feat: rename watch → toggle, auto-compile on start, built-in opener

Problem: :Preview watch only registered a BufWritePost autocmd without
compiling immediately, required boilerplate to open output files after
first compilation, and was misleadingly named.

Solution: Rename watch → toggle throughout. M.toggle now compiles
immediately on activation. Add an open field to ProviderConfig: true
calls vim.ui.open(), a string[] runs the command with the output path
appended, tracked per-buffer so the file opens only once. All presets
default to { 'xdg-open' }. Health check validates opener binaries.
Guard the async compile callback against invalid buffer ids.

README.md

@@ -1,10 +1,9 @@
 # preview.nvim
 
-Async document compilation for Neovim.
+**Async document compilation for Neovim**
 
-A framework for compiling documents (LaTeX, Typst, Markdown, etc.)
+An extensible framework for compiling documents (LaTeX, Typst, Markdown, etc.)
-asynchronously with error diagnostics. Ships with zero defaults — you configure
+asynchronously with error diagnostics.
-your own providers.
 
 ## Features
 
@@ -12,59 +11,68 @@ your own providers.
 - Compiler errors as native `vim.diagnostic`
 - User events for extensibility (`PreviewCompileStarted`,
   `PreviewCompileSuccess`, `PreviewCompileFailed`)
+- Built-in presets for Typst, LaTeX, Markdown, and GitHub-flavored Markdown
 - `:checkhealth` integration
 - Zero dependencies beyond Neovim 0.11.0+
 
 ## Requirements
 
-- Neovim >= 0.11.0
+- Neovim 0.11.0+
-- A compiler binary for each provider you configure
 
 ## Installation
 
-```lua
+Install with your package manager of choice or via
--- lazy.nvim
+[luarocks](https://luarocks.org/modules/barrettruth/preview.nvim):
-{ 'barrettruth/preview.nvim' }
+
 ```
-
+luarocks install preview.nvim
-```vim
-" luarocks
-:Rocks install preview.nvim
-```
-
-## Configuration
-
-Use built-in presets for common tools:
-
-```lua
-local presets = require('preview.presets')
-vim.g.preview = {
-  providers = {
-    typst = presets.typst,
-    tex = presets.latex,
-    markdown = presets.markdown,
-  },
-}
-```
-
-Or define providers manually:
-
-```lua
-vim.g.preview = {
-  providers = {
-    typst = {
-      cmd = { 'typst', 'compile' },
-      args = function(ctx)
-        return { ctx.file }
-      end,
-      output = function(ctx)
-        return ctx.file:gsub('%.typ$', '.pdf')
-      end,
-    },
-  },
-}
 ```
 
 ## Documentation
 
-See `:help preview.nvim` for full documentation.
+```vim
+:help preview.nvim
+```
+
+## FAQ
+
+**Q: How do I define a custom provider?**
+
+```lua
+require('preview').setup({
+  typst = {
+    cmd = { 'typst', 'compile' },
+    args = function(ctx)
+      return { ctx.file }
+    end,
+    output = function(ctx)
+      return ctx.file:gsub('%.typ$', '.pdf')
+    end,
+  },
+})
+```
+
+**Q: How do I override a preset?**
+
+```lua
+local presets = require('preview.presets')
+require('preview').setup({
+  typst = vim.tbl_deep_extend('force', presets.typst, {
+    env = { TYPST_FONT_PATHS = '/usr/share/fonts' },
+  }),
+})
+```
+
+**Q: How do I automatically open the output file?**
+
+Set `open = true` on your provider (all built-in presets have this enabled) to
+open the output with `vim.ui.open()` after the first successful compilation.
+For a specific application, pass a command table:
+
+```lua
+typst = vim.tbl_deep_extend('force', presets.typst, {
+  open = { 'sioyek', '--new-instance' },
+})
+```
+
+See `:h preview.nvim` for more information.

doc/preview.nvim.txt

@@ -37,18 +37,21 @@ With lazy.nvim:
 ==============================================================================
 CONFIGURATION                                      *preview.nvim-configuration*
 
-Configure via the `vim.g.preview` global table before the plugin loads.
+Configure via `require('preview').setup()`.
 
