JS: js/command-line-injection misses child_process argument arrays when the shell option is set #22825

Description of the issue

js/command-line-injection does not report remote input that reaches the argument array of spawn/execFile when the shell option is set, although Node.js then runs the joined command line in a shell. Checked with the latest release, CodeQL 2.27.2 (codeql/javascript-queries 2.4.7).

const cp = require("child_process");
const app = require("express")();

app.get("/a", (req, res) => {
  cp.exec("echo hello " + req.query.name); // reported
  res.send("ok");
});

app.get("/b", (req, res) => {
  cp.spawn("echo", ["hello", req.query.name], { shell: true }); // not reported
  res.send("ok");
});

app.get("/c", (req, res) => {
  cp.spawn("echo", ["hello", req.query.name], { shell: "/bin/sh" }); // not reported
  res.send("ok");
});

Only /a is reported, by js/command-line-injection. For /b and /c, no query in javascript-security-extended.qls reports a command injection. At runtime both run /bin/sh -c "echo hello <name>" (Node.js joins [file, ...args] with spaces when shell is truthy; see the spawn documentation), so name = "x; touch /tmp/marker" creates the file (Node.js v24.18.0).

As far as I can tell, CommandInjection::SystemCommandExecutionSink only uses getACommandArgument(), which for spawn/execFile is the program name. The argument array is treated as shell-interpreted only in UnsafeShellCommandConstruction (executesArrayAsShell), i.e. for library inputs, and even there only for
shell: true: with a string-valued shell such as "/bin/sh", js/shell-command-constructed-from-input misses the call as well.