feat(compiler): add configurable error output modes

Problem: all parse errors went to vim.diagnostic with no way to silence
them or route them to the quickfix list. Users wanting quickfix-style
error navigation had no option.

Solution: add an errors field to ProviderConfig accepting false,
'diagnostic' (default), or 'quickfix'. false suppresses error handling
entirely. 'quickfix' converts parsed diagnostics to qflist items
(1-indexed), calls setqflist, and opens the window. On success,
'quickfix' mode clears the qflist the same way 'diagnostic' mode clears
vim.diagnostic.

lua/preview/compiler.lua

@@ -86,9 +86,18 @@ function M.compile(bufnr, name, provider, ctx)
         return
       end
 
+      local errors_mode = provider.errors
+      if errors_mode == nil then
+        errors_mode = 'diagnostic'
+      end
+
       if result.code == 0 then
         log.dbg('compilation succeeded for buffer %d', bufnr)
-        diagnostic.clear(bufnr)
+        if errors_mode == 'diagnostic' then
+          diagnostic.clear(bufnr)
+        elseif errors_mode == 'quickfix' then
+          vim.fn.setqflist({}, 'r')
+        end
         vim.api.nvim_exec_autocmds('User', {
           pattern = 'PreviewCompileSuccess',
           data = { bufnr = bufnr, provider = name, output = output_file },
@@ -105,8 +114,27 @@ function M.compile(bufnr, name, provider, ctx)
         end
       else
         log.dbg('compilation failed for buffer %d (exit code %d)', bufnr, result.code)
-        if provider.error_parser then
-          diagnostic.set(bufnr, name, provider.error_parser, result.stderr or '', ctx)
+        if provider.error_parser and errors_mode then
+          local output = (result.stdout or '') .. (result.stderr or '')
+          if errors_mode == 'diagnostic' then
+            diagnostic.set(bufnr, name, provider.error_parser, output, ctx)
+          elseif errors_mode == 'quickfix' then
+            local ok, diagnostics = pcall(provider.error_parser, output, ctx)
+            if ok and diagnostics and #diagnostics > 0 then
+              local items = {}
+              for _, d in ipairs(diagnostics) do
+                table.insert(items, {
+                  bufnr = bufnr,
+                  lnum = d.lnum + 1,
+                  col = d.col + 1,
+                  text = d.message,
+                  type = d.severity == vim.diagnostic.severity.WARN and 'W' or 'E',
+                })
+              end
+              vim.fn.setqflist(items, 'r')
+              vim.cmd('copen')
+            end
+          end
         end
         vim.api.nvim_exec_autocmds('User', {
           pattern = 'PreviewCompileFailed',

lua/preview/diagnostic.lua

@@ -12,11 +12,11 @@ end
 
 ---@param bufnr integer
 ---@param name string
----@param error_parser fun(stderr: string, ctx: preview.Context): preview.Diagnostic[]
----@param stderr string
+---@param error_parser fun(output: string, ctx: preview.Context): preview.Diagnostic[]
+---@param output string
 ---@param ctx preview.Context
-function M.set(bufnr, name, error_parser, stderr, ctx)
-  local ok, diagnostics = pcall(error_parser, stderr, ctx)
+function M.set(bufnr, name, error_parser, output, ctx)
+  local ok, diagnostics = pcall(error_parser, output, ctx)
   if not ok then
     log.dbg('error_parser for "%s" failed: %s', name, diagnostics)
     return

lua/preview/init.lua

@@ -5,7 +5,8 @@
 ---@field cwd? string|fun(ctx: preview.Context): string
 ---@field env? table<string, string>
 ---@field output? string|fun(ctx: preview.Context): string
----@field error_parser? fun(stderr: string, ctx: preview.Context): preview.Diagnostic[]
+---@field error_parser? fun(output: string, ctx: preview.Context): preview.Diagnostic[]
+---@field errors? false|'diagnostic'|'quickfix'
 ---@field clean? string[]|fun(ctx: preview.Context): string[]
 ---@field open? boolean|string[]
 

