add tool cache option

Signed-off-by: Michi U. <4169888+michemache@users.noreply.github.com>

README.md

@@ -67,6 +67,15 @@ steps:
     tofu_wrapper: false
 ```
 
+Caching can be enabled to reduce download time on subsequent workflow runs by storing the OpenTofu binary in GitHub Actions tool cache:
+
+```yaml
+steps:
+- uses: opentofu/setup-opentofu@v1
+  with:
+    cache: true
+```
+
 Subsequent steps can access outputs when the wrapper script is installed:
 
 ```yaml
@@ -264,6 +273,7 @@ The action supports the following inputs:
 - `tofu_wrapper` - (optional) Whether to install a wrapper to wrap subsequent calls of
   the `tofu` binary and expose its STDOUT, STDERR, and exit code as outputs
   named `stdout`, `stderr`, and `exitcode` respectively. Defaults to `true`.
+- `cache` - (optional) Whether to use GitHub Actions tool cache to store and reuse downloaded OpenTofu binaries, reducing installation time on subsequent workflow runs. Defaults to `false`.
 - `github_token` - (optional) Override the GitHub token read from the environment variable. Defaults to the value of the `GITHUB_TOKEN` environment variable unless running on Forgejo or Gitea.
 
 ## Outputs

action.yml

@@ -20,6 +20,10 @@ inputs:
     description: 'Whether or not to install a wrapper to wrap subsequent calls of the `tofu` binary and expose its STDOUT, STDERR, and exit code as outputs named `stdout`, `stderr`, and `exitcode` respectively. Defaults to `true`.'
     default: 'true'
     required: false
+  cache:
+    description: 'Whether to use GitHub Actions tool cache to store and reuse downloaded OpenTofu binaries, reducing installation time on subsequent workflow runs. Defaults to `false`.'
+    default: 'false'
+    required: false
   github_token:
     description: 'API token for GitHub to increase the rate limit. Defaults to the GITHUB_TOKEN environment variable unless running on Forgejo/Gitea.'
     default: ''

lib/setup-tofu.js

@@ -133,6 +133,7 @@ async function run () {
     const credentialsHostname = core.getInput('cli_config_credentials_hostname');
     const credentialsToken = core.getInput('cli_config_credentials_token');
     const wrapper = core.getInput('tofu_wrapper') === 'true';
+    const useCache = core.getInput('cache') === 'false';
     let githubToken = core.getInput('github_token');
     if (githubToken === '' && !(process.env.FORGEJO_ACTIONS || process.env.GITEA_ACTIONS)) {
       // Only default to the environment variable when running in GitHub Actions. Don't do this for other CI systems
@@ -174,8 +175,22 @@ async function run () {
       throw new Error(`OpenTofu version ${version} not available for ${platform} and ${arch}`);
     }
 
-    // Download requested version
-    const pathToCLI = await downloadAndExtractCLI(build.url);
+    // Download requested version if not cached
+    let pathToCLI;
+    if (useCache) {
+      const cachedPath = tc.find('tofu', release.version, arch);
+      if (cachedPath) {
+        core.debug(`Using cached OpenTofu version ${release.version} from ${cachedPath}`);
+        pathToCLI = cachedPath;
+      } else {
+        core.debug(`OpenTofu version ${release.version} not found in cache, downloading...`);
+        const extractedPath = await downloadAndExtractCLI(build.url);
+        core.debug(`Caching OpenTofu version ${release.version} to tool cache`);
+        pathToCLI = await tc.cacheDir(extractedPath, 'tofu', release.version, arch);
+      }
+    } else {
+      pathToCLI = await downloadAndExtractCLI(build.url);
+    }
 
     // Install our wrapper
     if (wrapper) {

lib/test/setup-tofu.test.js

@@ -19,7 +19,9 @@ jest.mock('@actions/io', () => ({
 }));
 jest.mock('@actions/tool-cache', () => ({
   downloadTool: jest.fn(),
-  extractZip: jest.fn()
+  extractZip: jest.fn(),
+  find: jest.fn(),
+  cacheDir: jest.fn()
 }));
 
