fix: propagate rejection on pipe()

closes google#640

src/core.ts

@@ -472,6 +472,11 @@ export class ProcessPromise extends Promise<ProcessOutput> {
     }
     this._piped = true
     if (dest instanceof ProcessPromise) {
+      const _reject = this._reject
+      this._reject = function (v) {
+        _reject(v)
+        dest._reject(v)
+      }
       dest.stdio('pipe')
       dest._prerun = this.run.bind(this)
       dest._postrun = () => {

test/core.test.js

@@ -324,6 +324,27 @@ describe('core', () => {
         assert.equal(stdout, 'HELLO WORLD\n')
       })
 
+      test('propagates rejection', async () => {
+        const p1 = $`exit 1`
+        const p2 = p1.pipe($`echo hello`)
+
+        try {
+          await p1
+        } catch (e) {
+          assert.equal(e.exitCode, 1)
+        }
+
+        try {
+          await p2
+        } catch (e) {
+          assert.equal(e.exitCode, 1)
+        }
+
+        const p3 = await $({ nothrow: true })`echo hello && exit 1`.pipe($`cat`)
+        assert.equal(p3.exitCode, 0)
+        assert.equal(p3.stdout.trim(), 'hello')
+      })
+
       test('accepts Writable', async () => {
         let contents = ''
         let stream = new Writable({