Fix performance regression in src/resources/filters/quarto-pre/engine-escape.lua

news/changelog-1.9.md

@@ -212,3 +212,4 @@ All changes included in 1.9:
 - ([#13998](https://github.com/quarto-dev/quarto-cli/issues/13998)): Fix YAML validation error with CR-only line terminators (old Mac format). Documents using `\r` line endings no longer fail with "Expected YAML front matter to contain at least 2 lines".
 - ([#14012](https://github.com/quarto-dev/quarto-cli/issues/14012)): Add `fr-CA` language translation for Quebec French inclusive writing conventions, using parenthetical forms instead of middle dots for author labels. (author: @tdhock)
 - ([#14032](https://github.com/quarto-dev/quarto-cli/issues/14032)): Add `editor_options` with `chunk_output_type` to YAML schema for autocompletion and validation in RStudio and Positron.
+- ([#14156](https://github.com/quarto-dev/quarto-cli/issues/14156)): Avoid O(n^2) performance in handling large code blocks.

src/resources/filters/quarto-pre/engine-escape.lua

@@ -4,6 +4,38 @@
 local patterns = require("modules/patterns")
 
 function engine_escape()
+  -- Line-by-line replacement for the pattern (\n?[^`\n]+`+){({+([^<}]+)}+)}
+  -- which suffers from O(n^2) backtracking on long lines without backticks.
+  -- See https://github.com/quarto-dev/quarto-cli/issues/14156
+  --
+  -- The original pattern cannot cross newlines (due to [^`\n]+), so processing
+  -- per-line is semantically equivalent and avoids catastrophic backtracking.
+  local line_pattern = "([^`\n]+`+)" .. patterns.engine_escape
+  local function unescape_inline_engine_codes(text)
+    if not text:find("{{", 1, true) then
+      return text
+    end
+    local result = {}
+    local pos = 1
+    local len = #text
+    while pos <= len do
+      local nl = text:find("\n", pos, true)
+      local line
+      if nl then
+        line = text:sub(pos, nl)
+        pos = nl + 1
+      else
+        line = text:sub(pos)
+        pos = len + 1
+      end
+      if line:find("`", 1, true) and line:find("{{", 1, true) then
+        line = line:gsub(line_pattern, "%1%2")
+      end
+      result[#result + 1] = line
+    end
+    return table.concat(result)
+  end
+
   return {
     CodeBlock = function(el)
 
@@ -26,7 +58,7 @@ function engine_escape()
       end)
 
       -- handles escaped inline code cells within a code block
-      el.text = el.text:gsub("(\n?[^`\n]+`+)" .. patterns.engine_escape, "%1%2")
+      el.text = unescape_inline_engine_codes(el.text)
       return el
     end,
 
