pandoc-cli: add a Lua REPL

5 files changed, 51 insertions, 14 deletions

diff --git a/doc/pandoc-lua.md b/doc/pandoc-lua.md
index 5badbfb32..2a9a58594 100644
--- a/doc/pandoc-lua.md
+++ b/doc/pandoc-lua.md
@@ -18,8 +18,10 @@ Furthermore, the globals `PANDOC_VERSION`, `PANDOC_STATE`, and
 `PANDOC_API_VERSION` are set at startup.
 
 If no script argument is given, then the script is assumed to be
-passed in via *stdin*. Interactive mode is not supported at this
-time.
+passed in via *stdin*. When called without arguments, `pandoc-lua`
+behaves as `pandoc-lua -v -i` when the standard input (`stdin`) is
+a terminal, and as `pandoc-lua -` otherwise. On Windows the
+program will always behave as if it was connected to a terminal.
 
 When called without the option `-E`, the interpreter checks for an
 environment variable `LUA_INIT` before running any argument. If
@@ -41,7 +43,7 @@ the string itself.
 :   Show version information.
 
 `-i`
-:   Not supported yet; print a warning to that effect.
+:   Enter interactive mode after running *script*.
 
 `-E`
 :   Ignore environment variables. This is not fully implemented
@@ -51,9 +53,23 @@ the string itself.
 `-W`
 :   Turn warnings on.
 
+# INTERACTIVE MODE
+
+In interactive mode, the Lua interpreter repeatedly prompts and
+waits for a line. After reading a line, Lua first tries to
+interpret the line as an expression. If it succeeds, it prints its
+value. Otherwise, it interprets the line as a statement. If you
+write an incomplete statement, the interpreter waits for its
+completion by issuing a different prompt.
+
+Exit the interactive mode by pressing `Ctrl-D` or `Ctrl-C`, or by
+typing `os.exit()`. The *Isocline* library is used for line
+editing. Press `F1` to get a list of available keybindings; the
+`ctrl` key is abbreviated as `^` in that list.
+
 # AUTHORS
 
-Copyright 2022 John MacFarlane ([email protected]) and
+Copyright 2023 John MacFarlane ([email protected]) and
 contributors. Released under the [GPL], version 2 or later. This
 software carries no warranty of any kind. (See COPYRIGHT for full
 copyright and warranty notices.)
diff --git a/pandoc-cli/lua/PandocCLI/Lua.hs b/pandoc-cli/lua/PandocCLI/Lua.hs
index 368f9cf49..07259af04 100644
--- a/pandoc-cli/lua/PandocCLI/Lua.hs
+++ b/pandoc-cli/lua/PandocCLI/Lua.hs
@@ -11,6 +11,9 @@ module PandocCLI.Lua (runLuaInterpreter, getEngine) where
 
 import Control.Monad ((<=<))
 import HsLua.CLI (EnvBehavior (..), Settings (..), runStandalone)
+import System.Environment (lookupEnv)
+import System.IO.Temp (withSystemTempFile)
+import System.IO (hClose)
 import Text.Pandoc.Class (runIOorExplode)
 import Text.Pandoc.Error (handleError)
 import Text.Pandoc.Lua (runLua, runLuaNoEnv, getEngine)
@@ -18,16 +21,32 @@ import Text.Pandoc.Version (pandocVersionText)
 
