Expose a method getter api in Module

Summary:
It is sometimes useful for modules to be passed around in user space for user convenience, but for utilities those users interact with to operate on the methods directly.
This is a bit of a layering violation but it allows us to define narrower scoped helpers so I think its worth the risk that the user finds a way to trash the internal method object. In general method should be fairly robust to being trashed anyway since itself is a blessed front end api from the team.

Differential Revision: D77248983

Author: JacobSzwejbka

extension/module/module.cpp

@@ -228,6 +228,16 @@ runtime::Error Module::load_method(
   return runtime::Error::Ok;
 }
 
+ET_NODISCARD inline runtime::Result<Method*> Module::method(
+    const std::string& method_name) {
+  ET_CHECK_OR_RETURN_ERROR(
+      methods_.count(method_name) > 0,
+      InvalidArgument,
+      "no such method in program: %s",
+      method_name.c_str());
+  return methods_[method_name].method.get();
+}
+
 runtime::Result<MethodMeta> Module::method_meta(
     const std::string& method_name) {
   ET_CHECK_OK_OR_RETURN_ERROR(load());

extension/module/module.h

@@ -194,6 +194,20 @@ class Module {
     return load_method(method_name, nullptr, event_tracer);
   }
 
+  /**
+   * Get a method by it's name. Not recommended to use this method directly as
+   * an end user. It's exposed to allow for composability of module in apis that
+   * operate on method.
+   *
+   * @param[in] method_name The name of the method to get.
+   *
+   * @returns A Result object containing either a pointer to the requested
+   *          method or an error to indicate failure.
+   */
+  ET_NODISCARD inline runtime::Result<Method*> method(
+      const std::string& method_name);
+
+
   /**
    * Load the 'forward' method from the program and set up memory management if
    * needed. The loaded method is cached to reuse the next time it's executed.