-                                                            *preview.Config*
+                                                            *preview.setup()*
-Fields:~
+setup({opts?})
+
+  `opts` is a mixed table. Array entries are preset names (see
+  |preview.nvim-presets|). Hash entries with table values are custom
+  provider configs keyed by filetype.
+
+  Fields:~
 
   `debug`            boolean|string   Enable debug logging. A string value
                                     is treated as a log file path.
                                     Default: `false`
 
-  `providers`        table            Provider configurations keyed by
-                                    filetype. Default: `{}`
-
                                                     *preview.ProviderConfig*
 Provider fields:~
 
@@ -74,6 +77,12 @@ Provider fields:~
                                        If a function, receives a
                                        |preview.Context|.
 
+  `open`             boolean|string[]   Open the output file after the first
+                                       successful compilation. `true` uses
+                                       |vim.ui.open()|. A string[] is run as
+                                       a command with the output path appended.
+                                       Presets default to `{ 'xdg-open' }`.
+
                                                         *preview.Context*
 Context fields:~
 
@@ -82,38 +91,36 @@ Context fields:~
   `root`    string     Project root (git root or file directory).
   `ft`      string     Filetype.
 
-Example:~
+Example using preset names:~
 >lua
-    vim.g.preview = {
+    require('preview').setup({ 'typst', 'latex', 'markdown' })
-      providers = {
+<
-        typst = {
+
-          cmd = { 'typst', 'compile' },
+Example with a custom provider:~
-          args = function(ctx)
+>lua
-            return { ctx.file }
+    require('preview').setup({
-          end,
+      typst = {
-          output = function(ctx)
+        cmd = { 'typst', 'compile' },
-            return ctx.file:gsub('%.typ$', '.pdf')
+        args = function(ctx)
-          end,
+          return { ctx.file }
-          error_parser = function(stderr, ctx)
+        end,
-            local diagnostics = {}
+        output = function(ctx)
-            for line, col, msg in stderr:gmatch('error:.-(%d+):(%d+):%s*(.-)%\n') do
+          return ctx.file:gsub('%.typ$', '.pdf')
-              table.insert(diagnostics, {
+        end,
-                lnum = tonumber(line) - 1,
+        error_parser = function(stderr, ctx)
-                col = tonumber(col) - 1,
+          local diagnostics = {}
-                message = msg,
+          for line, col, msg in stderr:gmatch('error:.-(%d+):(%d+):%s*(.-)%\n') do
-                severity = vim.diagnostic.severity.ERROR,
+            table.insert(diagnostics, {
-              })
+              lnum = tonumber(line) - 1,
-            end
+              col = tonumber(col) - 1,
-            return diagnostics
+              message = msg,
-          end,
+              severity = vim.diagnostic.severity.ERROR,
-        },
+            })
-        tex = {
+          end
-          cmd = { 'latexmk' },
+          return diagnostics
-          args = { '-pdf', '-interaction=nonstopmode' },
+        end,
-          clean = { 'latexmk', '-c' },
-        },
       },
-    }
+    })
 <
 
 ==============================================================================
@@ -122,32 +129,24 @@ PRESETS                                                *preview.nvim-presets*
 preview.nvim ships with pre-built provider configurations for common tools.
 Import them from `preview.presets`:
 
-  `presets.typst`      typst compile → PDF
+  `presets.typst`              typst compile → PDF
-  `presets.latex`      latexmk -pdf → PDF (with clean support)
+  `presets.latex`              latexmk -pdf → PDF (with clean support)
-  `presets.markdown`   pandoc → PDF
+  `presets.markdown`           pandoc → HTML (standalone, embedded)
+  `presets.github`             pandoc → HTML (GitHub-styled)
 
-Example:~
+Pass preset names as array entries to `setup()`:
 >lua
-    local presets = require('preview.presets')
+    require('preview').setup({ 'typst', 'latex', 'markdown' })
-    vim.g.preview = {
-      providers = {
-        typst = presets.typst,
-        tex = presets.latex,
-        markdown = presets.markdown,
-      },
-    }
 <
 
