Swap outer and inner loops in write_python_part() (#2861)

Of the two loops (walking the directory tree and iterating over the
python packges), the directory traversal is the more expensive one. It
should be the outer loop so we only do it once.

Author: e-nomem

src/module_writer/mod.rs

@@ -102,35 +102,36 @@ pub fn write_python_part(
         python_packages.push(package_path);
     }
 
-    for package in python_packages {
-        for absolute in WalkBuilder::new(&project_layout.project_root)
-            .hidden(false)
-            .parents(false)
-            .git_global(false)
-            .git_exclude(false)
-            .build()
+    for absolute in WalkBuilder::new(&project_layout.project_root)
+        .hidden(false)
+        .parents(false)
+        .git_global(false)
+        .git_exclude(false)
+        .build()
+    {
+        let absolute = absolute?.into_path();
+        if !python_packages
+            .iter()
+            .any(|path| absolute.starts_with(path))
         {
-            let absolute = absolute?.into_path();
-            if !absolute.starts_with(package.as_path()) {
-                continue;
-            }
-            let relative = absolute.strip_prefix(python_dir).unwrap();
-            if !absolute.is_dir() {
-                // Ignore native libraries from develop, if any
-                if let Some(extension) = relative.extension() {
-                    if extension.to_string_lossy() == "so" {
-                        debug!("Ignoring native library {}", relative.display());
-                        continue;
-                    }
+            continue;
+        }
+        let relative = absolute.strip_prefix(python_dir).unwrap();
+        if !absolute.is_dir() {
+            // Ignore native libraries from develop, if any
+            if let Some(extension) = relative.extension() {
+                if extension.to_string_lossy() == "so" {
+                    debug!("Ignoring native library {}", relative.display());
+                    continue;
                 }
-                #[cfg(unix)]
-                let mode = absolute.metadata()?.permissions().mode();
-                #[cfg(not(unix))]
-                let mode = 0o644;
-                writer
-                    .add_file_with_permissions(relative, &absolute, mode)
-                    .context(format!("File to add file from {}", absolute.display()))?;
             }
+            #[cfg(unix)]
+            let mode = absolute.metadata()?.permissions().mode();
+            #[cfg(not(unix))]
+            let mode = 0o644;
+            writer
+                .add_file_with_permissions(relative, &absolute, mode)
+                .context(format!("File to add file from {}", absolute.display()))?;
         }
     }