move package name validation to TS part of action

src/model/input.test.ts

@@ -1,6 +1,9 @@
 import Input from './input';
+import fs from 'fs';
 
 jest.mock('./unity-version-parser');
+jest.mock('fs');
+const mockedFs = fs as jest.Mocked<typeof fs>;
 
 describe('Input', () => {
   describe('getFromUser', () => {
@@ -33,4 +36,63 @@ describe('Input', () => {
       expect(Input.isValidFolderName(folderName)).toStrictEqual(false);
     });
   });
+
+  describe('getPackageNameFromPackageJson', () => {
+    it('throws error if package.json cannot be found at the given project path', () => {
+      mockedFs.existsSync.mockReturnValue(false);
+
+      expect(() => Input.getPackageNameFromPackageJson('some/path')).toThrow(
+        'Invalid projectPath - Cannot find package.json at some/path/package.json',
+      );
+    });
+
+    it('throws error if package.json contents cannot be parsed', () => {
+      mockedFs.existsSync.mockReturnValue(true);
+      mockedFs.readFileSync.mockReturnValue(Buffer.from('DefinitelyNotJSON'));
+
+      expect(() => Input.getPackageNameFromPackageJson('some/path')).toThrow(
+        /Unable to parse package.json contents as JSON/,
+      );
+    });
+
+    it('throws error if name field in package.json is not present', () => {
+      mockedFs.existsSync.mockReturnValue(true);
+      mockedFs.readFileSync.mockReturnValue(
+        Buffer.from(JSON.stringify({ notName: 'some-package', alsoNotName: 'some-package' })),
+      );
+
+      expect(() => Input.getPackageNameFromPackageJson('some/path')).toThrow(
+        'Unable to parse package name from package.json - package name should be string, but was undefined',
+      );
+    });
+
+    it('throws error if name field in package.json is present but not a string', () => {
+      mockedFs.existsSync.mockReturnValue(true);
+      mockedFs.readFileSync.mockReturnValue(
+        Buffer.from(JSON.stringify({ name: 3, notName: 'some-package' })),
+      );
+
+      expect(() => Input.getPackageNameFromPackageJson('some/path')).toThrow(
+        'Unable to parse package name from package.json - package name should be string, but was number',
+      );
+    });
+
+    it('throws error if name field in package.json is present but empty', () => {
+      mockedFs.existsSync.mockReturnValue(true);
+      mockedFs.readFileSync.mockReturnValue(Buffer.from(JSON.stringify({ name: '', notName: 3 })));
+
+      expect(() => Input.getPackageNameFromPackageJson('some/path')).toThrow(
+        'Package name from package.json is a string, but is empty',
+      );
+    });
+
+    it('returns the name field in package.json if it is present as a non-empty string', () => {
+      mockedFs.existsSync.mockReturnValue(true);
+      mockedFs.readFileSync.mockReturnValue(
+        Buffer.from(JSON.stringify({ name: 'some-package', notName: 'not-what-we-want' })),
+      );
+
+      expect(Input.getPackageNameFromPackageJson('some/path')).toStrictEqual('some-package');
+    });
+  });
 });