parser: move code generation into a test

parser/Cargo.toml

@@ -14,6 +14,9 @@ categories = ["network-programming", "asynchronous"]
 [dependencies]
 async-graphql-value = { path = "../value", version = "3.0.38" }
 pest = "2.1.3"
-pest_derive = "2.1.0"
 serde_json = "1.0.64"
 serde = { version = "1.0.125", features = ["derive"] }
+
+[dev-dependencies]
+pest_generator = "2.1.3"
+proc-macro2 = "1.0.37"

parser/src/parse/mod.rs

@@ -7,20 +7,19 @@ use crate::types::*;
 use crate::{Error, Result};
 use pest::iterators::{Pair, Pairs};
 use pest::Parser;
-use pest_derive::Parser;
 use std::collections::hash_map::{self, HashMap};
 use utils::*;
 
 mod executable;
+mod generated;
 mod service;
 mod utils;
 
 use async_graphql_value::{ConstValue, Name, Number, Value};
 pub use executable::parse_query;
+use generated::Rule;
 pub use service::parse_schema;
 
-#[derive(Parser)]
-#[grammar = "graphql.pest"]
 struct GraphQLParser;
 
 fn parse_operation_type(

parser/tests/codegen.rs

@@ -0,0 +1,71 @@
+//! `pest_derive` crate has large dependency tree, and, as a build dependency,
+//! it imposes these deps onto our consumers.
+//!
+//! 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 = "\
+//! 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(), true);
+    let current =
+        String::from_utf8(fs::read("./src/parse/generated.rs").unwrap_or_default()).unwrap();
+
+    let normalized = normalize(match current.len() > PREAMBLE.len() {
+        true => &current[PREAMBLE.len()..],
+        false => current.as_str(),
+    });
+
+    let new = tokens.to_string();
+    let is_up_to_date = normalized == 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+    panic!("Generated code in the repository is outdated, updating...");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), "")
+}