lua/preview/presets.lua

@@ -1,11 +1,11 @@
 local M = {}
 
----@param stderr string
+---@param output string
 ---@return preview.Diagnostic[]
-local function parse_typst(stderr)
+local function parse_typst(output)
   local diagnostics = {}
-  for line in stderr:gmatch('[^\r\n]+') do
-    local file, lnum, col, severity, msg = line:match('^(.+):(%d+):(%d+): (%w+): (.+)$')
+  for line in output:gmatch('[^\r\n]+') do
+    local _, lnum, col, severity, msg = line:match('^(.+):(%d+):(%d+): (%w+): (.+)$')
     if lnum then
       local sev = vim.diagnostic.severity.ERROR
       if severity == 'warning' then
@@ -16,18 +16,17 @@ local function parse_typst(stderr)
         col = tonumber(col) - 1,
         message = msg,
         severity = sev,
-        source = file,
       })
     end
   end
   return diagnostics
 end
 
----@param stderr string
+---@param output string
 ---@return preview.Diagnostic[]
-local function parse_latexmk(stderr)
+local function parse_latexmk(output)
   local diagnostics = {}
-  for line in stderr:gmatch('[^\r\n]+') do
+  for line in output:gmatch('[^\r\n]+') do
     local _, lnum, msg = line:match('^%.?/?(.+%.tex):(%d+): (.+)$')
     if lnum then
       table.insert(diagnostics, {
@@ -51,41 +50,45 @@ local function parse_latexmk(stderr)
   return diagnostics
 end
 
----@param stderr string
+---@param output string
 ---@return preview.Diagnostic[]
-local function parse_pandoc(stderr)
+local function parse_pandoc(output)
   local diagnostics = {}
-  for line in stderr:gmatch('[^\r\n]+') do
-    local lnum, col, msg = line:match('Error at .+ %(line (%d+), column (%d+)%): (.+)$')
+  local lines = vim.split(output, '\n')
+  local i = 1
+  while i <= #lines do
+    local line = lines[i]
+    local lnum, col, msg = line:match('%(line (%d+), column (%d+)%):%s*(.*)$')
     if lnum then
-      table.insert(diagnostics, {
-        lnum = tonumber(lnum) - 1,
-        col = tonumber(col) - 1,
-        message = msg,
-        severity = vim.diagnostic.severity.ERROR,
-      })
-    else
-      local ylnum, ycol, ymsg =
-        line:match('YAML parse exception at line (%d+), column (%d+)[,:]%s*(.+)$')
-      if ylnum then
-        table.insert(diagnostics, {
-          lnum = tonumber(ylnum) - 1,
-          col = tonumber(ycol) - 1,
-          message = ymsg,
-          severity = vim.diagnostic.severity.ERROR,
-        })
-      else
-        local errmsg = line:match('^pandoc: (.+)$')
-        if errmsg and not errmsg:match('^Error at') then
-          table.insert(diagnostics, {
-            lnum = 0,
-            col = 0,
-            message = errmsg,
-            severity = vim.diagnostic.severity.ERROR,
-          })
+      if msg == '' then
+        for j = i + 1, math.min(i + 2, #lines) do
+          local next_line = lines[j]:match('^%s*(.+)$')
+          if next_line and not next_line:match('^YAML parse exception') then
+            msg = next_line
+            break
+          end
         end
       end
+      if msg ~= '' then
+        table.insert(diagnostics, {
+          lnum = tonumber(lnum) - 1,
+          col = tonumber(col) - 1,
+          message = msg,
+          severity = vim.diagnostic.severity.ERROR,
+        })
+      end
+    else
+      local errmsg = line:match('^pandoc: (.+)$')
+      if errmsg then
+        table.insert(diagnostics, {
+          lnum = 0,
+          col = 0,
+          message = errmsg,
+          severity = vim.diagnostic.severity.ERROR,
+        })
+      end
     end
+    i = i + 1
   end
   return diagnostics
 end
@@ -100,8 +103,8 @@ M.typst = {
   output = function(ctx)
     return (ctx.file:gsub('%.typ$', '.pdf'))
   end,
-  error_parser = function(stderr)
-    return parse_typst(stderr)
+  error_parser = function(output)
+    return parse_typst(output)
   end,
   open = true,
 }
@@ -121,8 +124,8 @@ M.latex = {
   output = function(ctx)
     return (ctx.file:gsub('%.tex$', '.pdf'))
   end,
-  error_parser = function(stderr)
-    return parse_latexmk(stderr)
+  error_parser = function(output)
+    return parse_latexmk(output)
   end,
   clean = function(ctx)
     return { 'latexmk', '-c', ctx.file }
@@ -141,8 +144,8 @@ M.markdown = {
   output = function(ctx)
     return (ctx.file:gsub('%.md$', '.html'))
   end,
-  error_parser = function(stderr)
-    return parse_pandoc(stderr)
+  error_parser = function(output)
+    return parse_pandoc(output)
   end,
   clean = function(ctx)
     return { 'rm', '-f', (ctx.file:gsub('%.md$', '.html')) }
@@ -171,8 +174,8 @@ M.github = {
   output = function(ctx)
     return (ctx.file:gsub('%.md$', '.html'))
   end,
-  error_parser = function(stderr)
-    return parse_pandoc(stderr)
+  error_parser = function(output)
+    return parse_pandoc(output)
   end,
   clean = function(ctx)
     return { 'rm', '-f', (ctx.file:gsub('%.md$', '.html')) }

