Fix incremental compilation by using separate target dir for front (#203

)

* fix incremental compilation by using separate target dir for front
* add documentation to README

README.md

@@ -188,6 +188,11 @@ lib-profile-release = "my-release-profile"
 #
 # Optional. Defaults to "debug".
 lib-profile-dev = "my-debug-profile"
+
+# Fixes cargo bug that prevents incremental compilation (see #203)
+#
+# Optional. Defaults to false
+separate-front-target-dir = true
 ```
 
 ## Site parameters

src/compile/front.rs

@@ -68,6 +68,11 @@ pub fn build_cargo_front_cmd(
         format!("--package={}", proj.lib.name.as_str()),
         "--lib".to_string(),
     ];
+
+    if let Some(path) = &proj.lib.front_target_path {
+        args.push(format!("--target-dir={path}"))
+    }
+
     if wasm {
         args.push("--target=wasm32-unknown-unknown".to_string());
     }

src/config/lib_package.rs

@@ -22,6 +22,7 @@ pub struct LibPackage {
     pub default_features: bool,
     pub output_name: String,
     pub src_paths: Vec<Utf8PathBuf>,
+    pub front_target_path: Option<Utf8PathBuf>,
     pub profile: Profile,
 }
 
@@ -65,9 +66,11 @@ impl LibPackage {
         );
 
         let wasm_file = {
-            let source = metadata
-                // Can't use absolute path because the path gets stored in snapshot testing, and it differs between developers
-                .rel_target_dir()
+            let mut source = metadata.rel_target_dir();
+            if config.separate_front_target_dir {
+                source = source.join("front");
+            }
+            let source = source
                 .join("wasm32-unknown-unknown")
                 .join(profile.to_string())
                 .join(name.replace('-', "_"))
@@ -92,6 +95,13 @@ impl LibPackage {
         } else {
             src_deps.push(rel_dir.join("src"));
         }
+
+        let front_target_path = if config.separate_front_target_dir {
+            Some(metadata.target_directory.join("front"))
+        } else {
+            None
+        };
+
         Ok(Self {
             name,
             abs_dir,
@@ -102,6 +112,7 @@ impl LibPackage {
             default_features: config.lib_default_features,
             output_name,
             src_paths: src_deps,
+            front_target_path,
             profile,
         })
     }

src/config/project.rs

@@ -186,6 +186,9 @@ pub struct ProjectConfig {
     #[serde(skip)]
     pub config_dir: Utf8PathBuf,
 
+    #[serde(default)]
+    pub separate_front_target_dir: bool,
+
     // Profiles
     pub lib_profile_dev: Option<String>,
     pub lib_profile_release: Option<String>,