fix: make output deterministic

src/generator.rs

@@ -118,4 +118,13 @@ mod test {
         let mut seeded_rng = rand::rngs::StdRng::seed_from_u64(42);
         insta::assert_snapshot!(gen.generate("S", &mut seeded_rng));
     }
+
+    #[test]
+    fn test_typed_set_algebra() {
+        let text = include_str!("../examples/set-algebra-typed.bnfgen");
+        let grammar = RawGrammar::parse(text).unwrap().to_checked().unwrap();
+        let gen = Generator { grammar };
+        let mut seeded_rng = rand::rngs::StdRng::seed_from_u64(42);
+        insta::assert_snapshot!(gen.generate("Program", &mut seeded_rng));
+    }
 }

src/grammar/checked.rs

@@ -2,14 +2,14 @@ use crate::grammar::production::WeightedProduction;
 use crate::grammar::state::State;
 use crate::grammar::symbol::Ty::Untyped;
 use crate::grammar::symbol::{NonTerminal, SymbolKind, Ty};
+use indexmap::IndexMap;
 use rand::prelude::SliceRandom;
 use rand::Rng;
-use std::collections::HashMap;
 use std::rc::Rc;
 
 #[derive(Debug)]
 pub struct CheckedGrammar {
-    pub(crate) rules: HashMap<NonTerminal, WeightedProduction>,
+    pub(crate) rules: IndexMap<NonTerminal, WeightedProduction>,
 }
 
 pub enum ReduceOutput {
@@ -37,7 +37,11 @@ impl CheckedGrammar {
                             .filter(|k| k.name == s.name)
                             .collect::<Vec<_>>();
                         self.rules
-                            .get(candidates.choose(state.rng()).unwrap())
+                            .get(
+                                *candidates
+                                    .choose(state.rng())
+                                    .expect("No candidates available"),
+                            )
                             .unwrap_or_else(|| panic!("Fail to find rule of {:?}", s))
                             .choose_by_state(state)
                     }

src/grammar/raw.rs

@@ -5,8 +5,8 @@ use crate::grammar::graph::GrammarGraph;
 use crate::grammar::rule::Rule;
 use crate::grammar::symbol::SymbolKind;
 use crate::lexer;
-use crate::span::Span;
 use crate::utils::convert_parse_error;
+use indexmap::IndexMap;
 use petgraph::graph::{DiGraph, NodeIndex};
 use std::collections::{HashMap, HashSet};
 
@@ -26,7 +26,7 @@ impl RawGrammar {
     pub fn to_checked(self) -> crate::error::Result<CheckedGrammar> {
         self.check_undefined()?.check_duplicate()?.check_repeats()?;
 
-        let mut rules = HashMap::new();
+        let mut rules = IndexMap::new();
         for rule in self.rules {
             rules.insert(rule.lhs, rule.production);
         }

src/grammar/symbol.rs

@@ -1,5 +1,6 @@
 use crate::regex::Regex;
 use crate::span::Span;
+use std::borrow::Borrow;
 use std::hash::Hash;
 use std::rc::Rc;
 

src/snapshots/bnfgen__generator__test__typed_generator.snap

@@ -2,15 +2,15 @@
 source: src/generator.rs
 expression: "gen.generate(\"S\", &mut seeded_rng)"
 ---
-true & false & true & false & false 
- 1 + 3 + 1 + 1 + 3 
- 3 
- true 
- true 
- true 
+1 + 3 + 2 + 2 + 3 
+ true & false & true & true & false 
+ false 
  1 
  2 
+ 1 
  true 
- 3 
  true 
- false
+ 2 
+ false 
+ 2 
+ 2