Fix output stream failures (Windows)

conans/client/output.py

@@ -58,18 +58,22 @@ def write(self, data, front=None, back=None, newline=False):
                 data = decode_text(data)  # Keep python 2 compatibility
 
         if self._color and (front or back):
-            color = "%s%s" % (front or '', back or '')
-            end = (Style.RESET_ALL + "\n") if newline else Style.RESET_ALL  # @UndefinedVariable
-            data = "%s%s%s" % (color, data, end)
-        else:
-            if newline:
-                data = "%s\n" % data
-
-        try:
-            self._stream.write(data)
-        except UnicodeError:
-            data = data.encode("utf8").decode("ascii", "ignore")
-            self._stream.write(data)
+            data = "%s%s%s%s" % (front or '', back or '', data, Style.RESET_ALL)
+        if newline:
+            data = "%s\n" % data
+
+        # https://github.com/conan-io/conan/issues/4277
+        # Windows output locks produce IOErrors
+        for _ in range(3):
+            try:
+                self._stream.write(data)
+                break
+            except IOError:
+                import time
+                time.sleep(0.02)
+            except UnicodeError:
+                data = data.encode("utf8").decode("ascii", "ignore")
+
         self._stream.flush()
 
     def info(self, data):

conans/test/unittests/client/conan_output_test.py

@@ -0,0 +1,30 @@
+# coding=utf-8
+
+import types
+import unittest
+
+from six import StringIO
+
+from conans.client.output import ConanOutput
+from mock import mock
+
+
+class ConanOutputTest(unittest.TestCase):
+
+    def test_blocked_output(self):
+        # https://github.com/conan-io/conan/issues/4277
+        stream = StringIO()
+
+        def write_raise(self, data):
+            write_raise.counter = getattr(write_raise, "counter", 0) + 1
+            if write_raise.counter < 2:
+                raise IOError("Stdout locked")
+            self.super_write(data)
+        stream.super_write = stream.write
+        stream.write = types.MethodType(write_raise, stream)
+        out = ConanOutput(stream)
+
+        with mock.patch("time.sleep") as sleep:
+            out.write("Hello world")
+            sleep.assert_any_call(0.02)
+        self.assertEqual("Hello world", stream.getvalue())

conans/util/progress_bar.py

@@ -1,4 +1,3 @@
-
 import os
 from contextlib import contextmanager
 
@@ -18,17 +17,15 @@ class _FileReaderWithProgressBar(object):
 
     def __init__(self, fileobj, output, desc=None):
         pb_kwargs = self.tqdm_defaults.copy()
-        self._ori_output = output
 
         # If there is no terminal, just print a beat every TIMEOUT_BEAT seconds.
         if not output.is_terminal:
             output = _NoTerminalOutput(output)
             pb_kwargs['mininterval'] = TIMEOUT_BEAT_SECONDS
 
-        self._output = output
         self._fileobj = fileobj
         self.seek(0, os.SEEK_END)
-        self._pb = tqdm(total=self.tell(), desc=desc, file=output, **pb_kwargs)
+        self._tqdm_bar = tqdm(total=self.tell(), desc=desc, file=output, **pb_kwargs)
         self.seek(0)
 
     def seekable(self):
@@ -43,15 +40,11 @@ def tell(self):
     def read(self, size):
         prev = self.tell()
         ret = self._fileobj.read(size)
-        self._pb.update(self.tell() - prev)
+        self._tqdm_bar.update(self.tell() - prev)
         return ret
 
     def pb_close(self):
-        self._pb.close()
-
-    def pb_write(self, message):
-        """ Allow to write messages to output without interfering with the progress bar """
-        tqdm.write(message, file=self._ori_output)
+        self._tqdm_bar.close()
 
 
 class _NoTerminalOutput(object):