assert: add compatibility for older Node.js versions

This makes sure the `AssertionError` still accepts the
`stackStartFunction` option as alternative to the `stackStartFn`.

PR-URL: https://github.com/nodejs/node/pull/27672
Fixes: https://github.com/nodejs/node/issues/27671
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

lib/internal/assert/assertion_error.js

@@ -298,7 +298,9 @@ class AssertionError extends Error {
     const {
       message,
       operator,
-      stackStartFn
+      stackStartFn,
+      // Compatibility with older versions.
+      stackStartFunction
     } = options;
     let {
       actual,
@@ -418,7 +420,7 @@ class AssertionError extends Error {
     this.expected = expected;
     this.operator = operator;
     // eslint-disable-next-line no-restricted-syntax
-    Error.captureStackTrace(this, stackStartFn);
+    Error.captureStackTrace(this, stackStartFn || stackStartFunction);
     // Create error message including the error code in the name.
     this.stack;
     // Reset the name.

test/parallel/test-assert.js

@@ -1203,3 +1203,21 @@ assert.throws(
   () => a.deepStrictEqual(),
   { code: 'ERR_MISSING_ARGS' }
 );
+
+// Verify that `stackStartFunction` works as alternative to `stackStartFn`.
+{
+  (function hidden() {
+    const err = new assert.AssertionError({
+      actual: 'foo',
+      operator: 'strictEqual',
+      stackStartFunction: hidden
+    });
+    const err2 = new assert.AssertionError({
+      actual: 'foo',
+      operator: 'strictEqual',
+      stackStartFn: hidden
+    });
+    assert(!err.stack.includes('hidden'));
+    assert(!err2.stack.includes('hidden'));
+  })();
+}