Handle gracefully parse errors in checksum file (#737)

fixes #727 

Note: The `package-lock.json` file modifications (results of `npm audit
fix`) are not related to the fix

sources/src/wrapper-validation/cache.ts

@@ -1,6 +1,7 @@
 import fs from 'fs'
 import path from 'path'
 import {ACTION_METADATA_DIR} from '../configuration'
+import * as core from '@actions/core'
 
 export class ChecksumCache {
     private readonly cacheFile: string
@@ -12,7 +13,11 @@ export class ChecksumCache {
     load(): string[] {
         // Load previously validated checksums saved in Gradle User Home
         if (fs.existsSync(this.cacheFile)) {
-            return JSON.parse(fs.readFileSync(this.cacheFile, 'utf-8'))
+            try {
+                return JSON.parse(fs.readFileSync(this.cacheFile, 'utf-8'))
+            } catch (e) {
+                core.warning(`Failed to parse checksum cache file: ${e}`)
+            }
         }
         return []
     }

sources/test/jest/wrapper-validation/validate.test.ts

@@ -4,6 +4,7 @@ import * as validate from '../../../src/wrapper-validation/validate'
 import {expect, test, jest} from '@jest/globals'
 import { WrapperChecksums, KNOWN_CHECKSUMS } from '../../../src/wrapper-validation/checksums'
 import { ChecksumCache } from '../../../src/wrapper-validation/cache'
+import { ACTION_METADATA_DIR } from '../../../src/configuration'
 
 jest.setTimeout(30000)
 
@@ -128,3 +129,14 @@ test('can save and load checksums', async () => {
   expect(checksumCache.load()).toEqual(['123', '456'])
   expect(fs.existsSync(cacheDir)).toBe(true)
 })
+
+test('can load empty checksum file', async () => {
+    const cacheDir = path.join(tmpDir, 'empty-wrapper-validation-cache')
+    const metadataDir = path.join(cacheDir, ACTION_METADATA_DIR)
+    const emptyChecksumFile = path.join(metadataDir, 'valid-wrappers.json')
+    fs.mkdirSync(metadataDir, { recursive: true });
+    fs.writeFileSync(emptyChecksumFile, '')
+    const checksumCache = new ChecksumCache(cacheDir)
+
+    expect(checksumCache.load()).toEqual([])
+})