Re: Printing lua tables

[William Lupton <wlupton-QSt+ys/nuMyEUIsrzH9SikB+6BGkLq7r@public.gmane.org>]

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All,

I've split this out into two functions (each currently in its own [attached
as .lua.txt] file):

   - dump(value, maxlen=70) that returns a possibly multi-line string
   representation of a value
   - output(...) that's a utility function that outputs space-separated
   arguments, each passed to dump() and with a terminating newline if needed

Here's an updated example filter (it uses output() and doesn't call dump()
directly):

local output = require 'output'
function Pandoc(doc)
    output('meta', doc.meta)
    output('blocks', doc.blocks)
end

Please feel free to do whatever you like with these functions.

In my environment I have an additional layer in which I derive a log-level
from PANDOC_STATE.{trace,verbosity} and use this in a set of logging
functions like this one (*please let me know if you'd like me to supply
these too*):

function error(...)
    if logLevel >= -1 then
        output('(E)', ...)
    end
end

Cheers,
William

On Tue, 7 Jun 2022 at 15:13, William Lupton <wlupton-QSt+ys/nuMyEUIsrzH9SikB+6BGkLq7r@public.gmane.org>
wrote:

> I'll need to extract the reporting functions. I'll do that soon, and post
> the result. This is currently working in pandoc 2.16.1 (and earlier). I
> haven't yet bitten the bullet of the move to 2.18.
>
> On Tue, 7 Jun 2022 at 14:55, John MacFarlane <jgm-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org> wrote:
>
>>
>> That looks nice.  Can you share your utils.lua?
>>
>> William Lupton <wlupton-QSt+ys/nuMyEUIsrzH9SikB+6BGkLq7r@public.gmane.org> writes:
>>
>> > I think I've mentioned this before... but I'd be happy to contribute
>> (in a
>> > suitable form) the somewhat-pandoc-aware utility that I use for this.
>> >
>> > Given this input:
>> >
>> > *% *cat doc.md
>> >
>> > ---
>> >
>> > a: 1
>> >
>> > b: |
>> >
>> >   2 3 4
>> >
>> > ---
>> >
>> >
>> > # Header
>> >
>> >
>> > This is a sentence (and a paragraph).
>> >
>> >
>> > * This is a list item
>> >
>> > * And another
>> >
>> >
>> > | Right | Left | Default | Center |
>> >
>> > |------:|:-----|---------|:------:|
>> >
>> > |   12  |  12  |    12   |    12  |
>> >
>> > |  123  |  123 |   123   |   123  |
>> >
>> > |    1  |    1 |     1   |     1  |
>> >
>> >
>> > : Demonstration of pipe table syntax.
>> >
>> > and this filter:
>> >
>> > *% *cat rep.lua
>> >
>> > local utils = require 'utils'
>> >
>> >
>> > -- do it this way to avoid reporting MetaBlocks twice
>> >
>> > function Pandoc(doc)
>> >
>> >     utils.temp('meta', doc.meta)
>> >
>> >     utils.temp('blocks', doc.blocks)
>> >
>> > end
>> >
>> > this command:
>> >
>> > pandoc doc.md -L rep.lua >/dev/null 2>doc.txt
>> >
>> > generates the attached.
>> >
>> > On Tue, 7 Jun 2022 at 08:57, <denis.maier-NSENcxR/0n0@public.gmane.org> wrote:
>> >
>> >> Hi,
>> >>
>> >> When playing around with filters I use pprint.lua or inspect.lua to
>> >> visualize lua tables. Would it make sense to include some sort of
>> «print
>> >> the contents of this table» to pandoc ?
>> >>
>> >> Best,
>> >>
>> >> Denis
>> >>
>> >> --
>>
>

