Add a YaccKind::SelfDescribing style.

cfgrammar/src/lib/yacc/ast.rs

@@ -14,6 +14,7 @@ use crate::Span;
 /// Contains a `GrammarAST` structure produced from a grammar source file.
 /// As well as any errors which occurred during the construction of the AST.
 pub struct ASTWithValidityInfo {
+    yacc_kind: YaccKind,
     ast: GrammarAST,
     errs: Vec<YaccGrammarError>,
 }
@@ -25,16 +26,18 @@ impl ASTWithValidityInfo {
     /// `Ok(YaccGrammar)` or an `Err` which includes these errors.
     pub fn new(yacc_kind: YaccKind, s: &str) -> Self {
         let mut errs = Vec::new();
-        let ast = match yacc_kind {
-            YaccKind::Original(_) | YaccKind::Grmtools | YaccKind::Eco => {
-                let mut yp = YaccParser::new(yacc_kind, s.to_string());
-                yp.parse().map_err(|e| errs.extend(e)).ok();
-                let mut ast = yp.ast();
-                ast.complete_and_validate().map_err(|e| errs.push(e)).ok();
-                ast
-            }
+        let (ast, yacc_kind) = {
+            let mut yp = YaccParser::new(yacc_kind, s.to_string());
+            yp.parse().map_err(|e| errs.extend(e)).ok();
+            let (yacc_kind, mut ast) = yp.finish();
+            ast.complete_and_validate().map_err(|e| errs.push(e)).ok();
+            (ast, yacc_kind)
         };
-        ASTWithValidityInfo { ast, errs }
+        ASTWithValidityInfo {
+            ast,
+            errs,
+            yacc_kind,
+        }
     }
 
     /// Returns a `GrammarAST` constructed as the result of parsing a source file.
@@ -55,6 +58,10 @@ impl ASTWithValidityInfo {
     pub fn errors(&self) -> &[YaccGrammarError] {
         self.errs.as_slice()
     }
+
+    pub fn yacc_kind(&self) -> &YaccKind {
+        &self.yacc_kind
+    }
 }
 
 /// An AST representing a grammar. This is built up gradually: when it is finished, the

cfgrammar/src/lib/yacc/grammar.rs

@@ -106,12 +106,11 @@ where
     /// though the actual name is a fresh name that is guaranteed to be unique) that references the
     /// user defined start rule.
     pub fn new_with_storaget(yacc_kind: YaccKind, s: &str) -> YaccGrammarResult<Self> {
-        let ast_validation = ast::ASTWithValidityInfo::new(yacc_kind, s);
-        Self::new_from_ast_with_validity_info(yacc_kind, &ast_validation)
+        let ast_validation = ast::ASTWithValidityInfo::new(yacc_kind.clone(), s);
+        Self::new_from_ast_with_validity_info(&ast_validation)
     }
 
     pub fn new_from_ast_with_validity_info(
-        yacc_kind: YaccKind,
         ast_validation: &ast::ASTWithValidityInfo,
     ) -> YaccGrammarResult<Self> {
         if !ast_validation.is_valid() {
@@ -149,7 +148,10 @@ where
 
         let implicit_rule;
         let implicit_start_rule;
-        match yacc_kind {
+        match ast_validation.yacc_kind() {
+            YaccKind::SelfDescribing(_) => {
+                unimplemented!("Concrete YaccKind must be known by this point")
+            }
             YaccKind::Original(_) | YaccKind::Grmtools => {
                 implicit_rule = None;
                 implicit_start_rule = None;

cfgrammar/src/lib/yacc/mod.rs

@@ -15,7 +15,7 @@ pub use self::{
 use serde::{Deserialize, Serialize};
 
 /// The particular Yacc variant this grammar makes use of.
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Debug)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum YaccKind {
     /// The original Yacc style as documented by
@@ -26,6 +26,21 @@ pub enum YaccKind {
     Grmtools,
     /// The variant used in the [Eco language composition editor](http://soft-dev.org/src/eco/)
     Eco,
+    /// A `SelfDescribing` grammar starts with an initial `%grmtools` directive specifying it's
+    /// yacckind.
+    ///
+    /// For example:
+    /// ``` yacc
+    /// %grmtools {
+    ///   yacckind Original(NoAction)
+    /// }
+    /// ...
+    /// ```
+    ///
+    /// The `Option<Box<YaccKind>>` value if specified will be used as the default format.
+    /// If the default kind is `None` and the file does not specify a yacc kind produce a
+    /// `MissingYaccKind` error.
+    SelfDescribing(Option<Box<YaccKind>>),
 }
 
 #[derive(Clone, Copy, Debug)]