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/cache.ts

@@ -0,0 +1,26 @@
+import fs from 'fs'
+import path from 'path'
+import {ACTION_METADATA_DIR} from '../configuration'
+
+export class ChecksumCache {
+    private readonly cacheFile: string
+
+    constructor(gradleUserHome: string) {
+        this.cacheFile = path.resolve(gradleUserHome, ACTION_METADATA_DIR, 'valid-wrappers.json')
+    }
+
+    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'))
+        }
+        return []
+    }
+
+    save(checksums: string[]): void {
+        const uniqueChecksums = [...new Set(checksums)]
+        // Save validated checksums to Gradle User Home
+        fs.mkdirSync(path.dirname(this.cacheFile), {recursive: true})
+        fs.writeFileSync(this.cacheFile, JSON.stringify(uniqueChecksums))
+    }
+}

sources/src/wrapper-validation/validate.ts

@@ -8,6 +8,7 @@ export async function findInvalidWrapperJars(
     minWrapperCount: number,
     allowSnapshots: boolean,
     allowedChecksums: string[],
+    previouslyValidatedChecksums: string[] = [],
     knownValidChecksums: checksums.WrapperChecksums = checksums.KNOWN_CHECKSUMS
 ): Promise<ValidationResult> {
     const wrapperJars = await find.findWrapperJars(gitRepoRoot)
@@ -21,7 +22,11 @@ export async function findInvalidWrapperJars(
         const notYetValidatedWrappers = []
         for (const wrapperJar of wrapperJars) {
             const sha = await hash.sha256File(resolve(gitRepoRoot, wrapperJar))
-            if (allowedChecksums.includes(sha) || knownValidChecksums.checksums.has(sha)) {
+            if (
+                allowedChecksums.includes(sha) ||
+                previouslyValidatedChecksums.includes(sha) ||
+                knownValidChecksums.checksums.has(sha)
+            ) {
                 result.valid.push(new WrapperJar(wrapperJar, sha))
             } else {
                 notYetValidatedWrappers.push(new WrapperJar(wrapperJar, sha))

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))
 }