improve error message when attempting to run a JSON filter

news/changelog-1.4.md

@@ -115,6 +115,7 @@
 - Add support for relative paths in `require()` calls.
 - ([#5242](https://github.com/quarto-dev/quarto-cli/issues/5242)): Add line numbers to error messages.
 - Add support `quarto.doc.add_resource` and `quarto.doc.add_supporting`. `add_resource` will add a resource file to the current render, copying that file to the same relative location in the output directory. `add_supporting` will add a supporting file to the current render, moving that file file to the same relative location in the output directory.
+- ([#6211](https://github.com/quarto-dev/quarto-cli/pull/6211)): Improve error message when a JSON filter (or a potentially misspelled Lua filter from an extension) is not found.
 
 ## Books
 

src/resources/filters/common/wrapped-filter.lua

@@ -113,7 +113,21 @@ function makeWrappedJsonFilter(scriptFile, filterHandler)
             return meta
           end
         })
-        local result = pandoc.utils.run_json_filter(doc, path)
+        local success, result = pcall(pandoc.utils.run_json_filter, doc, path)
+        if not success then
+          local pandoc_error = tostring(result)
+          local filename = pandoc.path.filename(path)
+          local message = {
+            "Could not run " .. path .. " as a JSON filter.",
+            "Please make sure the file exists and is executable.",
+            "\nDid you intend '" .. filename .. "' as a Lua filter in an extension?",
+            "If so, make sure you've spelled the name of the extension correctly.",
+            "\nThe original Pandoc error follows below.",
+            pandoc_error
+          }
+          fail(table.concat(message, "\n"))
+          return nil
+        end
         if has_custom_nodes then
           doc:walk({
             Meta = function(meta)