stream: lazy read ReadStream

mmomtchev · danielleadams · commit cb0b53edb190 · 2021-01-12T07:10:56.000-05:00
Using stream._construct would cause the Readable to incorrectly greedily start reading. Fixes: #36251 PR-URL: #36823 Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
diff --git a/lib/internal/streams/readable.js b/lib/internal/streams/readable.js
@@ -203,7 +203,9 @@ function Readable(options) {
   Stream.call(this, options);
 
   destroyImpl.construct(this, () => {
-    maybeReadMore(this, this._readableState);
+    if (this._readableState.needReadable) {
+      maybeReadMore(this, this._readableState);
+    }
   });
 }
 
diff --git a/test/parallel/test-stdin-from-file-spawn.js b/test/parallel/test-stdin-from-file-spawn.js
@@ -0,0 +1,42 @@
+'use strict';
+const common = require('../common');
+const process = require('process');
+
+let defaultShell;
+if (process.platform === 'linux' || process.platform === 'darwin') {
+  defaultShell = '/bin/sh';
+} else if (process.platform === 'win32') {
+  defaultShell = 'cmd.exe';
+} else {
+  common.skip('This is test exists only on Linux/Win32/OSX');
+}
+
+const { execSync } = require('child_process');
+const fs = require('fs');
+const path = require('path');
+const tmpdir = require('../common/tmpdir');
+
+const tmpDir = tmpdir.path;
+tmpdir.refresh();
+const tmpCmdFile = path.join(tmpDir, 'test-stdin-from-file-spawn-cmd');
+const tmpJsFile = path.join(tmpDir, 'test-stdin-from-file-spawn.js');
+fs.writeFileSync(tmpCmdFile, 'echo hello');
+fs.writeFileSync(tmpJsFile, `
+'use strict';
+const { spawn } = require('child_process');
+// Reference the object to invoke the getter
+process.stdin;
+setTimeout(() => {
+  let ok = false;
+  const child = spawn(process.env.SHELL || '${defaultShell}',
+    [], { stdio: ['inherit', 'pipe'] });
+  child.stdout.on('data', () => {
+    ok = true;
+  });
+  child.on('close', () => {
+    process.exit(ok ? 0 : -1);
+  });
+}, 100);
+`);
+
+execSync(`${process.argv[0]} ${tmpJsFile} < ${tmpCmdFile}`);
diff --git a/test/parallel/test-stream-construct.js b/test/parallel/test-stream-construct.js
@@ -268,3 +268,13 @@ testDestroy((opts) => new Writable({
     assert.strictEqual(constructed, true);
   }));
 }
+
+{
+  // Construct should not cause stream to read.
+  new Readable({
+    construct: common.mustCall((callback) => {
+      callback();
+    }),
+    read: common.mustNotCall()
+  });
+}

Original file line number	Diff line number	Diff line change
`@@ -203,7 +203,9 @@ function Readable(options) {`
`203`	`203`	`Stream.call(this, options);`
`204`	`204`
`205`	`205`	`destroyImpl.construct(this, () => {`
`206`		`- maybeReadMore(this, this._readableState);`
	`206`	`+ if (this._readableState.needReadable) {`
	`207`	`+ maybeReadMore(this, this._readableState);`
	`208`	`+ }`
`207`	`209`	`});`
`208`	`210`	`}`
`209`	`211`