local.rs

// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.

//! Code for local node_modules resolution.

use std::borrow::Cow;
use std::cmp::Ordering;
use std::collections::HashMap;
use std::collections::HashSet;
use std::fs;
use std::os::unix::fs::symlink;
use std::path::Path;
use std::path::PathBuf;
use std::sync::Arc;

use crate::cache::CACHE_PERM;
use crate::npm::cache_dir::mixed_case_package_name_decode;
use crate::util::fs::atomic_write_file;
use crate::util::fs::canonicalize_path_maybe_not_exists_with_fs;
use crate::util::fs::symlink_dir;
use crate::util::fs::LaxSingleProcessFsFlag;
use crate::util::progress_bar::ProgressBar;
use crate::util::progress_bar::ProgressMessagePrompt;
use async_trait::async_trait;
use deno_ast::ModuleSpecifier;
use deno_core::anyhow::bail;
use deno_core::anyhow::Context;
use deno_core::error::AnyError;
use deno_core::parking_lot::Mutex;
use deno_core::unsync::spawn;
use deno_core::unsync::JoinHandle;
use deno_core::url::Url;
use deno_npm::resolution::NpmResolutionSnapshot;
use deno_npm::NpmPackageCacheFolderId;
use deno_npm::NpmPackageId;
use deno_npm::NpmResolutionPackage;
use deno_npm::NpmSystemInfo;
use deno_runtime::deno_core::futures;
use deno_runtime::deno_fs;
use deno_runtime::deno_node::NodePermissions;
use deno_runtime::deno_node::NodeResolutionMode;
use deno_semver::package::PackageNv;
use serde::Deserialize;
use serde::Serialize;

use crate::npm::cache_dir::mixed_case_package_name_encode;
use crate::util::fs::copy_dir_recursive;
use crate::util::fs::hard_link_dir_recursive;

use super::super::super::common::types_package_name;
use super::super::cache::NpmCache;
use super::super::resolution::NpmResolution;
use super::common::NpmPackageFsResolver;
use super::common::RegistryReadPermissionChecker;

/// Resolver that creates a local node_modules directory
/// and resolves packages from it.
#[derive(Debug)]
pub struct LocalNpmPackageResolver {
  fs: Arc<dyn deno_fs::FileSystem>,
  cache: Arc<NpmCache>,
  progress_bar: ProgressBar,
  resolution: Arc<NpmResolution>,
  registry_url: Url,
  root_node_modules_path: PathBuf,
  root_node_modules_url: Url,
  system_info: NpmSystemInfo,
  registry_read_permission_checker: RegistryReadPermissionChecker,
}

impl LocalNpmPackageResolver {
  pub fn new(
    fs: Arc<dyn deno_fs::FileSystem>,
    cache: Arc<NpmCache>,
    progress_bar: ProgressBar,
    registry_url: Url,
    node_modules_folder: PathBuf,
    resolution: Arc<NpmResolution>,
    system_info: NpmSystemInfo,
  ) -> Self {
    Self {
      fs: fs.clone(),
      cache,
      progress_bar,
      resolution,
      registry_url,
      root_node_modules_url: Url::from_directory_path(&node_modules_folder)
        .unwrap(),
      root_node_modules_path: node_modules_folder.clone(),
      system_info,
      registry_read_permission_checker: RegistryReadPermissionChecker::new(
        fs,
        node_modules_folder,
      ),
    }
  }

  fn resolve_package_root(&self, path: &Path) -> PathBuf {
    let mut last_found = path;
    loop {
      let parent = last_found.parent().unwrap();
      if parent.file_name().unwrap() == "node_modules" {
        return last_found.to_path_buf();
      } else {
        last_found = parent;
      }
    }
  }

  fn resolve_folder_for_specifier(
    &self,
    specifier: &ModuleSpecifier,
  ) -> Result<Option<PathBuf>, AnyError> {
    let Some(relative_url) =
      self.root_node_modules_url.make_relative(specifier)
    else {
      return Ok(None);
    };
    if relative_url.starts_with("../") {
      return Ok(None);
    }
    // it's within the directory, so use it
    let Some(path) = specifier.to_file_path().ok() else {
      return Ok(None);
    };
    // Canonicalize the path so it's not pointing to the symlinked directory
    // in `node_modules` directory of the referrer.
    canonicalize_path_maybe_not_exists_with_fs(&path, self.fs.as_ref())
      .map(Some)
      .map_err(|err| err.into())
  }
}

