[Tooling]: tsc watch

[pranshuchittora]

As a developer, I use to make a lot of mistakes. As on now for every change, we need to build the package, this becomes quite frustrating.
Pls correct me if I am wrong.

Expected Behavior 🤔

Instantly build the changes, using tsc watch mode.

Current Behavior 😯

Huge development cycle.

Try this

diff --git a/packages/material-ui/package.json b/packages/material-ui/package.json
index 69c76bf..4064d98 100644
--- a/packages/material-ui/package.json
+++ b/packages/material-ui/package.json
@@ -30,7 +30,8 @@
     "prebuild": "rimraf build",
     "release": "yarn build && npm publish build --tag latest",
     "test": "cd ../../ && cross-env NODE_ENV=test mocha 'packages/material-ui/**/*.test.js' --exclude '**/node_modules/**'",
-    "typescript": "tslint -p tsconfig.json \"{src,test}/**/*.{ts,tsx}\" && tsc -p tsconfig.test.json"
+    "typescript": "tslint -p tsconfig.json \"{src,test}/**/*.{ts,tsx}\" && tsc -p tsconfig.test.json",
+    "watch": "npm run build && tsc -w"
   },
   "peerDependencies": {
     "react": "^16.8.0",

https://www.typescriptlang.org/docs/handbook/configuring-watch.html

[pranshuchittora]

Every time I run build the build directory gets deleted, hence the linking breaks.

Failed to compile.

../material-ui/packages/material-ui/build/esm/SvgIcon/index.js
Error: ENOENT: no such file or directory, open '/home/wasd/github/material-ui/packages/material-ui/build/esm/SvgIcon/index.js'

[merceyz]

We don't use tsc to build anything so what you'd want is to add --watch to any of the build scripts
https://babeljs.io/docs/en/babel-cli#compile-files

If you just want typechecking then you can use
tsc -p tsconfig.test.json -w

[eps1lon]

yarn workspace @material-ui/core typescript -w would incidentally already work. This script doesn't do what you think it does though. If you want to build the esm build in watchmode you can run yarn workspace @material-ui/core build:esm --watch.

For build --watch see #15497