From e792af18642c58523510177e92e222c3de2e30f7 Mon Sep 17 00:00:00 2001
From: Eashwar Ranganathan <eashwar@eashwar.com>
Date: Mon, 3 Nov 2025 21:34:55 -0800
Subject: [PATCH] Ensure parent directory exists before writing a file

---
 Changelog.md             |  1 +
 src/module_writer.rs     | 21 +++++++++++++++++++--
 tests/common/metadata.rs | 34 +++++++++++++++++++++++++++-------
 3 files changed, 47 insertions(+), 9 deletions(-)

diff --git a/Changelog.md b/Changelog.md
index c49c4abfc..476ee2361 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -3,6 +3,7 @@
 ## Unreleased
 
 * Fix generated WHEEL Tag metadata to be spec compliant.
+* Ensure parent directory is created before attempting to write a file in ModuleWriter
 
 ## [1.9.6]
 
diff --git a/src/module_writer.rs b/src/module_writer.rs
index 02ea901e3..66c04d459 100644
--- a/src/module_writer.rs
+++ b/src/module_writer.rs
@@ -53,6 +53,12 @@ pub trait ModuleWriter {
         bytes: &[u8],
     ) -> Result<()> {
         debug!("Adding {}", target.as_ref().display());
+
+        if let Some(parent_dir) = target.as_ref().parent() {
+            self.add_directory(parent_dir)
+                .with_context(|| format!("Failed to create directory {}", parent_dir.display()))?;
+        }
+
         // 0o644 is the default from the zip crate
         self.add_bytes_with_permissions(target, source, bytes, 0o644)
     }
@@ -86,6 +92,11 @@ pub trait ModuleWriter {
         let source = source.as_ref();
         debug!("Adding {} from {}", target.display(), source.display());
 
+        if let Some(parent_dir) = target.parent() {
+            self.add_directory(parent_dir)
+                .with_context(|| format!("Failed to create directory {}", parent_dir.display()))?;
+        }
+
         let read_failed_context = format!("Failed to read {}", source.display());
         let mut file = File::open(source).context(read_failed_context.clone())?;
         let mut buffer = Vec::new();
@@ -181,8 +192,10 @@ impl PathWriter {
 impl ModuleWriter for PathWriter {
     fn add_directory(&mut self, path: impl AsRef<Path>) -> Result<()> {
         let target = self.base_path.join(path);
-        debug!("Adding directory {}", target.display());
-        fs::create_dir_all(target)?;
+        if !target.exists() {
+            debug!("Adding directory {}", target.display());
+            fs::create_dir_all(target)?;
+        }
         Ok(())
     }
 
@@ -1388,6 +1401,10 @@ if __name__ == '__main__':
     let launcher_path = Path::new(&metadata.get_distribution_escaped())
         .join(bin_name.replace('-', "_"))
         .with_extension("py");
+
+    if let Some(parent_dir) = launcher_path.parent() {
+        writer.add_directory(parent_dir)?;
+    }
     writer.add_bytes_with_permissions(&launcher_path, None, entrypoint_script.as_bytes(), 0o755)?;
     Ok(())
 }
diff --git a/tests/common/metadata.rs b/tests/common/metadata.rs
index 1066c5882..e86e28f30 100644
--- a/tests/common/metadata.rs
+++ b/tests/common/metadata.rs
@@ -1,18 +1,27 @@
+use anyhow::Context;
 use anyhow::Result;
 use insta::assert_snapshot;
+use itertools::Itertools;
 use maturin::{write_dist_info, BuildOptions, CargoOptions, ModuleWriter};
 use std::collections::HashMap;
-use std::path::{Path, PathBuf};
+use std::collections::HashSet;
+use std::path::{Path, PathBuf, MAIN_SEPARATOR};
 
 #[derive(Default)]
 struct MockWriter {
+    directories: HashSet<String>,
     files: Vec<String>,
     contents: HashMap<String, String>,
 }
 
 impl ModuleWriter for MockWriter {
     fn add_directory(&mut self, path: impl AsRef<Path>) -> Result<()> {
-        self.files.push(path.as_ref().to_string_lossy().to_string());
+        let mut dir: String = "".into();
+        for component in path.as_ref().components() {
+            dir.push_str(&component.as_os_str().to_string_lossy());
+            self.directories.insert(dir.clone());
+            dir.push(MAIN_SEPARATOR);
+        }
         Ok(())
     }
 
@@ -23,10 +32,18 @@ impl ModuleWriter for MockWriter {
         bytes: &[u8],
         _permissions: u32,
     ) -> Result<()> {
-        self.files
-            .push(target.as_ref().to_string_lossy().to_string());
+        let target = target.as_ref();
+        if let Some(parent_dir) = target.parent() {
+            self.directories
+                .get(parent_dir.to_string_lossy().as_ref())
+                .with_context(|| {
+                    format!("Parent directory does not exist: {}", parent_dir.display())
+                })?;
+        }
+
+        self.files.push(target.to_string_lossy().to_string());
         self.contents.insert(
-            target.as_ref().to_string_lossy().into(),
+            target.to_string_lossy().into(),
             std::str::from_utf8(bytes).unwrap().to_string(),
         );
         Ok(())
@@ -58,13 +75,16 @@ fn metadata_hello_world_pep639() {
     .unwrap();
 
     assert_snapshot!(writer.files.join("\n").replace("\\", "/"), @r"
-    hello_world-0.1.0.dist-info
     hello_world-0.1.0.dist-info/METADATA
     hello_world-0.1.0.dist-info/WHEEL
-    hello_world-0.1.0.dist-info/licenses
     hello_world-0.1.0.dist-info/licenses/LICENSE
     hello_world-0.1.0.dist-info/licenses/licenses/AUTHORS.txt
     ");
+    assert_snapshot!(writer.directories.iter().sorted().join("\n").replace("\\", "/"), @r"
+    hello_world-0.1.0.dist-info
+    hello_world-0.1.0.dist-info/licenses
+    hello_world-0.1.0.dist-info/licenses/licenses
+    ");
     let metadata_path = Path::new("hello_world-0.1.0.dist-info")
         .join("METADATA")
         .to_str()