Prefix padding

bin/concurrently.spec.ts

@@ -305,6 +305,15 @@ describe('specifies custom prefix length', () => {
     });
 });
 
+describe('--pad-prefix', () => {
+    it('pads prefixes with spaces', async () => {
+        const lines = await run('--pad-prefix -n foo,barbaz "echo foo" "echo bar"').getLogLines();
+
+        expect(lines).toContainEqual(expect.stringContaining('[foo   ]'));
+        expect(lines).toContainEqual(expect.stringContaining('[barbaz]'));
+    });
+});
+
 describe('--restart-tries', () => {
     it('changes how many times a command will restart', async () => {
         const lines = await run('--restart-tries 1 "exit 1"').getLogLines();

bin/concurrently.ts

@@ -149,6 +149,10 @@ const args = yargs(argsBeforeSep)
             default: defaults.prefixLength,
             type: 'number',
         },
+        'pad-prefix': {
+            describe: 'Pads short prefixes with spaces so that the length of all prefixes match',
+            type: 'boolean',
+        },
         'timestamp-format': {
             alias: 't',
             describe: 'Specify the timestamp in moment/date-fns format.',
@@ -190,7 +194,7 @@ const args = yargs(argsBeforeSep)
         ['m', 'n', 'name-separator', 's', 'r', 'no-color', 'hide', 'g', 'timings', 'P'],
         'General',
     )
-    .group(['p', 'c', 'l', 't'], 'Prefix styling')
+    .group(['p', 'c', 'l', 't', 'pad-prefix'], 'Prefix styling')
     .group(['i', 'default-input-target'], 'Input handling')
     .group(['k', 'kill-others-on-fail', 'kill-signal'], 'Killing other processes')
     .group(['restart-tries', 'restart-after'], 'Restarting')
@@ -223,6 +227,7 @@ concurrently(
         prefix: args.prefix,
         prefixColors: args.prefixColors.split(','),
         prefixLength: args.prefixLength,
+        padPrefix: args.padPrefix,
         restartDelay:
             args.restartAfter === 'exponential' ? 'exponential' : Number(args.restartAfter),
         restartTries: args.restartTries,

src/flow-control/logger-padding.spec.ts

@@ -0,0 +1,67 @@
+import createMockInstance from 'jest-create-mock-instance';
+
+import { FakeCommand } from '../fixtures/fake-command';
+import { Logger } from '../logger';
+import { LoggerPadding } from './logger-padding';
+
+let logger: jest.Mocked<Logger>;
+let controller: LoggerPadding;
+let commands: FakeCommand[];
+
+beforeEach(() => {
+    commands = [new FakeCommand(), new FakeCommand()];
+    logger = createMockInstance(Logger);
+    controller = new LoggerPadding({ logger });
+});
+
+it('returns same commands', () => {
+    expect(controller.handle(commands)).toMatchObject({ commands });
+});
+
+it('sets the prefix length on handle', () => {
+    controller.handle(commands);
+    expect(logger.setPrefixLength).toHaveBeenCalledTimes(1);
+});
+
+it('updates the prefix length when commands emit a start timer', () => {
+    controller.handle(commands);
+    commands[0].timer.next({ startDate: new Date() });
+    expect(logger.setPrefixLength).toHaveBeenCalledTimes(2);
+
+    commands[1].timer.next({ startDate: new Date() });
+    expect(logger.setPrefixLength).toHaveBeenCalledTimes(3);
+});
+
+it('sets prefix length to the longest prefix of all commands', () => {
+    logger.getPrefixContent
+        .mockReturnValueOnce({ type: 'default', value: 'foobar' })
+        .mockReturnValueOnce({ type: 'default', value: 'baz' });
+
+    controller.handle(commands);
+    expect(logger.setPrefixLength).toHaveBeenCalledWith(6);
+});
+
+it('does not shorten the prefix length', () => {
+    logger.getPrefixContent
+        .mockReturnValueOnce({ type: 'default', value: '100' })
+        .mockReturnValueOnce({ type: 'default', value: '1' });
+
+    controller.handle(commands);
+    commands[0].timer.next({ startDate: new Date() });
+    expect(logger.setPrefixLength).toHaveBeenCalledWith(3);
+
+    commands[0].timer.next({ startDate: new Date() });
+    expect(logger.setPrefixLength).toHaveBeenCalledWith(3);
+});
+
+it('unsubscribes from start timers on finish', () => {
+    logger.getPrefixContent.mockReturnValue({ type: 'default', value: '1' });
+
+    const { onFinish } = controller.handle(commands);
+    commands[0].timer.next({ startDate: new Date() });
+    expect(logger.setPrefixLength).toHaveBeenCalledTimes(2);
+
+    onFinish();
+    commands[0].timer.next({ startDate: new Date() });
+    expect(logger.setPrefixLength).toHaveBeenCalledTimes(2);
+});

