fix: handle endless streams piping

closes #935

src/core.ts

@@ -358,8 +358,7 @@ export class ProcessPromise extends Promise<ProcessOutput> {
       from.pipe(dest.stdin)
       return dest
     }
-
-    from.pipe(dest)
+    from.once('end', () => dest.emit('end-piped-from')).pipe(dest)
     return promisifyStream(dest)
   }
 

src/util.ts

@@ -17,6 +17,7 @@ import path from 'node:path'
 import fs from 'node:fs'
 import { chalk } from './vendor-core.js'
 import type { Writable } from 'node:stream'
+import { pipeline } from 'node:stream/promises'
 
 export { isStringLiteral } from './vendor-core.js'
 
@@ -462,6 +463,7 @@ export const promisifyStream = <S extends Writable>(
             target
               .once('error', (e) => _rej(rej(e)))
               .once('finish', () => _res(res(target)))
+              .once('end-piped-from', () => _res(res(target)))
           )
       }
       const value = Reflect.get(target, key)

test/core.test.js

@@ -427,6 +427,11 @@ describe('core', () => {
           assert.equal((await fs.readFile(file)).toString(), 'HELLO\n')
           await fs.rm(file)
         })
+
+        test('$ > stdout', async () => {
+          const p = $`echo 1`.pipe(process.stdout)
+          assert.equal(await p, process.stdout)
+        })
       })
 
       it('supports delayed piping', async () => {