chore: align with suggested implementation

Author: dreamorosi

docs/core/metrics.md

@@ -66,12 +66,12 @@ The library requires two settings. You can set them as environment variables, or
 
 These settings will be used across all metrics emitted:
 
-| Setting              | Description                                                      | Environment variable               | Default           | Allowed Values | Example             | Constructor parameter |
-|----------------------|------------------------------------------------------------------|------------------------------------|-------------------|----------------|---------------------|-----------------------|
-| **Service**          | Optionally, sets **service** metric dimension across all metrics | `POWERTOOLS_SERVICE_NAME`          | `service_undefined` | Any string     | `serverlessAirline` | `serviceName`         |
-| **Metric namespace** | Logical container where all metrics will be placed               | `POWERTOOLS_METRICS_NAMESPACE`     | `default_namespace` | Any string     | `serverlessAirline` | `default_namespace`   |
-| **Function Name**    | Function name used as dimension for the `ColdStart` metric       | `POWERTOOLS_METRICS_FUNCTION_NAME` | [See docs](#capturing-a-cold-start-invocation-as-metric)         | Any string     | `my-function-name`  | `functionName`         |
-| **Enabled**          | Whether to emit metrics to standard output or not                | `POWERTOOLS_METRICS_ENABLED`       | `true`            | Boolean        | `false`             |                       |
+| Setting              | Description                                                      | Environment variable               | Default                                                  | Allowed Values | Example             | Constructor parameter |
+|----------------------|------------------------------------------------------------------|------------------------------------|----------------------------------------------------------|----------------|---------------------|-----------------------|
+| **Service**          | Optionally, sets **service** metric dimension across all metrics | `POWERTOOLS_SERVICE_NAME`          | `service_undefined`                                      | Any string     | `serverlessAirline` | `serviceName`         |
+| **Metric namespace** | Logical container where all metrics will be placed               | `POWERTOOLS_METRICS_NAMESPACE`     | `default_namespace`                                      | Any string     | `serverlessAirline` | `default_namespace`   |
+| **Function Name**    | Function name used as dimension for the `ColdStart` metric       | `POWERTOOLS_METRICS_FUNCTION_NAME` | [See docs](#capturing-a-cold-start-invocation-as-metric) | Any string     | `my-function-name`  | `functionName`        |
+| **Enabled**          | Whether to emit metrics to standard output or not                | `POWERTOOLS_METRICS_ENABLED`       | `true`                                                   | Boolean        | `false`             |                       |
 
 !!! tip
     Use your application name or main service as the metric namespace to easily group all metrics
@@ -425,7 +425,7 @@ The priority of the `function_name` dimension value is defined as:
 
 === "captureColdStartMetric method"
 
-    ```typescript hl_lines="8"
+    ```typescript hl_lines="12"
     --8<-- "examples/snippets/metrics/captureColdStartMetric.ts"
     ```
 

examples/snippets/metrics/captureColdStartMetric.ts

@@ -9,7 +9,6 @@ export const handler = async (
   _event: unknown,
   _context: unknown
 ): Promise<void> => {
-  // Capture cold start metric
   metrics.captureColdStartMetric('my-function-name');
 
   metrics.addMetric('successfulBooking', MetricUnit.Count, 1);

examples/snippets/metrics/functionName.ts

@@ -10,7 +10,6 @@ export const handler = async (
   _event: unknown,
   _context: unknown
 ): Promise<void> => {
-  // Capture cold start metric
   metrics.captureColdStartMetric();
 
   metrics.addMetric('successfulBooking', MetricUnit.Count, 1);

packages/metrics/src/Metrics.ts

@@ -29,7 +29,6 @@ import type {
   MetricsOptions,
   StoredMetrics,
 } from './types/index.js';
-import { getFirstDefinedValue } from './utils';
 
 /**
  * The Metrics utility creates custom metrics asynchronously by logging metrics to standard output following {@link https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch_Embedded_Metric_Format.html | Amazon CloudWatch Embedded Metric Format (EMF)}.
@@ -384,12 +383,11 @@ class Metrics extends Utility implements MetricsInterface {
         service: this.defaultDimensions.service,
       });
     }
-    const coldStartFunctionName = getFirstDefinedValue(
-      this.functionName,
-      functionName
-    );
-    if (coldStartFunctionName) {
-      singleMetric.addDimension('function_name', coldStartFunctionName);
+    for (const value of [this.functionName, functionName]) {
+      if (value && value.trim().length > 0) {
+        singleMetric.addDimension('function_name', value);
+        break;
+      }
     }
     singleMetric.addMetric(COLD_START_METRIC, MetricUnits.Count, 1);
   }
@@ -919,10 +917,12 @@ class Metrics extends Utility implements MetricsInterface {
   protected setFunctionNameForColdStartMetric(functionName?: string): void {
     const constructorFunctionName = functionName;
     const envFunctionName = this.getEnvVarsService().getFunctionName();
-    this.functionName = getFirstDefinedValue(
-      constructorFunctionName,
-      envFunctionName
-    );
+    for (const value of [constructorFunctionName, envFunctionName]) {
+      if (value && value.trim().length > 0) {
+        this.functionName = value;
+        break;
+      }
+    }
   }
 
   /**

packages/metrics/src/config/EnvironmentVariablesService.ts

@@ -13,7 +13,6 @@ class EnvironmentVariablesService
 {
   private readonly namespaceVariable = 'POWERTOOLS_METRICS_NAMESPACE';
   private readonly functionNameVariable = 'POWERTOOLS_METRICS_FUNCTION_NAME';
-
   private readonly disabledVariable = 'POWERTOOLS_METRICS_DISABLED';
 
   /**

packages/metrics/src/types/Metrics.ts

@@ -463,7 +463,7 @@ interface MetricsInterface {
    * @deprecated Override the function name for `ColdStart` metrics inferred from the context either via:
    * - `functionName` constructor parameter
    * - `POWERTOOLS_FUNCTION_NAME` environment variable
-   * - {@link Metrics.captureColdStartMetric | `captureColdStartMetric('myFunctionName')`} method
+   * - {@link MetricsInterface.captureColdStartMetric | `captureColdStartMetric()`} method
    */
   setFunctionName(name: string): void;
   /**