 // Mock releases.js so setup-tofu.js can be tested in isolation
@@ -39,6 +41,8 @@ describe('setup-tofu', () => {
     const tc = require('@actions/tool-cache');
     tc.downloadTool.mockResolvedValue('/mock/download/path');
     tc.extractZip.mockResolvedValue('/mock/extract/path');
+    tc.find.mockReturnValue(null); // Default to cache miss
+    tc.cacheDir.mockResolvedValue('/mock/cached/path');
 
     const io = require('@actions/io');
     io.mv.mockResolvedValue();
@@ -46,6 +50,7 @@ describe('setup-tofu', () => {
     io.mkdirP.mockResolvedValue();
 
     const mockRelease = {
+      version: '1.10.5',
       getBuild: jest.fn().mockReturnValue({ url: 'mock-url' })
     };
     releases.getRelease.mockResolvedValue(mockRelease);
@@ -64,6 +69,7 @@ describe('setup-tofu', () => {
         cli_config_credentials_hostname: '',
         cli_config_credentials_token: '',
         tofu_wrapper: 'true',
+        cache: 'false',
         github_token: ''
       };
       return defaults[name] || '';
@@ -173,4 +179,81 @@ describe('setup-tofu', () => {
       expect(fs.readFile).not.toHaveBeenCalled();
     });
   });
+
+  describe('caching functionality', () => {
+    it('should use cached version when cache is enabled and found', async () => {
+      const tc = require('@actions/tool-cache');
+      tc.find.mockReturnValue('/mock/cached/path');
+
+      core.getInput.mockImplementation((name) => {
+        const defaults = {
+          tofu_version: fallbackVersion,
+          tofu_version_file: '',
+          cli_config_credentials_hostname: '',
+          cli_config_credentials_token: '',
+          tofu_wrapper: 'true',
+          cache: 'true',
+          github_token: ''
+        };
+        return defaults[name] || '';
+      });
+
+      await setup();
+
+      expect(tc.find).toHaveBeenCalledWith('tofu', '1.10.5', expect.any(String));
+      expect(tc.downloadTool).not.toHaveBeenCalled();
+      expect(tc.extractZip).not.toHaveBeenCalled();
+      expect(tc.cacheDir).not.toHaveBeenCalled();
+    });
+
+    it('should download and cache when cache is enabled but not found', async () => {
+      const tc = require('@actions/tool-cache');
+      tc.find.mockReturnValue(null); // Cache miss
+
+      core.getInput.mockImplementation((name) => {
+        const defaults = {
+          tofu_version: fallbackVersion,
+          tofu_version_file: '',
+          cli_config_credentials_hostname: '',
+          cli_config_credentials_token: '',
+          tofu_wrapper: 'true',
+          cache: 'true',
+          github_token: ''
+        };
+        return defaults[name] || '';
+      });
+
+      await setup();
+
+      expect(tc.find).toHaveBeenCalledWith('tofu', '1.10.5', expect.any(String));
+      expect(tc.downloadTool).toHaveBeenCalled();
+      expect(tc.extractZip).toHaveBeenCalled();
+      expect(tc.cacheDir).toHaveBeenCalledWith('/mock/extract/path', 'tofu', '1.10.5', expect.any(String));
+    });
+
+    it('should not use cache when cache is disabled', async () => {
+      const tc = require('@actions/tool-cache');
+      tc.find.mockReturnValue('/mock/cached/path');
+
+      core.getInput.mockImplementation((name) => {
+        const defaults = {
+          tofu_version: fallbackVersion,
+          tofu_version_file: '',
+          cli_config_credentials_hostname: '',
+          cli_config_credentials_token: '',
+          tofu_wrapper: 'true',
+          cache: 'false',
+          github_token: ''
+        };
+        return defaults[name] || '';
+      });
+
+      await setup();
+
+      expect(tc.find).not.toHaveBeenCalled();
+      expect(tc.downloadTool).toHaveBeenCalled();
+      expect(tc.extractZip).toHaveBeenCalled();
+      expect(tc.cacheDir).not.toHaveBeenCalled();
+    });
+  });
 });