feat(core): add watch command

docs/generated/cli/watch.md

@@ -0,0 +1,74 @@
+---
+title: 'watch - CLI command'
+description: 'Watch for changes within projects, and execute commands'
+---
+
+# watch
+
+Watch for changes within projects, and execute commands
+
+## Usage
+
+```terminal
+nx watch
+```
+
+Install `nx` globally to invoke the command directly using `nx`, or use `npx nx`, `yarn nx`, or `pnpm nx`.
+
+### Examples
+
+Watch the "app" project and echo the project name and the files that changed:
+
+```terminal
+ nx watch --projects=app -- echo \$NX_PROJECT_NAME \$NX_FILE_CHANGES
+```
+
+Watch "app1" and "app2" and echo the project name whenever a specified project or its dependencies change:
+
+```terminal
+ nx watch --projects=app1,app2 --includeDependencies -- echo \$NX_PROJECT_NAME
+```
+
+Watch all projects (including newly created projects) in the workspace:
+
+```terminal
+ nx watch --all -- echo \$NX_PROJECT_NAME
+```
+
+## Options
+
+### all
+
+Type: `boolean`
+
+Watch all projects.
+
+### help
+
+Type: `boolean`
+
+Show help
+
+### includeDependentProjects
+
+Type: `boolean`
+
+When watching selected projects, include dependent projects as well.
+
+### projects
+
+Type: `string`
+
+Projects to watch (comma delimited).
+
+### verbose
+
+Type: `boolean`
+
+Run watch mode in verbose mode, where commands are logged before execution.
+
+### version
+
+Type: `boolean`
+
+Show version number

docs/generated/packages/nx.json

@@ -154,6 +154,13 @@
       "id": "exec",
       "file": "generated/cli/exec",
       "content": "---\ntitle: 'exec - CLI command'\ndescription: 'Executes any command as if it was a target on the project'\n---\n\n# exec\n\nExecutes any command as if it was a target on the project\n\n## Usage\n\n```terminal\nnx exec\n```\n\nInstall `nx` globally to invoke the command directly using `nx`, or use `npx nx`, `yarn nx`, or `pnpm nx`.\n\n## Options\n\n### configuration\n\nType: `string`\n\nThis is the configuration to use when performing tasks on projects\n\n### exclude\n\nType: `array`\n\nDefault: `[]`\n\nExclude certain projects from being processed\n\n### nx-bail\n\nType: `boolean`\n\nDefault: `false`\n\nStop command execution after the first failed task\n\n### nx-ignore-cycles\n\nType: `boolean`\n\nDefault: `false`\n\nIgnore cycles in the task graph\n\n### output-style\n\nType: `string`\n\nChoices: [dynamic, static, stream, stream-without-prefixes, compact]\n\nDefines how Nx emits outputs tasks logs\n\n### parallel\n\nType: `string`\n\nMax number of parallel processes [default is 3]\n\n### project\n\nType: `string`\n\nTarget project\n\n### runner\n\nType: `string`\n\nThis is the name of the tasks runner configured in nx.json\n\n### skip-nx-cache\n\nType: `boolean`\n\nDefault: `false`\n\nRerun the tasks even when the results are available in the cache\n\n### target\n\nType: `string`\n\nTask to run for affected projects\n\n### verbose\n\nType: `boolean`\n\nDefault: `false`\n\nPrints additional information about the commands (e.g., stack traces)\n\n### version\n\nType: `boolean`\n\nShow version number\n"
+    },
+    {
+      "name": "watch",
+      "id": "watch",
+      "tags": ["workspace-watching"],
+      "file": "generated/cli/watch",
+      "content": "---\ntitle: 'watch - CLI command'\ndescription: 'Watch for changes within projects, and execute commands'\n---\n\n# watch\n\nWatch for changes within projects, and execute commands\n\n## Usage\n\n```terminal\nnx watch\n```\n\nInstall `nx` globally to invoke the command directly using `nx`, or use `npx nx`, `yarn nx`, or `pnpm nx`.\n\n### Examples\n\nWatch the \"app\" project and echo the project name and the files that changed:\n\n```terminal\n nx watch --projects=app -- echo \\$NX_PROJECT_NAME \\$NX_FILE_CHANGES\n```\n\nWatch \"app1\" and \"app2\" and echo the project name whenever a specified project or its dependencies change:\n\n```terminal\n nx watch --projects=app1,app2 --includeDependencies -- echo \\$NX_PROJECT_NAME\n```\n\nWatch all projects (including newly created projects) in the workspace:\n\n```terminal\n nx watch --all -- echo \\$NX_PROJECT_NAME\n```\n\n## Options\n\n### all\n\nType: `boolean`\n\nWatch all projects.\n\n### help\n\nType: `boolean`\n\nShow help\n\n### includeDependentProjects\n\nType: `boolean`\n\nWhen watching selected projects, include dependent projects as well.\n\n### projects\n\nType: `string`\n\nProjects to watch (comma delimited).\n\n### verbose\n\nType: `boolean`\n\nRun watch mode in verbose mode, where commands are logged before execution.\n\n### version\n\nType: `boolean`\n\nShow version number\n"
     }
   ],
   "generators": [],

