Fix stack overflow when chaining an already chained wrapper

[chatman-media]

Summary

Fixes #2853.

_.chain(value).chain() — or any redundant .chain() call within a chained sequence — overflows the stack with RangeError: Maximum call stack size exceeded instead of behaving like a no-op and returning a wrapper of the same value.

_.chain([1]).chain();             // RangeError: Maximum call stack size exceeded
_([1]).chain().chain().value();   // RangeError: Maximum call stack size exceeded

Root cause

chainResult continues chaining intermediate results via _(obj).chain(). When obj is the value returned by the standalone chain function, it is already a wrapped _ instance. _(obj) therefore returns that same wrapper (per if (obj instanceof _) return obj;), and invoking the prototype chain method on it re-enters chainResult, which re-chains again — recursing without a base case until the stack overflows.

The recursion loop is: prototype chain → standalone chain (produces a wrapper) → chainResult re-chains that wrapper via prototype chain → repeat.

As noted in the issue, this was introduced together with #1691.

Fix

Call the standalone chain helper from chainResult instead of _(obj).chain(). chain sets the _chain flag on the (possibly already wrapped) value directly and returns, so chaining an already chained wrapper is idempotent and terminates:

return instance._chain ? chain(obj) : obj;

This is safe for every chainResult call site: the array-method wrappers pass a plain (unwrapped) value, and tap returns the unwrapped value too — only _.chain returns an _ instance, which is exactly the case that previously recursed.

Tests

Added a regression test in test/chaining.js (#2853). It verifies the redundant .chain() no longer throws, preserves the wrapped value, stays chained, and that further chaining keeps working.

• Without the fix the new test fails with Maximum call stack size exceeded (verified).
• With the fix the full suite passes (209 assertions) and eslint is clean.

No public API change; _.chain([1]).chain() now returns a chained wrapper of [1] as expected.