src/flow-control/logger-padding.ts

@@ -0,0 +1,41 @@
+import { Command } from '../command';
+import { Logger } from '../logger';
+import { FlowController } from './flow-controller';
+
+export class LoggerPadding implements FlowController {
+    private readonly logger: Logger;
+
+    constructor({ logger }: { logger: Logger }) {
+        this.logger = logger;
+    }
+
+    handle(commands: Command[]): { commands: Command[]; onFinish: () => void } {
+        // Sometimes there's limited concurrency, so not all commands will spawn straight away.
+        // Compute the prefix length now, which works for all styles but those with a PID.
+        let length = commands.reduce((length, command) => {
+            const content = this.logger.getPrefixContent(command);
+            return Math.max(length, content?.value.length || 0);
+        }, 0);
+        this.logger.setPrefixLength(length);
+
+        // The length of prefixes is somewhat stable, except for PIDs, which might change when a
+        // process spawns (e.g. PIDs might look like 1, 10 or 100), therefore listen to command starts
+        // and update the prefix length when this happens.
+        const subs = commands.map((command) =>
+            command.timer.subscribe((event) => {
+                if (!event.endDate) {
+                    const content = this.logger.getPrefixContent(command);
+                    length = Math.max(length, content?.value.length || 0);
+                    this.logger.setPrefixLength(length);
+                }
+            }),
+        );
+
+        return {
+            commands,
+            onFinish() {
+                subs.forEach((sub) => sub.unsubscribe());
+            },
+        };
+    }
+}

src/index.ts

@@ -16,6 +16,7 @@ import { LogError } from './flow-control/log-error';
 import { LogExit } from './flow-control/log-exit';
 import { LogOutput } from './flow-control/log-output';
 import { LogTimings } from './flow-control/log-timings';
+import { LoggerPadding } from './flow-control/logger-padding';
 import { RestartDelay, RestartProcess } from './flow-control/restart-process';
 import { Logger } from './logger';
 
@@ -37,6 +38,11 @@ export type ConcurrentlyOptions = Omit<BaseConcurrentlyOptions, 'abortSignal' |
      */
     prefixLength?: number;
 
+    /**
+     * Pads short prefixes with spaces so that all prefixes have the same length.
+     */
+    padPrefix?: boolean;
+
     /**
      * Whether output should be formatted to include prefixes and whether "event" logs will be logged.
      */
@@ -103,7 +109,7 @@ export function concurrently(
     const logger = new Logger({
         hide,
         prefixFormat: options.prefix,
-        prefixLength: options.prefixLength,
+        commandLength: options.prefixLength,
         raw: options.raw,
         timestampFormat: options.timestampFormat,
     });
@@ -121,6 +127,8 @@ export function concurrently(
         group: options.group,
         abortSignal: abortController.signal,
         controllers: [
+            // LoggerPadding needs to run before any other controllers that might output something
+            ...(options.padPrefix ? [new LoggerPadding({ logger })] : []),
             new LogError({ logger }),
             new LogOutput({ logger }),
             new LogExit({ logger }),

src/logger.spec.ts

@@ -158,14 +158,32 @@ describe('#logCommandText()', () => {
         expect(logger.log).toHaveBeenCalledWith(chalk.reset('[echo foo]') + ' ', 'foo', cmd);
     });
 
-    it('logs prefix using command line itself, capped at prefixLength bytes', () => {
-        const { logger } = createLogger({ prefixFormat: 'command', prefixLength: 6 });
+    it('logs prefix using command line itself, capped at commandLength bytes', () => {
+        const { logger } = createLogger({ prefixFormat: 'command', commandLength: 6 });
         const cmd = new FakeCommand();
         logger.logCommandText('foo', cmd);
 
         expect(logger.log).toHaveBeenCalledWith(chalk.reset('[ec..oo]') + ' ', 'foo', cmd);
     });
 
