feat(instrumentation): add getModuleDefinitions() instead of making init() public (#4475)

* feat(instrumentation): add getModuleDefinitions() instead of making init() public

* test(instrumetation): add tests for getModuleDefinitions()

* chore: changelog

Author: pichlermarc

experimental/CHANGELOG.md

@@ -9,7 +9,7 @@ All notable changes to experimental packages in this project will be documented
 ### :rocket: (Enhancement)
 
 * feat(instrumentation): allow LoggerProvider to be specified in Instrumentations [#4314](https://github.com/open-telemetry/opentelemetry-js/pull/4314) @hectorhdzg
-* feat(instrumentation): Make `init()` method public [#4418](https://github.com/open-telemetry/opentelemetry-js/pull/4418)
+* feat(instrumentation): add getModuleDefinitions() to InstrumentationBase [#4475](https://github.com/open-telemetry/opentelemetry-js/pull/4475) @pichlermarc
 * feat(exporter-metrics-otlp-http): add option to set the exporter aggregation preference  [#4409](https://github.com/open-telemetry/opentelemetry-js/pull/4409) @AkselAllas
 * feat(node-sdk): add spanProcessors option [#4454](https://github.com/open-telemetry/opentelemetry-js/pull/4454) @naseemkullah
 

experimental/packages/opentelemetry-instrumentation/src/instrumentation.ts

@@ -108,6 +108,23 @@ export abstract class InstrumentationAbstract<T = any>
     );
   }
 
+  /**
+   * @experimental
+   *
+   * Get module definitions defined by {@link init}.
+   * This can be used for experimental compile-time instrumentation.
+   *
+   * @returns an array of {@link InstrumentationModuleDefinition}
+   */
+  public getModuleDefinitions(): InstrumentationModuleDefinition<T>[] {
+    const initResult = this.init() ?? [];
+    if (!Array.isArray(initResult)) {
+      return [initResult];
+    }
+
+    return initResult;
+  }
+
   /**
    * Sets the new metric instruments with the current Meter.
    */
@@ -153,11 +170,8 @@ export abstract class InstrumentationAbstract<T = any>
   /**
    * Init method in which plugin should define _modules and patches for
    * methods.
-   * Use `enable()` if you are trying to turn on this plugin. This method
-   * will return objects to patch specific modules with the appropriate
-   * instrumentation (or not return anything).
    */
-  abstract init():
+  protected abstract init():
     | InstrumentationModuleDefinition<T>
     | InstrumentationModuleDefinition<T>[]
     | void;

experimental/packages/opentelemetry-instrumentation/test/common/Instrumentation.test.ts

@@ -19,6 +19,7 @@ import {
   Instrumentation,
   InstrumentationBase,
   InstrumentationConfig,
+  InstrumentationModuleDefinition,
 } from '../../src';
 
 import { MeterProvider } from '@opentelemetry/sdk-metrics';
@@ -132,4 +133,54 @@ describe('BaseInstrumentation', () => {
       assert.strictEqual(configuration.isActive, true);
     });
   });
+
+  describe('getModuleDefinitions', () => {
+    const moduleDefinition: InstrumentationModuleDefinition<unknown> = {
+      name: 'foo',
+      patch: moduleExports => {},
+      unpatch: moduleExports => {},
+      moduleExports: {},
+      files: [],
+      supportedVersions: ['*'],
+    };
+
+    it('should return single module definition from init() as array ', () => {
+      class TestInstrumentation2 extends TestInstrumentation {
+        override init() {
+          return moduleDefinition;
+        }
+      }
+      const instrumentation = new TestInstrumentation2();
+
+      assert.deepStrictEqual(instrumentation.getModuleDefinitions(), [
+        moduleDefinition,
+      ]);
+    });
+
+    it('should return multiple module definitions from init() as array ', () => {
+      class TestInstrumentation2 extends TestInstrumentation {
+        override init() {
+          return [moduleDefinition, moduleDefinition, moduleDefinition];
+        }
+      }
+      const instrumentation = new TestInstrumentation2();
+
+      assert.deepStrictEqual(instrumentation.getModuleDefinitions(), [
+        moduleDefinition,
+        moduleDefinition,
+        moduleDefinition,
+      ]);
+    });
+
+    it('should return void from init() as empty array ', () => {
+      class TestInstrumentation2 extends TestInstrumentation {
+        override init() {
+          return;
+        }
+      }
+      const instrumentation = new TestInstrumentation2();
+
+      assert.deepStrictEqual(instrumentation.getModuleDefinitions(), []);
+    });
+  });
 });