+    try:
+        yield os.environ.update(kwargs)
+    finally:
+        os.environ.clear()
+        os.environ.update(prev_env)

tests/__snapshots__/test_integration_default.ambr

@@ -74,7 +74,7 @@
           you do not want to see this line
           or this line
           this line should show up because it changes\n
-          this line should show up because it changes color
+          this line should show up because it changes color
           and this line does not exist in the first one
           '''
   E       AssertionError: assert snapshot == received

tests/test_extension_base.py

@@ -2,8 +2,6 @@
 
 from syrupy.extensions.base import SnapshotReporter
 
-from .utils import clean_output
-
 
 class SnapshotReporterNoContext(SnapshotReporter):
     @property
@@ -27,5 +25,6 @@ class TestSnapshotReporter:
         ],
         ids=lambda _: "",
     )
-    def test_diff_lines(self, a, b, Reporter, snapshot):
-        assert "\n".join(map(clean_output, Reporter().diff_lines(a, b))) == snapshot
+    def test_diff_lines(self, a, b, Reporter, snapshot, osenv):
+        with osenv(NO_COLOR="true"):
+            assert "\n".join(Reporter().diff_lines(a, b)) == snapshot

tests/test_integration_custom.py

@@ -1,7 +1,5 @@
 import pytest
 
-from .utils import clean_output
-
 
 @pytest.fixture
 def testcases(testdir):
@@ -56,8 +54,8 @@ def test_passed_custom(snapshot_custom):
 
 def test_warns_on_snapshot_name(testdir, testcases):
     testdir.makepyfile(test_file=testcases["passed"])
-    result = testdir.runpytest("-v", "--snapshot-update")
-    result_stdout = clean_output(result.stdout.str())
+    result = testdir.runpytest("-v", "--snapshot-update", "--snapshot-no-colors")
+    result_stdout = result.stdout.str()
     assert "2 snapshots generated" in result_stdout
     assert "Warning:" in result_stdout
     assert "Can not relate snapshot name" in result_stdout

tests/test_integration_default.py

@@ -2,11 +2,9 @@
 
 import pytest
 
-from .utils import clean_output
-
 
 def get_result_snapshot_summary(result: object) -> str:
-    result_stdout = clean_output(result.stdout.str())
+    result_stdout = result.stdout.str()
     start_idx = result_stdout.find("\n", result_stdout.find("---- snapshot report"))
     end_idx = result_stdout.find("====", start_idx)
     return result_stdout[start_idx:end_idx].strip()
@@ -120,7 +118,7 @@ def test_case_2(self, snapshot):
 
     test_filepath = Path(testdir.tmpdir, "test_content.py")
     result = testdir.runpytest(str(test_filepath), "-v", "-k test_case_2")
-    result_stdout = clean_output(result.stdout.str())
+    result_stdout = result.stdout.str()
     assert "1 snapshot passed" in result_stdout
     assert "snapshot unused" not in result_stdout
 
@@ -144,7 +142,7 @@ def test_case_2(snapshot):
 
     test_filepath = Path(testdir.tmpdir, "test_content.py")
     result = testdir.runpytest(str(test_filepath), "-v", "-k test_case_2")
-    result_stdout = clean_output(result.stdout.str())
+    result_stdout = result.stdout.str()
     assert "1 snapshot passed" in result_stdout
     assert "snapshot unused" not in result_stdout
 
@@ -161,7 +159,7 @@ def test_case_1(snapshot):
     testdir.makepyfile(test_content=test_content)
     result = testdir.runpytest("-v", "--snapshot-update")
 
-    result_stdout = clean_output(result.stdout.str())
+    result_stdout = result.stdout.str()
     assert "Can not relate snapshot name" not in result_stdout
 
 
@@ -305,8 +303,8 @@ def test_generated_snapshots(stubs, snapshot):
 def test_failing_snapshots_diff(stubs, testcases_updated, snapshot):
     testdir = stubs[1]
     testdir.makepyfile(test_file="\n\n".join(testcases_updated.values()))
-    result = testdir.runpytest("-vv")
-    result_stdout = clean_output(result.stdout.str())
+    result = testdir.runpytest("-vv", "--snapshot-no-colors")
+    result_stdout = result.stdout.str()
     start_index = result_stdout.find("\n", result_stdout.find("==== FAILURES"))
     end_index = result_stdout.find("\n", result_stdout.find("---- snapshot report"))
     assert result_stdout[start_index:end_index] == snapshot
@@ -426,7 +424,7 @@ def test_removed_hanging_snapshot_fossil(stubs, snapshot):
     hanging_filepath = Path(testdir.tmpdir, "__snapshots__/test_hanging.abc")
     assert hanging_filepath.exists()
     result = testdir.runpytest("-v", "--snapshot-update")
-    result_stdout = clean_output(result.stdout.str())
+    result_stdout = result.stdout.str()
     assert str(Path(filepath).relative_to(Path.cwd())) not in result_stdout
     assert "1 unused snapshot deleted" in result_stdout
     assert "unknown snapshot" in result_stdout
@@ -464,7 +462,7 @@ def test_snapshot_default_extension_option_failure(testdir, testcases, snapshot)
         "--snapshot-default-extension",
         "syrupy.extensions.amber.DoesNotExistExtension",
     )
-    result_stderr = clean_output(result.stderr.str())
+    result_stderr = result.stderr.str()
     assert "error: argument --snapshot-default-extension" in result_stderr
     assert "Member 'DoesNotExistExtension' not found" in result_stderr
     assert result.ret