#[async_trait]
impl NpmPackageFsResolver for LocalNpmPackageResolver {
  fn root_dir_url(&self) -> &Url {
    &self.root_node_modules_url
  }

  fn node_modules_path(&self) -> Option<&PathBuf> {
    Some(&self.root_node_modules_path)
  }

  fn package_folder(&self, id: &NpmPackageId) -> Result<PathBuf, AnyError> {
    match self.resolution.resolve_pkg_cache_folder_id_from_pkg_id(id) {
      // package is stored at:
      // node_modules/.deno/<package_cache_folder_id_folder_name>/node_modules/<package_name>
      Some(cache_folder_id) => Ok(
        self
          .root_node_modules_path
          .join(".deno")
          .join(get_package_folder_id_folder_name(&cache_folder_id))
          .join("node_modules")
          .join(&cache_folder_id.nv.name),
      ),
      None => bail!(
        "Could not find package information for '{}'",
        id.as_serialized()
      ),
    }
  }

  fn resolve_package_folder_from_package(
    &self,
    name: &str,
    referrer: &ModuleSpecifier,
    mode: NodeResolutionMode,
  ) -> Result<PathBuf, AnyError> {
    let Some(local_path) = self.resolve_folder_for_specifier(referrer)? else {
      bail!("could not find npm package for '{}'", referrer);
    };
    let package_root_path = self.resolve_package_root(&local_path);
    let mut current_folder = package_root_path.as_path();
    while let Some(parent_folder) = current_folder.parent() {
      current_folder = parent_folder;
      let node_modules_folder = if current_folder.ends_with("node_modules") {
        Cow::Borrowed(current_folder)
      } else {
        Cow::Owned(current_folder.join("node_modules"))
      };

      // attempt to resolve the types package first, then fallback to the regular package
      if mode.is_types() && !name.starts_with("@types/") {
        let sub_dir =
          join_package_name(&node_modules_folder, &types_package_name(name));
        if self.fs.is_dir_sync(&sub_dir) {
          return Ok(sub_dir);
        }
      }

      let sub_dir = join_package_name(&node_modules_folder, name);
      if self.fs.is_dir_sync(&sub_dir) {
        return Ok(sub_dir);
      }

      if current_folder == self.root_node_modules_path {
        break;
      }
    }

    bail!(
      "could not find package '{}' from referrer '{}'.",
      name,
      referrer
    );
  }

  fn resolve_package_folder_from_specifier(
    &self,
    specifier: &ModuleSpecifier,
  ) -> Result<Option<PathBuf>, AnyError> {
    let Some(local_path) = self.resolve_folder_for_specifier(specifier)? else {
      return Ok(None);
    };
    let package_root_path = self.resolve_package_root(&local_path);
    Ok(Some(package_root_path))
  }

  fn resolve_package_cache_folder_id_from_specifier(
    &self,
    specifier: &ModuleSpecifier,
  ) -> Result<Option<NpmPackageCacheFolderId>, AnyError> {
    let Some(folder_path) =
      self.resolve_package_folder_from_specifier(specifier)?
    else {
      return Ok(None);
    };
    let folder_name = folder_path.parent().unwrap().to_string_lossy();
    Ok(get_package_folder_id_from_folder_name(&folder_name))
  }

  async fn cache_packages(&self) -> Result<(), AnyError> {
    sync_resolution_with_fs(
      &self.resolution.snapshot(),
      &self.cache,
      &self.progress_bar,
      &self.registry_url,
      &self.root_node_modules_path,
      &self.system_info,
    )
    .await
  }

  fn ensure_read_permission(
    &self,
    permissions: &dyn NodePermissions,
    path: &Path,
  ) -> Result<(), AnyError> {
    self
      .registry_read_permission_checker
      .ensure_registry_read_permission(permissions, path)
  }
}

