xtask: move codegen to a module

xtask/src/codegen.rs

@@ -0,0 +1,46 @@
+//! We use code generation heavily in rust-analyzer.
+//!
+//! Rather then doing it via proc-macros, we use old-school way of just dumping
+//! the source code.
+//!
+//! This module's submodules define specific bits that we generate.
+
+mod gen_syntax;
+mod gen_parser_tests;
+
+use std::{fs, path::Path};
+
+use crate::Result;
+
+pub use self::{gen_parser_tests::generate_parser_tests, gen_syntax::generate_syntax};
+
+pub const GRAMMAR: &str = "crates/ra_syntax/src/grammar.ron";
+const GRAMMAR_DIR: &str = "crates/ra_parser/src/grammar";
+const OK_INLINE_TESTS_DIR: &str = "crates/ra_syntax/test_data/parser/inline/ok";
+const ERR_INLINE_TESTS_DIR: &str = "crates/ra_syntax/test_data/parser/inline/err";
+
+pub const SYNTAX_KINDS: &str = "crates/ra_parser/src/syntax_kind/generated.rs";
+pub const AST: &str = "crates/ra_syntax/src/ast/generated.rs";
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum Mode {
+    Overwrite,
+    Verify,
+}
+
+/// A helper to update file on disk if it has changed.
+/// With verify = false,
+pub fn update(path: &Path, contents: &str, mode: Mode) -> Result<()> {
+    match fs::read_to_string(path) {
+        Ok(ref old_contents) if old_contents == contents => {
+            return Ok(());
+        }
+        _ => (),
+    }
+    if mode == Mode::Verify {
+        Err(format!("`{}` is not up-to-date", path.display()))?;
+    }
+    eprintln!("updating {}", path.display());
+    fs::write(path, contents)?;
+    Ok(())
+}