From e871e552136afea1207bb72786337c5904c74374 Mon Sep 17 00:00:00 2001
From: Flakebi <flakebi@t-online.de>
Date: Fri, 16 Aug 2024 11:10:44 +0200
Subject: [PATCH] fix(android): avoid rebuilds if nothing changed

Unconditionally overwriting files where the build reruns if they changed
leads to rebuilds every time.
Only overwrite a file if its content is different to not rebuild in such
a case.
---
 core/tauri-build/src/mobile.rs | 37 ++++++++++++++++++++++++----------
 core/tauri/build.rs            |  8 +++++++-
 2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/core/tauri-build/src/mobile.rs b/core/tauri-build/src/mobile.rs
index 3c8e7c1cb797..4e60a9b335dd 100644
--- a/core/tauri-build/src/mobile.rs
+++ b/core/tauri-build/src/mobile.rs
@@ -80,20 +80,35 @@ dependencies {"
     }
   }
 
-  write(&gradle_settings_path, gradle_settings).context("failed to write tauri.settings.gradle")?;
+  // Overwrite only if changed to not trigger rebuilds
+  if std::fs::read_to_string(&gradle_settings_path)
+    .map(|o| o != gradle_settings)
+    .unwrap_or(true)
+  {
+    write(&gradle_settings_path, gradle_settings)
+      .context("failed to write tauri.settings.gradle")?;
+  }
 
-  write(&app_build_gradle_path, app_build_gradle)
-    .context("failed to write tauri.build.gradle.kts")?;
+  if std::fs::read_to_string(&app_build_gradle_path)
+    .map(|o| o != app_build_gradle)
+    .unwrap_or(true)
+  {
+    write(&app_build_gradle_path, app_build_gradle)
+      .context("failed to write tauri.build.gradle.kts")?;
+  }
 
   if !app_tauri_properties.is_empty() {
-    write(
-      &app_tauri_properties_path,
-      format!(
-        "// THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.\n{}",
-        app_tauri_properties.join("\n")
-      ),
-    )
-    .context("failed to write tauri.properties")?;
+    let app_tauri_properties_content = format!(
+      "// THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.\n{}",
+      app_tauri_properties.join("\n")
+    );
+    if std::fs::read_to_string(&app_tauri_properties_path)
+      .map(|o| o != app_tauri_properties_content)
+      .unwrap_or(true)
+    {
+      write(&app_tauri_properties_path, app_tauri_properties_content)
+        .context("failed to write tauri.properties")?;
+    }
   }
 
   println!("cargo:rerun-if-changed={}", gradle_settings_path.display());
diff --git a/core/tauri/build.rs b/core/tauri/build.rs
index b1935105d15d..1f7bfeb3592a 100644
--- a/core/tauri/build.rs
+++ b/core/tauri/build.rs
@@ -289,7 +289,13 @@ fn main() {
           .replace("{{library}}", &library);
 
         let out_path = kotlin_out_dir.join(file.file_name());
-        write(&out_path, content).expect("Failed to write kotlin file");
+        // Overwrite only if changed to not trigger rebuilds
+        if std::fs::read_to_string(&out_path)
+          .map(|o| o != content)
+          .unwrap_or(true)
+        {
+          write(&out_path, content).expect("Failed to write kotlin file");
+        }
         println!("cargo:rerun-if-changed={}", out_path.display());
       }
     }