fix: stop $ sequences in selected text corrupting the prompt

lib/build-url.js

@@ -21,7 +21,12 @@ function applyTemplate(template, query) {
   }
   const tpl = typeof template === "string" ? template : "";
   if (tpl.includes("{query}")) {
-    return tpl.replaceAll("{query}", query);
+    // Replacer function, not a replacement string: String.prototype.replaceAll
+    // gives $&, $`, $', and $$ special meaning in a replacement STRING, and
+    // `query` is arbitrary page-selected text that can contain any of those
+    // (shell one-liners routinely do). The function form disables that
+    // interpretation entirely. Do not "simplify" this back to the string form.
+    return tpl.replaceAll("{query}", () => query);
   }
   const trimmed = tpl.trim();
   return trimmed === "" ? query : `${trimmed} ${query}`;

test/build-url.test.js

@@ -133,3 +133,43 @@ test("a query needing no truncation is left byte-identical", () => {
   const raw = "a modest question about thermodynamics";
   assert.equal(queryOf(buildChatGptUrl(DEFAULT_SETTINGS, raw)), raw);
 });
+
+// String.prototype.replaceAll gives $&, $`, $', and $$ special meaning in the
+// REPLACEMENT string, and `query` (arbitrary page-selected text) is exactly
+// that argument. These selections are ordinary shell one-liners, not
+// adversarial input, and must round-trip byte-identically into `q`.
+test("a selection containing $& survives the default {query} template byte-identically", () => {
+  const raw = "awk print $& here";
+  const url = buildChatGptUrl(DEFAULT_SETTINGS, raw);
+  assert.equal(queryOf(url), raw);
+});
+
+test("a selection containing $& survives a prefix template byte-identically", () => {
+  const raw = "awk print $& here";
+  const url = buildChatGptUrl(withSettings({ promptTemplate: "Explain: {query}" }), raw);
+  assert.equal(queryOf(url), `Explain: ${raw}`);
+});
+
+test("a selection containing $` and $' survives the default {query} template byte-identically", () => {
+  const raw = "shell $` and $' here";
+  const url = buildChatGptUrl(DEFAULT_SETTINGS, raw);
+  assert.equal(queryOf(url), raw);
+});
+
+test("a selection containing $` and $' survives a prefix template byte-identically", () => {
+  const raw = "shell $` and $' here";
+  const url = buildChatGptUrl(withSettings({ promptTemplate: "Explain: {query}" }), raw);
+  assert.equal(queryOf(url), `Explain: ${raw}`);
+});
+
+test("a selection containing $$ survives the default {query} template byte-identically", () => {
+  const raw = "PID is $$ in bash";
+  const url = buildChatGptUrl(DEFAULT_SETTINGS, raw);
+  assert.equal(queryOf(url), raw);
+});
+
+test("a selection containing $$ survives a prefix template byte-identically", () => {
+  const raw = "PID is $$ in bash";
+  const url = buildChatGptUrl(withSettings({ promptTemplate: "Explain: {query}" }), raw);
+  assert.equal(queryOf(url), `Explain: ${raw}`);
+});