docs/map.json

@@ -1373,6 +1373,12 @@
               "name": "exec",
               "id": "exec",
               "file": "generated/cli/exec"
+            },
+            {
+              "name": "watch",
+              "id": "watch",
+              "tags": ["workspace-watching"],
+              "file": "generated/cli/watch"
             }
           ]
         },

e2e/nx-misc/src/watch.test.ts

@@ -0,0 +1,152 @@
+import {
+  cleanupProject,
+  createFile,
+  newProject,
+  runCLI,
+  uniq,
+  getPackageManagerCommand,
+  tmpProjPath,
+  getStrippedEnvironmentVariables,
+  updateJson,
+  isVerbose,
+} from '@nrwl/e2e/utils';
+import { exec, spawn } from 'child_process';
+
+describe('Nx Commands', () => {
+  let proj1 = uniq('proj1');
+  let proj2 = uniq('proj2');
+  let proj3 = uniq('proj3');
+  beforeAll(() => {
+    newProject({ packageManager: 'npm' });
+    runCLI(`generate @nrwl/workspace:lib ${proj1}`);
+    runCLI(`generate @nrwl/workspace:lib ${proj2}`);
+    runCLI(`generate @nrwl/workspace:lib ${proj3}`);
+  });
+
+  afterAll(() => cleanupProject());
+
+  it('should watch for project changes', async () => {
+    const getOutput = await runWatch(
+      `--projects=${proj1} -- echo \\$NX_PROJECT_NAME`
+    );
+    createFile(`libs/${proj1}/newfile.txt`, 'content');
+    createFile(`libs/${proj2}/newfile.txt`, 'content');
+    createFile(`libs/${proj1}/newfile2.txt`, 'content');
+    createFile(`libs/${proj3}/newfile2.txt`, 'content');
+    createFile(`newfile2.txt`, 'content');
+
+    expect(await getOutput()).toEqual([proj1]);
+  });
+
+  it('should watch for all projects and output the project name', async () => {
+    const getOutput = await runWatch(`--all -- echo \\$NX_PROJECT_NAME`);
+    createFile(`libs/${proj1}/newfile.txt`, 'content');
+    createFile(`libs/${proj2}/newfile.txt`, 'content');
+    createFile(`libs/${proj1}/newfile2.txt`, 'content');
+    createFile(`libs/${proj3}/newfile2.txt`, 'content');
+    createFile(`newfile2.txt`, 'content');
+
+    expect(await getOutput()).toEqual([proj1, proj2, proj3]);
+  });
+
+  it('should watch for all project changes and output the file name changes', async () => {
+    const getOutput = await runWatch(`--all -- echo \\$NX_FILE_CHANGES`);
+    createFile(`libs/${proj1}/newfile.txt`, 'content');
+    createFile(`libs/${proj2}/newfile.txt`, 'content');
+    createFile(`libs/${proj1}/newfile2.txt`, 'content');
+    createFile(`newfile2.txt`, 'content');
+
+    expect(await getOutput()).toEqual([
+      `libs/${proj1}/newfile.txt libs/${proj1}/newfile2.txt libs/${proj2}/newfile.txt`,
+    ]);
+  });
+
+  it('should watch for global workspace file changes', async () => {
+    const getOutput = await runWatch(
+      `--all --includeGlobalWorkspaceFiles -- echo \\$NX_FILE_CHANGES`
+    );
+    createFile(`libs/${proj1}/newfile.txt`, 'content');
+    createFile(`libs/${proj2}/newfile.txt`, 'content');
+    createFile(`libs/${proj1}/newfile2.txt`, 'content');