-Override individual fields with `vim.tbl_deep_extend`:
+Override individual fields using `vim.tbl_deep_extend`:
 >lua
     local presets = require('preview.presets')
-    vim.g.preview = {
+    require('preview').setup({
-      providers = {
+      typst = vim.tbl_deep_extend('force', presets.typst, {
-        typst = vim.tbl_deep_extend('force', presets.typst, {
+        env = { TYPST_FONT_PATHS = '/usr/share/fonts' },
-          env = { TYPST_FONT_PATHS = '/usr/share/fonts' },
+      }),
-        }),
+    })
-      },
-    }
 <
 
 ==============================================================================
@@ -160,7 +159,7 @@ COMMANDS                                              *preview.nvim-commands*
     `compile`    Compile the current buffer (default if omitted).
     `stop`       Kill active compilation for the current buffer.
     `clean`      Run the provider's clean command.
-    `watch`      Toggle auto-compile on save for the current buffer.
+    `toggle`     Toggle auto-compile on save for the current buffer.
     `status`     Echo compilation status (idle, compiling, watching).
 
 ==============================================================================
@@ -175,10 +174,10 @@ preview.stop({bufnr?})                                      *preview.stop()*
 preview.clean({bufnr?})                                    *preview.clean()*
     Run the provider's clean command for the buffer.
 
-preview.watch({bufnr?})                                    *preview.watch()*
+preview.toggle({bufnr?})                                  *preview.toggle()*
     Toggle watch mode for the buffer. When enabled, the buffer is
-    automatically compiled on each save (`BufWritePost`). Call again
+    immediately compiled and automatically recompiled on each save
-    to stop watching.
+    (`BufWritePost`). Call again to stop watching.
 
 preview.status({bufnr?})                                  *preview.status()*
     Returns a |preview.Status| table.
@@ -232,6 +231,7 @@ Run `:checkhealth preview` to verify:
 
 - Neovim version >= 0.11.0
 - Each configured provider's binary is executable
+- Each configured provider's opener binary (if any) is executable
 - Each configured provider's filetype mapping is valid
 
 ==============================================================================

lua/preview/commands.lua

@@ -1,6 +1,6 @@
 local M = {}
 
-local subcommands = { 'compile', 'stop', 'clean', 'watch', 'status' }
+local subcommands = { 'compile', 'stop', 'clean', 'toggle', 'status' }
 
 ---@param args string
 local function dispatch(args)
@@ -12,8 +12,8 @@ local function dispatch(args)
     require('preview').stop()
   elseif subcmd == 'clean' then
     require('preview').clean()
-  elseif subcmd == 'watch' then
+  elseif subcmd == 'toggle' then
-    require('preview').watch()
+    require('preview').toggle()
   elseif subcmd == 'status' then
     local s = require('preview').status()
     local parts = {}
@@ -47,7 +47,7 @@ function M.setup()
     complete = function(lead)
       return complete(lead)
     end,
-    desc = 'Compile, stop, clean, watch, or check status of document preview',
+    desc = 'Compile, stop, clean, toggle, or check status of document preview',
   })
 end
 

lua/preview/compiler.lua

@@ -9,6 +9,9 @@ local active = {}
 ---@type table<integer, integer>
 local watching = {}
 
+---@type table<integer, true>
+local opened = {}
+
 ---@param val string[]|fun(ctx: preview.Context): string[]
 ---@param ctx preview.Context
 ---@return string[]
@@ -68,6 +71,9 @@ function M.compile(bufnr, name, provider, ctx)
     },
     vim.schedule_wrap(function(result)
       active[bufnr] = nil
+      if not vim.api.nvim_buf_is_valid(bufnr) then
+        return
+      end
 
