Awesome
SWC-coverage-instrument
swc-coverage-instrument
is a set of packages to support istanbuljs compatible coverage instrumentation in SWC's transform passes. Instrumentation transform can be performed either via SWC's wasm-based plugin, or using custom passes in rust side transform chains.
What does compatible exactly means?
This instrumentation will generate a data struct mimics istanbuljs's FileCoverage
object conforms fixture test suite from istanbuljs itself.
However, this doesn't mean instrumentation supports exact same interfaces surrounding coverage object as well as supporting exact same options. There are some fundamental differences between runtime, and ast visitor architecture between different compilers does not allow identical behavior. This package will try best attempt
as possible.
NOTE: Package can have breaking changes without major semver bump
Given SWC's plugin interface itself is under experimental stage does not gaurantee semver-based major bump yet, this package also does not gaurantee semver compliant breaking changes yet. Please refer changelogs if you're encountering unexpected breaking behavior across versions.
Usage
Using SWC's wasm-based experimental plugin
First, install package via npm:
npm install --save-dev swc-plugin-coverage-instrument
Then add plugin into swc's configuration:
const pluginOptions: InstrumentationOptions = {...}
jsc: {
...
experimental: {
plugins: [
["swc-plugin-coverage-instrument", pluginOptions]
]
}
}
InstrumentationOptions
is a subset of istanbul's instrumentation options. Refer istanbul's option for the same configuration flags. However there are few exceptions or differences, referencing InstrumentOptions will list all possible options.
interface InstrumentationOptions {
coverageVariable?: String,
compact?: bool,
reportLogic?: bool,
ignoreClassMethods?: Array<String>,
inputSourceMap?: object,
instrumentLog: {
// Currently there aren't logs other than spans.
// Enabling >= info can display span traces.
level: 'trace' | 'warn' | 'error' | 'info'
// Emits spans along with any logs
// Only effective if level sets higher than info.
enableTrace: bool
},
unstableExclude?: Array<String>
}
Using custom transform pass in rust
There is a single interface exposed to create a visitor for the transform, which you can pass into before_custom_pass
.
let visitor = swc_coverage_instrument::create_coverage_instrumentation_visitor(
source_map: std::sync::Arc<SourceMapper>,
comments: C,
instrument_options: InstrumentOptions,
filename: String,
);
let fold = as_folder(visitor);
Building / Testing
This package runs istanbuljs' fixture tests against SWC with its wasm plugin & custom transform both. spec
contains set of the fixtures & unit test to run it, as well as supplimental packages to interop between instrumentation visitor to node.js runtime. swc-coverage-instrument-wasm
exposes FileCoverageInterop
allows to consume FileCoverage
struct inside of js, and swc-coverage-custom-transform
is an example implementation to run before_custom_pass
with swc-coverage-instrument
visitor.
Few npm scripts are supported for wrapping those setups.
build:all
: Build all relative packages as debug build.test
: Runs unit test for wasm plugin & custom transform.test:debug
: Runs unit test, but only fordebug-test.yaml
fixture. This is mainly for local dev debugging for individual test fixture behavior.