From 465c3d2b97cfebcf47cbcef1dc847e592d31f434 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Fri, 8 Mar 2019 00:49:42 +0100
Subject: Generate pest file manually in the hopes to reduce spurious
 recompilations

---
 dhall_parser/Cargo.toml |  3 ++-
 dhall_parser/build.rs   | 18 ++++++++++++++++++
 dhall_parser/src/lib.rs |  7 +------
 3 files changed, 21 insertions(+), 7 deletions(-)

(limited to 'dhall_parser')

diff --git a/dhall_parser/Cargo.toml b/dhall_parser/Cargo.toml
index a73d445..758c273 100644
--- a/dhall_parser/Cargo.toml
+++ b/dhall_parser/Cargo.toml
@@ -11,7 +11,8 @@ doctest = false
 
 [build-dependencies]
 abnf_to_pest = { path = "../abnf_to_pest" }
+pest_generator = "2.1"
+quote = "0.6.11"
 
 [dependencies]
 pest = { git = "https://github.com/pest-parser/pest" }
-pest_derive = "2.1"
diff --git a/dhall_parser/build.rs b/dhall_parser/build.rs
index a206517..bc342c1 100644
--- a/dhall_parser/build.rs
+++ b/dhall_parser/build.rs
@@ -1,6 +1,8 @@
 use std::collections::HashMap;
 use std::fs::File;
 use std::io::{BufRead, BufReader, Read, Write};
+use std::env;
+use std::path::Path;
 
 use abnf_to_pest::{abnf_to_pest, PestRuleSettings};
 
@@ -68,5 +70,21 @@ fn main() -> std::io::Result<()> {
         "final_expression = {{ SOI ~ complete_expression ~ EOI }}"
     )?;
 
+
+    // Generate pest parser manually to avoid spurious recompilations
+    let derived = {
+        let pest_path = "dhall.pest";
+        let pest = quote::quote! {
+            #[grammar = #pest_path]
+            pub struct DhallParser;
+        };
+        pest_generator::derive_parser(pest, false)
+    };
+
+    let out_dir = env::var("OUT_DIR").unwrap();
+    let grammar_path = Path::new(&out_dir).join("grammar.rs");
+    let mut file = File::create(grammar_path)?;
+    writeln!(file, "pub struct DhallParser;\n{}", derived,)?;
+
     Ok(())
 }
diff --git a/dhall_parser/src/lib.rs b/dhall_parser/src/lib.rs
index 452b4cd..94b49b5 100644
--- a/dhall_parser/src/lib.rs
+++ b/dhall_parser/src/lib.rs
@@ -1,6 +1 @@
-#[allow(unused_imports)]
-use pest_derive::*;
-
-#[derive(Parser)]
-#[grammar = "dhall.pest"]
-pub struct DhallParser;
+include!(concat!(env!("OUT_DIR"), "/grammar.rs"));
-- 
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