Remove unnecessary check from pt_visual_explain() (#915)

Author: adamchainz

src/django_mysql/models/query.py

@@ -24,7 +24,6 @@
     StopWatch,
     WeightedAverageRate,
     format_duration,
-    have_program,
     settings_to_cmd_args,
 )
 
@@ -723,9 +722,6 @@ def can_approx_count(queryset: QuerySetMixin) -> bool:
 
 
 def pt_visual_explain(queryset: models.QuerySet, display: bool = True) -> str:
-    if not have_program("pt-visual-explain"):  # pragma: no cover
-        raise OSError("pt-visual-explain doesn't appear to be installed")
-
     connection = connections[queryset.db]
     capturer = CaptureQueriesContext(connection)
     with capturer, connection.cursor() as cursor:

src/django_mysql/utils.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-import subprocess
 import time
 from collections import defaultdict
 from types import TracebackType
@@ -10,8 +9,6 @@
 from django.db.backends.base.base import BaseDatabaseWrapper
 from django.db.models import Model
 
-from django_mysql.compat import cache
-
 
 class WeightedAverageRate:
     """
@@ -128,12 +125,6 @@ def settings_to_cmd_args(settings_dict: dict[str, Any]) -> list[str]:
     return args
 
 
-@cache
-def have_program(program_name: str) -> bool:
-    status = subprocess.call(["which", program_name], stdout=subprocess.PIPE)
-    return status == 0
-
-
 def collapse_spaces(string: str) -> str:
     bits = string.replace("\n", " ").split(" ")
     return " ".join(filter(None, bits))

tests/testapp/test_models.py

@@ -2,7 +2,8 @@
 
 import pickle
 import re
-from unittest import mock, skipUnless
+import shutil
+from unittest import SkipTest, mock
 
 import pytest
 from django.contrib.contenttypes.models import ContentType
@@ -14,7 +15,7 @@
 from django.test.utils import captured_stdout, override_settings
 
 from django_mysql.models import ApproximateInt, SmartIterator, add_QuerySetMixin
-from django_mysql.utils import have_program, index_name
+from django_mysql.utils import index_name
 from tests.testapp.models import (
     Author,
     AuthorExtra,
@@ -756,8 +757,13 @@ def test_filter_and_delete(self):
         assert bad_authors.count() == 0
 
 
-@skipUnless(have_program("pt-visual-explain"), "pt-visual-explain must be installed")
 class VisualExplainTests(TestCase):
+    @classmethod
+    def setUpClass(cls):
+        if shutil.which("pt-visual-explain") is None:  # pragma: no cover
+            raise SkipTest("pt-visual-explain must be installed")
+        super().setUpClass()
+
     def test_basic(self):
         with captured_stdout() as capture:
             Author.objects.all().pt_visual_explain()