capture: remove some indirection in MultiCapture

Removing this indirection enables some further clean ups.

src/_pytest/capture.py

@@ -71,13 +71,13 @@ def pytest_load_initial_conftests(early_config: Config):
 
 def _get_multicapture(method: "_CaptureMethod") -> "MultiCapture":
     if method == "fd":
-        return MultiCapture(out=True, err=True, Capture=FDCapture)
+        return MultiCapture(in_=FDCapture(0), out=FDCapture(1), err=FDCapture(2))
     elif method == "sys":
-        return MultiCapture(out=True, err=True, Capture=SysCapture)
+        return MultiCapture(in_=SysCapture(0), out=SysCapture(1), err=SysCapture(2))
     elif method == "no":
-        return MultiCapture(out=False, err=False, in_=False)
+        return MultiCapture(in_=None, out=None, err=None)
     elif method == "tee-sys":
-        return MultiCapture(out=True, err=True, in_=False, Capture=TeeSysCapture)
+        return MultiCapture(in_=None, out=TeeSysCapture(1), err=TeeSysCapture(2))
     raise ValueError("unknown capturing method: {!r}".format(method))
 
 
@@ -354,7 +354,7 @@ class CaptureFixture:
     def _start(self):
         if self._capture is None:
             self._capture = MultiCapture(
-                out=True, err=True, in_=False, Capture=self.captureclass
+                in_=None, out=self.captureclass(1), err=self.captureclass(2),
             )
             self._capture.start_capturing()
 
@@ -418,17 +418,13 @@ CaptureResult = collections.namedtuple("CaptureResult", ["out", "err"])
 
 
 class MultiCapture:
-    out = err = in_ = None
     _state = None
     _in_suspended = False
 
-    def __init__(self, out=True, err=True, in_=True, Capture=None):
-        if in_:
-            self.in_ = Capture(0)
-        if out:
-            self.out = Capture(1)
-        if err:
-            self.err = Capture(2)
+    def __init__(self, in_, out, err) -> None:
+        self.in_ = in_
+        self.out = out
+        self.err = err
 
     def __repr__(self):
         return "<MultiCapture out={!r} err={!r} in_={!r} _state={!r} _in_suspended={!r}>".format(

src/_pytest/pytester.py

@@ -25,8 +25,7 @@ import py
 
 import pytest
 from _pytest._code import Source
-from _pytest.capture import MultiCapture
-from _pytest.capture import SysCapture
+from _pytest.capture import _get_multicapture
 from _pytest.compat import TYPE_CHECKING
 from _pytest.config import _PluggyPlugin
 from _pytest.config import Config
@@ -972,7 +971,7 @@ class Testdir:
         if syspathinsert:
             self.syspathinsert()
         now = time.time()
-        capture = MultiCapture(Capture=SysCapture)
+        capture = _get_multicapture("sys")
         capture.start_capturing()
         try:
             try:

testing/test_capture.py

@@ -19,16 +19,28 @@ from _pytest.config import ExitCode
 # pylib 1.4.20.dev2 (rev 13d9af95547e)
 
 
-def StdCaptureFD(out=True, err=True, in_=True):
-    return capture.MultiCapture(out, err, in_, Capture=capture.FDCapture)
+def StdCaptureFD(out: bool = True, err: bool = True, in_: bool = True) -> MultiCapture:
+    return capture.MultiCapture(
+        in_=capture.FDCapture(0) if in_ else None,
+        out=capture.FDCapture(1) if out else None,
+        err=capture.FDCapture(2) if err else None,
+    )
 
 
-def StdCapture(out=True, err=True, in_=True):
-    return capture.MultiCapture(out, err, in_, Capture=capture.SysCapture)
+def StdCapture(out: bool = True, err: bool = True, in_: bool = True) -> MultiCapture:
+    return capture.MultiCapture(
+        in_=capture.SysCapture(0) if in_ else None,
+        out=capture.SysCapture(1) if out else None,
+        err=capture.SysCapture(2) if err else None,
+    )
 
 
-def TeeStdCapture(out=True, err=True, in_=True):
-    return capture.MultiCapture(out, err, in_, Capture=capture.TeeSysCapture)
+def TeeStdCapture(out: bool = True, err: bool = True, in_: bool = True) -> MultiCapture:
+    return capture.MultiCapture(
+        in_=capture.TeeSysCapture(0) if in_ else None,
+        out=capture.TeeSysCapture(1) if out else None,
+        err=capture.TeeSysCapture(2) if err else None,
+    )
 
 
 class TestCaptureManager:
@@ -1154,7 +1166,11 @@ class TestStdCaptureFDinvalidFD:
             from _pytest import capture
 
             def StdCaptureFD(out=True, err=True, in_=True):
-                return capture.MultiCapture(out, err, in_, Capture=capture.FDCapture)
+                return capture.MultiCapture(
+                    in_=capture.FDCapture(0) if in_ else None,
+                    out=capture.FDCapture(1) if out else None,
+                    err=capture.FDCapture(2) if err else None,
+                )
 
             def test_stdout():
                 os.close(1)
@@ -1284,8 +1300,11 @@ def test_capturing_and_logging_fundamentals(testdir, method):
         import sys, os
         import py, logging
         from _pytest import capture
-        cap = capture.MultiCapture(out=False, in_=False,
-                                     Capture=capture.%s)
+        cap = capture.MultiCapture(
+            in_=None,
+            out=None,
+            err=capture.%s(2),
+        )
         cap.start_capturing()
 
         logging.warning("hello1")