deno/cli/resolver.rs

// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.

use deno_ast::MediaType;
use deno_core::anyhow::anyhow;
use deno_core::error::AnyError;
use deno_core::futures::future;
use deno_core::futures::future::LocalBoxFuture;
use deno_core::futures::FutureExt;
use deno_core::parking_lot::Mutex;
use deno_core::ModuleSpecifier;
use deno_graph::source::NpmPackageReqResolution;
use deno_graph::source::NpmResolver;
use deno_graph::source::ResolutionMode;
use deno_graph::source::ResolveError;
use deno_graph::source::Resolver;
use deno_graph::source::UnknownBuiltInNodeModuleError;
use deno_graph::source::DEFAULT_JSX_IMPORT_SOURCE_MODULE;
use deno_runtime::deno_fs::FileSystem;
use deno_runtime::deno_node::is_builtin_node_module;
use deno_runtime::deno_node::parse_npm_pkg_name;
use deno_runtime::deno_node::NodeResolution;
use deno_runtime::deno_node::NodeResolutionMode;
use deno_runtime::deno_node::NodeResolver;
use deno_runtime::deno_node::NpmResolver as DenoNodeNpmResolver;
use deno_runtime::permissions::PermissionsContainer;
use deno_semver::npm::NpmPackageReqReference;
use deno_semver::package::PackageReq;
use import_map::ImportMap;
use std::borrow::Cow;
use std::collections::HashMap;
use std::path::Path;
use std::path::PathBuf;
use std::sync::Arc;

use crate::args::package_json::PackageJsonDeps;
use crate::args::JsxImportSourceConfig;
use crate::args::PackageJsonDepsProvider;
use crate::graph_util::format_range_with_colors;
use crate::module_loader::CjsResolutionStore;
use crate::npm::ByonmCliNpmResolver;
use crate::npm::CliNpmResolver;
use crate::npm::InnerCliNpmResolverRef;
use crate::util::path::specifier_to_file_path;
use crate::util::sync::AtomicFlag;

/// Result of checking if a specifier is mapped via
/// an import map or package.json.
pub enum MappedResolution {
  None,
  PackageJson(ModuleSpecifier),
  ImportMap(ModuleSpecifier),
}

impl MappedResolution {
  pub fn into_specifier(self) -> Option<ModuleSpecifier> {
    match self {
      MappedResolution::None => Option::None,
      MappedResolution::PackageJson(specifier) => Some(specifier),
      MappedResolution::ImportMap(specifier) => Some(specifier),
    }
  }
}

/// Resolver for specifiers that could be mapped via an
/// import map or package.json.
#[derive(Debug)]
pub struct MappedSpecifierResolver {
  maybe_import_map: Option<Arc<ImportMap>>,
  package_json_deps_provider: Arc<PackageJsonDepsProvider>,
}

impl MappedSpecifierResolver {
  pub fn new(
    maybe_import_map: Option<Arc<ImportMap>>,
    package_json_deps_provider: Arc<PackageJsonDepsProvider>,
  ) -> Self {
    Self {
      maybe_import_map,
      package_json_deps_provider,
    }
  }

  pub fn resolve(
    &self,
    specifier: &str,
    referrer: &ModuleSpecifier,
  ) -> Result<MappedResolution, AnyError> {
    // attempt to resolve with the import map first
    let maybe_import_map_err = match self
      .maybe_import_map
      .as_ref()
      .map(|import_map| import_map.resolve(specifier, referrer))
    {
      Some(Ok(value)) => return Ok(MappedResolution::ImportMap(value)),
      Some(Err(err)) => Some(err),
      None => None,
    };

    // then with package.json
    if let Some(deps) = self.package_json_deps_provider.deps() {
      if let Some(specifier) = resolve_package_json_dep(specifier, deps)? {
        return Ok(MappedResolution::PackageJson(specifier));
      }
    }

