Disable rendering for large files

# Details

Adds a config parameter `max_file_size` that gets compared to the
file size in megabytes of the current buffer.

If the file is larger than this maximum size then this plugin
essentially becomes a NOOP.

Set the default value relatively high at 1.5 MB, at this value
performance gets pretty bad so no one should be using this
plugin with such files. Allows users to tune the value based
on their setup.

Add some `just` recipes to generate a large markdown file
for testing.

Author: MeanderingProgrammer

.gitignore

@@ -0,0 +1 @@
+large.md

README.md

@@ -18,6 +18,7 @@ Plugin to improve viewing Markdown files in Neovim
 - Replaces block quote leading `>` with provided character
 - Updates table borders with better border characters, does NOT automatically align
 - Basic support for `LaTeX` if `pylatexenc` is installed on system
+- Disable rendering when file is larger than provided value
 
 # Dependencies
 
@@ -64,6 +65,9 @@ by the user.
 require('render-markdown').setup({
     -- Configure whether Markdown should be rendered by default or not
     start_enabled = true,
+    -- Maximum file size (in MB) that this plugin will attempt to render
+    -- Any file larger than this will effectively be ignored
+    max_file_size = 1.5,
     -- Capture groups that get pulled from markdown
     markdown_query = [[
         (atx_heading [

doc/render-markdown.txt

@@ -1,4 +1,4 @@
-*render-markdown.txt*            For 0.10.0           Last change: 2024 May 16
+*render-markdown.txt*            For 0.10.0           Last change: 2024 May 17
 
 ==============================================================================
 Table of Contents                          *render-markdown-table-of-contents*
@@ -39,6 +39,7 @@ Plugin to improve viewing Markdown files in Neovim
 - Replaces block quote leading `>` with provided character
 - Updates table borders with better border characters, does NOT automatically align
 - Basic support for `LaTeX` if `pylatexenc` is installed on system
+- Disable rendering when file is larger than provided value
 
 
 ==============================================================================
@@ -93,6 +94,9 @@ modified by the user.
     require('render-markdown').setup({
         -- Configure whether Markdown should be rendered by default or not
         start_enabled = true,
+        -- Maximum file size (in MB) that this plugin will attempt to render
+        -- Any file larger than this will effectively be ignored
+        max_file_size = 1.5,
         -- Capture groups that get pulled from markdown
         markdown_query = [[
             (atx_heading [

justfile

@@ -2,25 +2,35 @@ init := "tests/minimal.lua"
 default_zoom := '2'
 
 test:
-    nvim --headless --noplugin -u {{init}} \
-      -c "PlenaryBustedDirectory tests { minimal_init = '{{init}}', sequential=true }"
+  nvim --headless --noplugin -u {{init}} \
+    -c "PlenaryBustedDirectory tests { minimal_init = '{{init}}', sequential=true }"
 
 demo zoom=default_zoom:
-    rm -f demo/demo.gif
-    python demo/record.py \
-      --zoom {{zoom}} \
-      --file demo/sample.md \
-      --cast demo.cast
-    # https://docs.asciinema.org/manual/agg/usage/
-    agg demo.cast demo/demo.gif \
-      --font-family "Monaspace Neon,Hack Nerd Font" \
-      --last-frame-duration 1
-    rm demo.cast
+  rm -f demo/demo.gif
+  python demo/record.py \
+    --zoom {{zoom}} \
+    --file demo/sample.md \
+    --cast demo.cast
+  # https://docs.asciinema.org/manual/agg/usage/
+  agg demo.cast demo/demo.gif \
+    --font-family "Monaspace Neon,Hack Nerd Font" \
+    --last-frame-duration 1
+  rm demo.cast
 
-docgen:
-    # https://github.com/kdheepak/panvimdoc
-    # https://pandoc.org/
-    ../../open-source/panvimdoc/panvimdoc.sh \
-      --project-name render-markdown \
-      --input-file README.md \
-      --vim-version 0.10.0
+gen-doc:
+  # https://github.com/kdheepak/panvimdoc
+  # https://pandoc.org/
+  ../../open-source/panvimdoc/panvimdoc.sh \
+    --project-name render-markdown \
+    --input-file README.md \
+    --vim-version 0.10.0
+
+[private]
+gen-file-text:
+  #!/usr/bin/env python
+  for i in range(100_000):
+    level = "#" * ((i % 6) + 1)
+    print(f"{level} Title {i}\n")
+
+gen-large-file:
+  just gen-file-text > large.md

lua/render-markdown/init.lua

@@ -35,6 +35,7 @@ local M = {}
 
 ---@class UserConfig
 ---@field public start_enabled? boolean
+---@field public max_file_size? number
 ---@field public markdown_query? string
 ---@field public inline_query? string
 ---@field public log_level? 'debug'|'error'
@@ -54,6 +55,7 @@ function M.setup(opts)
     ---@type Config
     local default_config = {
         start_enabled = true,
+        max_file_size = 1.5,
         markdown_query = [[
             (atx_heading [
                 (atx_h1_marker)

lua/render-markdown/state.lua

@@ -30,6 +30,7 @@
 
 ---@class Config
 ---@field public start_enabled boolean
+---@field public max_file_size number
 ---@field public markdown_query string
 ---@field public inline_query string
 ---@field public log_level 'debug'|'error'

lua/render-markdown/ui.lua

@@ -26,6 +26,9 @@ M.refresh = function()
     if not vim.tbl_contains(state.config.render_modes, vim.fn.mode()) then
         return
     end
+    if M.file_size_mb() > state.config.max_file_size then
+        return
+    end
 
     logger.start()
     vim.opt_local.conceallevel = state.config.conceal.rendered
@@ -49,4 +52,15 @@ M.refresh = function()
     logger.flush()
 end
 
+---@return number
+M.file_size_mb = function()
+    local ok, stats = pcall(function()
+        return vim.loop.fs_stat(vim.api.nvim_buf_get_name(0))
+    end)
+    if not (ok and stats) then
+        return 0
+    end
+    return stats.size / (1024 * 1024)
+end
+
 return M

tests/init_spec.lua

@@ -185,12 +185,12 @@ async_tests.describe('init', function()
             },
         })
 
-        -- Line break, TODO: fragile need to determine width
+        -- Line break
         vim.list_extend(expected, {
             {
                 row = { 38 },
                 col = { 0 },
-                virt_text = { { string.rep('—', 80), 'LineNr' } },
+                virt_text = { { string.rep('—', vim.opt.columns:get()), 'LineNr' } },
                 virt_text_pos = 'overlay',
             },
         })