Use balanced two-pass parsing for ambiguous escaped quotes

A backslash before a closing quote is inherently ambiguous between an
escaped quote ("say \"hello\" now") and a literal trailing path
separator ("C:\Program Files\Repo\"). Local lookahead cannot
distinguish them, so parse in two deterministic passes: pass 1 prefers
escaped quotes and is accepted when all quoted regions close; if it
ends with an open quote (the trailing-separator signature), pass 2
treats backslashes before the active closing quote as literal.
The whitespace/EOI lookahead special case is removed as subsumed.

Author: jugol

plugins/codex/scripts/lib/args.mjs

@@ -73,7 +73,7 @@ export function parseArgs(argv, config = {}) {
   return { options, positionals };
 }
 
-export function splitRawArgumentString(raw) {
+function parseRawArgumentString(raw, literalClosingQuoteBackslash) {
   const tokens = [];
   let current = "";
   let quote = null;
@@ -83,12 +83,7 @@ export function splitRawArgumentString(raw) {
 
     if (character === "\\") {
       const nextCharacter = raw[index + 1];
-      const characterAfterQuote = raw[index + 2];
-      const closesQuotedRegion =
-        quote !== null &&
-        nextCharacter === quote &&
-        (characterAfterQuote === undefined || /\s/.test(characterAfterQuote));
-      if (closesQuotedRegion) {
+      if (literalClosingQuoteBackslash && quote !== null && nextCharacter === quote) {
         current += character;
         continue;
       }
@@ -133,5 +128,14 @@ export function splitRawArgumentString(raw) {
     tokens.push(current);
   }
 
-  return tokens;
+  return { tokens, openQuote: quote };
+}
+
+export function splitRawArgumentString(raw) {
+  const escapePreferred = parseRawArgumentString(raw, false);
+  if (escapePreferred.openQuote === null) {
+    return escapePreferred.tokens;
+  }
+
+  return parseRawArgumentString(raw, true).tokens;
 }

tests/args.test.mjs

@@ -18,8 +18,7 @@ test("splitRawArgumentString preserves a quoted Windows path with spaces", () =>
 });
 
 test("splitRawArgumentString closes a quoted Windows path after a trailing backslash", () => {
-  assert.deepEqual(splitRawArgumentString(String.raw`--cwd "C:\Program Files\Repo\" --write`), [
-    "--cwd",
+  assert.deepEqual(splitRawArgumentString(String.raw`"C:\Program Files\Repo\" --write`), [
     "C:\\Program Files\\Repo\\",
     "--write"
   ]);
@@ -32,14 +31,31 @@ test("splitRawArgumentString closes a final quoted Windows path after a trailing
   ]);
 });
 
+test("splitRawArgumentString closes a trailing-backslash path before another quoted token", () => {
+  assert.deepEqual(splitRawArgumentString(String.raw`"C:\path\" "second"`), ["C:\\path\\", "second"]);
+});
+
 test("splitRawArgumentString accepts an escaped quote inside double quotes", () => {
   assert.deepEqual(splitRawArgumentString(String.raw`"say \"hello\""`), ['say "hello"']);
 });
 
+test("splitRawArgumentString preserves escaped quotes at word boundaries", () => {
+  assert.deepEqual(splitRawArgumentString(String.raw`"say \"hello\" now"`), ['say "hello" now']);
+});
+
 test("splitRawArgumentString preserves an escaped quote before a non-boundary character", () => {
   assert.deepEqual(splitRawArgumentString(String.raw`"say \"hi\"..."`), ['say "hi"...']);
 });
 
+test("splitRawArgumentString parses plain prompts with quoted phrases", () => {
+  assert.deepEqual(splitRawArgumentString(String.raw`run "quoted phrase" and "another phrase"`), [
+    "run",
+    "quoted phrase",
+    "and",
+    "another phrase"
+  ]);
+});
+
 test("splitRawArgumentString collapses an escaped backslash", () => {
   assert.deepEqual(splitRawArgumentString(String.raw`C:\\repo`), [String.raw`C:\repo`]);
 });