Text.Pandoc.App: Change `parseOptionsFromArgs` and `parseOptions`... (#8406)

They now return `Either OptInfo Opt`.

Add `OptInfo` type.

Add `handleOptInfo` function.  This performs the IO actions for
things like `--version` that were previously done in `parseOptionsFromArgs`.
An argument for a `ScriptingEngine` has been added, to facilitate
printing custom templates and custom extensions for Lua filters.
(However, at this stage nothing is yet done with it.)

[API change]

1 files changed, 6 insertions, 4 deletions

diff --git a/pandoc-cli/src/pandoc.hs b/pandoc-cli/src/pandoc.hs
index 3c0889d8e..6bf54bda3 100644
--- a/pandoc-cli/src/pandoc.hs
+++ b/pandoc-cli/src/pandoc.hs
@@ -16,7 +16,7 @@ module Main where
 import qualified Control.Exception as E
 import System.Environment (getArgs, getProgName)
 import Text.Pandoc.App ( convertWithOpts, defaultOpts, options
-                       , parseOptionsFromArgs )
+                       , parseOptionsFromArgs, handleOptInfo )
 import Text.Pandoc.Error (handleError)
 import qualified Text.Pandoc.UTF8 as UTF8
 import System.Exit (exitSuccess)
@@ -61,10 +61,12 @@ main = E.handle (handleError . Left) $ do
       case rawArgs of
         "lua" : args   -> runLuaInterpreter "pandoc lua" args
         "server": args -> runServer args
-        _              -> do
+        args           -> do
           engine <- getEngine
-          opts <- parseOptionsFromArgs options defaultOpts prg rawArgs
-          convertWithOpts engine opts
+          res <- parseOptionsFromArgs options defaultOpts prg args
+          case res of
+            Left e -> handleOptInfo engine e
+            Right opts -> convertWithOpts engine opts
 
 copyrightMessage :: String
 copyrightMessage =