/// Creates a pnpm style folder structure.
async fn sync_resolution_with_fs(
  snapshot: &NpmResolutionSnapshot,
  cache: &Arc<NpmCache>,
  progress_bar: &ProgressBar,
  registry_url: &Url,
  root_node_modules_dir_path: &Path,
  system_info: &NpmSystemInfo,
) -> Result<(), AnyError> {
  if snapshot.is_empty() {
    return Ok(()); // don't create the directory
  }

  let deno_local_registry_dir = root_node_modules_dir_path.join(".deno");
  let deno_node_modules_dir = deno_local_registry_dir.join("node_modules");
  fs::create_dir_all(&deno_node_modules_dir).with_context(|| {
    format!("Creating '{}'", deno_local_registry_dir.display())
  })?;
  let bin_node_modules_dir_path = root_node_modules_dir_path.join(".bin");
  fs::create_dir_all(&bin_node_modules_dir_path).with_context(|| {
    format!("Creating '{}'", bin_node_modules_dir_path.display())
  })?;

  let single_process_lock = LaxSingleProcessFsFlag::lock(
    deno_local_registry_dir.join(".deno.lock"),
    // similar message used by cargo build
    "waiting for file lock on node_modules directory",
  )
  .await;

  // load this after we get the directory lock
  let mut setup_cache =
    SetupCache::load(deno_local_registry_dir.join(".setup-cache.bin"));

  let pb_clear_guard = progress_bar.clear_guard(); // prevent flickering

  // 1. Write all the packages out the .deno directory.
  //
  // Copy (hardlink in future) <global_registry_cache>/<package_id>/ to
  // node_modules/.deno/<package_folder_id_folder_name>/node_modules/<package_name>
  let package_partitions =
    snapshot.all_system_packages_partitioned(system_info);
  let mut handles: Vec<JoinHandle<Result<(), AnyError>>> =
    Vec::with_capacity(package_partitions.packages.len());
  let mut newest_packages_by_name: HashMap<&String, &NpmResolutionPackage> =
    HashMap::with_capacity(package_partitions.packages.len());
  let bin_entries_to_setup = Arc::new(Mutex::new(Vec::with_capacity(16)));
  for package in &package_partitions.packages {
    if let Some(current_pkg) =
      newest_packages_by_name.get_mut(&package.id.nv.name)
    {
      if current_pkg.id.nv.cmp(&package.id.nv) == Ordering::Less {
        *current_pkg = package;
      }
    } else {
      newest_packages_by_name.insert(&package.id.nv.name, package);
    };

    let package_folder_name =
      get_package_folder_id_folder_name(&package.get_package_cache_folder_id());
    let folder_path = deno_local_registry_dir.join(&package_folder_name);
    let initialized_file = folder_path.join(".initialized");
    if !cache
      .cache_setting()
      .should_use_for_npm_package(&package.id.nv.name)
      || !initialized_file.exists()
    {
      // cache bust the dep from the dep setup cache so the symlinks
      // are forced to be recreated
      setup_cache.remove_dep(&package_folder_name);

      let pb = progress_bar.clone();
      let cache = cache.clone();
      let registry_url = registry_url.clone();
      let package = package.clone();
      let bin_entries_to_setup = bin_entries_to_setup.clone();
      let handle = spawn(async move {
        cache
          .ensure_package(&package.id.nv, &package.dist, &registry_url)
          .await?;
        let pb_guard = pb.update_with_prompt(
          ProgressMessagePrompt::Initialize,
          &package.id.nv.to_string(),
        );
        let sub_node_modules = folder_path.join("node_modules");
        let package_path =
          join_package_name(&sub_node_modules, &package.id.nv.name);
        fs::create_dir_all(&package_path)
          .with_context(|| format!("Creating '{}'", folder_path.display()))?;
        let cache_folder = cache
          .package_folder_for_name_and_version(&package.id.nv, &registry_url);
        if hard_link_dir_recursive(&cache_folder, &package_path).is_err() {
          // Fallback to copying the directory.
          //
          // Also handles EXDEV when when trying to hard link across volumes.
          copy_dir_recursive(&cache_folder, &package_path)?;
        }
        // write out a file that indicates this folder has been initialized
        fs::write(initialized_file, "")?;

        if package.bin.is_some() {
          bin_entries_to_setup
            .lock()
            .push((package.clone(), package_path));
        }

