help: add --info/--man/--pager/--cat flags, & choose best one by default (#579)

You can select a docs format/viewer with one of the `--info`, `--man`, `--pager`, `--cat` flags.
Otherwise, it will use info if available, otherwise man if available,
otherwise $PAGER if defined, otherwise less if available, otherwise it
prints on stdout (and always prints on stdout when piped).

Preferring info over man might not suit everyone.

hledger/Hledger/Cli/CliOptions.hs

@@ -25,6 +25,8 @@ module Hledger.Cli.CliOptions (
   argsFlag,
   showModeUsage,
   withAliases,
+  likelyExecutablesInPath,
+  hledgerExecutablesInPath,
 
   -- * CLI options
   CliOpts(..),
@@ -633,23 +635,27 @@ dropRedundantSourceVersion fs = fs
 compiledExts = ["",".com",".exe"] 
 
 
--- | Get the sorted unique filenames of all hledger-* executables in
--- the current user's PATH. Currently these are: files in any of the
--- PATH directories, named hledger-*, with either no extension (and no
--- periods in the name) or one of the addonExtensions.  Limitations:
--- we do not currently check that the file is really a file (not eg a
--- directory) or whether it has execute permission.
-hledgerExecutablesInPath :: IO [String]
-hledgerExecutablesInPath = do
+-- | Get all sorted unique filenames in the current user's PATH. 
+-- We do not currently filter out non-file objects or files without execute permission.
+likelyExecutablesInPath :: IO [String]
+likelyExecutablesInPath = do
   pathdirs <- splitOneOf "[:;]" `fmap` getEnvSafe "PATH"
   pathfiles <- concat `fmap` mapM getDirectoryContentsSafe pathdirs
-  return $ nub $ sort $ filter isHledgerExeName pathfiles
-  -- XXX should exclude directories and files without execute permission.
+  return $ nub $ sort pathfiles
+  -- exclude directories and files without execute permission.
   -- These will do a stat for each hledger-*, probably ok.
   -- But they need paths, not just filenames
-  -- hledgerexes  <- filterM doesFileExist hledgernamed
-  -- hledgerexes' <- filterM isExecutable hledgerexes
-  -- return hledgerexes
+  -- exes'  <- filterM doesFileExist exe'
+  -- exes'' <- filterM isExecutable exes'
+  -- return exes''
+
+-- | Get the sorted unique filenames of all hledger-* executables in
+-- the current user's PATH. These are files in any of the PATH directories,
+-- named hledger-*, with either no extension (and no periods in the name) 
+-- or one of the addonExtensions. 
+-- We do not currently filter out non-file objects or files without execute permission.
+hledgerExecutablesInPath :: IO [String]
+hledgerExecutablesInPath = filter isHledgerExeName <$> likelyExecutablesInPath
 
 -- isExecutable f = getPermissions f >>= (return . executable)
 

hledger/Hledger/Cli/DocFiles.hs

@@ -16,6 +16,7 @@ module Hledger.Cli.DocFiles (
   ,printHelpForTopic
   ,runManForTopic
   ,runInfoForTopic
+  ,runPagerForTopic
 
   ) where
 
@@ -94,6 +95,15 @@ printHelpForTopic :: Topic -> IO ()
 printHelpForTopic t =
   putStrLn $ lookupDocTxt t
 
+runPagerForTopic :: FilePath -> Topic -> IO ()
+runPagerForTopic exe t = do
+  (Just inp, _, _, ph) <- createProcess (proc exe []){
+    std_in=CreatePipe
+    }
+  hPutStrLn inp (lookupDocTxt t)
+  _ <- waitForProcess ph
+  return ()
+
 runManForTopic :: Topic -> IO ()
 runManForTopic t =
   withSystemTempFile ("hledger-"++t++".nroff") $ \f h -> do

hledger/Hledger/Cli/Help.hs

@@ -3,6 +3,8 @@
 The help command.
 
 |-}
+--TODO rename manuals
+--TODO substring matching
 
 module Hledger.Cli.Help (
 
@@ -14,29 +16,57 @@ module Hledger.Cli.Help (
 import Prelude ()
 import Prelude.Compat
 import Data.List
+import Data.Maybe
 import System.Console.CmdArgs.Explicit
+import System.Environment
+import System.IO
 
 import Hledger.Data.RawOptions
 import Hledger.Cli.CliOptions
 import Hledger.Cli.DocFiles
+--import Hledger.Utils.Debug
 
 helpmode = (defCommandMode $ ["help"] ++ aliases) {
-  modeHelp = "show any of the hledger manuals" `withAliases` aliases
+  modeHelp = "show any of the hledger manuals, as plain text. With no argument, list the manuals." `withAliases` aliases
  ,modeGroupFlags = Group {
-     groupUnnamed = []
+     groupUnnamed = [
+      flagNone ["info"]  (setboolopt "info")  "show the manual with info"
+     ,flagNone ["man"]   (setboolopt "man")   "show the manual with man"
+     ,flagNone ["pager"] (setboolopt "pager") "show the manual with $PAGER or less"
+     ,flagNone ["cat"]   (setboolopt "cat")   "show the manual on stdout"
+     ,flagNone ["help","h"]  (setboolopt "help")  "show this help"
+     ]
     ,groupHidden = []
     ,groupNamed = []
     }
- }
+ ,modeArgs = ([], Just $ argsFlag "[MANUAL]")
+}
   where aliases = []
 
