fix(migrate): reject nested command substitutions

packages/migrate/src/sources/conductor/project-config.test.ts

@@ -163,6 +163,7 @@ test("preserves literal or escaped Conductor names and rewrites active variables
         arithmeticOffset: { command: "serve --port $(( CONDUCTOR_PORT + 1 ))" },
         prefixExpansion: { command: "serve --length ${#CONDUCTOR_PORT}" },
         unicodePrefix: { command: 'printf 😀 "$CONDUCTOR_PORT"' },
+        commandSubstitution: { command: "printf \"$(printf '$CONDUCTOR_PORT')\"" },
       },
     },
   });
@@ -196,6 +197,11 @@ test("preserves literal or escaped Conductor names and rewrites active variables
     message:
       "scripts.prefixExpansion: Unsupported Conductor variables: CONDUCTOR_PORT. Command was not imported.",
   });
+  expect(inspected.notices).toContainEqual({
+    code: "conductor-setting-unsupported",
+    level: "warning",
+    message: "scripts.commandSubstitution: Command substitutions are not imported.",
+  });
 });
 
 test("skips cwd scripts on Windows instead of emitting POSIX shell syntax", () => {

packages/migrate/src/sources/conductor/project-config.ts

@@ -369,6 +369,10 @@ function rewriteExactCommand(
   notices: MigrationNotice[],
   platform: NodeJS.Platform,
 ): string | null {
+  if (containsActiveCommandSubstitution(command)) {
+    notices.push(unsupportedSetting(key, "Command substitutions are not imported."));
+    return null;
+  }
   if (containsActiveHereDocument(command)) {
     notices.push(unsupportedSetting(key, "Here-document commands are not imported."));
     return null;
@@ -727,6 +731,17 @@ function containsActiveHereDocument(command: string): boolean {
   return false;
 }
 
+function containsActiveCommandSubstitution(command: string): boolean {
+  const mask = activeShellMask(command);
+  for (const match of command.matchAll(/\$\((?!\()/g)) {
+    if (mask.slice(match.index, match.index + 2) === "$(") return true;
+  }
+  for (const match of command.matchAll(/`/g)) {
+    if (mask[match.index] === "`") return true;
+  }
+  return false;
+}
+
 function appendArgs(command: string, args: string[]): string {
   return args.length === 0 ? command : `${command} ${args.map(shellQuoteArgument).join(" ")}`;
 }