Defer pygments and pdb imports (9% speedup)

src/_pytest/_io/terminalwriter.py

@@ -9,17 +9,17 @@
 from typing import final
 from typing import Literal
 from typing import TextIO
-
-import pygments
-from pygments.formatters.terminal import TerminalFormatter
-from pygments.lexer import Lexer
-from pygments.lexers.diff import DiffLexer
-from pygments.lexers.python import PythonLexer
+from typing import TYPE_CHECKING
 
 from ..compat import assert_never
 from .wcwidth import wcswidth
 
 
+if TYPE_CHECKING:
+    from pygments.formatters.terminal import TerminalFormatter
+    from pygments.lexer import Lexer
+
+
 # This code was initially copied from py 1.8.1, file _io/terminalwriter.py.
 
 
@@ -207,13 +207,20 @@ def _write_source(self, lines: Sequence[str], indents: Sequence[str] = ()) -> No
 
     def _get_pygments_lexer(self, lexer: Literal["python", "diff"]) -> Lexer:
         if lexer == "python":
+            from pygments.lexers.python import PythonLexer
+
             return PythonLexer()
         elif lexer == "diff":
+            from pygments.lexers.diff import DiffLexer
+
             return DiffLexer()
         else:
             assert_never(lexer)
 
     def _get_pygments_formatter(self) -> TerminalFormatter:
+        from pygments.formatters.terminal import TerminalFormatter
+        import pygments.util
+
         from _pytest.config.exceptions import UsageError
 
         theme = os.getenv("PYTEST_THEME")
@@ -239,6 +246,8 @@ def _highlight(
         if not source or not self.hasmarkup or not self.code_highlight:
             return source
 
+        import pygments
+
         pygments_lexer = self._get_pygments_lexer(lexer)
         pygments_formatter = self._get_pygments_formatter()
 

src/_pytest/debugging.py

@@ -9,6 +9,8 @@
 from collections.abc import Generator
 import functools
 import importlib
+import importlib.machinery
+import importlib.util
 import sys
 import types
 from typing import Any
@@ -62,29 +64,82 @@ def pytest_addoption(parser: Parser) -> None:
     )
 
 
-def pytest_configure(config: Config) -> None:
-    import pdb
+class SetTracePatcher:
+    """Triggered on --pdb CLI opt and when a test fails.
+
+    Importing pdb on 3.14 imports asyncio, ssl and socket
+    """
+
+    def __init__(self) -> None:
+        self.module: Any = None
+        self.original: Callable[..., None] | None = None
+
+    def install(self) -> None:
+        module = sys.modules.get("pdb")
+        if module is not None:
+            self.patch(module)
+        else:
+            sys.meta_path.insert(0, self)
+
+    def uninstall(self) -> None:
+        if self.module is not None:
+            self.module.set_trace = self.original
+            self.module = None
+        elif self in sys.meta_path:
+            sys.meta_path.remove(self)
+
+    def find_spec(
+        self,
+        name: str,
+        path: Any = None,
+        target: types.ModuleType | None = None,
+    ) -> importlib.machinery.ModuleSpec | None:
+        if name != "pdb":
+            return None
+
+        sys.meta_path.remove(self)
+        spec = importlib.util.find_spec(name)
+        if spec is None or spec.loader is None or isinstance(spec.loader, type):
+            sys.meta_path.insert(0, self)
+            return None
 
+        exec_module = spec.loader.exec_module
+
+        def patching_exec_module(module: types.ModuleType) -> None:
+            exec_module(module)
+            self.patch(module)
+
+        spec.loader.exec_module = patching_exec_module  # type: ignore[method-assign]
+        return spec
+
+    def patch(self, module: Any) -> None:
+        self.module = module
+        self.original = module.set_trace
+        module.set_trace = pytestPDB.set_trace
+
+
+def pytest_configure(config: Config) -> None:
     if config.getvalue("trace"):
         config.pluginmanager.register(PdbTrace(), "pdbtrace")
     if config.getvalue("usepdb"):
         config.pluginmanager.register(PdbInvoke(), "pdbinvoke")
 
-    pytestPDB._saved.append(
-        (pdb.set_trace, pytestPDB._pluginmanager, pytestPDB._config)
-    )
-    pdb.set_trace = pytestPDB.set_trace
+    patcher = SetTracePatcher()
+    patcher.install()
+
+    pytestPDB._saved.append((patcher, pytestPDB._pluginmanager, pytestPDB._config))
     pytestPDB._pluginmanager = config.pluginmanager
     pytestPDB._config = config
 
     # NOTE: not using pytest_unconfigure, since it might get called although
     #       pytest_configure was not (if another plugin raises UsageError).
     def fin() -> None:
         (
-            pdb.set_trace,
+            saved_patcher,
             pytestPDB._pluginmanager,
             pytestPDB._config,
         ) = pytestPDB._saved.pop()
+        saved_patcher.uninstall()
 
     config.add_cleanup(fin)
 
@@ -94,9 +149,7 @@ class pytestPDB:
 
     _pluginmanager: PytestPluginManager | None = None
     _config: Config | None = None
-    _saved: list[
-        tuple[Callable[..., None], PytestPluginManager | None, Config | None]
-    ] = []
+    _saved: list[tuple[SetTracePatcher, PytestPluginManager | None, Config | None]] = []
     _recursive_debug = 0
     _wrapped_pdb_cls: tuple[type[Any], type[Any]] | None = None