Avoid constructor source scanning for classes without a base class in @loopback/context #11878

Describe the bug

On the first call to describeInjectedArguments() for a constructor, LoopBack calls shouldSkipBaseConstructorInjection(), which reads the class’s source and runs regular expressions to determine whether constructor injections should be inherited.

This work also runs for classes that do not extend another class. For those classes, there is no base constructor to inspect. The metadata cache avoids repeated work for the same class, but applications inspecting many distinct classes still incur this cost during startup.

The proposed change in describeInjectedArguments() is:

if (method === '') {
  if (
    Object.getPrototypeOf(target) !== Function.prototype &&
    shouldSkipBaseConstructorInjection(target)
  ) {
    options.ownMetadataOnly = true;
  }
}

Logs

Additional information

We measured the following application startup timings with @loopback/context 9.0.0, Node.js 22.23.4, and macOS 26.7 on an Apple M4 Pro:

These are medians of three fresh processes per variant, alternating between variants with other startup settings held constant. Of 3,948 inspected classes, 3,384 had no base class.

The improvement saves approximately 126 ms during registration. Constructor inspection is included in registration, so these savings are not additive or a claim about total application startup time.

Reproduction

https://github.com/tonynelson19/loopback-constructor-repro