Add cache-mode option to control cache usage

README.md

@@ -68,6 +68,12 @@ Currently, the following distributions are supported:
 ### Caching packages dependencies
 The action has a built-in functionality for caching and restoring dependencies. It uses [actions/cache](https://github.com/actions/cache) under hood for caching dependencies but requires less configuration settings. Supported package managers are gradle and maven. The cache input is optional, and caching is turned off by default.
 
+The interaction with the cache can be controlled by the `cache-mode` parameter. This allows for builds to
+be performed with no cache, and the output cached (`write` mode), builds to read the cache before running
+but not update the cache afterwards (`read` mode), or both (`both` mode). This feature allows you to
+populate the cache from your `main` branch, and then let PR builds benefit from that cache without polluting
+it with PR-specific build artifacts.
+
 #### Caching gradle dependencies
 ```yaml
 steps:

action.yml

@@ -56,6 +56,9 @@ inputs:
   cache:
     description: 'Name of the build platform to cache dependencies. It can be "maven" or "gradle".'
     required: false
+  cache-mode:
+    description: 'Whether the cache should be read from pre-build, written to afterwards, or both'
+    default: both
   job-status:
     description: 'Workaround to pass job status to post job step. This variable is not intended for manual setting'
     default: ${{ job.status }}

src/cleanup-java.ts

@@ -23,7 +23,9 @@ async function removePrivateKeyFromKeychain() {
 async function saveCache() {
   const jobStatus = isJobStatusSuccess();
   const cache = core.getInput(constants.INPUT_CACHE);
-  return jobStatus && cache ? save(cache) : Promise.resolve();
+  const cacheMode = core.getInput(constants.INPUT_CACHE_MODE)
+  const updateCache = Boolean(cacheMode === "both" || cacheMode === "write")
+  return jobStatus && cache && updateCache ? save(cache) : Promise.resolve();
 }
 
 /**

src/constants.ts

@@ -17,6 +17,7 @@ export const INPUT_DEFAULT_GPG_PRIVATE_KEY = undefined;
 export const INPUT_DEFAULT_GPG_PASSPHRASE = 'GPG_PASSPHRASE';
 
 export const INPUT_CACHE = 'cache';
+export const INPUT_CACHE_MODE = "cache-mode";
 export const INPUT_JOB_STATUS = 'job-status';
 
 export const STATE_GPG_PRIVATE_KEY_FINGERPRINT = 'gpg-private-key-fingerprint';

src/setup-java.ts

@@ -42,7 +42,9 @@ async function run() {
     core.info(`##[add-matcher]${path.join(matchersPath, 'java.json')}`);
 
     await auth.configureAuthentication();
-    if (cache) {
+    const cacheMode = core.getInput(constants.INPUT_CACHE_MODE)
+    const restoreCache = Boolean(cacheMode === "both" || cacheMode === "read")
+    if (cache && restoreCache) {
       await restore(cache);
     }
   } catch (error) {