+    it('logs default prefixes with padding', () => {
+        const { logger } = createLogger({});
+        const cmd = new FakeCommand('foo');
+        logger.setPrefixLength(5);
+        logger.logCommandText('bar', cmd);
+
+        expect(logger.log).toHaveBeenCalledWith(chalk.reset('[foo  ]') + ' ', 'bar', cmd);
+    });
+
+    it('logs templated prefixes with padding', () => {
+        const { logger } = createLogger({ prefixFormat: '{name}-{index}' });
+        const cmd = new FakeCommand('foo', undefined, 0);
+        logger.setPrefixLength(6);
+        logger.logCommandText('bar', cmd);
+
+        expect(logger.log).toHaveBeenCalledWith(chalk.reset('foo-0 ') + ' ', 'bar', cmd);
+    });
+
     it('logs prefix using prefixColor from command', () => {
         const { logger } = createLogger({});
         const cmd = new FakeCommand('', undefined, 1, {

src/logger.ts

@@ -10,9 +10,15 @@ export class Logger {
     private readonly hide: CommandIdentifier[];
     private readonly raw: boolean;
     private readonly prefixFormat?: string;
-    private readonly prefixLength: number;
+    private readonly commandLength: number;
     private readonly timestampFormat: string;
 
+    /**
+     * How many characters should a prefix have.
+     * Prefixes shorter than this will be padded with spaces to the right.
+     */
+    private prefixLength = 0;
+
     /**
      * Last character emitted.
      * If `undefined`, then nothing has been logged yet.
@@ -28,7 +34,7 @@ export class Logger {
     constructor({
         hide,
         prefixFormat,
-        prefixLength,
+        commandLength,
         raw = false,
         timestampFormat,
     }: {
@@ -50,9 +56,9 @@ export class Logger {
         prefixFormat?: string;
 
         /**
-         * How many characters should a prefix have at most, used when the prefix format is `command`.
+         * How many characters should a prefix have at most when the format is `command`.
          */
-        prefixLength?: number;
+        commandLength?: number;
 
         /**
          * Date format used when logging date/time.
@@ -63,17 +69,17 @@ export class Logger {
         this.hide = (hide || []).map(String);
         this.raw = raw;
         this.prefixFormat = prefixFormat;
-        this.prefixLength = prefixLength || defaults.prefixLength;
+        this.commandLength = commandLength || defaults.prefixLength;
         this.timestampFormat = timestampFormat || defaults.timestampFormat;
     }
 
     private shortenText(text: string) {
-        if (!text || text.length <= this.prefixLength) {
+        if (!text || text.length <= this.commandLength) {
             return text;
         }
 
         const ellipsis = '..';
-        const prefixLength = this.prefixLength - ellipsis.length;
+        const prefixLength = this.commandLength - ellipsis.length;
         const endLength = Math.floor(prefixLength / 2);
         const beginningLength = prefixLength - endLength;
 
@@ -84,33 +90,53 @@ export class Logger {
 
     private getPrefixesFor(command: Command): Record<string, string> {
         return {
-            pid: String(command.pid),
+            // When there's limited concurrency, the PID might not be immediately available,
+            // so avoid the string 'undefined' from becoming a prefix
+            pid: command.pid != null ? String(command.pid) : '',
             index: String(command.index),
             name: command.name,
             command: this.shortenText(command.command),
             time: formatDate(Date.now(), this.timestampFormat),
         };
     }
 
-    getPrefix(command: Command) {
+    getPrefixContent(
+        command: Command,
+    ): { type: 'default' | 'template'; value: string } | undefined {
         const prefix = this.prefixFormat || (command.name ? 'name' : 'index');
         if (prefix === 'none') {
-            return '';
+            return;
         }
 
         const prefixes = this.getPrefixesFor(command);
         if (Object.keys(prefixes).includes(prefix)) {
-            return `[${prefixes[prefix]}]`;
+            return { type: 'default', value: prefixes[prefix] };
         }
 
-        return _.reduce(
+        const value = _.reduce(
             prefixes,
             (prev, val, key) => {
                 const keyRegex = new RegExp(_.escapeRegExp(`{${key}}`), 'g');
                 return prev.replace(keyRegex, String(val));
             },
             prefix,
         );
+        return { type: 'template', value };
+    }
+
+    getPrefix(command: Command): string {
+        const content = this.getPrefixContent(command);
+        if (!content) {
+            return '';
+        }
+
+        return content.type === 'template'
+            ? content.value.padEnd(this.prefixLength, ' ')
+            : `[${content.value.padEnd(this.prefixLength, ' ')}]`;
+    }
+
+    setPrefixLength(length: number) {
+        this.prefixLength = length;
     }
 
     colorText(command: Command, text: string) {