spec/compiler_spec.lua

@@ -132,6 +132,108 @@ describe('compiler', function()
     end)
   end)
 
+  describe('errors mode', function()
+    it('errors = false suppresses error parser', function()
+      local bufnr = helpers.create_buffer({ 'hello' }, 'text')
+      vim.api.nvim_buf_set_name(bufnr, '/tmp/preview_test_errors_false.txt')
+      vim.bo[bufnr].modified = false
+
+      local parser_called = false
+      local provider = {
+        cmd = { 'false' },
+        errors = false,
+        error_parser = function()
+          parser_called = true
+          return {}
+        end,
+      }
+      local ctx = {
+        bufnr = bufnr,
+        file = '/tmp/preview_test_errors_false.txt',
+        root = '/tmp',
+        ft = 'text',
+      }
+
+      compiler.compile(bufnr, 'falsecmd', provider, ctx)
+
+      vim.wait(2000, function()
+        return compiler._test.active[bufnr] == nil
+      end, 50)
+
+      assert.is_false(parser_called)
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('errors = quickfix populates quickfix list', function()
+      local bufnr = helpers.create_buffer({ 'hello' }, 'text')
+      vim.api.nvim_buf_set_name(bufnr, '/tmp/preview_test_errors_qf.txt')
+      vim.bo[bufnr].modified = false
+
+      local provider = {
+        cmd = { 'sh', '-c', 'echo "line 1 error" >&2; exit 1' },
+        errors = 'quickfix',
+        error_parser = function()
+          return {
+            { lnum = 0, col = 0, message = 'test error', severity = vim.diagnostic.severity.ERROR },
+          }
+        end,
+      }
+      local ctx = {
+        bufnr = bufnr,
+        file = '/tmp/preview_test_errors_qf.txt',
+        root = '/tmp',
+        ft = 'text',
+      }
+
+      vim.fn.setqflist({}, 'r')
+      compiler.compile(bufnr, 'qfcmd', provider, ctx)
+
+      vim.wait(2000, function()
+        return compiler._test.active[bufnr] == nil
+      end, 50)
+
+      local qflist = vim.fn.getqflist()
+      assert.are.equal(1, #qflist)
+      assert.are.equal('test error', qflist[1].text)
+      assert.are.equal(1, qflist[1].lnum)
+
+      vim.fn.setqflist({}, 'r')
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('errors = quickfix clears quickfix on success', function()
+      local bufnr = helpers.create_buffer({ 'hello' }, 'text')
+      vim.api.nvim_buf_set_name(bufnr, '/tmp/preview_test_errors_qf_clear.txt')
+      vim.bo[bufnr].modified = false
+
+      vim.fn.setqflist({ { text = 'old error', lnum = 1 } }, 'r')
+      assert.are.equal(1, #vim.fn.getqflist())
+
+      local provider = {
+        cmd = { 'true' },
+        errors = 'quickfix',
+        error_parser = function()
+          return {}
+        end,
+      }
+      local ctx = {
+        bufnr = bufnr,
+        file = '/tmp/preview_test_errors_qf_clear.txt',
+        root = '/tmp',
+        ft = 'text',
+      }
+
+      compiler.compile(bufnr, 'truecmd', provider, ctx)
+
+      vim.wait(2000, function()
+        return compiler._test.active[bufnr] == nil
+      end, 50)
+
+      assert.are.equal(0, #vim.fn.getqflist())
+      helpers.delete_buffer(bufnr)
+    end)
+  end)
+
   describe('stop', function()
     it('does nothing when no process is active', function()
       assert.has_no.errors(function()

