Do not read streams more than once (#330)

index.js

@@ -4,6 +4,7 @@ const childProcess = require('child_process');
 const crossSpawn = require('cross-spawn');
 const stripFinalNewline = require('strip-final-newline');
 const npmRunPath = require('npm-run-path');
+const onetime = require('onetime');
 const makeError = require('./lib/error');
 const normalizeStdio = require('./lib/stdio');
 const {spawnedKill, spawnedCancel, setupTimeout, setExitHandler} = require('./lib/kill');
@@ -144,13 +145,15 @@ const execa = (file, args, options) => {
 		};
 	};
 
+	const handlePromiseOnce = onetime(handlePromise);
+
 	crossSpawn._enoent.hookChildProcess(spawned, parsed.parsed);
 
 	handleInput(spawned, parsed.options.input);
 
 	spawned.all = makeAllStream(spawned);
 
-	return mergePromise(spawned, handlePromise);
+	return mergePromise(spawned, handlePromiseOnce);
 };
 
 module.exports = execa;

package.json

@@ -43,6 +43,7 @@
 		"is-stream": "^2.0.0",
 		"merge-stream": "^2.0.0",
 		"npm-run-path": "^3.0.0",
+		"onetime": "^5.1.0",
 		"p-finally": "^2.0.0",
 		"signal-exit": "^3.0.2",
 		"strip-final-newline": "^2.0.0"

test/test.js

@@ -138,6 +138,12 @@ test('child_process.spawnSync() errors are propagated with a correct shape', t =
 	t.true(failed);
 });
 
+test('do not try to consume streams twice', async t => {
+	const cp = execa('noop', ['foo']);
+	t.is((await cp).stdout, 'foo');
+	t.is((await cp).stdout, 'foo');
+});
+
 test('use relative path with \'..\' chars', async t => {
 	const pathViaParentDir = path.join('..', path.basename(path.dirname(__dirname)), 'test', 'fixtures', 'noop');
 	const {stdout} = await execa(pathViaParentDir, ['foo']);