From e3df353e1cbd04c4824960f629319d1b9082b18e Mon Sep 17 00:00:00 2001
From: Brad Neimann <brad.neimann@hotmail.com>
Date: Thu, 18 Jul 2019 14:27:26 +1000
Subject: [PATCH] Inhibit errors from terminal-size

When attempting to detect the size of a Windows terminal, stty can
sometimes fail with an error message, which the terminal-size package
then prints to the console. This causes unexpected error messages when
attempting to use Stack in such a terminal. These error messages can
also interfere with tools such as Intero, which rely on Stack's output.
---
 ChangeLog.md         | 3 +++
 package.yaml         | 1 +
 src/Stack/Runners.hs | 6 +++++-
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index 6e9fe15352..129eae1c41 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -19,6 +19,9 @@ Other enhancements:
 
 Bug fixes:
 
+* Errors from the `terminal-size` package are now silenced. See
+  [#4901](https://github.com/commercialhaskell/stack/issues/4901)
+
 
 ## v2.1.3.1
 
diff --git a/package.yaml b/package.yaml
index b12aae76ef..fb4801ead8 100644
--- a/package.yaml
+++ b/package.yaml
@@ -108,6 +108,7 @@ dependencies:
 - rio
 - rio-prettyprint
 - semigroups
+- silently
 - split
 - stm
 - streaming-commons
diff --git a/src/Stack/Runners.hs b/src/Stack/Runners.hs
index 7d666dbad3..5af148204f 100644
--- a/src/Stack/Runners.hs
+++ b/src/Stack/Runners.hs
@@ -36,6 +36,8 @@ import           Stack.Types.Nix (nixEnable)
 import           Stack.Types.Version (stackMinorVersion, stackVersion, minorVersion)
 import           System.Console.ANSI (hSupportsANSIWithoutEmulation)
 import           System.Console.Terminal.Size (size, width)
+import           System.IO.Silently (hSilence)
+import           System.IO (stderr)
 
 -- | Ensure that no project settings are used when running 'withConfig'.
 withGlobalProject :: RIO Runner a -> RIO Runner a
@@ -145,8 +147,10 @@ withRunnerGlobal go inner = do
     ColorAlways -> return True
     ColorAuto -> fromMaybe True <$>
                           hSupportsANSIWithoutEmulation stderr
+  -- In certain situations the call to 'size' prints error messages on stderr even when the operation
+  -- succeeds, so we silence stderr to avoid these errors
   termWidth <- clipWidth <$> maybe (fromMaybe defaultTerminalWidth
-                                    <$> fmap (fmap width) size)
+                                    <$> fmap (fmap width) (hSilence [stderr] size))
                                    pure (globalTermWidth go)
   menv <- mkDefaultProcessContext
   logOptions0 <- logOptionsHandle stderr False