Add new option `--variable-json`.

This allows non-string values (booleans, lists, maps)
to be given to template variables on the command line.

Closes #10341.
Supersedes #10342.

2 files changed, 29 insertions, 0 deletions

diff --git a/MANUAL.txt b/MANUAL.txt
index 5025aba82..ef71be2aa 100644
--- a/MANUAL.txt
+++ b/MANUAL.txt
@@ -789,6 +789,17 @@ header when requesting a document from a URL:
     `-V keyword=Joe -V author=Sue` makes `author` contain a list
     of strings: `Joe` and `Sue`.
 
+`--variable-json=`*KEY*[`=`:*JSON*]
+
+:   Set the template variable *KEY* to the value specified by a JSON
+    string (this may be a boolean, a string, a list, or a mapping;
+    a number will be treated as a string). For example,
+    `--variable-json foo=false` will give `foo` the boolean false
+    value, while `--variable-json foo='"false"'` will give it the
+    string value `"false"`. Either `:` or `=` may be used to
+    separate *KEY* from *VAL*. If the variable already has a
+    value, this value will be replaced.
+
 `--sandbox[=true|false]`
 
 :   Run pandoc in a sandbox, limiting IO operations in readers
diff --git a/src/Text/Pandoc/App/CommandLineOptions.hs b/src/Text/Pandoc/App/CommandLineOptions.hs
index e65bb65ae..a4fec880d 100644
--- a/src/Text/Pandoc/App/CommandLineOptions.hs
+++ b/src/Text/Pandoc/App/CommandLineOptions.hs
@@ -25,6 +25,7 @@ module Text.Pandoc.App.CommandLineOptions (
 import Control.Monad.Trans
 import Control.Monad.State.Strict
 import Data.Containers.ListUtils (nubOrd)
+import Data.Aeson (eitherDecode)
 import Data.Aeson.Encode.Pretty (encodePretty', Config(..), keyOrder,
          defConfig, Indent(..), NumberFormat(..))
 import Data.Bifunctor (second)
@@ -372,6 +373,23 @@ options =
                   "KEY[:VALUE]")
                  ""
 
+    , Option "" ["variable-json"]
+                 (ReqArg
+                  (\arg opt -> do
+                     let (key, json) = splitField arg
+                     case eitherDecode (B.fromStrict . UTF8.fromString $ json) of
+                       Right (val :: Val Text) ->
+                         return opt{ optVariables =
+                                      let Context m = optVariables opt
+                                       in Context $ M.insert (T.pack key) val m }
+                           -- note that this replaces any existing value, which
+                           -- is different from what --variable does
+                       Left err'  -> optError $ PandocOptionError $
+                          "Could not parse '" <> T.pack json <> "' as JSON:\n" <>
+                           T.pack err')
+                  "KEY[:JSON]")
+                 ""
+
     , Option "" ["wrap"]
                  (ReqArg
                   (\arg opt ->