        // finally stop showing the progress bar
        drop(pb_guard); // explicit for clarity
        Ok(())
      });
      handles.push(handle);
    }
  }

  let results = futures::future::join_all(handles).await;
  for result in results {
    result??; // surface the first error
  }

  // 2. Create any "copy" packages, which are used for peer dependencies
  for package in &package_partitions.copy_packages {
    let package_cache_folder_id = package.get_package_cache_folder_id();
    let destination_path = deno_local_registry_dir
      .join(get_package_folder_id_folder_name(&package_cache_folder_id));
    let initialized_file = destination_path.join(".initialized");
    if !initialized_file.exists() {
      let sub_node_modules = destination_path.join("node_modules");
      let package_path =
        join_package_name(&sub_node_modules, &package.id.nv.name);
      fs::create_dir_all(&package_path).with_context(|| {
        format!("Creating '{}'", destination_path.display())
      })?;
      let source_path = join_package_name(
        &deno_local_registry_dir
          .join(get_package_folder_id_folder_name(
            &package_cache_folder_id.with_no_count(),
          ))
          .join("node_modules"),
        &package.id.nv.name,
      );
      hard_link_dir_recursive(&source_path, &package_path)?;
      // write out a file that indicates this folder has been initialized
      fs::write(initialized_file, "")?;
    }
  }

  // 3. Symlink all the dependencies into the .deno directory.
  //
  // Symlink node_modules/.deno/<package_id>/node_modules/<dep_name> to
  // node_modules/.deno/<dep_id>/node_modules/<dep_package_name>
  for package in package_partitions.iter_all() {
    let package_folder_name =
      get_package_folder_id_folder_name(&package.get_package_cache_folder_id());
    let sub_node_modules = deno_local_registry_dir
      .join(&package_folder_name)
      .join("node_modules");
    let mut dep_setup_cache = setup_cache.with_dep(&package_folder_name);
    for (name, dep_id) in &package.dependencies {
      let dep = snapshot.package_from_id(dep_id).unwrap();
      if package.optional_dependencies.contains(name)
        && !dep.system.matches_system(system_info)
      {
        continue; // this isn't a dependency for the current system
      }
      let dep_cache_folder_id = dep.get_package_cache_folder_id();
      let dep_folder_name =
        get_package_folder_id_folder_name(&dep_cache_folder_id);
      if dep_setup_cache.insert(name, &dep_folder_name) {
        let dep_folder_path = join_package_name(
          &deno_local_registry_dir
            .join(dep_folder_name)
            .join("node_modules"),
          &dep_id.nv.name,
        );
        symlink_package_dir(
          &dep_folder_path,
          &join_package_name(&sub_node_modules, name),
        )?;
      }
    }
  }

  // 4. Create all the top level packages in the node_modules folder, which are symlinks.
  //
  // Symlink node_modules/<package_name> to
  // node_modules/.deno/<package_id>/node_modules/<package_name>
  let mut found_names = HashSet::new();
  let mut ids = snapshot.top_level_packages().collect::<Vec<_>>();
  ids.sort_by(|a, b| b.cmp(a)); // create determinism and only include the latest version
  for id in ids {
    if !found_names.insert(&id.nv.name) {
      continue; // skip, already handled
    }
    let package = snapshot.package_from_id(id).unwrap();
    let target_folder_name =
      get_package_folder_id_folder_name(&package.get_package_cache_folder_id());
    if setup_cache.insert_root_symlink(&id.nv.name, &target_folder_name) {
      let local_registry_package_path = join_package_name(
        &deno_local_registry_dir
          .join(target_folder_name)
          .join("node_modules"),
        &id.nv.name,
      );

      symlink_package_dir(
        &local_registry_package_path,
        &join_package_name(root_node_modules_dir_path, &id.nv.name),
      )?;
    }
  }