       if result.code == 0 then
         log.dbg('compilation succeeded for buffer %d', bufnr)
@@ -76,6 +82,16 @@ function M.compile(bufnr, name, provider, ctx)
           pattern = 'PreviewCompileSuccess',
           data = { bufnr = bufnr, provider = name, output = output_file },
         })
+        if provider.open and not opened[bufnr] and output_file ~= '' then
+          if provider.open == true then
+            vim.ui.open(output_file)
+          elseif type(provider.open) == 'table' then
+            local open_cmd = vim.list_extend({}, provider.open)
+            table.insert(open_cmd, output_file)
+            vim.system(open_cmd)
+          end
+          opened[bufnr] = true
+        end
       else
         log.dbg('compilation failed for buffer %d (exit code %d)', bufnr, result.code)
         if provider.error_parser then
@@ -146,7 +162,7 @@ end
 ---@param name string
 ---@param provider preview.ProviderConfig
 ---@param ctx_builder fun(bufnr: integer): preview.Context
-function M.watch(bufnr, name, provider, ctx_builder)
+function M.toggle(bufnr, name, provider, ctx_builder)
   if watching[bufnr] then
     M.unwatch(bufnr)
     return
@@ -168,6 +184,7 @@ function M.watch(bufnr, name, provider, ctx_builder)
     once = true,
     callback = function()
       M.unwatch(bufnr)
+      opened[bufnr] = nil
     end,
   })
 
@@ -175,6 +192,8 @@ function M.watch(bufnr, name, provider, ctx_builder)
     pattern = 'PreviewWatchStarted',
     data = { bufnr = bufnr, provider = name },
   })
+
+  M.compile(bufnr, name, provider, ctx_builder(bufnr))
 end
 
 ---@param bufnr integer
@@ -244,6 +263,7 @@ end
 M._test = {
   active = active,
   watching = watching,
+  opened = opened,
 }
 
 return M

lua/preview/health.lua

@@ -25,6 +25,14 @@ function M.check()
     else
       vim.health.error('filetype "' .. ft .. '": ' .. bin .. ' not found')
     end
+    if type(provider.open) == 'table' then
+      local opener = provider.open[1]
+      if vim.fn.executable(opener) == 1 then
+        vim.health.ok('filetype "' .. ft .. '": opener ' .. opener .. ' found')
+      else
+        vim.health.error('filetype "' .. ft .. '": opener ' .. opener .. ' not found')
+      end
+    end
   end
 end
 

lua/preview/init.lua

@@ -1,4 +1,5 @@
 ---@class preview.ProviderConfig
+---@field ft? string
 ---@field cmd string[]
 ---@field args? string[]|fun(ctx: preview.Context): string[]
 ---@field cwd? string|fun(ctx: preview.Context): string
@@ -6,6 +7,7 @@
 ---@field output? string|fun(ctx: preview.Context): string
 ---@field error_parser? fun(stderr: string, ctx: preview.Context): preview.Diagnostic[]
 ---@field clean? string[]|fun(ctx: preview.Context): string[]
+---@field open? boolean|string[]
 
 ---@class preview.Config
 ---@field debug boolean|string
@@ -32,10 +34,11 @@
 ---@field output_file string
 
 ---@class preview
+---@field setup fun(opts?: table)
 ---@field compile fun(bufnr?: integer)
 ---@field stop fun(bufnr?: integer)
 ---@field clean fun(bufnr?: integer)
----@field watch fun(bufnr?: integer)
+---@field toggle fun(bufnr?: integer)
 ---@field status fun(bufnr?: integer): preview.Status
 ---@field get_config fun(): preview.Config
 local M = {}
@@ -52,39 +55,48 @@ local default_config = {
 ---@type preview.Config
 local config = vim.deepcopy(default_config)
 
-local initialized = false
+---@param opts? table
+function M.setup(opts)
+  opts = opts or {}
+  vim.validate('preview.setup opts', opts, 'table')
 
-local function init()
+  local presets = require('preview.presets')
-  if initialized then
+  local providers = {}
-    return
+  local debug = false
-  end
-  initialized = true
 
-  local opts = vim.g.preview or {}
+  for k, v in pairs(opts) do
-
+    if k == 'debug' then
-  vim.validate('preview config', opts, 'table')
+      vim.validate('preview.setup opts.debug', v, { 'boolean', 'string' })
-  if opts.debug ~= nil then
+      debug = v
-    vim.validate('preview config.debug', opts.debug, { 'boolean', 'string' })
+    elseif type(k) == 'number' then
-  end
+      vim.validate('preview.setup preset name', v, 'string')
-  if opts.providers ~= nil then
+      local preset = presets[v]
-    vim.validate('preview config.providers', opts.providers, 'table')
+      if preset then
+        providers[preset.ft] = preset
+      end
+    else
+      vim.validate('preview.setup provider config', v, 'table')
+      providers[k] = v
+    end
   end
 
