docs: add comments to plugin patching operations

plugins/node/opentelemetry-koa-instrumentation/src/koa.ts

@@ -42,6 +42,9 @@ export class KoaInstrumentation extends BasePlugin<typeof koa> {
     super('@opentelemetry/koa-instrumentation', VERSION);
   }
 
+  /**
+   * Patches Koa operations by wrapping the Koa.use function
+   */
   protected patch(): typeof koa {
     this._logger.debug('Patching Koa');
 
@@ -54,6 +57,10 @@ export class KoaInstrumentation extends BasePlugin<typeof koa> {
 
     return this._moduleExports;
   }
+
+  /**
+   * Unpatches all Koa operations
+   */
   protected unpatch(): void {
     const appProto = this._moduleExports.prototype;
     shimmer.unwrap(appProto, 'use');
@@ -62,7 +69,7 @@ export class KoaInstrumentation extends BasePlugin<typeof koa> {
   /**
    * Patches the Koa.use function in order to instrument each original
    * middleware layer which is introduced
-   * @param original
+   * @param {KoaMiddleware} middleware - the original middleware function
    */
   private _getKoaUsePatch(original: (middleware: KoaMiddleware) => koa) {
     return function use(
@@ -86,6 +93,13 @@ export class KoaInstrumentation extends BasePlugin<typeof koa> {
     } as any;
   }
 
+  /**
+   * Patches the dispatch function used by @koa/router. This function
+   * goes through each routed middleware and adds instrumentation via a call
+   * to the @function _patchLayer function.
+   * @param {KoaMiddleware} dispatchLayer - the original dispatch function which dispatches
+   * routed middleware
+   */
   private _patchRouterDispatch(dispatchLayer: KoaMiddleware) {
     this._logger.debug('Patching @koa/router dispatch');
 
@@ -108,6 +122,15 @@ export class KoaInstrumentation extends BasePlugin<typeof koa> {
     return dispatcher;
   }
 
+  /**
+   * Patches each individual @param middlewareLayer function in order to create the
+   * span and propagate context. It does not create spans when there is no parent span.
+   * @param {KoaMiddleware} middlewareLayer - the original middleware function.
+   * @param {boolean} isRouter - tracks whether the original middleware function
+   * was dispatched by the router originally
+   * @param {string?} layerPath - if present, provides additional data from the
+   * router about the routed path which the middleware is attached to
+   */
   private _patchLayer(
     middlewareLayer: KoaMiddleware,
     isRouter: boolean,

plugins/node/opentelemetry-koa-instrumentation/test/koa.test.ts

@@ -99,7 +99,6 @@ describe('Koa Instrumentation - Core Tests', () => {
       app.use(customMiddleware);
       app.use(simpleResponse);
 
-
       const server = http.createServer(app.callback());
       await new Promise(resolve => server.listen(0, resolve));
       const port = (server.address() as AddressInfo).port;