fix: get artifact and metafile paths from sls function object

Gets the paths to the metadata file and the zipped artifact from the
FunctionDefinitionHandler object exposed by the Serverless API. This
makes the plugin work correctly when e.g. the handler path is something
like `src/myFunctionHandler.main`.

Previously this was failing for me where e.g. the function name in
Serverless was 'myFunction' but the file path was
`myFunctionHandler.ts`.

plugin/bundleVisualizer.ts

@@ -1,6 +1,7 @@
 import { exec } from 'child_process';
 import { readdirSync, statSync } from 'fs';
-import { join } from 'path';
+import { join, parse } from 'path';
+import { FunctionDefinitionHandler } from 'serverless';
 
 import type { ServerlessAnalyzeBundlePlugin } from './serverlessAnalyzeBundle';
 
@@ -43,12 +44,10 @@ async function bundleVisualizer(this: ServerlessAnalyzeBundlePlugin): Promise<vo
   if (functionName === undefined) {
     return;
   }
+  const slsFunction = this.serverless.service.getFunction(functionName);
 
-  const functionZipName = this.serverless.service
-    .getAllFunctionsNames()
-    .find(fullFunctionName => fullFunctionName.endsWith(functionName));
-
-  if (functionZipName === undefined) {
+  const fullZipPath = slsFunction.package?.artifact;
+  if (fullZipPath === undefined) {
     this.serverless.cli.log(
       `🤯 Analyze failed: function ${functionName} was not found`,
       'ServerlessAnalyzeBundlePlugin',
@@ -57,6 +56,7 @@ async function bundleVisualizer(this: ServerlessAnalyzeBundlePlugin): Promise<vo
 
     return;
   }
+  const functionZipName = parse(fullZipPath).base;
 
   this.serverless.cli.log(`⏳ Analyzing function ${functionName}`, 'ServerlessAnalyzeBundlePlugin');
 
@@ -65,10 +65,22 @@ async function bundleVisualizer(this: ServerlessAnalyzeBundlePlugin): Promise<vo
 
   await pExec(`unzip .serverless/${functionZipName} -d ${TEMP_DIR_LOCATION}`);
 
-  const test = getAllFiles(`${TEMP_DIR_LOCATION}`);
-  const metafileName = test.filter(
-    fileName => fileName.includes(`/${functionName}/`) && fileName.endsWith('-meta.json'),
+  const allFiles = getAllFiles(`${TEMP_DIR_LOCATION}`);
+  const handlerPath = (slsFunction as FunctionDefinitionHandler).handler.split('.')[0];
+  const metafileName = allFiles.filter(
+    fileName => fileName.includes(handlerPath) && fileName.endsWith('-meta.json'),
   )[0];
+
+  if (!metafileName) {
+    this.serverless.cli.log(
+      `🤯 Analyze failed: function ${functionName} metadata was not found`,
+      'ServerlessAnalyzeBundlePlugin',
+      { color: 'red' },
+    );
+
+    return;
+  }
+
   await pExec(
     [
       'node_modules/.bin/esbuild-visualizer',