-  config = vim.tbl_deep_extend('force', default_config, opts)
+  config = vim.tbl_deep_extend('force', default_config, {
+    debug = debug,
+    providers = providers,
+  })
+
   log.set_enabled(config.debug)
   log.dbg('initialized with %d providers', vim.tbl_count(config.providers))
 end
 
 ---@return preview.Config
 function M.get_config()
-  init()
   return config
 end
 
 ---@param bufnr? integer
 ---@return string?
 function M.resolve_provider(bufnr)
-  init()
   bufnr = bufnr or vim.api.nvim_get_current_buf()
   local ft = vim.bo[bufnr].filetype
   if not config.providers[ft] then
@@ -97,7 +109,6 @@ end
 ---@param bufnr? integer
 ---@return preview.Context
 function M.build_context(bufnr)
-  init()
   bufnr = bufnr or vim.api.nvim_get_current_buf()
   local file = vim.api.nvim_buf_get_name(bufnr)
   local root = vim.fs.root(bufnr, { '.git' }) or vim.fn.fnamemodify(file, ':h')
@@ -111,42 +122,38 @@ end
 
 ---@param bufnr? integer
 function M.compile(bufnr)
-  init()
   bufnr = bufnr or vim.api.nvim_get_current_buf()
   local name = M.resolve_provider(bufnr)
   if not name then
     vim.notify('[preview.nvim] no provider configured for this filetype', vim.log.levels.WARN)
     return
   end
-  local provider = config.providers[name]
   local ctx = M.build_context(bufnr)
+  local provider = config.providers[name]
   compiler.compile(bufnr, name, provider, ctx)
 end
 
 ---@param bufnr? integer
 function M.stop(bufnr)
-  init()
   bufnr = bufnr or vim.api.nvim_get_current_buf()
   compiler.stop(bufnr)
 end
 
 ---@param bufnr? integer
 function M.clean(bufnr)
-  init()
   bufnr = bufnr or vim.api.nvim_get_current_buf()
   local name = M.resolve_provider(bufnr)
   if not name then
     vim.notify('[preview.nvim] no provider configured for this filetype', vim.log.levels.WARN)
     return
   end
-  local provider = config.providers[name]
   local ctx = M.build_context(bufnr)
+  local provider = config.providers[name]
   compiler.clean(bufnr, name, provider, ctx)
 end
 
 ---@param bufnr? integer
-function M.watch(bufnr)
+function M.toggle(bufnr)
-  init()
   bufnr = bufnr or vim.api.nvim_get_current_buf()
   local name = M.resolve_provider(bufnr)
   if not name then
@@ -154,7 +161,7 @@ function M.watch(bufnr)
     return
   end
   local provider = config.providers[name]
-  compiler.watch(bufnr, name, provider, M.build_context)
+  compiler.toggle(bufnr, name, provider, M.build_context)
 end
 
 ---@class preview.Status
@@ -166,7 +173,6 @@ end
 ---@param bufnr? integer
 ---@return preview.Status
 function M.status(bufnr)
-  init()
   bufnr = bufnr or vim.api.nvim_get_current_buf()
   return compiler.status(bufnr)
 end
@@ -174,7 +180,6 @@ end
 M._test = {
   ---@diagnostic disable-next-line: assign-type-mismatch
   reset = function()
-    initialized = false
     config = vim.deepcopy(default_config)
   end,
 }

lua/preview/presets.lua

@@ -2,6 +2,7 @@ local M = {}
 
 ---@type preview.ProviderConfig
 M.typst = {
+  ft = 'typst',
   cmd = { 'typst', 'compile' },
   args = function(ctx)
     return { ctx.file }
@@ -9,10 +10,12 @@ M.typst = {
   output = function(ctx)
     return ctx.file:gsub('%.typ$', '.pdf')
   end,
+  open = { 'xdg-open' },
 }
 
