More work on pytest-dev#4597

AUTHORS

@@ -52,6 +52,7 @@ Carl Friedrich Bolz
 Carlos Jenkins
 Ceridwen
 Charles Cloud
+Charles Machalow
 Charnjit SiNGH (CCSJ)
 Chris Lamb
 Christian Boelsen

changelog/4597.feature.rst

@@ -0,0 +1 @@
+Add tee-stdio capture mechanism to allow both live printing and capturing of test output.

doc/en/capture.rst

@@ -24,7 +24,7 @@ a test.
 Setting capturing methods or disabling capturing
 -------------------------------------------------
 
-There are two ways in which ``pytest`` can perform capturing:
+There are three ways in which ``pytest`` can perform capturing:
 
 * file descriptor (FD) level capturing (default): All writes going to the
   operating system file descriptors 1 and 2 will be captured.
@@ -33,15 +33,22 @@ There are two ways in which ``pytest`` can perform capturing:
   and ``sys.stderr`` will be captured.  No capturing of writes to
   filedescriptors is performed.
 
+* tee-stdio capturing: Python writes to ``sys.stdout`` and ``sys.stderr``
+  will be captured, however the writes will also be passed-through to
+  the actual ``sys.stdout`` and ``sys.stderr``. This allows output to be
+  'live printed' and captured for plugin use, such as junitxml.
+
 .. _`disable capturing`:
 
 You can influence output capturing mechanisms from the command line:
 
 .. code-block:: bash
 
-    pytest -s            # disable all capturing
-    pytest --capture=sys # replace sys.stdout/stderr with in-mem files
-    pytest --capture=fd  # also point filedescriptors 1 and 2 to temp file
+    pytest -s                  # disable all capturing
+    pytest --capture=sys       # replace sys.stdout/stderr with in-mem files
+    pytest --capture=fd        # also point filedescriptors 1 and 2 to temp file
+    pytest --capture=tee-stdio # 'combines sys and -s' by both capturing sys.stdout/stderr
+                               #   and passing it along to the actual sys.stdout/stderr
 
 .. _printdebugging:
 

src/_pytest/capture.py

@@ -24,8 +24,8 @@ def pytest_addoption(parser):
         action="store",
         default="fd" if hasattr(os, "dup") else "sys",
         metavar="method",
-        choices=["fd", "sys", "no", "tee-stdui"],
-        help="per-test capturing method: one of fd|sys|no|tee-stdui.",
+        choices=["fd", "sys", "no", "tee-stdio"],
+        help="per-test capturing method: one of fd|sys|no|tee-stdio.",
     )
     group._addoption(
         "-s",
@@ -90,7 +90,7 @@ def _getcapture(self, method):
             return MultiCapture(out=True, err=True, Capture=SysCapture)
         elif method == "no":
             return MultiCapture(out=False, err=False, in_=False)
-        elif method == "tee-stdui":
+        elif method == "tee-stdio":
             return MultiCapture(out=True, err=True, in_=False, Capture=TeeSysCapture)
         raise ValueError("unknown capturing method: %r" % method)  # pragma: no cover
 

src/_pytest/compat.py

@@ -371,14 +371,10 @@ def getvalue(self) -> str:
         assert isinstance(self.buffer, io.BytesIO)
         return self.buffer.getvalue().decode("UTF-8")
 
-class CaptureAndPassthroughIO(io.TextIOWrapper):
+class CaptureAndPassthroughIO(CaptureIO):
     def __init__(self, other) -> None:
         self._other = other
-        super().__init__(io.BytesIO(), encoding="UTF-8", newline="", write_through=True)
-
-    def getvalue(self) -> str:
-        assert isinstance(self.buffer, io.BytesIO)
-        return self.buffer.getvalue().decode("UTF-8")
+        super().__init__()
 
     def write(self, s) -> int:
         super().write(s)

testing/test_capture.py

@@ -32,6 +32,10 @@ def StdCapture(out=True, err=True, in_=True):
     return capture.MultiCapture(out, err, in_, Capture=capture.SysCapture)
 
 
+def TeeStdCapture(out=True, err=True, in_=True):
+    return capture.MultiCapture(out, err, in_, Capture=capture.TeeSysCapture)
+
+
 class TestCaptureManager:
     def test_getmethod_default_no_fd(self, monkeypatch):
         from _pytest.capture import pytest_addoption
@@ -816,6 +820,26 @@ def test_write_bytes_to_buffer(self):
         assert f.getvalue() == "foo\r\n"
 
 
+class TestCaptureAndPassthroughIO(TestCaptureIO):
+    def test_text(self):
+        sio = io.StringIO()
+        f = capture.CaptureAndPassthroughIO(sio)
+        f.write("hello")
+        s1 = f.getvalue()
+        assert s1 == "hello"
+        s2 = sio.getvalue()
+        assert s2 == s1
+        f.close()
+        sio.close()
+
+    def test_unicode_and_str_mixture(self):
+        sio = io.StringIO()
+        f = capture.CaptureAndPassthroughIO(sio)
+        f.write("\u00f6")
+        pytest.raises(TypeError, f.write, b"hello")
+
+
+
 def test_dontreadfrominput():
     from _pytest.capture import DontReadFromInput
 
@@ -1112,6 +1136,22 @@ def test_stdin_nulled_by_default(self):
             pytest.raises(IOError, sys.stdin.read)
 
 
+class TestTeeStdCapture(TestStdCapture):
+    captureclass = staticmethod(TeeStdCapture)
+
+    def test_capturing_error_recursive(self):
+        ''' for TeeStdCapture since we passthrough stderr/stdout, cap1
+        should get all output, while cap2 should only get "cap2\n" '''
+
+        with self.getcapture() as cap1:
+            print("cap1")
+            with self.getcapture() as cap2:
+                print("cap2")
+                out2, err2 = cap2.readouterr()
+                out1, err1 = cap1.readouterr()
+        assert out1 == "cap1\ncap2\n"
+        assert out2 == "cap2\n"
+
 class TestStdCaptureFD(TestStdCapture):
     pytestmark = needsosdup
     captureclass = staticmethod(StdCaptureFD)
@@ -1252,7 +1292,7 @@ def test_capture_again():
     )
 
 
-@pytest.mark.parametrize("method", ["SysCapture", "FDCapture"])
+@pytest.mark.parametrize("method", ["SysCapture", "FDCapture", "TeeSysCapture"])
 def test_capturing_and_logging_fundamentals(testdir, method):
     if method == "StdCaptureFD" and not hasattr(os, "dup"):
         pytest.skip("need os.dup")