Fixes #55 Add artifact validation which check to ensure it's not a directory

src/ArtifactPathValidator.ts

@@ -0,0 +1,43 @@
+import * as core from "@actions/core";
+import {statSync} from "fs";
+
+export class ArtifactPathValidator {
+    private readonly errorsFailBuild: boolean;
+    private paths: string[];
+    private readonly pattern: string
+    
+    constructor(errorsFailBuild: boolean, paths: string[], pattern: string) {
+        this.paths = paths;
+        this.pattern = pattern
+        this.errorsFailBuild = errorsFailBuild;
+    }
+    
+    validate(): string[] {
+        this.verifyPathsNotEmpty()
+        return this.paths.filter((path) => this.verifyNotDirectory(path))
+    }
+    
+    private verifyPathsNotEmpty() {
+        if (this.paths.length == 0) {
+            const message = `Artifact pattern:${this.pattern} did not match any files`
+            this.reportError(message)
+        }
+    }
+    
+    private verifyNotDirectory(path: string): boolean {
+        const isDir = statSync(path).isDirectory()
+        if (isDir) {
+            const message = `Artifact is a directory:${path}. Directories can not be uploaded to a release.`
+            this.reportError(message)
+        }
+        return !isDir
+    }
+    
+    private reportError(message: string) {
+        if (this.errorsFailBuild) {
+            throw Error(message)
+        } else {
+            core.warning(message)
+        }
+    }
+}