 ---@type preview.ProviderConfig
 M.latex = {
+  ft = 'tex',
   cmd = { 'latexmk' },
   args = function(ctx)
     return { '-pdf', '-interaction=nonstopmode', ctx.file }
@@ -23,18 +26,49 @@ M.latex = {
   clean = function(ctx)
     return { 'latexmk', '-c', ctx.file }
   end,
+  open = { 'xdg-open' },
 }
 
 ---@type preview.ProviderConfig
 M.markdown = {
+  ft = 'markdown',
   cmd = { 'pandoc' },
   args = function(ctx)
-    local output = ctx.file:gsub('%.md$', '.pdf')
+    local output = ctx.file:gsub('%.md$', '.html')
-    return { ctx.file, '-o', output }
+    return { ctx.file, '-s', '--embed-resources', '-o', output }
   end,
   output = function(ctx)
-    return ctx.file:gsub('%.md$', '.pdf')
+    return ctx.file:gsub('%.md$', '.html')
   end,
+  clean = function(ctx)
+    return { 'rm', '-f', (ctx.file:gsub('%.md$', '.html')) }
+  end,
+  open = { 'xdg-open' },
+}
+
+---@type preview.ProviderConfig
+M.github = {
+  ft = 'markdown',
+  cmd = { 'pandoc' },
+  args = function(ctx)
+    local output = ctx.file:gsub('%.md$', '.html')
+    return {
+      ctx.file,
+      '-s',
+      '--embed-resources',
+      '--css',
+      'https://cdn.jsdelivr.net/gh/pixelbrackets/gfm-stylesheet@master/github.css',
+      '-o',
+      output,
+    }
+  end,
+  output = function(ctx)
+    return ctx.file:gsub('%.md$', '.html')
+  end,
+  clean = function(ctx)
+    return { 'rm', '-f', (ctx.file:gsub('%.md$', '.html')) }
+  end,
+  open = { 'xdg-open' },
 }
 
 return M

spec/commands_spec.lua

@@ -35,10 +35,10 @@ describe('commands', function()
       end)
     end)
 
-    it('does not error on :Preview watch with no provider', function()
+    it('does not error on :Preview toggle with no provider', function()
       require('preview.commands').setup()
       assert.has_no.errors(function()
-        vim.cmd('Preview watch')
+        vim.cmd('Preview toggle')
       end)
     end)
   end)

spec/compiler_spec.lua

@@ -174,7 +174,7 @@ describe('compiler', function()
     end)
   end)
 
-  describe('watch', function()
+  describe('toggle', function()
     it('registers autocmd and tracks in watching table', function()
       local bufnr = helpers.create_buffer({ 'hello' }, 'text')
       vim.api.nvim_buf_set_name(bufnr, '/tmp/preview_test_watch.txt')
@@ -184,7 +184,7 @@ describe('compiler', function()
         return { bufnr = b, file = '/tmp/preview_test_watch.txt', root = '/tmp', ft = 'text' }
       end
 
-      compiler.watch(bufnr, 'echo', provider, ctx_builder)
+      compiler.toggle(bufnr, 'echo', provider, ctx_builder)
       assert.is_not_nil(compiler._test.watching[bufnr])
 
       helpers.delete_buffer(bufnr)
@@ -208,7 +208,7 @@ describe('compiler', function()
         return { bufnr = b, file = '/tmp/preview_test_watch_event.txt', root = '/tmp', ft = 'text' }
       end
 
-      compiler.watch(bufnr, 'echo', provider, ctx_builder)
+      compiler.toggle(bufnr, 'echo', provider, ctx_builder)
       assert.is_true(fired)
 
       compiler.unwatch(bufnr)
@@ -224,10 +224,10 @@ describe('compiler', function()
         return { bufnr = b, file = '/tmp/preview_test_watch_toggle.txt', root = '/tmp', ft = 'text' }
       end
 
-      compiler.watch(bufnr, 'echo', provider, ctx_builder)
+      compiler.toggle(bufnr, 'echo', provider, ctx_builder)
       assert.is_not_nil(compiler._test.watching[bufnr])
 
