feat: ability to enable and disable atx and setext heading rendering

## Details

Request: #381

Adds `heading.atx` and `heading.setext` boolean options. These let you
disable rendering for a specific subset of heading types rather than an
all or nothing. By default both remain enabled. Mostly helpful for
`setext` headings since their syntax can overlap with nested lists.

Author: MeanderingProgrammer

README.md

@@ -303,6 +303,10 @@ require('render-markdown').setup({
         enabled = true,
         -- Additional modes to render headings.
         render_modes = false,
+        -- Turn on / off atx heading rendering.
+        atx = true,
+        -- Turn on / off setext heading rendering.
+        setext = true,
         -- Turn on / off any sign column related rendering.
         sign = true,
         -- Replaces '#+' of 'atx_h._marker'.
@@ -827,6 +831,10 @@ require('render-markdown').setup({
         enabled = true,
         -- Additional modes to render headings.
         render_modes = false,
+        -- Turn on / off atx heading rendering.
+        atx = true,
+        -- Turn on / off setext heading rendering.
+        setext = true,
         -- Turn on / off any sign column related rendering.
         sign = true,
         -- Replaces '#+' of 'atx_h._marker'.

doc/render-markdown.txt

@@ -1,4 +1,4 @@
-*render-markdown.txt*           For 0.10.0          Last change: 2025 March 28
+*render-markdown.txt*           For 0.10.0          Last change: 2025 March 30
 
 ==============================================================================
 Table of Contents                          *render-markdown-table-of-contents*
@@ -368,6 +368,10 @@ Default Configuration ~
             enabled = true,
             -- Additional modes to render headings.
             render_modes = false,
+            -- Turn on / off atx heading rendering.
+            atx = true,
+            -- Turn on / off setext heading rendering.
+            setext = true,
             -- Turn on / off any sign column related rendering.
             sign = true,
             -- Replaces '#+' of 'atx_h._marker'.
@@ -890,6 +894,10 @@ Heading Configuration ~
             enabled = true,
             -- Additional modes to render headings.
             render_modes = false,
+            -- Turn on / off atx heading rendering.
+            atx = true,
+            -- Turn on / off setext heading rendering.
+            setext = true,
             -- Turn on / off any sign column related rendering.
             sign = true,
             -- Replaces '#+' of 'atx_h._marker'.

lua/render-markdown/health.lua

@@ -5,7 +5,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '8.1.22'
+M.version = '8.1.23'
 
 function M.check()
     M.start('version')

lua/render-markdown/init.lua

@@ -261,6 +261,8 @@ local M = {}
 ---@alias render.md.heading.Width 'full'|'block'
 
 ---@class (exact) render.md.UserHeading: render.md.UserBaseComponent
+---@field atx? boolean
+---@field setext? boolean
 ---@field sign? boolean
 ---@field icons? render.md.heading.Icons
 ---@field position? render.md.heading.Position
@@ -482,6 +484,10 @@ M.default_config = {
         enabled = true,
         -- Additional modes to render headings.
         render_modes = false,
+        -- Turn on / off atx heading rendering.
+        atx = true,
+        -- Turn on / off setext heading rendering.
+        setext = true,
         -- Turn on / off any sign column related rendering.
         sign = true,
         -- Replaces '#+' of 'atx_h._marker'.

lua/render-markdown/render/heading.lua

@@ -43,11 +43,11 @@ function Render:setup()
     local atx = nil
     local marker = nil
     local level = nil
-    if self.node.type == 'atx_heading' then
+    if self.node.type == 'atx_heading' and self.heading.atx then
         atx = true
         marker = assert(self.node:child_at(0), 'atx heading expected child marker')
         level = Str.width(marker.text)
-    elseif self.node.type == 'setext_heading' then
+    elseif self.node.type == 'setext_heading' and self.heading.setext then
         atx = false
         marker = assert(self.node:child_at(1), 'ext heading expected child underline')
         level = marker.type == 'setext_h1_underline' and 1 or 2

lua/render-markdown/state.lua

@@ -167,7 +167,7 @@ function M.validate()
             end)
             :nested('heading', function(heading)
                 component_rules(heading)
-                    :type({ 'sign', 'border_virtual', 'border_prefix' }, 'boolean')
+                    :type({ 'atx', 'setext', 'sign', 'border_virtual', 'border_prefix' }, 'boolean')
                     :type({ 'above', 'below' }, 'string')
                     :list('border', 'boolean', 'boolean')
                     :list({ 'left_margin', 'left_pad', 'right_pad', 'min_width' }, 'number', 'number')

lua/render-markdown/types.lua

@@ -176,6 +176,8 @@
 ---@field min_width integer
 
 ---@class (exact) render.md.Heading: render.md.BaseComponent
+---@field atx boolean
+---@field setext boolean
 ---@field sign boolean
 ---@field icons render.md.heading.Icons
 ---@field position render.md.heading.Position