build: handle default sub command in json help output

This change is needed to handle default subcommands which are used in `ng generate` default subcommands are prefixed with `$0` or `*`.

More info: https://github.com/yargs/yargs/blob/main/docs/advanced.md#default-commands

Author: alan-agius4

packages/angular/cli/src/command-builder/utilities/json-help.ts

@@ -40,6 +40,8 @@ export interface JsonHelp extends JsonHelpDescription {
   subcommands?: JsonHelpSubcommand[];
 }
 
+const yargsDefaultCommandRegExp = /^\$0|\*/;
+
 export function jsonHelpUsage(): string {
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   const localYargs = yargs as any;
@@ -106,23 +108,26 @@ export function jsonHelpUsage(): string {
       deprecated: string | boolean,
     ][]
   )
-    .map(([name, rawDescription, _, aliases, deprecated]) => ({
-      name: name.split(' ', 1)[0],
-      command: name,
+    .map(([name, rawDescription, isDefault, aliases, deprecated]) => ({
+      name: name.split(' ', 1)[0].replace(yargsDefaultCommandRegExp, ''),
+      command: name.replace(yargsDefaultCommandRegExp, ''),
+      default: isDefault || undefined,
       ...parseDescription(rawDescription),
       aliases,
       deprecated,
     }))
     .sort((a, b) => a.name.localeCompare(b.name));
 
   const [command, rawDescription] = usageInstance.getUsage()[0] ?? [];
+  const defaultSubCommand = subcommands.find((x) => x.default)?.command ?? '';
+  const otherSubcommands = subcommands.filter((s) => !s.default);
 
   const output: JsonHelp = {
     name: [...context.commands].pop(),
-    command: command?.replace('$0', localYargs['$0']),
+    command: `${command?.replace(yargsDefaultCommandRegExp, localYargs['$0'])}${defaultSubCommand}`,
     ...parseDescription(rawDescription),
     options: normalizeOptions.sort((a, b) => a.name.localeCompare(b.name)),
-    subcommands: subcommands.length ? subcommands : undefined,
+    subcommands: otherSubcommands.length ? otherSubcommands : undefined,
   };
 
   return JSON.stringify(output, undefined, 2);

scripts/json-help.ts

@@ -7,7 +7,7 @@
  */
 
 import { logging } from '@angular-devkit/core';
-import { spawn } from 'child_process';
+import { spawn, spawnSync } from 'child_process';
 import { promises as fs } from 'fs';
 import * as os from 'os';
 import { JsonHelp } from 'packages/angular/cli/src/command-builder/utilities/json-help';
@@ -38,32 +38,18 @@ export default async function ({ temporaryProjectRoot }: JsonHelpOptions, logger
 
   await fs.mkdir(helpOutputRoot);
 
-  const runNgCommandJsonHelp = async (args: string[]) => {
-    const process = spawn(ngPath, [...args, '--json-help', '--help'], {
+  const runNgCommandJsonHelp = (args: string[]): Promise<JsonHelp> => {
+    const { stdout, status } = spawnSync(ngPath, [...args, '--json-help', '--help'], {
       cwd: newProjectRoot,
+      maxBuffer: 200_0000,
       stdio: ['ignore', 'pipe', 'inherit'],
     });
 
-    let result = '';
-    process.stdout.on('data', (data) => {
-      result += data.toString();
-    });
-
-    return new Promise<JsonHelp>((resolve, reject) => {
-      process
-        .on('close', (code) => {
-          if (code === 0) {
-            resolve(JSON.parse(result.trim()));
-          } else {
-            reject(
-              new Error(
-                `Command failed: ${ngPath} ${args.map((x) => JSON.stringify(x)).join(', ')}`,
-              ),
-            );
-          }
-        })
-        .on('error', (err) => reject(err));
-    });
+    if (status === 0) {
+      return Promise.resolve(JSON.parse(stdout.toString().trim()));
+    } else {
+      throw new Error(`Command failed: ${ngPath} ${args.map((x) => JSON.stringify(x)).join(', ')}`);
+    }
   };
 
   const { subcommands: commands = [] } = await runNgCommandJsonHelp([]);