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.
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.
Tsickle is designed to do whatever is necessary to make the code acceptable by Closure compiler. We view its output as a necessary intermediate form for communicating to the Closure compiler, and not something for humans. This means the tsickle output may be kind of ugly to read. Its only real use is to pass it on to the compiler.
For one example, the syntax of types tsickle produces are specific to Closure.
The type {!Foo} means "Foo, excluding null" and a type alias becomes a var
statement that is tagged with @typedef.
Tsickle emits modules using Closure's goog.module module system. This system
is similar to but different from ES modules, and was supported by Closure before
the ES module system was finalized.
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 { ... }
We use bazel to build, and are pinned to an old version
of it in package.json. So unless you have that specific version of bazel installed,
you should run run yarn bazel instead of bazel in any of the below commands.
Run bazel run @nodejs//:yarn --script_path=yarn_install.sh && ./yarn_install.sh
to install the dependencies.
This avoids occupying the
bazelserver, so thatyarncan callbazelagain. Ideally we should just usebazel-run.sh @nodejs//:yarn, see https://stackoverflow.com/questions/47082298/how-can-users-get-bazel-run-sh
ibazel test test:unit_testexecutes the unit tests in watch mode (usebazel test test:unit_testfor a single run),bazel test test:e2e_testexecutes the e2e tests,bazel test test:golden_testexecutes the golden tests,node check-format.jschecks the source code formatting usingclang-format,yarn testruns unit tests, e2e tests and checks the source code formatting.
You can debug tests by using bazel run and passing --node_options=--inspect. For example, to
debug a specific golden test:
TEST_FILTER=my_golden_test ibazel run //test:golden_test -- --node_options=--inspectThen open [about:inspect] in Chrome and choose "about:inspect". Chrome will launch a debugging
session on any node process that starts with a debugger listening on one of the listed ports. The
tsickle tests and Chrome both default to localhost:9229, so things should work out of the box.
VS Code can also connect using the inspect protocol. It doesn't support automatically reconnecting
or any way to re-run the test suite though, so it is a less convenient. You can start the node
process passing an extra --node_options=--debug-brk (in addition to the parameters above) to have
Node wait before program execution, so you have time to attach VS Code.
Run UPDATE_GOLDENS=y bazel run test:golden_test to have the test suite update
the goldens in test_files/....
Pass the flag --action_env=TEST_FILTER=<REGEX> to bazel test to limit the
end-to-end test (found in test_files/...) run tests with a name matching the
regex.
On a new branch, run
# tsickle releases are all minor releases for now, see npm help version.
$ npm version minor
This will update the version in package.json, commit the changes, and
create a git tag.
Push the branch and get it reviewed, but do not merge. If you click the "rebase and merge" button in the Github UI it changes the commit, so the git tag that was created would point at the wrong commit.
Instead, push the branch to master directly via:
$ git push origin mybranch:master
Note that Github will block non-fast-forward pushes to master, so if there have been other intervening commits you'll need to recreate the release.
Also push the tag.
$ git push origin v0.32.0 # but use correct version
Once the versioned tag is pushed to Github the release (as found on https://github.com/angular/tsickle/releases) will be implicitly created.
Run bazel run :npm_package.publish from the master branch
(you must be logged into the angular shared npm account).