112: brush up docs r=matklad a=matklad

@kjeremy @aochagavia @DJMcNab anything else significant to add here?

Co-authored-by: Aleksey Kladov <aleksey.kladov@gmail.com>
This commit is contained in:
bors[bot] 2018-10-14 22:15:25 +00:00
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# Architecture
This document describes high-level architecture of rust-analyzer.
If you want to familiarize yourself with the code base, you are just
in the right place!
## Code generation
Some of the components of this repository are generated through automatic
processes. These are outlined below:
- `gen-kinds`: The kinds of tokens are reused in several places, so a generator
is used. We use tera templates to generate the files listed below, based on
the grammar described in [grammar.ron]:
- [ast/generated.rs][ast generated] in `ra_syntax` based on
[ast/generated.tera.rs][ast source]
- [syntax_kinds/generated.rs][syntax_kinds generated] in `ra_syntax` based on
[syntax_kinds/generated.tera.rs][syntax_kinds source]
[tera]: https://tera.netlify.com/
[grammar.ron]: ./crates/ra_syntax/src/grammar.ron
[ast generated]: ./crates/ra_syntax/src/ast/generated.rs
[ast source]: ./crates/ra_syntax/src/ast/generated.rs.tera
[syntax_kinds generated]: ./crates/ra_syntax/src/syntax_kinds/generated.rs
[syntax_kinds source]: ./crates/ra_syntax/src/syntax_kinds/generated.rs.tera
## Code Walk-Through
### `crates/ra_syntax`
Rust syntax tree structure and parser. See
[RFC](https://github.com/rust-lang/rfcs/pull/2256) for some design
notes.
- [rowan](https://github.com/rust-analyzer/rowan) library is used for constructing syntax trees.
- `grammar` module is the actual parser. It is a hand-written recursive descent parsers, which
produces a sequence of events like "start node X", "finish not Y". It works similarly to [kotlin parser](https://github.com/JetBrains/kotlin/blob/4d951de616b20feca92f3e9cc9679b2de9e65195/compiler/frontend/src/org/jetbrains/kotlin/parsing/KotlinParsing.java),
which is a good source for inspiration for dealing with syntax errors and incomplete input. Original [libsyntax parser](https://github.com/rust-lang/rust/blob/6b99adeb11313197f409b4f7c4083c2ceca8a4fe/src/libsyntax/parse/parser.rs)
is what we use for the definition of the Rust language.
- `parser_api/parser_impl` bridges the tree-agnostic parser from `grammar` with `rowan` trees.
This is the thing that turns a flat list of events into a tree (see `EventProcessor`)
- `ast` a type safe API on top of the raw `rowan` tree.
- `grammar.ron` RON description of the grammar, which is used to
generate `syntax_kinds` and `ast` modules, using `cargo gen-kinds` command.
- `algo`: generic tree algorithms, including `walk` for O(1) stack
space tree traversal (this is cool) and `visit` for type-driven
visiting the nodes (this is double plus cool, if you understand how
`Visitor` works, you understand rust-analyzer).
Test for ra_syntax are mostly data-driven: `tests/data/parser` contains a bunch of `.rs`
(test vectors) and `.txt` files with corresponding syntax trees. During testing, we check
`.rs` against `.txt`. If the `.txt` file is missing, it is created (this is how you update
tests). Additionally, running `cargo gen-tests` will walk the grammar module and collect
all `//test test_name` comments into files inside `tests/data` directory.
See [#93](https://github.com/rust-analyzer/rust-analyzer/pull/93) for an example PR which
fixes a bug in the grammar.
### `crates/ra_editor`
All IDE features which can be implemented if you only have access to a
single file. `ra_editor` could be used to enhance editing of Rust code
without the need to fiddle with build-systems, file
synchronization and such.
In a sense, `ra_editor` is just a bunch of pure functions which take a
syntax tree as an input.
The tests for `ra_editor` are `#[cfg(test)] mod tests` unit-tests spread
throughout its modules.
### `crates/salsa`
An implementation of red-green incremental compilation algorithm from
rust compiler. It makes all rust-analyzer features on-demand. To be replaced
with `salsa-rs/salsa` soon.
### `crates/ra_analysis`
A stateful library for analyzing many Rust files as they change.