 -- | Runs pandoc as a Lua interpreter that is (mostly) compatible with
 -- the default @lua@ program shipping with Lua.
+--
+-- The filename for the history of the REPL is taken from the
+-- @PANDOC_REPL_HISTORY@ environment variable if possible. Otherwise a
+-- new temporary file is used; it is removed after the REPL finishes.
 runLuaInterpreter :: String    -- ^ Program name
                   -> [String]  -- ^ Command line arguments
                   -> IO ()
 runLuaInterpreter progName args = do
-  let settings = Settings
-        { settingsVersionInfo = "\nEmbedded in pandoc " <> pandocVersionText
-        , settingsRunner = runner
-        }
-  runStandalone settings progName args
+  -- We need some kind of temp
+  mbhistfile <- lookupEnv "PANDOC_REPL_HISTORY"
+  case mbhistfile of
+    Just histfile -> runStandaloneWithHistory histfile
+    Nothing -> withSystemTempFile "pandoc-hist" $ \fp handle -> do
+      -- We cannot pass a handle to the repl; the file will be re-opened
+      -- there.
+      hClose handle
+      runStandaloneWithHistory fp
   where
+    runStandaloneWithHistory histfile =  do
+      let settings = Settings
+            { settingsVersionInfo = "\nEmbedded in pandoc " <>
+                                    pandocVersionText
+            , settingsRunner = runner
+            , settingsHistory = Just histfile
+            }
+      runStandalone settings progName args
     runner envBehavior =
       let runLua' = case envBehavior of
                       IgnoreEnvVars  -> runLuaNoEnv
diff --git a/pandoc-cli/pandoc-cli.cabal b/pandoc-cli/pandoc-cli.cabal
index 8d9df6c38..0d28b0f9d 100644
--- a/pandoc-cli/pandoc-cli.cabal
+++ b/pandoc-cli/pandoc-cli.cabal
@@ -85,8 +85,9 @@ executable pandoc
     hs-source-dirs:  no-server
 
   if flag(lua)
-    build-depends:   hslua-cli         >= 1.3 && < 1.4,
-                     pandoc-lua-engine >= 0.1 && < 0.2
+    build-depends:   hslua-cli         >= 1.4 && < 1.5,
+                     pandoc-lua-engine >= 0.1 && < 0.2,
+                     temporary         >= 1.1 && < 1.4
     hs-source-dirs:  lua
   else
     hs-source-dirs:  no-lua
diff --git a/pandoc-lua-engine/pandoc-lua-engine.cabal b/pandoc-lua-engine/pandoc-lua-engine.cabal
index abaae611d..697dd3bda 100644
--- a/pandoc-lua-engine/pandoc-lua-engine.cabal
+++ b/pandoc-lua-engine/pandoc-lua-engine.cabal
@@ -114,7 +114,7 @@ library
                      , lpeg                  >= 1.0.4   && < 1.1
                      , mtl                   >= 2.2     && < 2.4
                      , pandoc                >= 3.1     && < 3.2
-                     , pandoc-lua-marshal    >= 0.2.1   && < 0.3
+                     , pandoc-lua-marshal    >= 0.2.2   && < 0.3
                      , pandoc-types          >= 1.22    && < 1.24
                      , parsec                >= 3.1     && < 3.2
                      , text                  >= 1.1.1   && < 2.1
diff --git a/stack.yaml b/stack.yaml
index 6a536199a..918d7d46e 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -13,7 +13,7 @@ extra-deps:
 - hslua-2.3.0
 - hslua-aeson-2.3.0.1
 - hslua-classes-2.3.0
-- hslua-cli-1.3.0
+- hslua-cli-1.4.0
 - hslua-core-2.3.0
 - hslua-list-1.1.0.1
 - hslua-marshalling-2.3.0
@@ -25,6 +25,7 @@ extra-deps:
 - hslua-module-zip-1.1.0
 - hslua-objectorientation-2.3.0
 - hslua-packaging-2.3.0
+- hslua-repl-0.1.0
 - hslua-typing-0.1.0
 - jira-wiki-markup-1.5.1
 - lua-2.3.0
@@ -35,7 +36,7 @@ extra-deps:
 - texmath-0.12.6
 - citeproc-0.8.1
 - pandoc-types-1.23
-- pandoc-lua-marshal-0.2.1.1
+- pandoc-lua-marshal-0.2.2
 - commonmark-pandoc-0.2.1.3
 - skylighting-0.13.2.1
 - skylighting-core-0.13.2.1