Fix single-quoted strings with embedded newlines, and make heredoc body parts lazy-loadable

src/lexer.ts

@@ -937,7 +937,7 @@ export class Lexer {
       if (c === CH_BACKSLASH) i++; // skip escaped char
     }
     if (!hasExpansion) return null;
-    return new WordImpl(body, bodyPos, bodyPos + body.length);
+    return new WordImpl(body, bodyPos, bodyPos + body.length, this.src, WordImpl._resolveHeredocBody);
   }
 
   private _wordText = "";

src/parser.ts

@@ -40,10 +40,11 @@ import type {
 } from "./types.ts";
 import { LexContext, Token, Lexer, TokenValue } from "./lexer.ts";
 import { parseArithmeticExpression } from "./arithmetic.ts";
-import { computeWordParts } from "./parts.ts";
+import { computeWordParts, computeHereDocBodyParts } from "./parts.ts";
 import { WordImpl } from "./word.ts";
 
-WordImpl._resolve = computeWordParts;
+WordImpl._resolveWord = computeWordParts;
+WordImpl._resolveHeredocBody = computeHereDocBodyParts;
 
 class ArithmeticCommandImpl implements ArithmeticCommand {
   type = "ArithmeticCommand" as const;

src/parts.ts

@@ -10,14 +10,25 @@ import { parse } from "./parser.ts";
  */
 export function computeWordParts(source: string, word: Word): WordPart[] | undefined {
   const lexer = new Lexer(source);
-  let parts: import("./types.ts").WordPart[] | null;
+  const parts = lexer.buildWordParts(word.pos);
+  if (!parts) return undefined;
 
-  // Heredoc bodies contain newlines — use dedicated scanning
-  if (word.text.includes("\n") && word.pos > 0) {
-    parts = lexer.buildHereDocParts(word.pos, word.end);
-  } else {
-    parts = lexer.buildWordParts(word.pos);
+  // Resolve command expansions: parse inner scripts
+  for (const exp of lexer.getCollectedExpansions()) {
+    resolveExpansion(exp);
   }
+
+  return parts;
+}
+
+/**
+ * Compute parts for an unquoted heredoc body.
+ * Heredoc bodies use different scanning rules than shell words: newlines are
+ * literal and single/double quotes have no special meaning.
+ */
+export function computeHereDocBodyParts(source: string, word: Word): WordPart[] | undefined {
+  const lexer = new Lexer(source);
+  const parts = lexer.buildHereDocParts(word.pos, word.end);
   if (!parts) return undefined;
 
   // Resolve command expansions: parse inner scripts

src/word.ts

@@ -1,6 +1,6 @@
 import type { DoubleQuotedChild, Word, WordPart } from "./types.ts";
 
-type PartsResolver = (source: string, word: Word) => WordPart[] | undefined;
+export type PartsResolver = (source: string, word: Word) => WordPart[] | undefined;
 
 function dequoteValue(parts: DoubleQuotedChild[]): string {
   let s = "";
@@ -9,20 +9,23 @@ function dequoteValue(parts: DoubleQuotedChild[]): string {
 }
 
 export class WordImpl implements Word {
-  static _resolve: PartsResolver;
+  static _resolveWord: PartsResolver;
+  static _resolveHeredocBody: PartsResolver;
 
   text: string;
   pos: number;
   end: number;
   #source: string;
+  #resolver: PartsResolver;
   #parts: WordPart[] | undefined | null;
   #value: string | null = null;
 
-  constructor(text: string, pos: number, end: number, source?: string) {
+  constructor(text: string, pos: number, end: number, source?: string, resolver?: PartsResolver) {
     this.text = text;
     this.pos = pos;
     this.end = end;
     this.#source = source ?? "";
+    this.#resolver = resolver ?? WordImpl._resolveWord;
     this.#parts = source !== undefined ? null : undefined;
   }
 
