[Typescript] Build mode of tsc: tsc -b

A long-awaited feature is smart incremental builds for TypeScript projects. In 3.0 you can use the --build flag with tsc. This is effectively a new entry point for tsc that behaves more like a build orchestrator than a simple compiler.

Running tsc --build (tsc -b for short) will do the following:

• Find all referenced projects
• Detect if they are up-to-date
• Build out-of-date projects in the correct order

You can provide tsc -b with multiple config file paths (e.g. tsc -b src test). Just like tsc -p, specifying the config file name itself is unnecessary if it’s named tsconfig.json.

> tsc -b                            # Use the tsconfig.json in the current directory
 > tsc -b src                        # Use src/tsconfig.json
 > tsc -b foo/prd.tsconfig.json bar  # Use foo/prd.tsconfig.json and bar/tsconfig.json

Don’t worry about ordering the files you pass on the commandline - tsc will re-order them if needed so that dependencies are always built first.

There are also some flags specific to tsc -b:

• --verbose: Prints out verbose logging to explain what’s going on (may be combined with any other flag)
• --dry: Shows what would be done but doesn’t actually build anything
• --clean: Deletes the outputs of the specified projects (may be combined with --dry)
• --force: Act as if all projects are out of date
• --watch: Watch mode (may not be combined with any flag except --verbose)