mirror of
https://github.com/swc-project/swc.git
synced 2024-12-01 01:13:56 +03:00
154 lines
3.9 KiB
Markdown
154 lines
3.9 KiB
Markdown
# SWC architecture
|
|
|
|
This document gives a high level overview of SWC internals. You may find it useful if you want to contribute to SWC or if you are interested in the inner workings of SWC.
|
|
|
|
## Macros
|
|
|
|
<!-- TODO: fix link -->
|
|
<!-- See [blog post about SWC macros](https://swc.rs/blog/2020/01/04/pmutil#macros-built-with-pmutil). -->
|
|
|
|
SWC uses proc macro extensively to reduce work. Please see links below to know what each macro do.
|
|
|
|
- [enum_kind][]
|
|
- [string_enum][]
|
|
- [ast_node][]
|
|
|
|
And some adhoc-macros are used.
|
|
|
|
- [parser_macros][]
|
|
- [codegen_macros][]
|
|
|
|
These macro breaks macro hygiene.
|
|
|
|
## Structure
|
|
|
|
### [`/crates/swc_atoms`](crates/swc_atoms)
|
|
|
|
Handle string interning for the SWC project. The crate depends on [hstr](https://github.com/dudykr/ddbase).
|
|
|
|
### [`/crates/swc_common`](crates/swc_common)
|
|
|
|
Contains code related to span, hygiene and error reporting.
|
|
|
|
Also, it contains / re-exports codes for visitor pattern. `Visit<T>` is non-mutating visitor, while `Fold<T>` is a mutating visitor.
|
|
|
|
### [`/crates/swc_ecma_ast`](crates/swc_ecma_ast)
|
|
|
|
Contains AST nodes for javascript and typescript.
|
|
|
|
### [`/crates/swc_ecma_codegen`](crates/swc_ecma_codegen)
|
|
|
|
Converts javascript AST into javascript code.
|
|
|
|
### [`/crates/swc_ecma_parser`](crates/swc_ecma_parser)
|
|
|
|
Parses javascript and typescript
|
|
|
|
### [`/crates/swc_ecma_transforms_base`](crates/swc_ecma_transforms_base)
|
|
|
|
There are three core transforms named `resolver`, `hygiene`, `fixer`. Other transforms depend on them.
|
|
|
|
#### [`/crates/swc_ecma_transforms_base/src/resolver`](crates/swc_ecma_transforms_base/src/resolver)
|
|
|
|
This pass resolves and marks all identifiers in the file.
|
|
|
|
e.g.
|
|
|
|
```js
|
|
let a = 1;
|
|
{
|
|
let a = 1;
|
|
}
|
|
```
|
|
|
|
becomes
|
|
|
|
```js
|
|
let a#0 = 1;
|
|
{
|
|
let a#1 = 1;
|
|
}
|
|
```
|
|
|
|
where the number after the hash (`#`) denotes the hygiene id. If two identifiers have the same symbol but different hygiene ids, they are considered different.
|
|
|
|
#### [`/crates/swc_ecma_transforms_base/src/hygiene`](crates/swc_ecma_transforms_base/src/hygiene)
|
|
|
|
The hygiene pass actually changes symbols of identifiers with the same symbol but different hygiene ids to different symbols.
|
|
|
|
```js
|
|
let a#0 = 1;
|
|
{
|
|
let a#1 = 2;
|
|
}
|
|
```
|
|
|
|
becomes
|
|
|
|
```js
|
|
let a = 1;
|
|
{
|
|
let a1 = 2;
|
|
}
|
|
```
|
|
|
|
#### [`/crates/swc_ecma_transforms_base/src/fixer`](crates/swc_ecma_transforms_base/src/fixer)
|
|
|
|
Fixes broken AST. This allow us to simply fold types like `BinExpr` without caring about operator precedence.
|
|
|
|
It means,
|
|
|
|
```rust
|
|
let v = BinExpr {
|
|
left: "1 + 2",
|
|
op: "*",
|
|
right: "3",
|
|
};
|
|
```
|
|
|
|
(other passes generate AST like this)
|
|
|
|
is converted into
|
|
|
|
```rust
|
|
let v = BinExpr {
|
|
left: "(1 + 2)",
|
|
op: "*",
|
|
right: "3",
|
|
};
|
|
```
|
|
|
|
and printed as
|
|
|
|
```js
|
|
(1 + 2) * 3;
|
|
```
|
|
|
|
<!-- TODO: add correct references to files -->
|
|
<!-- #### `/ecmascript/transforms/src/compat`
|
|
|
|
Contains code related to converting new generation javascript code into code understood by old browsers.
|
|
|
|
#### `/ecmascript/transforms/src/modules`
|
|
|
|
Contains code related to transforming es6 modules to other modules.
|
|
|
|
#### `/ecmascript/transforms/src/optimization`
|
|
|
|
Contains code related to making code faster on runtime. Currently only a small set of optimizations is implemented. -->
|
|
|
|
## Tests
|
|
|
|
SWC uses the [official ecmascript conformance test suite called test262][test262] for testing.
|
|
|
|
Parser tests ensure that the parsed results of `test262/pass` are identical with `test262/pass-explicit`.
|
|
|
|
Codegen tests ensure that the generated code is equivalent to the golden fixture files located at [tests/references](crates/swc_ecma_codegen/tests).
|
|
|
|
[enum_kind]: https://rustdoc.swc.rs/enum_kind/derive.Kind.html
|
|
[string_enum]: https://rustdoc.swc.rs/string_enum/derive.StringEnum.html
|
|
[ast_node]: https://rustdoc.swc.rs/ast_node/index.html
|
|
[parser_macros]: https://rustdoc.swc.rs/swc_ecma_parser_macros/index.html
|
|
[codegen_macros]: https://rustdoc.swc.rs/swc_ecma_codegen_macros/index.html
|
|
[test262]: https://github.com/tc39/test262
|