Add a code generator for making tests of the examples.

build.rs

@@ -1,5 +1,84 @@
 extern crate lalrpop;
 
+use std::env;
+use std::fs::{self, File};
+use std::io::Write;
+use std::path::{Path, PathBuf};
+
 fn main() {
     lalrpop::process_root().unwrap();
+    if let Err(e) = generate_example_tests() {
+        eprintln!("Failure building example tests: {}", e);
+        std::process::exit(3);
+    }
+}
+
+fn generate_example_tests() -> std::io::Result<()> {
+    let out_dir = env::var_os("OUT_DIR").expect("OUT_DIR");
+    let dest_path = Path::new(&out_dir).join("examples.rs");
+    let mut output = File::create(dest_path)?;
+
+    generate_tests(&mut output, PathBuf::from("examples"))?;
+
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed=example.rs");
+    Ok(())
+}
+
+fn generate_tests(f: &mut File, path_so_far: PathBuf) -> std::io::Result<()> {
+    for entry in fs::read_dir(path_so_far)? {
+        let entry = entry?;
+        let file_name = entry
+            .file_name()
+            .into_string()
+            .expect("reasonable file name");
+        let name = file_name.trim_end_matches(".ngr");
+
+        if entry.file_type()?.is_dir() {
+            writeln!(f, "mod {} {{", name)?;
+            writeln!(f, "  use super::*;")?;
+            generate_tests(f, entry.path())?;
+            writeln!(f, "}}")?;
+        } else {
+            writeln!(f, "#[test]")?;
+            writeln!(f, "fn {}() {{", name)?;
+            writeln!(f, "  let mut file_database = SimpleFiles::new();")?;
+            writeln!(
+                f,
+                "  let syntax = Syntax::parse_file(&mut file_database, {:?});",
+                entry.path().display()
+            )?;
+            if entry.path().to_string_lossy().contains("broken") {
+                writeln!(f, "  if syntax.is_err() {{")?;
+                writeln!(f, "     return;")?;
+                writeln!(f, "  }}")?;
+                writeln!(f, "  let (errors, _) = syntax.unwrap().validate();")?;
+                writeln!(
+                    f,
+                    "  assert_ne!(errors.len(), 0, \"should have seen an error\");"
+                )?;
+            } else {
+                writeln!(
+                    f,
+                    "  let syntax = syntax.expect(\"file should have parsed\");"
+                )?;
+                writeln!(f, "  let (errors, _) = syntax.validate();")?;
+                writeln!(
+                    f,
+                    "  assert_eq!(errors.len(), 0, \"file should have no validation errors\");"
+                )?;
+                writeln!(f, "  let syntax_result = syntax.eval();")?;
+                writeln!(f, "  let ir = IR::from(syntax);")?;
+                writeln!(
+                    f,
+                    "  assert_eq!(syntax_result, ir.eval(), \"syntax equivalent to IR\");"
+                )?;
+                writeln!(f, "  let compiled_result = Backend::<JITModule>::eval(ir);")?;
+                writeln!(f, "  assert_eq!(syntax_result, compiled_result);")?;
+            }
+            writeln!(f, "}}")?;
+        }
+    }
+
+    Ok(())
 }

src/examples.rs

@@ -0,0 +1,7 @@
+use codespan_reporting::files::SimpleFiles;
+use crate::backend::Backend;
+use crate::ir::Program as IR;
+use crate::syntax::Program as Syntax;
+use cranelift_jit::JITModule;
+
+include!(concat!(env!("OUT_DIR"), "/examples.rs"));

src/lib.rs

@@ -63,6 +63,8 @@
 //!
 pub mod backend;
 pub mod eval;
+#[cfg(test)]
+mod examples;
 pub mod ir;
 pub mod syntax;