-      compiler.watch(bufnr, 'echo', provider, ctx_builder)
+      compiler.toggle(bufnr, 'echo', provider, ctx_builder)
       assert.is_nil(compiler._test.watching[bufnr])
 
       helpers.delete_buffer(bufnr)
@@ -251,7 +251,7 @@ describe('compiler', function()
         return { bufnr = b, file = '/tmp/preview_test_watch_stop.txt', root = '/tmp', ft = 'text' }
       end
 
-      compiler.watch(bufnr, 'echo', provider, ctx_builder)
+      compiler.toggle(bufnr, 'echo', provider, ctx_builder)
       compiler.unwatch(bufnr)
       assert.is_true(stopped)
       assert.is_nil(compiler._test.watching[bufnr])
@@ -273,7 +273,7 @@ describe('compiler', function()
         }
       end
 
-      compiler.watch(bufnr, 'echo', provider, ctx_builder)
+      compiler.toggle(bufnr, 'echo', provider, ctx_builder)
       assert.is_not_nil(compiler._test.watching[bufnr])
 
       compiler.stop_all()
@@ -294,7 +294,7 @@ describe('compiler', function()
         return { bufnr = b, file = '/tmp/preview_test_watch_status.txt', root = '/tmp', ft = 'text' }
       end
 
-      compiler.watch(bufnr, 'echo', provider, ctx_builder)
+      compiler.toggle(bufnr, 'echo', provider, ctx_builder)
       s = compiler.status(bufnr)
       assert.is_true(s.watching)
 

spec/helpers.lua

@@ -20,8 +20,11 @@ function M.delete_buffer(bufnr)
 end
 
 function M.reset_config(opts)
-  vim.g.preview = opts
+  local preview = require('preview')
-  require('preview')._test.reset()
+  preview._test.reset()
+  if opts then
+    preview.setup(opts)
+  end
 end
 
 return M

spec/init_spec.lua

@@ -9,13 +9,7 @@ describe('preview', function()
   end)
 
   describe('config', function()
-    it('accepts nil config', function()
+    it('returns defaults before setup is called', function()
-      assert.has_no.errors(function()
-        preview.get_config()
-      end)
-    end)
-
-    it('applies default values', function()
       local config = preview.get_config()
       assert.is_false(config.debug)
       assert.are.same({}, config.providers)
@@ -28,26 +22,44 @@ describe('preview', function()
       assert.are.same({}, config.providers)
     end)
 
-    it('accepts full provider config', function()
+    it('accepts full provider config via hash entry', function()
       helpers.reset_config({
-        providers = {
+        typst = {
-          typst = {
+          cmd = { 'typst', 'compile' },
-            cmd = { 'typst', 'compile' },
+          args = { '%s' },
-            args = { '%s' },
-          },
         },
       })
       local config = require('preview').get_config()
       assert.is_not_nil(config.providers.typst)
     end)
+
+    it('resolves array preset names to provider configs', function()
+      helpers.reset_config({ 'typst', 'markdown' })
+      local config = require('preview').get_config()
+      local presets = require('preview.presets')
+      assert.are.same(presets.typst, config.providers.typst)
+      assert.are.same(presets.markdown, config.providers.markdown)
+    end)
+
+    it('resolves latex preset under tex filetype', function()
+      helpers.reset_config({ 'latex' })
+      local config = require('preview').get_config()
+      local presets = require('preview.presets')
+      assert.are.same(presets.latex, config.providers.tex)
+    end)
+
+    it('resolves github preset under markdown filetype', function()
+      helpers.reset_config({ 'github' })
+      local config = require('preview').get_config()
+      local presets = require('preview.presets')
+      assert.are.same(presets.github, config.providers.markdown)
+    end)
   end)
 
   describe('resolve_provider', function()
     before_each(function()
       helpers.reset_config({
-        providers = {
+        typst = { cmd = { 'typst', 'compile' } },
-          typst = { cmd = { 'typst', 'compile' } },
-        },
       })
       preview = require('preview')
     end)