  // 5. Create a node_modules/.deno/node_modules/<package-name> directory with
  // the remaining packages
  for package in newest_packages_by_name.values() {
    if !found_names.insert(&package.id.nv.name) {
      continue; // skip, already handled
    }

    let target_folder_name =
      get_package_folder_id_folder_name(&package.get_package_cache_folder_id());
    if setup_cache.insert_deno_symlink(&package.id.nv.name, &target_folder_name)
    {
      let local_registry_package_path = join_package_name(
        &deno_local_registry_dir
          .join(target_folder_name)
          .join("node_modules"),
        &package.id.nv.name,
      );

      symlink_package_dir(
        &local_registry_package_path,
        &join_package_name(&deno_node_modules_dir, &package.id.nv.name),
      )?;
    }
  }

  // 6. Set up `node_modules/.bin` entries for packages that need it.
  {
    let bin_entries = bin_entries_to_setup.lock();
    if !bin_entries.is_empty() && !bin_node_modules_dir_path.exists() {
      fs::create_dir_all(&bin_node_modules_dir_path).with_context(|| {
        format!("Creating '{}'", bin_node_modules_dir_path.display())
      })?;
    }
    for (package, package_path) in &*bin_entries {
      let package = snapshot.package_from_id(&package.id).unwrap();
      if let Some(bin_entries) = &package.bin {
        match bin_entries {
          deno_npm::registry::NpmPackageVersionBinEntry::String(script) => {
            let name = package
              .id
              .nv
              .name
              .rsplit_once('/')
              .map_or(package.id.nv.name.as_str(), |(_, name)| name);
            symlink_bin_entry(
              name,
              script,
              package_path,
              &bin_node_modules_dir_path,
            )?;
          }
          deno_npm::registry::NpmPackageVersionBinEntry::Map(entries) => {
            for (name, script) in entries {
              symlink_bin_entry(
                name,
                script,
                package_path,
                &bin_node_modules_dir_path,
              )?;
            }
          }
        }
      }
    }
  }

  setup_cache.save();
  drop(single_process_lock);
  drop(pb_clear_guard);

  Ok(())
}

/// Represents a dependency at `node_modules/.deno/<package_id>/`
struct SetupCacheDep<'a> {
  previous: Option<&'a HashMap<String, String>>,
  current: &'a mut HashMap<String, String>,
}

impl<'a> SetupCacheDep<'a> {
  pub fn insert(&mut self, name: &str, target_folder_name: &str) -> bool {
    self
      .current
      .insert(name.to_string(), target_folder_name.to_string());
    if let Some(previous_target) = self.previous.and_then(|p| p.get(name)) {
      previous_target != target_folder_name
    } else {
      true
    }
  }
}

#[derive(Debug, Default, Serialize, Deserialize, PartialEq, Eq)]
struct SetupCacheData {
  root_symlinks: HashMap<String, String>,
  deno_symlinks: HashMap<String, String>,
  dep_symlinks: HashMap<String, HashMap<String, String>>,
}

/// It is very slow to try to re-setup the symlinks each time, so this will
/// cache what we've setup on the last run and only update what is necessary.
/// Obviously this could lead to issues if the cache gets out of date with the
/// file system, such as if the user manually deletes a symlink.
struct SetupCache {
  file_path: PathBuf,
  previous: Option<SetupCacheData>,
  current: SetupCacheData,
}

impl SetupCache {
  pub fn load(file_path: PathBuf) -> Self {
    let previous = std::fs::read(&file_path)
      .ok()
      .and_then(|data| bincode::deserialize(&data).ok());
    Self {
      file_path,
      previous,
      current: Default::default(),
    }
  }

  pub fn save(&self) -> bool {
    if let Some(previous) = &self.previous {
      if previous == &self.current {
        return false; // nothing to save
      }
    }

    bincode::serialize(&self.current).ok().and_then(|data| {
      atomic_write_file(&self.file_path, data, CACHE_PERM).ok()
    });
    true
  }

  /// Inserts and checks for the existence of a root symlink
  /// at `node_modules/<package_name>` pointing to
  /// `node_modules/.deno/<package_id>/`
  pub fn insert_root_symlink(
    &mut self,
    name: &str,
    target_folder_name: &str,
  ) -> bool {
    self
      .current
      .root_symlinks
      .insert(name.to_string(), target_folder_name.to_string());
    if let Some(previous_target) = self
      .previous
      .as_ref()
      .and_then(|p| p.root_symlinks.get(name))
    {
      previous_target != target_folder_name
    } else {
      true
    }
  }

