Generate actual parsing code in grammar! macro

Cargo.lock

@@ -62,6 +62,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "either"
+version = "1.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
+
 [[package]]
 name = "encode_unicode"
 version = "1.0.0"
@@ -81,6 +87,15 @@ dependencies = [
  "similar",
 ]
 
+[[package]]
+name = "itertools"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2b192c782037fadd9cfa75548310488aabdbf3d2da73885b31bd0abd03351285"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.15"
@@ -131,6 +146,7 @@ checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
 name = "peg_macro"
 version = "0.1.0"
 dependencies = [
+ "itertools",
  "proc-macro2",
  "quote",
  "syn",

peg_macro/Cargo.toml

@@ -7,6 +7,7 @@ edition = "2024"
 proc-macro = true
 
 [dependencies]
+itertools = "0.14.0"
 proc-macro2 = "1.0.95"
 quote = "1.0.40"
 syn = "2.0.101"

peg_macro/src/lib.rs

@@ -1,3 +1,4 @@
+use itertools::{Itertools, Position};
 use proc_macro::TokenStream;
 use quote::quote;
 use syn::{
@@ -68,16 +69,52 @@ impl Term {
     fn generate_code(&self) -> proc_macro2::TokenStream {
         match self {
             Term::Rule(ident) => quote! {
-                println!("call subrule");
+                #ident(p)
-                // call subrule
             },
             Term::Literal(lit_str) => quote! {
-                println!("parse literal");
+                p.literal(#lit_str)
-                // call p.literal()
             },
-            Term::Sequence(terms) => quote! {
+            Term::Sequence(terms) => {
-                println!("sequence");
+                let parts: Vec<_> = terms
+                    .iter()
+                    .with_position()
+                    .map(|(pos, term)| {
+                        let code = term.generate_wrapped_code();
+                        match pos {
+                            Position::First => quote! {
+                                let result = #code;
+                                if !result {
+                                    return false;
+                                }
+                            },
+                            Position::Middle => quote! {
+                                let result = #code;
+                                if !result {
+                                    p.restore(save);
+                                    return false;
+                                }
+                            },
+                            _ => code,
+                        }
+                    })
+                    .collect();
+                quote! {
+                    let save = p.save();
+                    #(#parts)*
+                }
+            }
+        }
+    }
+
+    fn generate_wrapped_code(&self) -> proc_macro2::TokenStream {
+        let code = self.generate_code();
+        match self {
+            Term::Sequence(_) => quote! {
+                (|| {
+                    #code
+                })()
             },
+            _ => code,
         }
     }
 }
@@ -116,24 +153,24 @@ pub fn grammar(ts: TokenStream) -> TokenStream {
         .map(|r| {
             let fn_name = &r.name;
 
-            // Generate a string for debugging
+            // // Generate a string for debugging
-            fn term2str(t: &Term) -> String {
+            // fn term2str(t: &Term) -> String {
-                match t {
+            //     match t {
-                    Term::Rule(ident) => format!("rule {}", ident.to_string()),
+            //         Term::Rule(ident) => format!("rule {}", ident.to_string()),
-                    Term::Literal(lit_str) => format!("literal \"{}\"", lit_str.value()),
+            //         Term::Literal(lit_str) => format!("literal \"{}\"", lit_str.value()),
-                    Term::Sequence(terms) => {
+            //         Term::Sequence(terms) => {
-                        let parts: Vec<_> = terms.iter().map(term2str).collect();
+            //             let parts: Vec<_> = terms.iter().map(term2str).collect();
-                        format!("sequence [{}]", parts.join(", "))
+            //             format!("sequence [{}]", parts.join(", "))
-                    }
+            //         }
-                }
+            //     }
-            }
+            // }
-            let text = format!("I'm generated! ({})", term2str(&r.definition));
+            // let text = format!("I'm generated! ({})", term2str(&r.definition));
 
             let generated = r.definition.generate_code();
             quote! {
-                fn #fn_name(p: &mut crate::peg::ParseState) -> String {
+                fn #fn_name(p: &mut crate::peg::ParseState) -> bool {
+                    // println!(#text.into());
                     #generated
-                    #text.into()
                 }
             }
         })

src/peg/peg.rs

@@ -1,5 +1,3 @@
-use peg_macro::grammar;
-
 #[derive(Debug)]
 #[allow(dead_code)]
 pub enum Foo {
@@ -64,17 +62,18 @@ fn parse_oo(p: &mut ParseState) -> bool {
     p.literal("oo")
 }
 
-grammar! {
-    generated_this = foo;
-    generated_that = "bar" baz;
-}
-
 #[cfg(test)]
 mod tests {
-    use insta::assert_snapshot;
+    use peg_macro::grammar;
 
     use super::*;
 
+    grammar! {
+        fake_csv = line "\n" line;
+        line = foo "," foo;
+        foo = "foo";
+    }
+
     #[test]
     fn test_parser() {
         let mut p = ParseState::new("foo");
@@ -85,8 +84,9 @@ mod tests {
 
     #[test]
     fn test_generated() {
-        let mut p = ParseState::new("");
+        let mut p = ParseState::new("foo,foo\nfoo,foo");
-        assert_snapshot!(generated_this(&mut p), @"I'm generated! (rule foo)");
+        assert!(fake_csv(&mut p));
-        assert_snapshot!(generated_that(&mut p), @r#"I'm generated! (sequence [literal "bar", rule baz])"#);
+        let mut p = ParseState::new("foo,foo\nfoo;foo");
+        assert!(!fake_csv(&mut p));
     }
 }