`AnalysisHost` is a mutable entity (clojure's atom) which holds
current state, incorporates changes and handles out `Analysis` --- an
immutable consistent snapshot of world state at a point in time, which
actually powers analysis.
### `crates/ra_lsp_server`
An LSP implementation which uses `ra_analysis` for managing state and
`ra_editor` for actually doing useful stuff.
See [#79](https://github.com/rust-analyzer/rust-analyzer/pull/79/) as an
example of PR which adds a new feature to `ra_editor` and exposes it
to `ra_lsp_server`.
### `crates/cli`
A CLI interface to rust-analyzer.
### `crate/tools`
Custom Cargo tasks used to develop rust-analyzer:
- `cargo gen-kinds` -- generate `ast` and `syntax_kinds`
- `cargo gen-tests` -- collect inline tests from grammar
- `cargo install-code` -- build and install VS Code extension and server
### `editors/code`
VS Code plugin
## Common workflows
To try out VS Code extensions, run `cargo install-code`. This installs both the
`ra_lsp_server` binary and VS Code extension. To install only the binary, `use
cargo install --path crates/ra_lsp_server --force`
To see logs from the language server, set `RUST_LOG=info` env variable. To see
all communication between the server and the client, use
`RUST_LOG=gen_lsp_server=debug` (will print quite a bit of stuff).
To run tests, just `cargo test`.
To work on VS Code extension, launch code inside `editors/code` and use `F5` to
launch/debug. To automatically apply formatter and linter suggestions, use `npm
run fix`.

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The project is in its early stages: contributions are welcome and would be
**very** helpful, but the project is not _yet_ optimized for contribution.
Moreover, it is doubly experimental, so there's no guarantee that any work here
would reach production. That said, here are some areas where contributions would
be **especially** welcome:
would reach production.
- Designing internal data structures: RFC only outlines the constraints, it's an
open question how to satisfy them in the optimal way. See `ARCHITECTURE.md`
for current design questions.
To get an idea of how rust-analyzer works, take a look at the [ARCHITECTURE.md](./ARCHITECTURE.md)
document.
- Porting libsyntax parser to rust-analyzer: currently rust-analyzer parses only
a tiny subset of Rust. This should be fixed by porting parsing functions from
libsyntax one by one. Take a look at the [libsyntax parser] for "what to port"
and at the [Kotlin parser] for "how to port".
Useful labels on the issue tracker:
* [E-mentor](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AE-mentor)
issues have links to the code in question and tests,
* [E-easy](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AE-easy),
[E-medium](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AE-medium),
[E-hard](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AE-hard),
labels are *estimates* for how hard would be to write a fix.
- Writing validators: by design, rust-analyzer is very lax about the input. For
example, the lexer happily accepts unclosed strings. The idea is that there
should be a higher level visitor, which walks the syntax tree after parsing
and produces all the warnings. Alas, there's no such visitor yet :( Would you
like to write one? :)
- Creating tests: it would be tremendously helpful to read each of libsyntax and
rust-analyzer parser functions and crate a small separate test cases to cover
each and every edge case.
- Building stuff with rust-analyzer: it would be really cool to compile
rust-analyzer to WASM and add _client side_ syntax validation to rust
playground!
Do take a look at the issue tracker.
If you don't know where to start, or have _any_ questions or suggestions, don't
hesitate to chat at [Gitter]!
# Code generation
Some of the components of this repository are generated through automatic
processes. These are outlined below:
- `gen-kinds`: The kinds of tokens are reused in several places, so a generator
is used. This process uses [tera] to generate, using data in [grammar.ron],
the files:
- [ast/generated.rs][ast generated] in `ra_syntax` based on
[ast/generated.tera.rs][ast source]
- [syntax_kinds/generated.rs][syntax_kinds generated] in `ra_syntax` based on
[syntax_kinds/generated.tera.rs][syntax_kinds source]
[libsyntax parser]:
https://github.com/rust-lang/rust/blob/6b99adeb11313197f409b4f7c4083c2ceca8a4fe/src/libsyntax/parse/parser.rs
[kotlin parser]:
https://github.com/JetBrains/kotlin/blob/4d951de616b20feca92f3e9cc9679b2de9e65195/compiler/frontend/src/org/jetbrains/kotlin/parsing/KotlinParsing.java
[gitter]: https://gitter.im/libsyntax2/Lobby
[tera]: https://tera.netlify.com/
[grammar.ron]: ./crates/ra_syntax/src/grammar.ron
[ast generated]: ./crates/ra_syntax/src/ast/generated.rs
[ast source]: ./crates/ra_syntax/src/ast/generated.tera.rs
[syntax_kinds generated]: ./crates/ra_syntax/src/syntax_kinds/generated.rs
[syntax_kinds source]: ./crates/ra_syntax/src/syntax_kinds/generated.tera.rs
There's no formal PR check list: everything that passes CI (we use [bors](https://bors.tech/)) is valid,
but it's a good idea to write nice commit messages, test code thoroughly, maintain consistent style, etc.

