don't write unnecessarily from azalea-client's build script

1 files changed, 16 insertions, 10 deletions

diff --git a/azalea-client/build.rs b/azalea-client/build.rs
index 49ef62db..156f73a6 100644
--- a/azalea-client/build.rs
+++ b/azalea-client/build.rs
@@ -1,11 +1,12 @@
 use std::{
-    fs::{self, File},
-    io::Write,
+    fmt::Write,
+    fs::{self},
+    path::Path,
 };
 
 fn main() {
     // Tell Cargo that if the given file changes, to rerun this build script.
-    println!("cargo::rerun-if-changed=tests");
+    println!("cargo::rerun-if-changed=tests/simulation");
 
     let Ok(paths) = fs::read_dir("tests/simulation") else {
         return;
@@ -29,15 +30,20 @@ fn main() {
         modules.push(mod_name);
     }
 
-    let Ok(mut mod_rs) = File::create("tests/simulation/mod.rs") else {
-        return;
-    };
-    let _ = writeln!(
-        mod_rs,
-        "// This file is @generated by `azalea-client/build.rs`.\n"
-    );
+    let mut mod_rs = String::new();
+
+    mod_rs.push_str("// This file is @generated by `azalea-client/build.rs`.\n\n");
     modules.sort();
     for mod_name in modules {
         let _ = writeln!(mod_rs, "mod {mod_name};");
     }
+
+    let mod_rs_path = Path::new("tests/simulation/mod.rs");
+
+    let existing_mod_rs = fs::read_to_string(mod_rs_path).unwrap_or_default();
+    if mod_rs == existing_mod_rs {
+        // this would cause the build script to run again
+        return;
+    }
+    let _ = fs::write(mod_rs_path, mod_rs);
 }