Merge pull request #1062 from rsdy/test-codegen

Resurrect code generation through tests

parser/Cargo.toml

@@ -17,6 +17,6 @@ pest = "2.2.1"
 serde = { version = "1.0.125", features = ["derive"] }
 serde_json = "1.0.64"
 
-[build-dependencies]
+[dev-dependencies]
 pest_generator = "2.2.1"
 proc-macro2 = "1.0.37"

parser/build.rs

@@ -1,32 +0,0 @@
-use std::{error::Error, fs};
-
-const PREAMBLE: &str = "\
-//! This is @generated code, do not edit by hand.
-//! See `graphql.pest` and `tests/codegen.rs`.
-#![allow(unused_attributes)]
-use super::GraphQLParser;
-";
-
-fn main() -> Result<(), Box<dyn Error>> {
-    generated_code()?;
-    println!("cargo:rerun-if-changed=src/graphql.pest");
-    Ok(())
-}
-
-fn generated_code() -> Result<(), Box<dyn Error>> {
-    let input = r###"
-#[derive(Parser)]
-#[grammar = r#"graphql.pest"#]
-struct GraphQLParser;
-"###
-    .parse::<proc_macro2::TokenStream>()
-    .unwrap();
-    let tokens = pest_generator::derive_parser(input, false);
-    let new = tokens.to_string();
-    let code = format!("{}\n{}", PREAMBLE, &new);
-    let current_code = fs::read_to_string("./src/parse/generated.rs").unwrap();
-    if current_code != code {
-        fs::write("./src/parse/generated.rs", code).unwrap();
-    }
-    Ok(())
-}

parser/tests/codegen.rs

@@ -3,3 +3,70 @@
 //!
 //! To avoid that, let's just dump generated code to string into this
 //! repository, and add a test that checks that the code is fresh.
+use std::{
+    fs,
+    io::Write,
+    process::{Command, Stdio},
+};
+
+const PREAMBLE: &str = r#"
+//! This is @generated code, do not edit by hand.
+//! See `graphql.pest` and `tests/codegen.rs`.
+#![allow(unused_attributes)]
+use super::GraphQLParser;
+"#;
+
+#[test]
+fn generated_code_is_fresh() {
+    let input = format!(
+        r###"
+#[derive(Parser)]
+#[grammar = r#"graphql.pest"#]
+struct GraphQLParser;
+"###,
+    )
+    .parse::<proc_macro2::TokenStream>()
+    .unwrap();
+
+    let tokens = pest_generator::derive_parser(input.into(), false);
+    let current =
+        String::from_utf8(fs::read("./src/parse/generated.rs").unwrap_or_default()).unwrap();
+
+    let current_content = match current.len() > PREAMBLE.len() {
+        true => &current[PREAMBLE.len()..],
+        false => current.as_str(),
+    };
+
+    let new = tokens.to_string();
+    let is_up_to_date = normalize(&current_content) == normalize(&new);
+
+    if is_up_to_date {
+        return;
+    }
+
+    let code = format!("{}\n{}", PREAMBLE, reformat(&new));
+    fs::write("./src/parse/generated.rs", code).unwrap();
+    panic!("Generated code in the repository is outdated, updating...");
+}
+
+fn reformat(code: &str) -> String {
+    let mut cmd = Command::new("rustfmt")
+        .args(&["--config", "tab_spaces=2"])
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .spawn()
+        .unwrap();
+
+    cmd.stdin
+        .take()
+        .unwrap()
+        .write_all(code.as_bytes())
+        .unwrap();
+    let output = cmd.wait_with_output().unwrap();
+    assert!(output.status.success());
+    String::from_utf8(output.stdout).unwrap()
+}
+
+fn normalize(code: &str) -> String {
+    code.replace(|c: char| c.is_ascii_whitespace() || "{},".contains(c), "")
+}