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* to quickly bootstrap usable and useful language server: solution
that covers 80% of Rust code will be useful for IDEs, and will be
vastly simpler than 100% solution.
* to understand how the consumer-side of compiler API should look like
(especially it's on-demand aspects). If you have
`get_expression_type` function, you can write a ton of purely-IDE
features on top of it, even if the function is only partially
correct. Plugin in the precise function afterwards should just make
IDE features more reliable.
The long term plan is to merge with the mainline rustc compiler,
probably around the HIR boundary? That is, use rust analyzer for
parsing, macro expansion and related bits of name resolution, but
leave the rest (including type inference and trait selection) to the
existing rustc.
## Code Walk-Through
### `crates/ra_syntax`
Rust syntax tree structure and parser. See
[RFC](https://github.com/rust-lang/rfcs/pull/2256) for some design
notes.
- `yellow`, red/green syntax tree, heavily inspired [by this](https://github.com/apple/swift/tree/ab68f0d4cbf99cdfa672f8ffe18e433fddc8b371/lib/Syntax)
- `grammar`, the actual parser
- `parser_api/parser_impl` bridges the tree-agnostic parser from `grammar` with `yellow` trees
- `grammar.ron` RON description of the grammar, which is used to
generate `syntax_kinds` and `ast` modules.
- `algo`: generic tree algorithms, including `walk` for O(1) stack
space tree traversal (this is cool) and `visit` for type-driven
visiting the nodes (this is double plus cool, if you understand how
`Visitor` works, you understand rust-analyzer).
### `crates/ra_editor`
All IDE features which can be implemented if you only have access to a
single file. `ra_editor` could be used to enhance editing of Rust code
without the need to fiddle with build-systems, file
synchronization and such.
In a sense, `ra_editor` is just a bunch of pure functions which take a
syntax tree as an input.
### `crates/salsa`
An implementation of red-green incremental compilation algorithm from
rust compiler. It makes all rust-analyzer features on-demand.
### `crates/ra_analysis`
A stateful library for analyzing many Rust files as they change.
`AnalysisHost` is a mutable entity (clojure's atom) which holds
current state, incorporates changes and handles out `Analysis` --- an
immutable consistent snapshot of world state at a point in time, which
actually powers analysis.
### `crates/ra_lsp_server`
An LSP implementation which uses `ra_analysis` for managing state and
`ra_editor` for actually doing useful stuff.
### `crates/cli`
A CLI interface to libsyntax
### `crate/tools`
Code-gen tasks, used to develop rust-analyzer:
- `cargo gen-kinds` -- generate `ast` and `syntax_kinds`
- `cargo gen-tests` -- collect inline tests from grammar
- `cargo install-code` -- build and install VS Code extension and server
### `editors/code`
VS Code plugin
## Performance
Non-incremental, but seems pretty fast:
```
$ cargo build --release --package ra_cli
$ wc -l ~/projects/rust/src/libsyntax/parse/parser.rs
7546 /home/matklad/projects/rust/src/libsyntax/parse/parser.rs
$ ./target/release/ra_cli parse < ~/projects/rust/src/libsyntax/parse/parser.rs --no-dump > /dev/null
parsing: 21.067065ms
```
## Getting in touch
@matklad can be found at Rust
@ -161,6 +82,11 @@ parsing: 21.067065ms
#ides-and-editors.
## Contributing
See [CONTRIBUTING.md](./CONTRIBUTING.md) and [ARCHITECTURE.md](./ARCHITECTURE.md)
## License
Rust analyzer is primarily distributed under the terms of both the MIT