pest is a PEG parser built with simplicity and speed in mind.
pest works mainly through two
Input defines the capabilities of
an input source, while
Parser provides an interface to the parsing functionality. Since
Parser is a
trait, parsing needs to be defined either though the
attribute, or manually through the
Position API. The use of the
derive is highly encouraged since this is the only way you can make use of pest's PEG
grammar, while manual parser definition can be used where highly specific or efficient parsing
pest comes with a procedural macro crate--
pest_derive--which needs to be included in
Cargo.toml in order to enable the
pest_derive = "*"
Grammar definitions reside in custom
.pest files located in the
src directory. Their path is
src and is specified between the
derive attribute and an empty
Parser will be derived on.
Because of a limitation in procedural macros, there is no way for Cargo to know that a module
needs to be recompiled based on the file that the procedural macro is opening. This leads to the
case where modifying a
.pest file without touching the file where the
derive is does not
recompile it if it already has a working binary in the cache. To avoid this issue, the grammar
file can be included in a dummy
const definition while debugging.
const _GRAMMAR: &'static = include_str!("path/to/my_grammar.pest"); // relative to this file #[derive(Parser)] #[grammar = "path/to/my_grammar.pest"] // relative to src struct MyParser;
The grammar of
.pest files is documented in the