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-- output() outputs to stderr

local dump = require 'dump'

local function output(...)
    local need_newline = false
    for i, item in ipairs({...}) do
        -- XXX space logic could be cleverer, e.g. no space after newline
        local maybe_space = i > 1 and ' ' or ''
        local text = ({table=1, userdata=1})[type(item)] and
            dump(item) or tostring(item)
        io.stderr:write(maybe_space, text)
        need_newline = text:sub(-1) ~= '\n'
    end
    if need_newline then
        io.stderr:write('\n')
    end
end

return output

[-- Attachment #3: dump.lua.txt --]
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-- pandoc-aware object dumper

-- helper function to return a sensible typename
-- XXX is there a better way of doing this? using metatables?
local function getTypename(value)
    local typ = type(value)
    if typ == 'table' and value.tag and value.t then
        return value.tag
    elseif typ == 'userdata' then
        if value.tag and value.t then
            return value.tag
        else
            -- e.g., Attributes is userdata but doesn't have tag and t
            return typ
        end
    else
        return typ
    end
end

-- helper function
-- note: don't use anything from the pandoc module (so can test standalone)
-- XXX should detect repetition/recursion
-- XXX would like maxlen logic to apply at all levels? but not trivial
local function helper(prefix, value, maxlen, level, add)
    local buffer = {}
    if prefix == nil then prefix = '' end
    if level == nil then level = 0 end
    if add == nil then add = function(item) table.insert(buffer, item) end end
    local indent = maxlen and '' or ('  '):rep(level)
    local typename = getTypename(value)
    local typ = (({boolean=1, number=1, string=1, table=1, userdata=1})
                 [typename] and '' or typename)
    if ({table=1, userdata=1})[type(value)] then
        local numKeys, lastKey = 0, nil
        for key, val in pairs(value) do
            -- pandoc >= 2.15 includes 'tag', nil values and functions
            if key ~= 'tag' and val and type(val) ~= 'function' then
                numKeys = numKeys + 1
                lastKey = key
            end
        end
        if numKeys == 0 then
            -- XXX this wouldn't be needed with proper maxlen handling
            value = '{}'
        elseif numKeys == 1 and lastKey == 'content' then
            typ = string.format('content: %s', typ)
            value = value.content
        elseif numKeys == 1 and lastKey == 'text' and typename == 'Str' then
            typename = 'string'
            typ = 'Str text:'
            value = value.text
        end
    end
    local presep = #prefix > 0 and ' ' or ''
    local typsep = #typ > 0 and ' ' or ''
    local valtyp = type(value)
    if ({boolean=1, number=1, string=1})[valtyp] then
        local fmt = typename == 'string' and '%q' or '%s'
        add(string.format('%s%s%s%s%s' .. fmt, indent, prefix, presep,
                          typ, typsep, value))
    elseif ({table=1, userdata=1})[valtyp] then
        add(string.format('%s%s%s%s%s{', indent, prefix, presep, typ, typsep))
        -- Attr and Attr.attributes have both numeric and string keys, so
        -- ignore the numeric ones (no longer the case for pandoc >= 2.15?)
        if prefix ~= 'attributes:' and typ ~= 'Attr' then
            for i, val in ipairs(value) do
                local pre = maxlen and i > 1 and ', ' or ''
                local text = helper(string.format('%s[%s]', pre, i), val,
                                    maxlen, level + 1, add)
            end
        end
        local first = true
        for key, val in pairs(value) do
            -- pandoc >= 2.15 includes 'tag'
            if not tonumber(key) and key ~= 'tag' then
                local pre = maxlen and not first and ', ' or ''
                local text = helper(string.format('%s%s:', pre, key), val,
                                    maxlen, level + 1, add)
            end
            first = false
        end
        add(string.format('%s}', indent))
    end
    return table.concat(buffer, maxlen and '' or '\n')
end

local function dump(value, maxlen)
    if maxlen == nil then maxlen = 70 end
    local text = helper(nil, value, maxlen)
    if #text > maxlen then
        text = helper(nil, value, nil)
    end
    return text
end

return dump