How to tell an Inlines object from a table in a Lua filter?

How to tell an Inlines object from a table in a Lua filter?

[Shane Liesegang]

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Is there a way to tell whether a given object is a pandoc.Inlines as 
opposed to a plain Lua table? When I call `type(obj)` on it, it just 
returns "table." I note that if I print it, it shows "Inlines:" instead of 
"table:" but is there any smarter way to determine? 

I see some code in the Lua filters example repository 
<https://github.com/pandoc/lua-filters/blob/03c0fef0e56274ec9c958cdfe508a20618a1b623/scholarly-metadata/scholarly-metadata.lua#L45> 
that does this kind of check, but I don't know if it's crucial to that code 
or not, if something has changed recently, etc. 

(My use case here is walking through my Meta object and building something 
that will get passed to different functions -- if it encounters a nested 
table of data, I need to recurse, but if it's an Inlines object, I want to 
stringify it.) 

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Re: How to tell an Inlines object from a table in a Lua filter?

[Shane Liesegang]

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I've figured out a workaround, but just wondering if there's a better way 
than diving into the metatables: 

~~~
function fix_table_strings(t)
  for k, v in pairs(t) do
    if type(v) == "table" then
      local metatable = getmetatable(v)
      if metatable ~= nil and metatable.__name == "Inlines" then
        t[k] = pandoc.utils.stringify(v)
      else
        fix_table_strings(t[k])
      end
    end
  end
end
~~~

On Tuesday, May 24, 2022 at 9:30:41 AM UTC+3 Shane Liesegang wrote:

> Is there a way to tell whether a given object is a pandoc.Inlines as 
> opposed to a plain Lua table? When I call `type(obj)` on it, it just 
> returns "table." I note that if I print it, it shows "Inlines:" instead of 
> "table:" but is there any smarter way to determine? 
>
> I see some code in the Lua filters example repository 
> <https://github.com/pandoc/lua-filters/blob/03c0fef0e56274ec9c958cdfe508a20618a1b623/scholarly-metadata/scholarly-metadata.lua#L45> 
> that does this kind of check, but I don't know if it's crucial to that code 
> or not, if something has changed recently, etc. 
>
> (My use case here is walking through my Meta object and building something 
> that will get passed to different functions -- if it encounters a nested 
> table of data, I need to recurse, but if it's an Inlines object, I want to 
> stringify it.) 
>
>

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Re: How to tell an Inlines object from a table in a Lua filter?

[BPJ]

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You can use the pandoc.utils.type() function. It will return a string
'Inlines' for an Inlines object but 'table' for a regular table.

Unfortunately metadata mappings are now represented as regular tables so
you may have to check whether a regular table is an array or a mapping. I
usually do that with a function like this:

``````lua
local function is_map (val)
  if 'table' == pandoc.utils.type(val) then
    if 0 == #val then
      if next(val) then return true end
    end
  end
  return false
end
``````


Den tis 24 maj 2022 08:50Shane Liesegang <liesegang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> skrev:

> I've figured out a workaround, but just wondering if there's a better way
> than diving into the metatables:
>
> ~~~
> function fix_table_strings(t)
>   for k, v in pairs(t) do
>     if type(v) == "table" then
>       local metatable = getmetatable(v)
>       if metatable ~= nil and metatable.__name == "Inlines" then
>         t[k] = pandoc.utils.stringify(v)
>       else
>         fix_table_strings(t[k])
>       end
>     end
>   end
> end
> ~~~
>
> On Tuesday, May 24, 2022 at 9:30:41 AM UTC+3 Shane Liesegang wrote:
>
>> Is there a way to tell whether a given object is a pandoc.Inlines as
>> opposed to a plain Lua table? When I call `type(obj)` on it, it just
>> returns "table." I note that if I print it, it shows "Inlines:" instead of
>> "table:" but is there any smarter way to determine?
>>
>> I see some code in the Lua filters example repository
>> <https://github.com/pandoc/lua-filters/blob/03c0fef0e56274ec9c958cdfe508a20618a1b623/scholarly-metadata/scholarly-metadata.lua#L45>
>> that does this kind of check, but I don't know if it's crucial to that code
>> or not, if something has changed recently, etc.
>>
>> (My use case here is walking through my Meta object and building
>> something that will get passed to different functions -- if it encounters a
>> nested table of data, I need to recurse, but if it's an Inlines object, I
>> want to stringify it.)
>>
>> --
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> .
>

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