Tsickle converts TypeScript code into a form acceptable to the Closure Compiler. This allows using TypeScript to transpile your sources, and then using Closure Compiler to bundle and optimize them, while taking advantage of type information in Closure Compiler.
A (non-exhaustive) list of the sorts of transformations Tsickle applies:
- inserts Closure-compatible JSDoc annotations on functions/classes/etc
- converts ES6 modules into
goog.modulemodules - generates externs.js from TypeScript d.ts (and
declare, see below) - declares types for class member variables
- translates
export * from ...into a form Closure accepts - converts TypeScript enums into a form Closure accepts
- reprocesses all jsdoc to strip Closure-invalid tags
In general the goal is that you write valid TypeScript and Tsickle handles making it valid Closure Compiler code.
We already use tsickle within Google to minify our apps (including those using Angular), but we have less experience using tsickle with the various JavaScript builds that are seen outside of Google.
We would like to make tsickle usable for everyone but right now if you'd like to try it you should expect to spend some time debugging and reporting bugs.
- Execute
npm ito install the dependencies.
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.
Run tsickle --help for the full syntax, but basically you provide any tsickle
specific options and use it as a TypeScript compiler.
Closure and TypeScript are not identical. Tsickle hides most of the differences, but users must still be aware of some differences.
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.)
An exporting decorator is a decorator that has @ExportDecoratedItems in its
JSDoc.
The names of elements that have an exporting decorator are preserved through
the Closure compilation process by applying an @export tag to them.
Example:
/** @ExportDecoratedItems */
function myDecorator() {
// ...
}
@myDecorator()
class DoNotRenameThisClass { ... }
gulp watchexecutes the unit tests in watch mode (usegulp test.unitfor a single run),gulp test.e2eexecutes the e2e tests,guld test.goldenexecutes the golden tests,gulp test.check-formatchecks the source code formatting usingclang-format,gulp testruns unit tests, e2e tests and checks the source code formatting.
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.