Tsickle - TypeScript to Closure Annotator

Tsickle processes TypeScript and adds Closure Compiler-compatible JSDoc annotations. This allows using TypeScript to transpile your sources, and then Closure Compiler to bundle and optimize them, while taking advantage of type information in Closure Compiler.

Installation

• Execute npm i to install the dependencies.

Usage

Project Setup

Tsickle works by wrapping tsc. To use it, you must set up your project such that it builds correctly when you run tsc from the command line, by configuring the settings in tsconfig.json.

If you have complicated tsc command lines and flags in a build file (like a gulpfile etc.) Tsickle won't know about it. Another reason it's nice to put everything in tsconfig.json is so your editor inherits all these settings as well.

Invocation

Run tsickle --help for the full syntax, but basically you provide any tsickle specific options and use it as a TypeScript compiler.

Differences from TypeScript

Closure and TypeScript are not identical. Tsickle hides most of the differences, but users must still be aware of some differences.

declare

Any declaration in a .d.ts file, as well as any declaration tagged with declare ..., is intepreted by Tsickle as a name that should be preserved through Closure compilation (i.e. not renamed into something shorter). Use it any time the specific string names of your fields are significant. That would most often happen when the object either coming from outside your program, or being passed out of the program.

Example:

declare interface JSONResult {
    username: string;
}
let r = JSON.parse(input) as JSONResult;
console.log(r.username);

By adding declare to the interface (or if it were in a .d.ts file), Tsickle will inform Closure that it must use exactly the field name .username (and not e.g. .a) in the output JS. This matters for this example because the input JSON probably uses the string 'username' and not whatever name Closure would invent for it. (Note: declare on an interface has no additional meaning in pure TypeScript.)

Development

Gulp tasks

• gulp watch executes the unit tests in watch mode (use gulp test.unit for a single run),
• gulp test.e2e executes the e2e tests,
• gulp test.check-format checks the source code formatting using clang-format,
• gulp test runs unit tests, e2e tests and checks the source code formatting.

Environment variables

Export the environment variable UPDATE_GOLDENS=1 to have the test suite rewrite the golden files when you run it.

Export the environment variable TEST_FILTER, a regex, to limit the end-to-end tests (found in test_files/...) run tests with a name matching the regex.