pandoc-cli: support "lua" and "serve" as commands

Pandoc behaves like `pandoc-lua` and `pandoc-server` if the first
argument is `lua` and `serve`, respectively.

MANUAL.txt

@@ -7081,10 +7081,10 @@ metadata field (see [EPUB Metadata], above).
 # Running pandoc as a web server
 
 If you rename (or symlink) the pandoc executable to
-`pandoc-server`, it will start up a web server with a JSON
-API. This server exposes most of the conversion functionality
-of pandoc.  For full documentation, see the [pandoc-server]
-man page.
+`pandoc-server`, or if you call pandoc with `serve` as the first
+argument, it will start up a web server with a JSON API. This
+server exposes most of the conversion functionality of pandoc. For
+full documentation, see the [pandoc-server] man page.
 
 If you rename (or symlink) the pandoc executable to
 `pandoc-server.cgi`, it will function as a CGI program
@@ -7098,12 +7098,12 @@ will be performed on the server during pandoc conversions.
 
 # Running pandoc as a Lua interpreter
 
-Calling the pandoc executable under the name `pandoc-lua` will
-make it function as a standalone Lua interpreter. The behavior is
-mostly identical to that of the [standalone `lua`
-executable][lua standalone], version 5.4. However, there is no
-REPL yet, and the options `-W`, `-E`, and `-i` currently don't
-have any effect.
+Calling the pandoc executable under the name `pandoc-lua` or with
+`lua` as the first argument will make it function as a standalone
+Lua interpreter. The behavior is mostly identical to that of the
+[standalone `lua` executable][lua standalone], version 5.4.
+However, there is no REPL yet, and the options `-W`, `-E`, and
+`-i` currently don't have any effect.
 
 [lua standalone]: https://www.lua.org/manual/5.4/manual.html#7
 

pandoc-cli/no-server/PandocCLI/Server.hs

@@ -23,8 +23,8 @@ runCGI = serverUnsupported
 
 -- | Placeholder function for the HTTP server; prints an error message
 -- and exists with error code.
-runServer :: IO ()
-runServer = serverUnsupported
+runServer :: [String] -> IO ()
+runServer _args = serverUnsupported
 
 serverUnsupported :: IO ()
 serverUnsupported = do

pandoc-cli/server/PandocCLI/Server.hs

@@ -17,7 +17,7 @@ import qualified Network.Wai.Handler.Warp as Warp
 import Network.Wai.Middleware.Timeout (timeout)
 import Safe (readDef)
 import System.Environment (lookupEnv)
-import Text.Pandoc.Server (ServerOpts(..), parseServerOpts, app)
+import Text.Pandoc.Server (ServerOpts(..), parseServerOptsFromArgs, app)
 
 -- | Runs the CGI server.
 runCGI :: IO ()
@@ -26,7 +26,7 @@ runCGI = do
   CGI.run (timeout cgiTimeout app)
 
 -- | Runs the HTTP server.
-runServer :: IO ()
-runServer = do
-  sopts <- parseServerOpts
+runServer :: [String] -> IO ()
+runServer args = do
+  sopts <- parseServerOptsFromArgs args
   Warp.run (serverPort sopts) (timeout (serverTimeout sopts) app)

pandoc-cli/src/pandoc.hs

@@ -31,10 +31,14 @@ main = E.handle (handleError . Left) $ do
   rawArgs <- map UTF8.decodeArg <$> getArgs
   case prg of
     "pandoc-server.cgi" -> runCGI
-    "pandoc-server"     -> runServer
+    "pandoc-server"     -> runServer rawArgs
     "pandoc-lua"        -> runLuaInterpreter prg rawArgs
-    _ -> parseOptionsFromArgs options defaultOpts prg rawArgs
-         >>= convertWithOpts
+    _ ->
+      case rawArgs of
+        "lua" : args   -> runLuaInterpreter "pandoc lua" args
+        "serve" : args -> runServer args
+        _              -> parseOptionsFromArgs options defaultOpts prg rawArgs
+                          >>= convertWithOpts
 
 -- | Runs pandoc as a Lua interpreter that is (mostly) compatible with
 -- the default @lua@ program shipping with Lua.

pandoc-server/src/Text/Pandoc/Server.hs

@@ -10,6 +10,7 @@ module Text.Pandoc.Server
     , Params(..)
     , Blob(..)
     , parseServerOpts
+    , parseServerOptsFromArgs
     ) where
 
 import Data.Aeson
@@ -94,6 +95,10 @@ cliOptions =
 parseServerOpts :: IO ServerOpts
 parseServerOpts = do
   args <- getArgs
+  parseServerOptsFromArgs args
+
+parseServerOptsFromArgs :: [String] -> IO ServerOpts
+parseServerOptsFromArgs args = do
   let handleUnknownOpt x = "Unknown option: " <> x
   case getOpt' Permute cliOptions args of
     (os, ns, unrecognizedOpts, es) -> do
@@ -426,4 +431,3 @@ server = convertBytes
     case res of
       Left e -> throwError $ PandocTemplateError (T.pack e)
       Right tpl -> return tpl
-