    // otherwise, surface the import map error or try resolving when has no import map
    if let Some(err) = maybe_import_map_err {
      Err(err.into())
    } else {
      Ok(MappedResolution::None)
    }
  }
}

/// A resolver that takes care of resolution, taking into account loaded
/// import map, JSX settings.
#[derive(Debug)]
pub struct CliGraphResolver {
  fs: Arc<dyn FileSystem>,
  sloppy_imports_resolver: Option<UnstableSloppyImportsResolver>,
  mapped_specifier_resolver: MappedSpecifierResolver,
  maybe_default_jsx_import_source: Option<String>,
  maybe_jsx_import_source_module: Option<String>,
  maybe_vendor_specifier: Option<ModuleSpecifier>,
  cjs_resolutions: Option<Arc<CjsResolutionStore>>,
  node_resolver: Option<Arc<NodeResolver>>,
  npm_resolver: Option<Arc<dyn CliNpmResolver>>,
  found_package_json_dep_flag: Arc<AtomicFlag>,
  bare_node_builtins_enabled: bool,
}

pub struct CliGraphResolverOptions<'a> {
  pub fs: Arc<dyn FileSystem>,
  pub cjs_resolutions: Option<Arc<CjsResolutionStore>>,
  pub sloppy_imports_resolver: Option<UnstableSloppyImportsResolver>,
  pub node_resolver: Option<Arc<NodeResolver>>,
  pub npm_resolver: Option<Arc<dyn CliNpmResolver>>,
  pub package_json_deps_provider: Arc<PackageJsonDepsProvider>,
  pub maybe_jsx_import_source_config: Option<JsxImportSourceConfig>,
  pub maybe_import_map: Option<Arc<ImportMap>>,
  pub maybe_vendor_dir: Option<&'a PathBuf>,
  pub bare_node_builtins_enabled: bool,
}

impl CliGraphResolver {
  pub fn new(options: CliGraphResolverOptions) -> Self {
    let is_byonm = options
      .npm_resolver
      .as_ref()
      .map(|n| n.as_byonm().is_some())
      .unwrap_or(false);
    Self {
      fs: options.fs,
      cjs_resolutions: options.cjs_resolutions,
      sloppy_imports_resolver: options.sloppy_imports_resolver,
      mapped_specifier_resolver: MappedSpecifierResolver::new(
        options.maybe_import_map,
        if is_byonm {
          // don't resolve from the root package.json deps for byonm
          Arc::new(PackageJsonDepsProvider::new(None))
        } else {
          options.package_json_deps_provider
        },
      ),
      maybe_default_jsx_import_source: options
        .maybe_jsx_import_source_config
        .as_ref()
        .and_then(|c| c.default_specifier.clone()),
      maybe_jsx_import_source_module: options
        .maybe_jsx_import_source_config
        .map(|c| c.module),
      maybe_vendor_specifier: options
        .maybe_vendor_dir
        .and_then(|v| ModuleSpecifier::from_directory_path(v).ok()),
      node_resolver: options.node_resolver,
      npm_resolver: options.npm_resolver,
      found_package_json_dep_flag: Default::default(),
      bare_node_builtins_enabled: options.bare_node_builtins_enabled,
    }
  }

  pub fn as_graph_resolver(&self) -> &dyn Resolver {
    self
  }

  pub fn as_graph_npm_resolver(&self) -> &dyn NpmResolver {
    self
  }

  pub fn found_package_json_dep(&self) -> bool {
    self.found_package_json_dep_flag.is_raised()
  }

  fn check_surface_byonm_node_error(
    &self,
    specifier: &str,
    referrer: &ModuleSpecifier,
    mode: NodeResolutionMode,
    original_err: AnyError,
    resolver: &ByonmCliNpmResolver,
  ) -> Result<(), AnyError> {
    if let Ok((pkg_name, _, _)) = parse_npm_pkg_name(specifier, referrer) {
      match resolver
        .resolve_package_folder_from_package(&pkg_name, referrer, mode)
      {
        Ok(_) => {
          return Err(original_err);
        }
        Err(_) => {
          if resolver
            .find_ancestor_package_json_with_dep(&pkg_name, referrer)
            .is_some()
          {
            return Err(anyhow!(
              concat!(
                "Could not resolve \"{}\", but found it in a package.json. ",
                "Deno expects the node_modules/ directory to be up to date. ",
                "Did you forget to run `npm install`?"
              ),
              specifier
            ));
          }
        }
      }
    }
    Ok(())
  }
}

