use quote! macro to generate grammar

We already use syn&quote elsewhere (transitively), so it make sense to
cut down on the number of technologies and get rid of tera

crates/ra_tools/src/codegen.rs

@@ -1,27 +1,162 @@
-use std::{collections::BTreeMap, fs, path::Path};
+use std::{
+    collections::BTreeMap,
+    fs,
+    io::Write,
+    path::Path,
+    process::{Command, Stdio},
+};
 
-use quote::quote;
+use heck::{ShoutySnakeCase, SnakeCase};
+use quote::{format_ident, quote};
 use ron;
 use serde::Deserialize;
 
-use crate::{project_root, Mode, Result, AST, GRAMMAR};
+use crate::{project_root, Mode, Result, AST, GRAMMAR, SYNTAX_KINDS};
 
 pub fn generate(mode: Mode) -> Result<()> {
     let grammar = project_root().join(GRAMMAR);
-    // let syntax_kinds = project_root().join(SYNTAX_KINDS);
-    let ast = project_root().join(AST);
-    generate_ast(&grammar, &ast, mode)
-}
-
-fn generate_ast(grammar_src: &Path, dst: &Path, mode: Mode) -> Result<()> {
-    let src: Grammar = {
-        let text = fs::read_to_string(grammar_src)?;
+    let grammar: Grammar = {
+        let text = fs::read_to_string(grammar)?;
         ron::de::from_str(&text)?
     };
-    eprintln!("{:#?}", src);
+
+    let _syntax_kinds = project_root().join(SYNTAX_KINDS);
+    let _ast = project_root().join(AST);
+
+    let ast = generate_ast(&grammar)?;
+    println!("{}", ast);
     Ok(())
 }
 
+fn generate_ast(grammar: &Grammar) -> Result<String> {
+    let nodes = grammar.ast.iter().map(|(name, ast_node)| {
+        let variants =
+            ast_node.variants.iter().map(|var| format_ident!("{}", var)).collect::<Vec<_>>();
+        let name = format_ident!("{}", name);
+
+        let kinds = if variants.is_empty() { vec![name.clone()] } else { variants.clone() }
+            .into_iter()
+            .map(|name| format_ident!("{}", name.to_string().to_shouty_snake_case()))
+            .collect::<Vec<_>>();
+
+        let variants = if variants.is_empty() {
+            None
+        } else {
+            let kind_enum = format_ident!("{}Kind", name);
+            Some(quote!(
+                pub enum #kind_enum {
+                    #(#variants(#variants),)*
+                }
+
+                #(
+                impl From<#variants> for #name {
+                    fn from(node: #variants) -> #name {
+                        #name { syntax: node.syntax }
+                    }
+                }
+                )*
+
+                impl #name {
+                    pub fn kind(&self) -> #kind_enum {
+                        let syntax = self.syntax.clone();
+                        match syntax.kind() {
+                            #(
+                            #kinds =>
+                                #kind_enum::#variants(#variants { syntax }),
+                            )*
+                            _ => unreachable!(),
+                        }
+                    }
+                }
+            ))
+        };
+
+        let traits = ast_node.traits.iter().map(|trait_name| {
+            let trait_name = format_ident!("{}", trait_name);
+            quote!(impl ast::#trait_name for #name {})
+        });
+
+        let collections = ast_node.collections.iter().map(|(name, kind)| {
+            let method_name = format_ident!("{}", name);
+            let kind = format_ident!("{}", kind);
+            quote! {
+                pub fn #method_name(&self) -> AstChildren<#kind> {
+                    AstChildren::new(&self.syntax)
+                }
+            }
+        });
+
+        let options = ast_node.options.iter().map(|attr| {
+            let method_name = match attr {
+                Attr::Type(t) => format_ident!("{}", t.to_snake_case()),
+                Attr::NameType(n, _) => format_ident!("{}", n),
+            };
+            let ty = match attr {
+                Attr::Type(t) | Attr::NameType(_, t) => format_ident!("{}", t),
+            };
+            quote! {
+                pub fn #method_name(&self) -> Option<#ty> {
+                    AstChildren::new(&self.syntax).next()
+                }
+            }
+        });
+
+        quote! {
+            #[derive(Debug, Clone, PartialEq, Eq, Hash)]
+            pub struct #name {
+                pub(crate) syntax: SyntaxNode,
+            }
+
+            impl AstNode for #name {
+                fn can_cast(kind: SyntaxKind) -> bool {
+                    match kind {
+                        #(#kinds)|* => true,
+                        _ => false,
+                    }
+                }
+                fn cast(syntax: SyntaxNode) -> Option<Self> {
+                    if Self::can_cast(syntax.kind()) { Some(Self { syntax }) } else { None }
+                }
+                fn syntax(&self) -> &SyntaxNode { &self.syntax }
+            }
+
+            #variants
+
+            #(#traits)*
+
+            impl #name {
+                #(#collections)*
+                #(#options)*
+            }
+        }
+    });
+
+    let ast = quote! {
+        use crate::{
+            SyntaxNode, SyntaxKind::{self, *},
+            ast::{self, AstNode, AstChildren},
+        };
+
+        #(#nodes)*
+    };
+
+    let pretty = reformat(ast)?;
+    Ok(pretty)
+}
+
+fn reformat(text: impl std::fmt::Display) -> Result<String> {
+    let mut rustfmt = Command::new("rustfmt")
+        .arg("--config-path")
+        .arg(project_root().join("rustfmt.toml"))
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .spawn()?;
+    write!(rustfmt.stdin.take().unwrap(), "{}", text)?;
+    let output = rustfmt.wait_with_output()?;
+    let stdout = String::from_utf8(output.stdout)?;
+    Ok(stdout)
+}
+
 #[derive(Deserialize, Debug)]
 struct Grammar {
     single_byte_tokens: Vec<(String, String)>,
@@ -35,10 +170,14 @@ struct Grammar {
 
 #[derive(Deserialize, Debug)]
 struct AstNode {
+    #[serde(default)]
+    #[serde(rename = "enum")]
+    variants: Vec<String>,
+
     #[serde(default)]
     traits: Vec<String>,
     #[serde(default)]
-    collections: Vec<Attr>,
+    collections: Vec<(String, String)>,
     #[serde(default)]
     options: Vec<Attr>,
 }