isProgramUptoDate wrongfully returns true

[yacinehmito]

TypeScript Version: On master (commit d6c05a135840dc3045ec8f3bbec1da5ffabb6593)

Search Terms: isProgramUptoDate, synchronize program update program.

Code

I was playing around with the TypeScript API and I noticed that if you update the root files of a watcher program with the same number of root files, the source files are not updated.

import * as ts from 'typescript';

const watchHost = ts.createWatchCompilerHost(['path/to/foo']);
const program = ts.createWatchProgram(watchHost);
console.log(const program.getProgram().getSourceFiles()); // <- This has the expected sources
program.updateRootFileNames(['/path/to/bar']);
console.log(const program.getProgram().getSourceFiles()); // <- This has the same source, but it shouldn't

Expected behavior:

The source files should be the expected ones (so include /path/to/bar).

Actual behavior:

The source files didn't change.

Playground Link: Can't reproduce in the playground as it's an API bug.

Related Issues: Didn't find any related issues.

---

This is the culprit:

TypeScript/src/compiler/program.ts

Line 575 in 3b396e6

if (program.getRootFileNames().length !== rootFileNames.length) {

It should check for array equality, not just array length. I'll make a PR real soon.