@@ -46,156 +78,151 @@ end
 
 -- FIXME these should be determined dynamically
 local kHighlightClasses = {
-  "abc",
-  "actionscript",
-  "ada",
-  "agda",
-  "apache",
-  "asn1",
-  "asp",
-  "ats",
-  "awk",
-  "bash",
-  "bibtex",
-  "boo",
-  "c",
-  "changelog",
-  "clojure",
-  "cmake",
-  "coffee",
-  "coldfusion",
-  "comments",
-  "commonlisp",
-  "cpp",
-  "cs",
-  "css",
-  "curry",
-  "d",
-  "default",
-  "diff",
-  "djangotemplate",
-  "dockerfile",
-  "dot",
-  "doxygen",
-  "doxygenlua",
-  "dtd",
-  "eiffel",
-  "elixir",
-  "elm",
-  "email",
-  "erlang",
-  "fasm",
-  "fortranfixed",
-  "fortranfree",
-  "fsharp",
-  "gap",
-  "gcc",
-  "glsl",
-  "gnuassembler",
-  "go",
-  "graphql",
-  "groovy",
-  "hamlet",
-  "haskell",
-  "haxe",
-  "html",
-  "idris",
-  "ini",
-  "isocpp",
-  "j",
-  "java",
-  "javadoc",
-  "javascript",
-  "javascriptreact",
-  "json",
-  "jsp",
-  "julia",
-  "kotlin",
-  "latex",
-  "lex",
-  "lilypond",
-  "literatecurry",
-  "literatehaskell",
-  "llvm",
-  "lua",
-  "m4",
-  "makefile",
-  "mandoc",
-  "markdown",
-  "mathematica",
-  "matlab",
-  "maxima",
-  "mediawiki",
-  "metafont",
-  "mips",
-  "modelines",
-  "modula2",
-  "modula3",
-  "monobasic",
-  "mustache",
-  "nasm",
-  "nim",
-  "noweb",
-  "objectivec",
-  "objectivecpp",
-  "ocaml",
-  "octave",
-  "opencl",
-  "pascal",
-  "perl",
-  "php",
-  "pike",
-  "postscript",
-  "povray",
-  "powershell",
-  "prolog",
-  "protobuf",
-  "pure",
-  "purebasic",
-  "python",
-  "qml",
-  "r",
-  "raku",
-  "relaxng",
-  "relaxngcompact",
-  "rest",
-  "rhtml",
-  "roff",
-  "ruby",
-  "rust",
-  "scala",
-  "scheme",
-  "sci",
-  "sed",
-  "sgml",
-  "sml",
-  "spdxcomments",
-  "sql",
-  "sqlmysql",
-  "sqlpostgresql",
-  "stata",
-  "swift",
-  "tcl",
-  "tcsh",
-  "texinfo",
-  "toml",
-  "typescript",
-  "verilog",
-  "vhdl",
-  "xml",
-  "xorg",
-  "xslt",
-  "xul",
-  "yacc",
-  "yaml",
-  "zsh"
+  ["abc"] = true,
+  ["actionscript"] = true,
+  ["ada"] = true,
+  ["agda"] = true,
+  ["apache"] = true,
+  ["asn1"] = true,
+  ["asp"] = true,
+  ["ats"] = true,
+  ["awk"] = true,
+  ["bash"] = true,
+  ["bibtex"] = true,
+  ["boo"] = true,
+  ["c"] = true,
+  ["changelog"] = true,
+  ["clojure"] = true,
+  ["cmake"] = true,
+  ["coffee"] = true,
+  ["coldfusion"] = true,
+  ["comments"] = true,
+  ["commonlisp"] = true,
+  ["cpp"] = true,
+  ["cs"] = true,
+  ["css"] = true,
+  ["curry"] = true,
+  ["d"] = true,
+  ["default"] = true,
+  ["diff"] = true,
+  ["djangotemplate"] = true,
+  ["dockerfile"] = true,
+  ["dot"] = true,
+  ["doxygen"] = true,
+  ["doxygenlua"] = true,
+  ["dtd"] = true,
+  ["eiffel"] = true,
+  ["elixir"] = true,
+  ["elm"] = true,
+  ["email"] = true,
+  ["erlang"] = true,
+  ["fasm"] = true,
+  ["fortranfixed"] = true,
+  ["fortranfree"] = true,
+  ["fsharp"] = true,
+  ["gap"] = true,
+  ["gcc"] = true,
+  ["glsl"] = true,
+  ["gnuassembler"] = true,
+  ["go"] = true,
+  ["graphql"] = true,
+  ["groovy"] = true,
+  ["hamlet"] = true,
+  ["haskell"] = true,
+  ["haxe"] = true,
+  ["html"] = true,
+  ["idris"] = true,
+  ["ini"] = true,
+  ["isocpp"] = true,
+  ["j"] = true,
+  ["java"] = true,
+  ["javadoc"] = true,
+  ["javascript"] = true,
+  ["javascriptreact"] = true,
+  ["json"] = true,
+  ["jsp"] = true,
+  ["julia"] = true,
+  ["kotlin"] = true,
+  ["latex"] = true,
+  ["lex"] = true,
+  ["lilypond"] = true,
+  ["literatecurry"] = true,
+  ["literatehaskell"] = true,
+  ["llvm"] = true,
+  ["lua"] = true,
+  ["m4"] = true,
+  ["makefile"] = true,
+  ["mandoc"] = true,
+  ["markdown"] = true,
+  ["mathematica"] = true,
+  ["matlab"] = true,
+  ["maxima"] = true,
+  ["mediawiki"] = true,
+  ["metafont"] = true,
+  ["mips"] = true,
+  ["modelines"] = true,
+  ["modula2"] = true,
+  ["modula3"] = true,
+  ["monobasic"] = true,
+  ["mustache"] = true,
+  ["nasm"] = true,
+  ["nim"] = true,
+  ["noweb"] = true,
+  ["objectivec"] = true,
+  ["objectivecpp"] = true,
+  ["ocaml"] = true,
+  ["octave"] = true,
+  ["opencl"] = true,
+  ["pascal"] = true,
+  ["perl"] = true,
+  ["php"] = true,
+  ["pike"] = true,
+  ["postscript"] = true,
+  ["povray"] = true,
+  ["powershell"] = true,
+  ["prolog"] = true,
+  ["protobuf"] = true,
+  ["pure"] = true,
+  ["purebasic"] = true,
+  ["python"] = true,
+  ["qml"] = true,
+  ["r"] = true,
+  ["raku"] = true,
+  ["relaxng"] = true,
+  ["relaxngcompact"] = true,
+  ["rest"] = true,
+  ["rhtml"] = true,
+  ["roff"] = true,
+  ["ruby"] = true,
+  ["rust"] = true,
+  ["scala"] = true,
+  ["scheme"] = true,
+  ["sci"] = true,
+  ["sed"] = true,
+  ["sgml"] = true,
+  ["sml"] = true,
+  ["spdxcomments"] = true,
+  ["sql"] = true,
+  ["sqlmysql"] = true,
+  ["sqlpostgresql"] = true,
+  ["stata"] = true,
+  ["swift"] = true,
+  ["tcl"] = true,
+  ["tcsh"] = true,
+  ["texinfo"] = true,
+  ["toml"] = true,
+  ["typescript"] = true,
+  ["verilog"] = true,
+  ["vhdl"] = true,
+  ["xml"] = true,
+  ["xorg"] = true,
+  ["xslt"] = true,
+  ["xul"] = true,
+  ["yacc"] = true,
+  ["yaml"] = true,
+  ["zsh"] = true
 }
 
 function isHighlightClass(class)
-  for _, v in ipairs (kHighlightClasses) do
-    if v == class then
-      return true
-    end
-  end
-  return false
+  if kHighlightClasses[class] then return true else return false end
 end