Cache validated checksums for later executions

The most common case for validation will be that the wrapper jars are unchanged
from a previous workflow run. In this case, we cache the validated wrapper
checksums to minimise the work required on a subsequent run.

Fixes #172

sources/src/wrapper-validation/wrapper-validator.ts

@@ -1,17 +1,33 @@
 import * as core from '@actions/core'
+
 import {WrapperValidationConfig} from '../configuration'
+import {ChecksumCache} from './cache'
 import {findInvalidWrapperJars} from './validate'
 import {JobFailure} from '../errors'
 
-export async function validateWrappers(config: WrapperValidationConfig, workspaceRoot: string): Promise<void> {
+export async function validateWrappers(
+    config: WrapperValidationConfig,
+    workspaceRoot: string,
+    gradleUserHome: string
+): Promise<void> {
     if (!config.doValidateWrappers()) {
         return // Wrapper validation is disabled
     }
+    const checksumCache = new ChecksumCache(gradleUserHome)
 
     const allowedChecksums = process.env['ALLOWED_GRADLE_WRAPPER_CHECKSUMS']?.split(',') || []
-    const result = await findInvalidWrapperJars(workspaceRoot, 0, config.allowSnapshotWrappers(), allowedChecksums)
+    const previouslyValidatedChecksums = checksumCache.load()
+
+    const result = await findInvalidWrapperJars(
+        workspaceRoot,
+        0,
+        config.allowSnapshotWrappers(),
+        allowedChecksums,
+        previouslyValidatedChecksums
+    )
     if (result.isValid()) {
         await core.group('All Gradle Wrapper jars are valid', async () => {
+            core.info(`Loaded previously validated checksums from cache: ${previouslyValidatedChecksums.join(', ')}`)
             core.info(result.toDisplayString())
         })
     } else {
@@ -20,4 +36,6 @@ export async function validateWrappers(config: WrapperValidationConfig, workspac
             `Gradle Wrapper Validation Failed!\n  See https://github.com/gradle/actions/blob/main/docs/wrapper-validation.md#reporting-failures\n${result.toDisplayString()}`
         )
     }
+
+    checksumCache.save(result.valid.map(wrapper => wrapper.checksum))
 }