+    createFile(`newfile2.txt`, 'content');
+
+    expect(await getOutput()).toEqual([
+      `libs/${proj1}/newfile.txt libs/${proj1}/newfile2.txt libs/${proj2}/newfile.txt newfile2.txt`,
+    ]);
+  });
+
+  it('should watch selected projects only', async () => {
+    const getOutput = await runWatch(
+      `--projects=${proj1},${proj3} -- echo \\$NX_PROJECT_NAME`
+    );
+    createFile(`libs/${proj1}/newfile.txt`, 'content');
+    createFile(`libs/${proj2}/newfile.txt`, 'content');
+    createFile(`libs/${proj1}/newfile2.txt`, 'content');
+    createFile(`libs/${proj3}/newfile2.txt`, 'content');
+    createFile(`newfile2.txt`, 'content');
+
+    expect(await getOutput()).toEqual([proj1, proj3]);
+  });
+
+  it('should watch projects including their dependencies', async () => {
+    updateJson(`libs/${proj3}/project.json`, (json) => {
+      json.implicitDependencies = [proj1];
+      return json;
+    });
+
+    const getOutput = await runWatch(
+      `--projects=${proj3} --includeDependentProjects -- echo \\$NX_PROJECT_NAME`
+    );
+    createFile(`libs/${proj1}/newfile.txt`, 'content');
+    createFile(`libs/${proj2}/newfile.txt`, 'content');
+    createFile(`libs/${proj1}/newfile2.txt`, 'content');
+    createFile(`libs/${proj3}/newfile2.txt`, 'content');
+    createFile(`newfile2.txt`, 'content');
+
+    expect(await getOutput()).toEqual([proj3, proj1]);
+  });
+});
+
+async function wait(timeout = 200) {
+  return new Promise<void>((res) => {
+    setTimeout(() => {
+      res();
+    }, timeout);
+  });
+}
+
+async function runWatch(command: string) {
+  const output = [];
+  const pm = getPackageManagerCommand();
+  const runCommand = `npx -c 'nx watch --verbose ${command}'`;
+  isVerbose() && console.log(runCommand);
+  return new Promise<(timeout?: number) => Promise<string[]>>((resolve) => {
+    const p = spawn(runCommand, {
+      cwd: tmpProjPath(),
+      env: {
+        CI: 'true',
+        ...getStrippedEnvironmentVariables(),
+        FORCE_COLOR: 'false',
+      },
+      shell: true,
+      stdio: 'pipe',
+    });
+
+    p.stdout?.on('data', (data) => {
+      const s = data.toString().trim();
+      isVerbose() && console.log(s);
+      if (s.includes('watch process waiting')) {
+        resolve(async (timeout = 6000) => {
+          await wait(timeout);
+          p.kill();
+          return output;
+        });
+      } else {
+        if (s.length == 0 || s.includes('NX')) {
+          return;
+        }
+        output.push(s);
+      }
+    });
+  });
+}

e2e/utils/index.ts

@@ -80,7 +80,7 @@ export const e2eRoot = isCI
   ? dirSync({ prefix: 'nx-e2e-' }).name
   : '/tmp/nx-e2e';
 
-function isVerbose() {
+export function isVerbose() {
   return (
     process.env.NX_VERBOSE_LOGGING === 'true' ||
     process.argv.includes('--verbose')
@@ -1012,7 +1012,7 @@ export async function expectJestTestsToPass(
   expect(results.combinedOutput).toContain('Test Suites: 1 passed, 1 total');
 }
 
