feat: allow html.comment.text to be a function

## Details

Request: #574

The `html.comment.text` field can now be a function which takes as input
a context table that includes the text of the comment. Users can use
this to transform the raw input text into a more useful representation
of the information.

Author: MeanderingProgrammer

README.md

@@ -887,9 +887,16 @@ require('render-markdown').setup({
         -- Additional modes to render HTML.
         render_modes = false,
         comment = {
+            -- Useful context to have when evaluating values.
+            -- | text | text value of the comment node |
+
             -- Turn on / off HTML comment concealing.
             conceal = true,
-            -- Optional text to inline before the concealed comment.
+            -- Text to inline before the concealed comment.
+            -- Output is evaluated depending on the type.
+            -- | function | `value(context)` |
+            -- | string   | `value`          |
+            -- | nil      | nothing          |
             text = nil,
             -- Highlight for the inlined text.
             highlight = 'RenderMarkdownHtmlComment',

doc/render-markdown.txt

@@ -1,4 +1,4 @@
-*render-markdown.txt*      For NVIM v0.11.5      Last change: 2025 December 16
+*render-markdown.txt*       For NVIM v0.11.5      Last change: 2026 January 02
 
 ==============================================================================
 Table of Contents                          *render-markdown-table-of-contents*
@@ -953,9 +953,16 @@ Default Configuration ~
             -- Additional modes to render HTML.
             render_modes = false,
             comment = {
+                -- Useful context to have when evaluating values.
+                -- | text | text value of the comment node |
+    
                 -- Turn on / off HTML comment concealing.
                 conceal = true,
-                -- Optional text to inline before the concealed comment.
+                -- Text to inline before the concealed comment.
+                -- Output is evaluated depending on the type.
+                -- | function | `value(context)` |
+                -- | string   | `value`          |
+                -- | nil      | nothing          |
                 text = nil,
                 -- Highlight for the inlined text.
                 highlight = 'RenderMarkdownHtmlComment',

lua/render-markdown/health.lua

@@ -6,7 +6,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '8.10.9'
+M.version = '8.10.10'
 
 function M.check()
     M.start('versions')

lua/render-markdown/render/html/comment.lua

@@ -19,12 +19,27 @@ function Render:run()
         return
     end
     self.marks:over(self.config, true, self.node, { conceal = '' })
-    if config.text then
+    local text = Render.get_string(config.text, { text = self.node.text })
+    if text then
         self.marks:start(self.config, true, self.node, {
-            virt_text = { { config.text, config.highlight } },
+            virt_text = { { text, config.highlight } },
             virt_text_pos = 'inline',
         })
     end
 end
 
+---@private
+---@param value? render.md.html.comment.String
+---@param ctx render.md.html.comment.Context
+---@return string?
+function Render.get_string(value, ctx)
+    if not value then
+        return nil
+    elseif type(value) == 'function' then
+        return value(ctx)
+    else
+        return value
+    end
+end
+
 return Render

lua/render-markdown/settings.lua

@@ -958,9 +958,16 @@ M.html = {}
 
 ---@class (exact) render.md.html.comment.Config
 ---@field conceal boolean
----@field text? string
+---@field text? render.md.html.comment.String
 ---@field highlight string
 
+---@class (exact) render.md.html.comment.Context
+---@field text string
+
+---@alias render.md.html.comment.String
+---| string
+---| fun(ctx: render.md.html.comment.Context): string?
+
 ---@class (exact) render.md.html.Tag
 ---@field icon? string
 ---@field highlight? string
@@ -973,9 +980,16 @@ M.html.default = {
     -- Additional modes to render HTML.
     render_modes = false,
     comment = {
+        -- Useful context to have when evaluating values.
+        -- | text | text value of the comment node |
+
         -- Turn on / off HTML comment concealing.
         conceal = true,
-        -- Optional text to inline before the concealed comment.
+        -- Text to inline before the concealed comment.
+        -- Output is evaluated depending on the type.
+        -- | function | `value(context)` |
+        -- | string   | `value`          |
+        -- | nil      | nothing          |
         text = nil,
         -- Highlight for the inlined text.
         highlight = 'RenderMarkdownHtmlComment',
@@ -1002,7 +1016,10 @@ function M.html.schema()
         comment = {
             record = {
                 conceal = { type = 'boolean' },
-                text = { optional = true, type = 'string' },
+                text = {
+                    optional = true,
+                    union = { { type = 'string' }, { type = 'function' } },
+                },
                 highlight = { type = 'string' },
             },
         },

lua/render-markdown/types.lua

@@ -177,7 +177,7 @@
 
 ---@class (exact) render.md.html.comment.UserConfig
 ---@field conceal? boolean
----@field text? string
+---@field text? render.md.html.comment.String
 ---@field highlight? string
 
 ---@class (exact) render.md.indent.UserConfig: render.md.base.UserConfig