@@ -57,7 +60,7 @@ export class WordImpl implements Word {
 
   get parts(): WordPart[] | undefined {
     if (this.#parts === null) {
-      this.#parts = WordImpl._resolve(this.#source, this) ?? undefined;
+      this.#parts = this.#resolver(this.#source, this) ?? undefined;
     }
     return this.#parts;
   }

test/heredoc-expansion.test.ts

@@ -2,9 +2,8 @@ import assert from "node:assert/strict";
 import test from "node:test";
 import { parse } from "../src/parser.ts";
 import type { Command, Redirect } from "../src/types.ts";
-import { computeWordParts } from "../src/parts.ts";
 
-const wp = (s: string, w: import("../src/types.ts").Word) => computeWordParts(s, w);
+const wp = (_s: string, w: import("../src/types.ts").Word) => w.parts;
 
 const getRedirect = (src: string, i = 0, ri = 0): Redirect => {
   const ast = parse(src);

test/quoting.test.ts

@@ -188,3 +188,55 @@ test("line continuation in whitespace between tokens", () => {
   const ast = parse("echo; \\\nls");
   assert.equal(ast.commands.length, 2);
 });
+
+// ── Single-quoted strings are fully literal ───────────────────────────
+// Everything inside single quotes is literal, including backticks, $(),
+// ${}, $var, etc. No expansions of any kind occur.
+
+test("backticks inside single quotes are literal (not command substitution)", () => {
+  const ast = parse("echo '`cmd`'");
+  const word = getCmd(ast).suffix[0];
+  assert.equal(word.parts?.length, 1, "should have exactly one part");
+  assert.equal(word.parts?.[0]?.type, "SingleQuoted", "should be SingleQuoted part");
+  assert.equal(word.parts?.[0]?.value, "`cmd`", "backticks should be literal in value");
+});
+
+test("$() inside single quotes is literal (not command substitution)", () => {
+  const ast = parse("echo '$(cmd)'");
+  const word = getCmd(ast).suffix[0];
+  assert.equal(word.parts?.length, 1, "should have exactly one part");
+  assert.equal(word.parts?.[0]?.type, "SingleQuoted", "should be SingleQuoted part");
+  assert.equal(word.parts?.[0]?.value, "$(cmd)", "$() should be literal in value");
+});
+
+test("${} inside single quotes is literal (not parameter expansion)", () => {
+  const ast = parse("echo '${var}'");
+  const word = getCmd(ast).suffix[0];
+  assert.equal(word.parts?.length, 1, "should have exactly one part");
+  assert.equal(word.parts?.[0]?.type, "SingleQuoted", "should be SingleQuoted part");
+  assert.equal(word.parts?.[0]?.value, "${var}", "${} should be literal in value");
+});
+
+test("multiline single-quoted string with backticks is one SingleQuoted part", () => {
+  const ast = parse(`echo '
+const x = \`hello\`;
+console.log(x);
+'`);
+  const word = getCmd(ast).suffix[0];
+  assert.equal(word.parts?.length, 1, "should have exactly one part");
+  assert.equal(word.parts?.[0]?.type, "SingleQuoted", "should be SingleQuoted part");
+  // The value should contain the backticks literally
+  assert.ok(word.parts?.[0]?.value?.includes("`hello`"), "value should contain literal backticks");
+});
+
+test("multiline single-quoted string with $() is one SingleQuoted part", () => {
+  const ast = parse(`echo '
+const src = "for (( i = $(start); i < $(limit); i++ )); do echo $i; done";
+'`);
+  const word = getCmd(ast).suffix[0];
+  assert.equal(word.parts?.length, 1, "should have exactly one part");
+  assert.equal(word.parts?.[0]?.type, "SingleQuoted", "should be SingleQuoted part");
+  // The value should contain $() literally
+  assert.ok(word.parts?.[0]?.value?.includes("$(start)"), "value should contain literal $(start)");
+  assert.ok(word.parts?.[0]?.value?.includes("$(limit)"), "value should contain literal $(limit)");
+});