fix(core): running just 'nx' should show help (#26871)

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## Current Behavior
Running `nx` errors

## Expected Behavior
`nx` show's help

## Related Issue(s)
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merged. -->

Fixes #

e2e/nx/src/misc.test.ts

@@ -334,6 +334,12 @@ describe('Nx Commands', () => {
       }
     }, 300000);
   });
+
+  it('should show help if no command provided', () => {
+    const output = runCLI('', { silenceError: true });
+    expect(output).toContain('Smart Monorepos · Fast CI');
+    expect(output).toContain('Commands:');
+  });
 });
 
 // TODO(colum): Change the fetcher to allow incremental migrations over multiple versions, allowing for beforeAll

packages/nx/src/command-line/run/command-object.ts

@@ -1,4 +1,4 @@
-import { CommandModule } from 'yargs';
+import { CommandModule, showHelp } from 'yargs';
 import {
   withBatch,
   withOverrides,
@@ -40,6 +40,11 @@ export const yargsNxInfixCommand: CommandModule = {
     const exitCode = await handleErrors(
       (args.verbose as boolean) ?? process.env.NX_VERBOSE_LOGGING === 'true',
       async () => {
+        // Yargs parses <target> as 'undefined' if running just 'nx'
+        if (!args.target || args.target === 'undefined') {
+          showHelp();
+          process.exit(1);
+        }
         return (await import('./run-one')).runOne(
           process.cwd(),
           withOverrides(args, 0)