fix: Use POSIX API to compute tty width (#2332)

On some systems, TERM is set to a value that doesn't have a valid
terminfo entry. Rather than hackily fall back on a value for TERM that
appears to work in most contexts (TERM=dumb) but which isn't guaranteed
anywhere to be valid, use proper POSIX ioctls to get the tty width.

This has the added bonus of also working on Windows.

In fact, we already settled on computing the terminal size in this way
in hledger-lib, so this commit centralizes the choice of the logic
there.

Also added a note for alternative methods and their tradeoffs, in case
this turns out to be fragile on some systems.

hledger-lib/Hledger/Utils/IO.hs

@@ -413,8 +413,30 @@ hasOutputFile = do
 
 -- Terminal size
 
+-- [NOTE: Alternative methods of getting the terminal size]
+-- terminal-size uses the TIOCGWINSZ ioctl to get the window size on Unix
+-- systems, which may not be completely portable according to people in
+-- #linux@liberachat.
+--
+-- If this turns out to be the case, supplementary coverage can be given by
+-- using the terminfo package.
+--
+-- Conversely, terminfo on its own is not a full solution, firstly because it
+-- only works on Unix (not Windows), and secondly since in some scenarios (eg
+-- stripped-down build systems) the terminfo database may be limited and lack
+-- the correct entries. (A hack that sometimes works but which isn't robust
+-- enough to be relied upon is to set TERM=dumb -- while this advice does appear
+-- in some places, it's not guaranteed to work)
+--
+-- In any case, $LINES/$COLUMNS should not be used as a source for the terminal
+-- size -- that is a bashism, and in particular they aren't updated as the
+-- terminal is resized.
+--
+-- See #2332 for details
+
 -- | An alternative to ansi-terminal's getTerminalSize, based on
 -- the more robust-looking terminal-size package.
+--
 -- Tries to get stdout's terminal's current height and width.
 getTerminalHeightWidth :: IO (Maybe (Int,Int))
 getTerminalHeightWidth = fmap (fmap unwindow) size

hledger/Hledger/Cli/CliOptions.hs

@@ -107,9 +107,7 @@ import String.ANSI
 import System.Console.CmdArgs hiding (Default,def)
 import System.Console.CmdArgs.Explicit
 import System.Console.CmdArgs.Text
-#ifndef mingw32_HOST_OS
-import System.Console.Terminfo
-#endif
+import Hledger.Utils.IO (getTerminalWidth)
 import System.Directory
 import System.Environment
 import System.Exit (exitSuccess)
@@ -618,13 +616,7 @@ rawOptsToCliOpts rawopts = do
   let iopts = rawOptsToInputOpts day usecolor postingaccttags rawopts
   rspec <- either error' pure $ rawOptsToReportSpec day usecolor rawopts  -- PARTIAL:
   mcolumns <- readMay <$> getEnvSafe "COLUMNS"
-  mtermwidth <-
-#ifdef mingw32_HOST_OS
-    return Nothing
-#else
-    (`getCapability` termColumns) <$> setupTermFromEnv
-    -- XXX Throws a SetupTermError if the terminfo database could not be read, should catch
-#endif
+  mtermwidth <- getTerminalWidth
   let availablewidth = NE.head $ NE.fromList $ catMaybes [mcolumns, mtermwidth, Just defaultWidth]  -- PARTIAL: fromList won't fail because non-null list
   return defcliopts {
               rawopts_         = rawopts

hledger/hledger.cabal

@@ -98,11 +98,6 @@ flag debug
   manual: True
   default: False
 
-flag terminfo
-  description: On POSIX systems, build with the terminfo lib for detecting terminal width
-  manual: False
-  default: True
-
 flag threaded
   description: Build with support for multithreaded execution
   manual: False
@@ -195,9 +190,6 @@ library
     , utility-ht >=0.0.13
     , wizards >=1.0
   default-language: Haskell2010
-  if (!(os(windows))) && (flag(terminfo))
-    build-depends:
-        terminfo
   if (flag(debug))
     cpp-options: -DDEBUG
 
@@ -247,9 +239,6 @@ executable hledger
     , utility-ht >=0.0.13
     , wizards >=1.0
   default-language: Haskell2010
-  if (!(os(windows))) && (flag(terminfo))
-    build-depends:
-        terminfo
   if (flag(debug))
     cpp-options: -DDEBUG
   if flag(threaded)
@@ -300,9 +289,6 @@ test-suite unittest
     , utility-ht >=0.0.13
     , wizards >=1.0
   default-language: Haskell2010
-  if (!(os(windows))) && (flag(terminfo))
-    build-depends:
-        terminfo
   if (flag(debug))
     cpp-options: -DDEBUG
 
@@ -353,8 +339,5 @@ benchmark bench
     , wizards >=1.0
   buildable: False
   default-language: Haskell2010
-  if (!(os(windows))) && (flag(terminfo))
-    build-depends:
-        terminfo
   if (flag(debug))
     cpp-options: -DDEBUG