-function getStrippedEnvironmentVariables() {
+export function getStrippedEnvironmentVariables() {
   const strippedVariables = new Set(['NX_TASK_TARGET_PROJECT']);
   return Object.fromEntries(
     Object.entries(process.env).filter(

packages/nx/src/command-line/examples.ts

@@ -340,4 +340,23 @@ export const examples: Record<string, Example[]> = {
         'Create a dedicated commit for each successfully completed migration. You can customize the prefix used for each commit by additionally setting --commit-prefix="PREFIX_HERE "',
     },
   ],
+  watch: [
+    {
+      command:
+        'watch --projects=app -- echo \\$NX_PROJECT_NAME \\$NX_FILE_CHANGES',
+      description:
+        'Watch the "app" project and echo the project name and the files that changed',
+    },
+    {
+      command:
+        'watch --projects=app1,app2 --includeDependencies -- echo \\$NX_PROJECT_NAME',
+      description:
+        'Watch "app1" and "app2" and echo the project name whenever a specified project or its dependencies change',
+    },
+    {
+      command: 'watch --all -- echo \\$NX_PROJECT_NAME',
+      description:
+        'Watch all projects (including newly created projects) in the workspace',
+    },
+  ],
 };

packages/nx/src/command-line/nx-commands.ts

@@ -7,6 +7,7 @@ import { examples } from './examples';
 import { workspaceRoot } from '../utils/workspace-root';
 import { getPackageManagerCommand } from '../utils/package-manager';
 import { writeJsonFile } from '../utils/fileutils';
+import { WatchArguments } from './watch';
 
 // Ensure that the output takes up the available width of the terminal.
 yargs.wrap(yargs.terminalWidth());
@@ -381,6 +382,15 @@ export const commandsObject = yargs
       process.exit(0);
     },
   })
+  .command({
+    command: 'watch',
+    describe: 'Watch for changes within projects, and execute commands',
+    builder: (yargs) =>
+      linkToNxDevAndExamples(withWatchOptions(yargs), 'watch'),
+    handler: async (args) => {
+      await import('./watch').then((m) => m.watch(args as WatchArguments));
+    },
+  })
   .help()
   .version(nxVersion);
 
@@ -927,6 +937,61 @@ function withMigrationOptions(yargs: yargs.Argv) {
     });
 }
 
+function withWatchOptions(yargs: yargs.Argv) {
+  return yargs
+    .parserConfiguration({
+      'strip-dashed': true,
+      'populate--': true,
+    })
+    .option('projects', {
+      type: 'array',
+      string: true,
+      coerce: parseCSV,
+      description: 'Projects to watch (comma delimited).',
+    })
+    .option('all', {
+      type: 'boolean',
+      description: 'Watch all projects.',
+    })
+    .option('includeDependentProjects', {
+      type: 'boolean',
+      description:
+        'When watching selected projects, include dependent projects as well.',
+      alias: 'd',
+    })
+    .option('includeGlobalWorkspaceFiles', {
+      type: 'boolean',
+      description:
+        'Include global workspace files that are not part of a project. For example, the root eslint, or tsconfig file.',
+      alias: 'g',
+      hidden: true,
+    })
+    .option('command', { type: 'string', hidden: true })
+    .option('verbose', {
+      type: 'boolean',
+      description:
+        'Run watch mode in verbose mode, where commands are logged before execution.',
+    })
+    .conflicts({
+      all: 'projects',
+    })
+    .check((args) => {
+      if (!args.all && !args.projects) {
+        throw Error('Please specify either --all or --projects');
+      }
+
+      return true;
+    })
+    .middleware((args) => {
+      const { '--': doubledash } = args;
+      if (doubledash && Array.isArray(doubledash)) {
+        args.command = (doubledash as string[]).join(' ');
+      } else {
+        throw Error('No command specified for watch mode.');
+      }
+    }, true);
+}
+
 function parseCSV(args: string[]) {
   if (!args) {
     return args;