  /// Inserts and checks for the existence of a symlink at
  /// `node_modules/.deno/node_modules/<package_name>` pointing to
  /// `node_modules/.deno/<package_id>/`
  pub fn insert_deno_symlink(
    &mut self,
    name: &str,
    target_folder_name: &str,
  ) -> bool {
    self
      .current
      .deno_symlinks
      .insert(name.to_string(), target_folder_name.to_string());
    if let Some(previous_target) = self
      .previous
      .as_ref()
      .and_then(|p| p.deno_symlinks.get(name))
    {
      previous_target != target_folder_name
    } else {
      true
    }
  }

  pub fn remove_dep(&mut self, parent_name: &str) {
    if let Some(previous) = &mut self.previous {
      previous.dep_symlinks.remove(parent_name);
    }
  }

  pub fn with_dep(&mut self, parent_name: &str) -> SetupCacheDep<'_> {
    SetupCacheDep {
      previous: self
        .previous
        .as_ref()
        .and_then(|p| p.dep_symlinks.get(parent_name)),
      current: self
        .current
        .dep_symlinks
        .entry(parent_name.to_string())
        .or_default(),
    }
  }
}

fn get_package_folder_id_folder_name(
  folder_id: &NpmPackageCacheFolderId,
) -> String {
  let copy_str = if folder_id.copy_index == 0 {
    "".to_string()
  } else {
    format!("_{}", folder_id.copy_index)
  };
  let nv = &folder_id.nv;
  let name = if nv.name.to_lowercase() == nv.name {
    Cow::Borrowed(&nv.name)
  } else {
    Cow::Owned(format!("_{}", mixed_case_package_name_encode(&nv.name)))
  };
  format!("{}@{}{}", name, nv.version, copy_str).replace('/', "+")
}

fn get_package_folder_id_from_folder_name(
  folder_name: &str,
) -> Option<NpmPackageCacheFolderId> {
  let folder_name = folder_name.replace('+', "/");
  let (name, ending) = folder_name.rsplit_once('@')?;
  let name = if let Some(encoded_name) = name.strip_prefix('_') {
    mixed_case_package_name_decode(encoded_name)?
  } else {
    name.to_string()
  };
  let (raw_version, copy_index) = match ending.split_once('_') {
    Some((raw_version, copy_index)) => {
      let copy_index = copy_index.parse::<u8>().ok()?;
      (raw_version, copy_index)
    }
    None => (ending, 0),
  };
  let version = deno_semver::Version::parse_from_npm(raw_version).ok()?;
  Some(NpmPackageCacheFolderId {
    nv: PackageNv { name, version },
    copy_index,
  })
}

fn symlink_bin_entry(
  bin_name: &str,
  bin_script: &str,
  package_path: &Path,
  bin_node_modules_dir_path: &Path,
) -> Result<(), AnyError> {
  let link = bin_node_modules_dir_path.join(bin_name);
  let original = package_path.join(bin_script);

  // Don't bother setting up another link if it already exists
  if link.exists() {
    let resolved = std::fs::read_link(&link).ok();
    if let Some(resolved) = resolved {
      if resolved != original {
        log::warn!(
          "{} Trying to set up '{}' bin for \"{}\", but an entry pointing to \"{}\" already exists. Skipping...", 
          deno_terminal::colors::yellow("Warning"), 
          bin_name,
          resolved.display(),
          original.display()
        );
        return Ok(());
      }
    }
  }

  #[cfg(target_family = "windows")]
  {
    todo!();
  }
  #[cfg(target_family = "unix")]
  {
    use std::os::unix::fs::PermissionsExt;
    let mut perms = std::fs::metadata(&original).unwrap().permissions();
    if perms.mode() & 0o111 == 0 {
      // if the original file is not executable, make it executable
      perms.set_mode(perms.mode() | 0o111);
      std::fs::set_permissions(&original, perms).with_context(|| {
        format!("Setting permissions on '{}'", original.display())
      })?;
    }
    let original_relative =
      pathdiff::diff_paths(&original, bin_node_modules_dir_path)
        .unwrap_or(original);
    symlink(&original_relative, &link).with_context(|| {
      format!(
        "Can't set up '{}' bin at {}",
        bin_name,
        original_relative.display()
      )
    })?;
  }
  Ok(())
}

fn symlink_package_dir(
  old_path: &Path,
  new_path: &Path,
) -> Result<(), AnyError> {
  let new_parent = new_path.parent().unwrap();
  if new_parent.file_name().unwrap() != "node_modules" {
    // create the parent folder that will contain the symlink
    fs::create_dir_all(new_parent)
      .with_context(|| format!("Creating '{}'", new_parent.display()))?;
  }

