From 88171e86a1a52889516b9aa8e478f9a5c674a490 Mon Sep 17 00:00:00 2001
From: Daniel Vigovszky <daniel.vigovszky@gmail.com>
Date: Mon, 1 Apr 2024 11:31:02 +0200
Subject: [PATCH] Better build script

---
 Cargo.lock | 10 ++++++++++
 Cargo.toml |  1 +
 build.rs   | 18 ++++++++++++++----
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 0e125df..f519683 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -190,6 +190,15 @@ dependencies = [
  "syn 1.0.109",
 ]
 
+[[package]]
+name = "dir-diff"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a7ad16bf5f84253b50d6557681c58c3ab67c47c77d39fed9aeb56e947290bd10"
+dependencies = [
+ "walkdir",
+]
+
 [[package]]
 name = "fancy-regex"
 version = "0.13.0"
@@ -210,6 +219,7 @@ dependencies = [
  "clap",
  "copy_dir",
  "derive_more",
+ "dir-diff",
  "fancy-regex",
  "golem-wit",
  "include_dir",
diff --git a/Cargo.toml b/Cargo.toml
index 2518f43..2e8e2e8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,6 +23,7 @@ clap = { version = "4.4.17", features = ["derive"], optional = true }
 [build-dependencies]
 cargo_metadata = "0.18.1"
 copy_dir = "0.1.3"
+dir-diff = "0.3.3"
 
 [features]
 build-binary = ["clap"]
diff --git a/build.rs b/build.rs
index d50a92b..3e85e46 100644
--- a/build.rs
+++ b/build.rs
@@ -5,12 +5,22 @@ use std::path::PathBuf;
 
 fn main() {
     let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
-    let golem_wit_root = find_package_root("golem-wit");
+    let golem_wit_root = PathBuf::from(find_package_root("golem-wit"));
 
-    println!("Output dir: {out_dir:?}");
-    println!("Golem WIT root: {golem_wit_root:?}");
+    println!("cargo:warning=Output dir: {out_dir:?}");
+    println!("cargo:warning=Golem WIT root: {golem_wit_root:?}");
 
-    copy_dir(golem_wit_root, out_dir.join("golem-wit")).unwrap();
+    let target = out_dir.join("golem-wit");
+    if target.exists() {
+        if dir_diff::is_different(&golem_wit_root, &target).unwrap_or(true) {
+            std::fs::remove_dir_all(&target).unwrap();
+            copy_dir(golem_wit_root, target).unwrap();
+        } else {
+            println!("cargo:warning=Golem WIT is up to date in {target:?}");
+        }
+    } else {
+        copy_dir(golem_wit_root, target).unwrap();
+    }
 }
 
 fn find_package_root(name: &str) -> String {