mega-linter-runner: Improve check if running as script or module (#3233)

CHANGELOG.md

@@ -14,6 +14,7 @@ Note: Can be used with `oxsecurity/megalinter@beta` in your GitHub Action mega-l
   - mega-linter-runner: Remove container by default, except of `no-remove-container` option is sent
   - Upgrade base image from python:3.11.6-alpine3.18 to python:3.11.7-alpine3.18, by @echoix in [#3212](https://github.com/oxsecurity/megalinter/pull/3212)
   - Upgrade actions/upload-artifact@v3 to actions/upload-artifact@v4 in default workflows
+  - mega-linter-runner: Improve check if running as script or module, by @echoix in [#3233](https://github.com/oxsecurity/megalinter/pull/3233)
 
 - Media
 

mega-linter-runner/lib/index.js

@@ -3,11 +3,26 @@
 import { MegaLinterRunner } from "./runner.js";
 import { MegaLinterRunnerCli } from "./cli.js";
 
+import { realpathSync } from "fs";
+import { pathToFileURL } from "url";
+
 // Run only if called by script
-const runningAsScript = (this === undefined);
+// This check handles symlinks as well
+// See https://stackoverflow.com/a/71925565 and
+// https://exploringjs.com/nodejs-shell-scripting/ch_nodejs-path.html#detecting-if-module-is-main
+function wasCalledAsScript() {
+  // We use realpathSync to resolve symlinks, as cli scripts will often
+  // be executed from symlinks in the `node_modules/.bin`-folder
+  const realPath = realpathSync(process.argv[1]);
+
+  // Convert the file-path to a file-url before comparing it
+  const realPathAsUrl = pathToFileURL(realPath).href;
+
+  return import.meta.url === realPathAsUrl;
+}
 
 // Run asynchronously to use the returned status for process.exit
-if (runningAsScript) {
+if (wasCalledAsScript()) {
   (async () => {
     await new MegaLinterRunnerCli().run(process.argv);
   })();