  // need to delete the previous symlink before creating a new one
  let _ignore = fs::remove_dir_all(new_path);

  #[cfg(windows)]
  return junction_or_symlink_dir(old_path, new_path);
  #[cfg(not(windows))]
  symlink_dir(old_path, new_path)
}

#[cfg(windows)]
fn junction_or_symlink_dir(
  old_path: &Path,
  new_path: &Path,
) -> Result<(), AnyError> {
  // Use junctions because they're supported on ntfs file systems without
  // needing to elevate privileges on Windows

  match junction::create(old_path, new_path) {
    Ok(()) => Ok(()),
    Err(junction_err) => {
      if cfg!(debug) {
        // When running the tests, junctions should be created, but if not then
        // surface this error.
        log::warn!("Error creating junction. {:#}", junction_err);
      }

      match symlink_dir(old_path, new_path) {
        Ok(()) => Ok(()),
        Err(symlink_err) => bail!(
          concat!(
            "Failed creating junction and fallback symlink in node_modules folder.\n\n",
            "{:#}\n\n{:#}",
          ),
          junction_err,
          symlink_err,
        ),
      }
    }
  }
}

fn join_package_name(path: &Path, package_name: &str) -> PathBuf {
  let mut path = path.to_path_buf();
  // ensure backslashes are used on windows
  for part in package_name.split('/') {
    path = path.join(part);
  }
  path
}

#[cfg(test)]
mod test {
  use deno_npm::NpmPackageCacheFolderId;
  use deno_semver::package::PackageNv;
  use test_util::TempDir;

  use super::*;

  #[test]
  fn test_get_package_folder_id_folder_name() {
    let cases = vec![
      (
        NpmPackageCacheFolderId {
          nv: PackageNv::from_str("@types/foo@1.2.3").unwrap(),
          copy_index: 1,
        },
        "@types+foo@1.2.3_1".to_string(),
      ),
      (
        NpmPackageCacheFolderId {
          nv: PackageNv::from_str("JSON@3.2.1").unwrap(),
          copy_index: 0,
        },
        "_jjju6tq@3.2.1".to_string(),
      ),
    ];
    for (input, output) in cases {
      assert_eq!(get_package_folder_id_folder_name(&input), output);
      let folder_id = get_package_folder_id_from_folder_name(&output).unwrap();
      assert_eq!(folder_id, input);
    }
  }

  #[test]
  fn test_setup_cache() {
    let temp_dir = TempDir::new();
    let cache_bin_path = temp_dir.path().join("cache.bin").to_path_buf();
    let mut cache = SetupCache::load(cache_bin_path.clone());
    assert!(cache.insert_deno_symlink("package-a", "package-a@1.0.0"));
    assert!(cache.insert_root_symlink("package-a", "package-a@1.0.0"));
    assert!(cache
      .with_dep("package-a")
      .insert("package-b", "package-b@1.0.0"));
    assert!(cache.save());

    let mut cache = SetupCache::load(cache_bin_path.clone());
    assert!(!cache.insert_deno_symlink("package-a", "package-a@1.0.0"));
    assert!(!cache.insert_root_symlink("package-a", "package-a@1.0.0"));
    assert!(!cache
      .with_dep("package-a")
      .insert("package-b", "package-b@1.0.0"));
    assert!(!cache.save());
    assert!(cache.insert_root_symlink("package-b", "package-b@0.2.0"));
    assert!(cache.save());

    let mut cache = SetupCache::load(cache_bin_path);
    cache.remove_dep("package-a");
    assert!(cache
      .with_dep("package-a")
      .insert("package-b", "package-b@1.0.0"));
  }
}