fix(presets): correct error parsers for real compiler output (#11)

Problem: all three built-in error parsers were broken against real
compiler output. Typst set source to the relative file path, overriding
the provider name. LaTeX errors go to stdout but the parser only
received stderr. Pandoc's pattern matched "Error at" but not the real
"Error parsing YAML metadata at" format, and single-line parsing missed
multiline messages.

Solution: pass combined stdout+stderr to error_parser so LaTeX stdout
errors are visible. Remove source = file from the Typst parser so
diagnostic.lua defaults it to the provider name. Rewrite the Pandoc
parser with line-based lookahead: match (line N, column N) regardless
of prefix text, skip YAML parse exception lines when looking ahead for
the human-readable message. Rename stderr param to output throughout
diagnostic.lua, presets.lua, and init.lua annotations.

lua/preview/compiler.lua

@@ -106,7 +106,8 @@ function M.compile(bufnr, name, provider, ctx)
       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)
+          local output = (result.stdout or '') .. (result.stderr or '')
+          diagnostic.set(bufnr, name, provider.error_parser, output, ctx)
         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 error_parser fun(output: string, ctx: preview.Context): preview.Diagnostic[]
----@param stderr string
+---@param output string
 ---@param ctx preview.Context
-function M.set(bufnr, name, error_parser, stderr, ctx)
+function M.set(bufnr, name, error_parser, output, ctx)
-  local ok, diagnostics = pcall(error_parser, stderr, 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 +5,7 @@
 ---@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 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
+  for line in output:gmatch('[^\r\n]+') do
-    local file, lnum, col, severity, msg = line:match('^(.+):(%d+):(%d+): (%w+): (.+)$')
+    local _, lnum, col, severity, msg = line:match('^(.+):(%d+):(%d+): (%w+): (.+)$')
     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 lines = vim.split(output, '\n')
-    local lnum, col, msg = line:match('Error at .+ %(line (%d+), column (%d+)%): (.+)$')
+  local i = 1
+  while i <= #lines do
+    local line = lines[i]
+    local lnum, col, msg = line:match('%(line (%d+), column (%d+)%):%s*(.*)$')
     if lnum then
-      table.insert(diagnostics, {
+      if msg == '' then
-        lnum = tonumber(lnum) - 1,
+        for j = i + 1, math.min(i + 2, #lines) do
-        col = tonumber(col) - 1,
+          local next_line = lines[j]:match('^%s*(.+)$')
-        message = msg,
+          if next_line and not next_line:match('^YAML parse exception') then
-        severity = vim.diagnostic.severity.ERROR,
+            msg = next_line
-      })
+            break
-    else
+          end
-      local ylnum, ycol, ymsg =
-        line:match('YAML parse exception at line (%d+), column (%d+)[,:]%s*(.+)$')
-      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: (.+)$')
-        if errmsg and not errmsg:match('^Error at') then
-          table.insert(diagnostics, {
-            lnum = 0,
-            col = 0,
-            message = errmsg,
-            severity = vim.diagnostic.severity.ERROR,
-          })
         end
       end
+      if msg ~= '' then
+        table.insert(diagnostics, {
+          lnum = tonumber(lnum) - 1,
+          col = tonumber(col) - 1,
+          message = msg,
+          severity = vim.diagnostic.severity.ERROR,
+        })
+      end
+    else
+      local errmsg = line:match('^pandoc: (.+)$')
+      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$', '.pdf'))
   end,
-  error_parser = function(stderr)
+  error_parser = function(output)
-    return parse_typst(stderr)
+    return parse_typst(output)
   end,
   open = true,
 }
@@ -121,8 +124,8 @@ M.latex = {
   output = function(ctx)
     return (ctx.file:gsub('%.tex$', '.pdf'))
   end,
-  error_parser = function(stderr)
+  error_parser = function(output)
-    return parse_latexmk(stderr)
+    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$', '.html'))
   end,
-  error_parser = function(stderr)
+  error_parser = function(output)
-    return parse_pandoc(stderr)
+    return parse_pandoc(output)
   end,
   clean = function(ctx)
     return { 'rm', '-f', (ctx.file:gsub('%.md$', '.html')) }
@@ -171,8 +174,8 @@ M.github = {
   output = function(ctx)
     return (ctx.file:gsub('%.md$', '.html'))
   end,
-  error_parser = function(stderr)
+  error_parser = function(output)
-    return parse_pandoc(stderr)
+    return parse_pandoc(output)
   end,
   clean = function(ctx)
     return { 'rm', '-f', (ctx.file:gsub('%.md$', '.html')) }

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()
+    it('parses file-line-error format from output', function()
-      local stderr = table.concat({
+      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()
+    it('parses YAML metadata errors with multiline message', function()
-      local stderr = 'Error at "source" (line 75, column 1): unexpected end of input'
+      local output = table.concat({
-      local diagnostics = presets.markdown.error_parser(stderr, md_ctx)
+        '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()
+    it('parses generic pandoc errors', function()
-      local stderr =
+      local output = 'pandoc: Could not find data file templates/default.html5'
-        '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(output, md_ctx)
-      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)
       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()
+    it('parses YAML metadata errors with multiline message', function()
-      local stderr = 'Error at "document.md" (line 12, column 5): unexpected "}" expecting letter'
+      local output = table.concat({
-      local diagnostics = presets.github.error_parser(stderr, md_ctx)
+        '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)