spec/presets_spec.lua

@@ -49,7 +49,7 @@ describe('presets', function()
       assert.are.equal(22, diagnostics[1].col)
       assert.are.equal('unexpected token', diagnostics[1].message)
       assert.are.equal(vim.diagnostic.severity.ERROR, diagnostics[1].severity)
-      assert.are.equal('main.typ', diagnostics[1].source)
+      assert.is_nil(diagnostics[1].source)
       assert.are.equal(11, diagnostics[2].lnum)
       assert.are.equal(0, diagnostics[2].col)
       assert.are.equal('unused variable', diagnostics[2].message)
@@ -105,14 +105,14 @@ describe('presets', function()
       assert.is_true(presets.latex.open)
     end)
 
-    it('parses file-line-error format from stderr', function()
-      local stderr = table.concat({
+    it('parses file-line-error format from output', function()
+      local output = table.concat({
         './document.tex:10: Undefined control sequence.',
         'l.10 \\badcommand',
         'Collected error summary (may duplicate other messages):',
         "  pdflatex: Command for 'pdflatex' gave return code 256",
       }, '\n')
-      local diagnostics = presets.latex.error_parser(stderr, tex_ctx)
+      local diagnostics = presets.latex.error_parser(output, tex_ctx)
       assert.is_table(diagnostics)
       assert.is_true(#diagnostics > 0)
       assert.are.equal(9, diagnostics[1].lnum)
@@ -122,12 +122,12 @@ describe('presets', function()
     end)
 
     it('parses collected error summary', function()
-      local stderr = table.concat({
+      local output = table.concat({
         'Latexmk: Errors, so I did not complete making targets',
         'Collected error summary (may duplicate other messages):',
         "  pdflatex: Command for 'pdflatex' gave return code 256",
       }, '\n')
-      local diagnostics = presets.latex.error_parser(stderr, tex_ctx)
+      local diagnostics = presets.latex.error_parser(output, tex_ctx)
       assert.is_table(diagnostics)
       assert.are.equal(1, #diagnostics)
       assert.are.equal(0, diagnostics[1].lnum)
@@ -185,9 +185,24 @@ describe('presets', function()
       assert.is_true(presets.markdown.open)
     end)
 
