Lua filters: allow filtering of element lists (#6040)

Lists of Inline and Block elements can now be filtered via `Inlines` and
`Blocks` functions, respectively. This is helpful if a filter conversion
depends on the order of elements rather than a single element.

For example, the following filter can be used to remove all spaces
before a citation:

    function isSpaceBeforeCite (spc, cite)
      return spc and spc.t == 'Space'
       and cite and cite.t == 'Cite'
    end

    function Inlines (inlines)
      for i = #inlines-1,1,-1 do
        if isSpaceBeforeCite(inlines[i], inlines[i+1]) then
          inlines:remove(i)
        end
      end
      return inlines
    end

Closes: #6038

1 files changed, 24 insertions, 1 deletions

diff --git a/test/Tests/Lua.hs b/test/Tests/Lua.hs
index 7683df09f..5e01266c0 100644
--- a/test/Tests/Lua.hs
+++ b/test/Tests/Lua.hs
@@ -23,7 +23,8 @@ import Text.Pandoc.Arbitrary ()
 import Text.Pandoc.Builder (bulletList, definitionList, displayMath, divWith,
                             doc, doubleQuoted, emph, header, lineBlock,
                             linebreak, math, orderedList, para, plain, rawBlock,
-                            singleQuoted, space, str, strong)
+                            singleQuoted, space, str, strong,
+                            HasMeta (setMeta))
 import Text.Pandoc.Class (runIOorExplode, setUserDataDir)
 import Text.Pandoc.Definition (Block (BlockQuote, Div, Para), Inline (Emph, Str),
                                Attr, Meta, Pandoc, pandocTypesVersion)
@@ -129,6 +130,28 @@ tests = map (localOption (QuickCheckTests 20))
       (doc $ divWith ("", [], kv_before) (para "nil"))
       (doc $ divWith ("", [], kv_after) (para "nil"))
 
+  , testCase "Filter list of inlines" $
+      assertFilterConversion "List of inlines"
+      "inlines-filter.lua"
+      (doc $ para ("Hello," <> linebreak <> "World! Wassup?"))
+      (doc $ para "Hello, World! Wassup?")
+
+  , testCase "Filter list of blocks" $
+      assertFilterConversion "List of blocks"
+      "blocks-filter.lua"
+      (doc $ para "one." <> para "two." <> para "three.")
+      (doc $ plain "3")
+
+  , testCase "Filter Meta" $
+    let setMetaBefore = setMeta "old" ("old" :: T.Text)
+                      . setMeta "bool" False
+        setMetaAfter  = setMeta "new" ("new" :: T.Text)
+                      . setMeta "bool" True
+    in assertFilterConversion "Meta filtering"
+      "meta.lua"
+      (setMetaBefore . doc $ mempty)
+      (setMetaAfter . doc $ mempty)
+
   , testCase "Script filename is set" $
     assertFilterConversion "unexpected script name"
       "script-name.lua"