The `text` module is preloaded in lua. The module contains some UTF-8
aware string functions, implemented in Haskell. The module is loaded on
request only, e.g.:
text = require 'text'
function Str (s)
s.text = text.upper(s.text)
return s
end
Refactored some code from Text.Pandoc.Lua.PandocModule
into new internal module Text.Pandoc.Lua.Filter.
Add `walk_inline` and `walk_block` in pandoc lua module.
This is standard for lua scripts, and I see no reason
to depart from the standard here.
Also, "arg" is now pushed onto the stack before the script
is loaded. Previously it was not, and thus "PandocParameters"
was not available at the top level.
This change makes it possible to define a catch-all function using lua's
metatable lookup functionality.
function catch_all(el)
…
end
return {
setmetatable({}, {__index = function(_) return catch_all end})
}
A further effect of this change is that the map with filter functions
now only contains functions corresponding to AST element constructors.
Stack instances for common data types are now provides by hslua. The
instance for Either was useful only for a very specific case; the
function that was using the `ToLuaStack Either` instance was rewritten
to work without it.
Closes: #3805
in Text.Pandoc.Lua. Also to pushPandocModule.
This change allows users to override pandoc.lua with a file
in their local data directory, adding custom functions, etc.
@tarleb, if you think this is a bad idea, you can revert this.
But in general our data files are all overridable.
Also, now we check before running walkM that the function
table actually does contain something relevant. E.g. if
your filter just defines Str, there's no need to run walkM
for blocks, meta, or the whole document. This should
help performance a bit (and it does, in my tests).
No more SingleQuoted, DoubleQuoted, InlineMath, DisplayMath.
This makes everything uniform and predictable, though it does
open up a difference btw lua filters and custom writers.
I tested this with the str.lua filter on MANUAL.txt, and
I could see no significant performance degradation.
Doing things this way will ease maintenance, as we won't
have to manually modify this module when types change.
@tarleb, do we really need special cases for things like
DoubleQuoted and InlineMath?
The code still allowed to pass an arbitrary number of arguments to the
filter function, as element properties were passed as function arguments
at some point. Now we only pass the element as the single arg, so the
code to handle multiple arguments is no longer necessary.
Using the registry directly instead of a custom table is cleaner and
more efficient. The performance improvement is especially noticable when
filtering on frequent elements like Str.
The implicitly defined global filter (i.e. all element filtering
functions defined in the global lua environment) is used if no filter is
returned from a lua script. This allows to just write top-level
functions in order to define a lua filter. E.g
function Emph(elem) return pandoc.Strong(elem.content) end
Filtering functions take element components as arguments instead of the
whole block elements. This resembles the way elements are handled in
custom writers.
Instead of taking the whole inline element, forcing users to destructure it
themselves, the components of the elements are passed to the filtering
functions.
Plain text readers are exposed to lua scripts via the `pandoc.reader`
submodule, which is further subdivided by format. Converting e.g. a
markdown string into a pandoc document is possible from within lua:
doc = pandoc.reader.markdown.read_doc("Hello, World!")
A `read_block` convenience function is provided for all formats,
although it will still parse the whole string but return only the first
block as the result.
Custom reader options are not supported yet, default options are used
for all parsing operations.
* Add `--lua-filter` option. This works like `--filter` but takes pathnames of special lua filters and uses the lua interpreter baked into pandoc, so that no external interpreter is needed. Note that lua filters are all applied after regular filters, regardless of their position on the command line.
* Add Text.Pandoc.Lua, exporting `runLuaFilter`. Add `pandoc.lua` to data files.
* Add private module Text.Pandoc.Lua.PandocModule to supply the default lua module.
* Add Tests.Lua to tests.
* Add data/pandoc.lua, the lua module pandoc imports when processing its lua filters.
* Document in MANUAL.txt.
