Look at stderr for terminal detection.

bazel prints all the progress to stderr, yet the decision to switch between
"smart" and "dumb" output modes is done based on the stdout and stderr
connected terminals.  That breaks for a command like this:

  bazel query 'something' | wc -l

Even though all the progress is still output to the terminal through stderr,
bazel switches to "dumb" mode, printing progress messages one per line.

It seems reasonable to make the "smart"/"dumb" output mode decision based on
the stderr only.

Tested:
  With the change "bazel query '...' | wc -l" prints "smart" progress messages.

RELNOTES: Check stderr to detect if connected to a terminal.  Deprecate --isatty.
PiperOrigin-RevId: 161243017

1 files changed, 5 insertions, 4 deletions

diff --git a/src/main/cpp/blaze_util_platform.h b/src/main/cpp/blaze_util_platform.h
index b553518b36..4faa171169 100644
--- a/src/main/cpp/blaze_util_platform.h
+++ b/src/main/cpp/blaze_util_platform.h
@@ -203,12 +203,13 @@ std::string GetUserName();
 // Returns true iff the current terminal is running inside an Emacs.
 bool IsEmacsTerminal();
 
-// Returns true iff the current terminal can support color and cursor movement.
-bool IsStandardTerminal();
+// Returns true if stderr is connected to a terminal that can support color
+// and cursor movement.
+bool IsStderrStandardTerminal();
 
-// Returns the number of columns of the terminal to which stdout is
+// Returns the number of columns of the terminal to which stderr is
 // connected, or 80 if there is no such terminal.
-int GetTerminalColumns();
+int GetStderrTerminalColumns();
 
 }  // namespace blaze