Function DownloadTFProviders

testutil/terraform_cache.go:116–173

DownloadTFProviders ensures Terraform providers are downloaded and cached locally in a unique directory for the test. Uses `terraform init` then `mirror` to populate the cache if needed. Returns the cache directory path.

(t *testing.T, rootDir string, testName string, templateFiles map[string]string)

// Uses `terraform init` then `mirror` to populate the cache if needed.
// Returns the cache directory path.
func DownloadTFProviders(t *testing.T, rootDir string, testName string, templateFiles map[string]string) string {
	t.Helper()

	dir := GetTestTFCacheDir(t, rootDir, testName, templateFiles)
	if _, err := os.Stat(dir); err == nil {
		t.Logf("%s: using cached terraform providers", testName)
		return dir
	}
	filesDir := filepath.Join(dir, cacheTemplateFilesDirName)
	defer func() {
		// The files dir will contain a copy of terraform providers generated
		// by the terraform init command. We don't want to persist them since
		// we already have a registry mirror in the providers dir.
		if err := os.RemoveAll(filesDir); err != nil {
			t.Logf("failed to remove files dir %s: %s", filesDir, err)
		}
		if !t.Failed() {
			return
		}
		// If `DownloadTFProviders` function failed, clean up the cache dir.
		// We don't want to leave it around because it may be incomplete or corrupted.
		if err := os.RemoveAll(dir); err != nil {
			t.Logf("failed to remove dir %s: %s", dir, err)
		}
	}()

	require.NoError(t, os.MkdirAll(filesDir, 0o700))

	for fileName, file := range templateFiles {
		filePath := filepath.Join(filesDir, fileName)
		require.NoError(t, os.MkdirAll(filepath.Dir(filePath), 0o700))
		require.NoError(t, os.WriteFile(filePath, []byte(file), 0o600))
	}

	providersDir := filepath.Join(dir, cacheProvidersDirName)
	require.NoError(t, os.MkdirAll(providersDir, 0o700))

	// We need to run init because if a test uses modules in its template,
	// the mirror command will fail without it.
	runCmd(t, filesDir, "terraform", "init")
	// Now, mirror the providers into `providersDir`. We use this explicit mirror
	// instead of relying only on the standard Terraform plugin cache.
	//
	// Why? Because this mirror, when used with the CLI config from `WriteCliConfig`,
	// prevents Terraform from hitting the network registry during `plan`. This cuts
	// down on network calls, making CI tests less flaky.
	//
	// In contrast, the standard cache *still* contacts the registry for metadata
	// during `init`, even if the plugins are already cached locally - see link below.
	//
	// Ref: https://developer.hashicorp.com/terraform/cli/config/config-file#provider-plugin-cache
	// > When a plugin cache directory is enabled, the terraform init command will
	// > still use the configured or implied installation methods to obtain metadata
	// > about which plugins are available
	runCmd(t, filesDir, "terraform", "providers", "mirror", providersDir)

	return dir
}