spec/presets_spec.lua

@@ -13,6 +13,10 @@ describe('presets', function()
   }
 
   describe('typst', function()
+    it('has ft', function()
+      assert.are.equal('typst', presets.typst.ft)
+    end)
+
     it('has cmd', function()
       assert.are.same({ 'typst', 'compile' }, presets.typst.cmd)
     end)
@@ -28,6 +32,10 @@ describe('presets', function()
       assert.is_string(output)
       assert.are.equal('/tmp/document.pdf', output)
     end)
+
+    it('has open enabled', function()
+      assert.are.same({ 'xdg-open' }, presets.typst.open)
+    end)
   end)
 
   describe('latex', function()
@@ -38,6 +46,10 @@ describe('presets', function()
       ft = 'tex',
     }
 
+    it('has ft', function()
+      assert.are.equal('tex', presets.latex.ft)
+    end)
+
     it('has cmd', function()
       assert.are.same({ 'latexmk' }, presets.latex.cmd)
     end)
@@ -59,6 +71,10 @@ describe('presets', function()
       assert.is_table(clean)
       assert.are.same({ 'latexmk', '-c', '/tmp/document.tex' }, clean)
     end)
+
+    it('has open enabled', function()
+      assert.are.same({ 'xdg-open' }, presets.latex.open)
+    end)
   end)
 
   describe('markdown', function()
@@ -69,20 +85,84 @@ describe('presets', function()
       ft = 'markdown',
     }
 
+    it('has ft', function()
+      assert.are.equal('markdown', presets.markdown.ft)
+    end)
+
     it('has cmd', function()
       assert.are.same({ 'pandoc' }, presets.markdown.cmd)
     end)
 
-    it('returns args with file and output flag', function()
+    it('returns args with standalone and embed-resources flags', function()
       local args = presets.markdown.args(md_ctx)
       assert.is_table(args)
-      assert.are.same({ '/tmp/document.md', '-o', '/tmp/document.pdf' }, args)
+      assert.are.same(
+        { '/tmp/document.md', '-s', '--embed-resources', '-o', '/tmp/document.html' },
+        args
+      )
     end)
 
-    it('returns pdf output path', function()
+    it('returns html output path', function()
       local output = presets.markdown.output(md_ctx)
       assert.is_string(output)
-      assert.are.equal('/tmp/document.pdf', output)
+      assert.are.equal('/tmp/document.html', output)
+    end)
+
+    it('returns clean command', function()
+      local clean = presets.markdown.clean(md_ctx)
+      assert.is_table(clean)
+      assert.are.same({ 'rm', '-f', '/tmp/document.html' }, clean)
+    end)
+
+    it('has open enabled', function()
+      assert.are.same({ 'xdg-open' }, presets.markdown.open)
+    end)
+  end)
+
+  describe('github', function()
+    local md_ctx = {
+      bufnr = 1,
+      file = '/tmp/document.md',
+      root = '/tmp',
+      ft = 'markdown',
+    }
+
+    it('has ft', function()
+      assert.are.equal('markdown', presets.github.ft)
+    end)
+
+    it('has cmd', function()
+      assert.are.same({ 'pandoc' }, presets.github.cmd)
+    end)
+
+    it('returns args with standalone, embed-resources, and css flags', function()
+      local args = presets.github.args(md_ctx)
+      assert.is_table(args)
+      assert.are.same({
+        '/tmp/document.md',
+        '-s',
+        '--embed-resources',
+        '--css',
+        'https://cdn.jsdelivr.net/gh/pixelbrackets/gfm-stylesheet@master/github.css',
+        '-o',
+        '/tmp/document.html',
+      }, args)
+    end)
+
+    it('returns html output path', function()
+      local output = presets.github.output(md_ctx)
+      assert.is_string(output)
+      assert.are.equal('/tmp/document.html', output)
+    end)
+
+    it('returns clean command', function()
+      local clean = presets.github.clean(md_ctx)
+      assert.is_table(clean)
+      assert.are.same({ 'rm', '-f', '/tmp/document.html' }, clean)
+    end)
+
+    it('has open enabled', function()
+      assert.are.same({ 'xdg-open' }, presets.github.open)
     end)
   end)
 end)