--- | Print detailed help on various topics.
+-- | List or display one of the hledger manuals in various formats. 
+-- You can select a docs viewer with one of the `--info`, `--man`, `--pager`, `--cat` flags.
+-- Otherwise it will use the first available of: info, man, $PAGER, less, stdout
+-- (and always stdout if output is non-interactive). 
 help' :: CliOpts -> IO ()
 help' opts = do
-  let args = listofstringopt "args" $ rawopts_ opts
+  exes <- likelyExecutablesInPath
+  pagerprog <- fromMaybe "less" <$> lookupEnv "PAGER"
+  interactive <- hIsTerminalDevice stdout
+  let
+    args = take 1 $ listofstringopt "args" $ rawopts_ opts
+    [info, man, pager, cat] = 
+      [runInfoForTopic, runManForTopic, runPagerForTopic pagerprog, printHelpForTopic]
+    viewer
+      | boolopt "info"  $ rawopts_ opts = info
+      | boolopt "man"   $ rawopts_ opts = man
+      | boolopt "pager" $ rawopts_ opts = pager
+      | boolopt "cat"   $ rawopts_ opts = cat
+      | not interactive                 = cat 
+      | "info"    `elem` exes           = info
+      | "man"     `elem` exes           = man
+      | pagerprog `elem` exes           = pager
+      | otherwise                       = cat 
   case args of
-    []    -> putStrLn $
-             "Choose a topic, eg: hledger help cli\n" ++
-             intercalate ", " docTopics
-    topic:_ -> printHelpForTopic topic
+    [t] -> viewer t
+    _   -> putStrLn $ "Please choose a manual:\nhledger help " ++ intercalate "|" docTopics
 

hledger/Hledger/Cli/Main.hs

@@ -128,10 +128,7 @@ PROGNAME CMD [--] [OPTS] [ARGS]  run a command (use -- with addon commands)
 PROGNAME-CMD [OPTS] [ARGS]       or run addon commands directly
 PROGNAME -h                      show general usage
 PROGNAME CMD -h                  show command usage
-PROGNAME help                    list available manuals
-PROGNAME help MANUAL             show a manual as plain text
-PROGNAME man  MANUAL             show a manual as man page
-PROGNAME info MANUAL             show a manual as info manual
+PROGNAME help [MANUAL]           show any of the hledger manuals in various formats
 |]
  }
 
@@ -263,7 +260,7 @@ OTHERCMDS
 Help:
  hledger -h           show general usage
  hledger CMD -h       show command usage
- help|man|info        show any of the hledger manuals in plain text/man/info format
+ help                 show any of the hledger manuals in various formats
 |]
 
 knownCommands :: [String]

hledger/doc/commands.m4.md

@@ -304,18 +304,18 @@ you can alter the report mode with `--change`/`--cumulative`/`--historical`.
 ## help
 Show any of the hledger manuals.
 
-The `help` command displays any of the main [hledger man pages](/docs.html).
-(Unlike `hledger --help`, which displays only the hledger man page.)
-Run it with no arguments to list available topics (their names are shortened for easier typing),
-and run `hledger help TOPIC` to select one.
-The output is similar to a man page, but fixed width.
-It may be long, so you may wish to pipe it into a pager.
-See also [info](#info) and [man](#man).
+The `help` command displays any of the main [hledger manuals](/docs.html), in one of several ways.
+Run it with no argument to list the manuals (their names are shortened for easier typing),
+and run `hledger help MANUAL` to select one.
+
+hledger help will choose one of these docs viewers, in order of preference: 
+info, man, $PAGER, less, stdout (and it always prints on stdout when piped). 
+Or you can force a particular viewer with the `--info`, `--man`, `--pager`, `--cat` flags.
 
 _shell_({{
 $ hledger help
-Choose a topic, eg: hledger help cli
-cli, ui, web, api, journal, csv, timeclock, timedot
+Please choose a manual:
+hledger help cli|ui|web|api|journal|csv|timeclock|timedot
 }})
 
 _shell_({{
@@ -329,9 +329,7 @@ NAME
        hledger - a command-line accounting tool
 
 SYNOPSIS
-       hledger [-f FILE] COMMAND [OPTIONS] [CMDARGS]
-       hledger [-f FILE] ADDONCMD -- [OPTIONS] [CMDARGS]
-:
+       hledger [-f FILE] COMMAND [OPTIONS] [ARGS]
 }})
 
 ## incomestatement
@@ -404,6 +402,7 @@ Normally incomestatement shows revenues/expenses per period, though
 as with [multicolumn balance reports](#multicolumn-balance-reports)
 you can alter the report mode with `--change`/`--cumulative`/`--historical`.
 
+...
 ## info
 Show any of the hledger manuals using info.
 
@@ -423,6 +422,7 @@ This will fit the text to your terminal width, and probably invoke a pager autom
 It requires the "man" program to be available in your PATH.
 
 As with [help](#help), run it with no arguments to list available topics (manuals).
+```
 
 ## print
 Show transactions from the journal.