add: formalize era as an mandatory option

cli/src/commands/options.ts

@@ -57,6 +57,25 @@ function positiveBigNumberFromString(amount: any) {
     return parsedValue;
 }
 
+// Session
+export const eraOption = new Option('--era [era]', 'Specify era to distribute rewards for').argParser(parseEra);
+
+// Era parsing
+export function parseEra(value: string): number {
+    // Only positive integers are allowed
+    const parsedEra = parseInt(value, 10);
+
+    if (isNaN(parsedEra)) {
+        throw new InvalidArgumentError('Not a valid era.');
+    }
+
+    if (parsedEra < 0) {
+        throw new InvalidArgumentError('Era must be a positive integer.');
+    }
+
+    return parsedEra;
+}
+
 // I/O
 export const jsonOption = new Option('--json', 'Output as JSON');
 export const noInputOption = new Option('--no-input', 'Do not prompt for input');

cli/src/commands/staking/distribute.ts

@@ -4,13 +4,13 @@ import { initCallerKeyring } from '../../lib/account/keyring';
 import { requiredInput, parseIntegerOrExit } from '../../lib/parsing';
 import { requireEnoughFundsToSend, signSendAndWatch } from '../../lib/tx';
 import { checkEraIsInHistory } from '../../lib/staking/era';
-import { substrateAddressOption } from '../options';
+import { eraOption, substrateAddressOption } from '../options';
 
 export function makeDistributeRewardsCommand() {
     const cmd = new Command('distribute-rewards');
     cmd.description('Distribute all pending rewards for a particular validator');
     cmd.addOption(substrateAddressOption.makeOptionMandatory());
-    cmd.option('-e, --era [era]', 'Specify era to distribute rewards for');
+    cmd.addOption(eraOption.makeOptionMandatory());
     cmd.action(distributeRewardsAction);
     return cmd;
 }
@@ -43,13 +43,6 @@ async function distributeRewardsAction(options: OptionValues) {
 
 function parseOptions(options: OptionValues) {
     const validator = options.substrateAddress as string;
-
-    const era = parseIntegerOrExit(requiredInput(options.era, 'Failed to distribute rewards: Must specify an era'));
-
-    if (era < 0) {
-        console.error(`Failed to distribute rewards: Era ${era} is invalid; must be a positive integer`);
-        process.exit(1);
-    }
-
+    const era = options.era as number;
     return { validator, era };
 }