textparse
A Rust library to declaratively implement parsers that are based on Packrat Parsing.
Examples
The following code implements a parser for a JSON subset format:
use textparse::{
components::{AnyChar, Char, Digit, Eos, Items, NonEmpty, Not, Str, While, Whitespace},
Parse, Parser, Position, Span,
};
#[derive(Clone, Span, Parse)]
struct JsonValue(WithoutWhitespaces<JsonValueInner>);
#[derive(Clone, Span, Parse)]
#[parse(name = "a JSON value")]
enum JsonValueInner {
Null(JsonNull),
String(JsonString),
Number(JsonNumber),
Array(JsonArray),
Object(JsonObject),
}
#[derive(Clone, Span, Parse)]
struct JsonNull(Str<'n', 'u', 'l', 'l'>);
#[derive(Clone, Span, Parse)]
#[parse(name = "a JSON string")]
struct JsonString(Char<'"'>, While<(Not<Char<'"'>>, AnyChar)>, Char<'"'>);
#[derive(Clone, Span, Parse)]
#[parse(name = "a JSON number")]
struct JsonNumber(NonEmpty<While<Digit>>);
#[derive(Clone, Span, Parse)]
#[parse(name = "a JSON array")]
struct JsonArray(Char<'['>, Csv<JsonValue>, Char<']'>);
#[derive(Clone, Span, Parse)]
#[parse(name = "a JSON object")]
struct JsonObject(Char<'{'>, Csv<JsonObjectItem>, Char<'}'>);
#[derive(Clone, Span, Parse)]
struct JsonObjectItem(WithoutWhitespaces<JsonString>, Char<':'>, JsonValue);
#[derive(Clone, Span, Parse)]
struct Csv<T>(Items<T, Char<','>>);
#[derive(Clone, Span, Parse)]
struct WithoutWhitespaces<T>(While<Whitespace>, T, While<Whitespace>);You can run the above parser via examples/check_json.rs as follows:
$ echo '["foo",null,{"key": "value"}, 123]' | cargo run --example check_json
OK: the input string is a JSON text.
$ echo '["foo" null]' | cargo run --example check_json
Error: expected one of ',', or ']'
--> <STDIN>:1:8
|
1 | ["foo" null]
| ^ expected one of ',', or ']'
