feat: Add support for $env in the js task runner (no-changelog) (#11177)

packages/workflow/src/WorkflowDataProxyEnvProvider.ts

@@ -0,0 +1,75 @@
+import { ExpressionError } from './errors/expression.error';
+
+export type EnvProviderState = {
+	isProcessAvailable: boolean;
+	isEnvAccessBlocked: boolean;
+	env: Record<string, string>;
+};
+
+/**
+ * Captures a snapshot of the environment variables and configuration
+ * that can be used to initialize an environment provider.
+ */
+export function createEnvProviderState(): EnvProviderState {
+	const isProcessAvailable = typeof process !== 'undefined';
+	const isEnvAccessBlocked = isProcessAvailable
+		? process.env.N8N_BLOCK_ENV_ACCESS_IN_NODE === 'true'
+		: false;
+	const env: Record<string, string> =
+		!isProcessAvailable || isEnvAccessBlocked ? {} : (process.env as Record<string, string>);
+
+	return {
+		isProcessAvailable,
+		isEnvAccessBlocked,
+		env,
+	};
+}
+
+/**
+ * Creates a proxy that provides access to the environment variables
+ * in the `WorkflowDataProxy`. Use the `createEnvProviderState` to
+ * create the default state object that is needed for the proxy,
+ * unless you need something specific.
+ *
+ * @example
+ * createEnvProvider(
+ *   runIndex,
+ *   itemIndex,
+ *   createEnvProviderState(),
+ * )
+ */
+export function createEnvProvider(
+	runIndex: number,
+	itemIndex: number,
+	providerState: EnvProviderState,
+): Record<string, string> {
+	return new Proxy(
+		{},
+		{
+			has() {
+				return true;
+			},
+
+			get(_, name) {
+				if (name === 'isProxy') return true;
+
+				if (!providerState.isProcessAvailable) {
+					throw new ExpressionError('not accessible via UI, please run node', {
+						runIndex,
+						itemIndex,
+					});
+				}
+				if (providerState.isEnvAccessBlocked) {
+					throw new ExpressionError('access to env vars denied', {
+						causeDetailed:
+							'If you need access please contact the administrator to remove the environment variable ‘N8N_BLOCK_ENV_ACCESS_IN_NODE‘',
+						runIndex,
+						itemIndex,
+					});
+				}
+
+				return providerState.env[name.toString()];
+			},
+		},
+	);
+}