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

---
 Cargo.lock              | 13 ++-----------
 dhall_parser/Cargo.toml |  3 ++-
 dhall_parser/build.rs   | 18 ++++++++++++++++++
 dhall_parser/src/lib.rs |  7 +------
 4 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 4dbe2e4..6130c94 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -77,7 +77,8 @@ version = "0.1.0"
 dependencies = [
  "abnf_to_pest 0.1.0",
  "pest 2.1.0 (git+https://github.com/pest-parser/pest)",
- "pest_derive 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pest_generator 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -163,15 +164,6 @@ dependencies = [
  "ucd-trie 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
-[[package]]
-name = "pest_derive"
-version = "2.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "pest 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "pest_generator 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
 [[package]]
 name = "pest_generator"
 version = "2.1.0"
@@ -309,7 +301,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum nom 4.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "4836e9d6036552017e107edc598c97b2dee245161ff1b1ad4af215004774b354"
 "checksum pest 2.1.0 (git+https://github.com/pest-parser/pest)" = "<none>"
 "checksum pest 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "54f0c72a98d8ab3c99560bfd16df8059cc10e1f9a8e83e6e3b97718dd766e9c3"
-"checksum pest_derive 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "833d1ae558dc601e9a60366421196a8d94bc0ac980476d0b67e1d0988d72b2d0"
 "checksum pest_generator 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "63120576c4efd69615b5537d3d052257328a4ca82876771d6944424ccfd9f646"
 "checksum pest_meta 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f5a3492a4ed208ffc247adcdcc7ba2a95be3104f58877d0d02f0df39bf3efb5e"
 "checksum pretty 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f60c0d9f6fc88ecdd245d90c1920ff76a430ab34303fc778d33b1d0a4c3bf6d3"
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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