Alder

Warning: Library is under development and may be subject to change.

Hand written recursive descent and non-backtracking parsing "combinator" library designed with nice error in mind and lossless data.

Goals

• [x] Almost no backtracking
• [x] Lossless tree generation (for formatters and IDE approach)
• [x] UTF-8 support
• [ ] Nice informative errors with contexts.
• [ ] AST generation based on CST (some macro and trait magic)

I'm somehow inspired by this post. It's about parser generators but I prefer writing them manually.

TODO

• [ ] Documentation (right now I have only WIP JSON example)
• [ ] Maybe incremental parsing...

Install

Use cargo-edit: sh cargo add alder

Or add it manually: toml alder = "0.4.0"

You may want to enable a derive feature as well:

toml alder = { version = "0.4.0" , features = ["derive"] }

Example

``rust // Doc tests are treated as a test cases for snapshots. // To enable them usederivefeature and add#[alder_test]` macro. // It also supports /* multiline comments */ /// [] /// [true] /// [true,false] /// [ ] /// [ true ] /// [ true, false ] /// [ true, false, ] /// [trua, falsa] /// [truadsadsa, falsa] /// [true, false /// [truad sadsa, falsa] /* [ true, false, "foo" ] */

[alder_test]

fn array() -> impl Parser { withextra( extra(), node(Json::Array, |state| { state.add("["); match peek(1).parse(state).asref() { "]" => (), _ => 'outer: loop { state.add(value()); 'inner: loop { // Until we find either ']' or ',' match peek(1).parse(state).asref() { "]" => { break 'outer; } "," => { state.add(recover(",")); if let "]" = peek(1).parse(state).asref() { // Trailing comma break 'outer; } break 'inner; } "" => { // EOF state.add(raise(Problem::InvalidTokenArray, 1)); break 'outer; } _ => state.add(raise(Problem::InvalidTokenArray, 1)), }; } }, } state.add(recover("]")); }), ) } ```

Parsers should return information about what happened and where it happened: `` --------------------------------- SYNTAX ERROR --------------------------------- I was parsing Boolean when found issue: 0 |[truadsadsa, falsa]\EOF ~ | ^^^^^^^^^^ I expectedtrue`

--------------------------------- SYNTAX ERROR --------------------------------- I was parsing Boolean when found issue: 0 |[truadsadsa, falsa]\EOF ~ | ^^^^^ I expected false ```