-    it('parses pandoc parse errors from stderr', function()
-      local stderr = 'Error at "source" (line 75, column 1): unexpected end of input'
-      local diagnostics = presets.markdown.error_parser(stderr, md_ctx)
+    it('parses YAML metadata errors with multiline message', function()
+      local output = table.concat({
+        'Error parsing YAML metadata at "/tmp/test.md" (line 1, column 1):',
+        'YAML parse exception at line 1, column 9:',
+        'mapping values are not allowed in this context',
+      }, '\n')
+      local diagnostics = presets.markdown.error_parser(output, md_ctx)
+      assert.is_table(diagnostics)
+      assert.are.equal(1, #diagnostics)
+      assert.are.equal(0, diagnostics[1].lnum)
+      assert.are.equal(0, diagnostics[1].col)
+      assert.are.equal('mapping values are not allowed in this context', diagnostics[1].message)
+      assert.are.equal(vim.diagnostic.severity.ERROR, diagnostics[1].severity)
+    end)
+
+    it('parses Error at format', function()
+      local output = 'Error at "source" (line 75, column 1): unexpected end of input'
+      local diagnostics = presets.markdown.error_parser(output, md_ctx)
       assert.is_table(diagnostics)
       assert.are.equal(1, #diagnostics)
       assert.are.equal(74, diagnostics[1].lnum)
@@ -196,20 +211,9 @@ describe('presets', function()
       assert.are.equal(vim.diagnostic.severity.ERROR, diagnostics[1].severity)
     end)
 
-    it('parses YAML parse exceptions from stderr', function()
-      local stderr =
-        'YAML parse exception at line 3, column 2, while scanning a block scalar: did not find expected comment or line break'
-      local diagnostics = presets.markdown.error_parser(stderr, md_ctx)
-      assert.is_table(diagnostics)
-      assert.are.equal(1, #diagnostics)
-      assert.are.equal(2, diagnostics[1].lnum)
-      assert.are.equal(1, diagnostics[1].col)
-      assert.is_string(diagnostics[1].message)
-    end)
-
-    it('parses generic pandoc errors from stderr', function()
-      local stderr = 'pandoc: Could not find data file templates/default.html5'
-      local diagnostics = presets.markdown.error_parser(stderr, md_ctx)
+    it('parses generic pandoc errors', function()
+      local output = 'pandoc: Could not find data file templates/default.html5'
+      local diagnostics = presets.markdown.error_parser(output, md_ctx)
       assert.is_table(diagnostics)
       assert.are.equal(1, #diagnostics)
       assert.are.equal(0, diagnostics[1].lnum)
@@ -217,7 +221,7 @@ describe('presets', function()
       assert.are.equal('Could not find data file templates/default.html5', diagnostics[1].message)
     end)
 
-    it('returns empty table for clean stderr', function()
+    it('returns empty table for clean output', function()
       local diagnostics = presets.markdown.error_parser('', md_ctx)
       assert.are.same({}, diagnostics)
     end)
@@ -284,9 +288,23 @@ describe('presets', function()
       assert.is_true(presets.github.open)
     end)
 
-    it('parses pandoc parse errors from stderr', function()
-      local stderr = 'Error at "document.md" (line 12, column 5): unexpected "}" expecting letter'
-      local diagnostics = presets.github.error_parser(stderr, md_ctx)
+    it('parses YAML metadata errors with multiline message', function()
+      local output = table.concat({
+        'Error parsing YAML metadata at "/tmp/test.md" (line 1, column 1):',
+        'YAML parse exception at line 1, column 9:',
+        'mapping values are not allowed in this context',
+      }, '\n')
+      local diagnostics = presets.github.error_parser(output, md_ctx)
+      assert.is_table(diagnostics)
+      assert.are.equal(1, #diagnostics)
+      assert.are.equal(0, diagnostics[1].lnum)
+      assert.are.equal(0, diagnostics[1].col)
+      assert.are.equal('mapping values are not allowed in this context', diagnostics[1].message)
+    end)
+
+    it('parses Error at format', function()
+      local output = 'Error at "document.md" (line 12, column 5): unexpected "}" expecting letter'
+      local diagnostics = presets.github.error_parser(output, md_ctx)
       assert.is_table(diagnostics)
       assert.are.equal(1, #diagnostics)
       assert.are.equal(11, diagnostics[1].lnum)
@@ -295,7 +313,7 @@ describe('presets', function()
       assert.are.equal(vim.diagnostic.severity.ERROR, diagnostics[1].severity)
     end)
 
-    it('returns empty table for clean stderr', function()
+    it('returns empty table for clean output', function()
       local diagnostics = presets.github.error_parser('', md_ctx)
       assert.are.same({}, diagnostics)
     end)