impl Resolver for CliGraphResolver {
  fn default_jsx_import_source(&self) -> Option<String> {
    self.maybe_default_jsx_import_source.clone()
  }

  fn jsx_import_source_module(&self) -> &str {
    self
      .maybe_jsx_import_source_module
      .as_deref()
      .unwrap_or(DEFAULT_JSX_IMPORT_SOURCE_MODULE)
  }

  fn resolve(
    &self,
    specifier: &str,
    referrer_range: &deno_graph::Range,
    mode: ResolutionMode,
  ) -> Result<ModuleSpecifier, ResolveError> {
    fn to_node_mode(mode: ResolutionMode) -> NodeResolutionMode {
      match mode {
        ResolutionMode::Execution => NodeResolutionMode::Execution,
        ResolutionMode::Types => NodeResolutionMode::Types,
      }
    }

    let referrer = &referrer_range.specifier;
    let result = match self
      .mapped_specifier_resolver
      .resolve(specifier, referrer)?
    {
      MappedResolution::ImportMap(specifier) => Ok(specifier),
      MappedResolution::PackageJson(specifier) => {
        // found a specifier in the package.json, so mark that
        // we need to do an "npm install" later
        self.found_package_json_dep_flag.raise();
        Ok(specifier)
      }
      MappedResolution::None => {
        deno_graph::resolve_import(specifier, &referrer_range.specifier)
          .map_err(|err| err.into())
      }
    };

    // do sloppy imports resolution if enabled
    let result =
      if let Some(sloppy_imports_resolver) = &self.sloppy_imports_resolver {
        result.map(|specifier| {
          sloppy_imports_resolve(
            sloppy_imports_resolver,
            specifier,
            referrer_range,
          )
        })
      } else {
        result
      };

    // When the user is vendoring, don't allow them to import directly from the vendor/ directory
    // as it might cause them confusion or duplicate dependencies. Additionally, this folder has
    // special treatment in the language server so it will definitely cause issues/confusion there
    // if they do this.
    if let Some(vendor_specifier) = &self.maybe_vendor_specifier {
      if let Ok(specifier) = &result {
        if specifier.as_str().starts_with(vendor_specifier.as_str()) {
          return Err(ResolveError::Other(anyhow!("Importing from the vendor directory is not permitted. Use a remote specifier instead or disable vendoring.")));
        }
      }
    }

    if let Some(resolver) =
      self.npm_resolver.as_ref().and_then(|r| r.as_byonm())
    {
      match &result {
        Ok(specifier) => {
          if let Ok(npm_req_ref) =
            NpmPackageReqReference::from_specifier(specifier)
          {
            let package_folder = resolver
              .resolve_pkg_folder_from_deno_module_req(
                npm_req_ref.req(),
                referrer,
              )?;
            let node_resolver = self.node_resolver.as_ref().unwrap();
            let package_json_path = package_folder.join("package.json");
            if !self.fs.exists_sync(&package_json_path) {
              return Err(ResolveError::Other(anyhow!(
                "Could not find '{}'. Deno expects the node_modules/ directory to be up to date. Did you forget to run `npm install`?",
                package_json_path.display()
              )));
            }
            let maybe_resolution = node_resolver
              .resolve_package_subpath_from_deno_module(
                &package_folder,
                npm_req_ref.sub_path(),
                referrer,
                to_node_mode(mode),
                &PermissionsContainer::allow_all(),
              )?;
            match maybe_resolution {
              Some(resolution) => {
                if let Some(cjs_resolutions) = &self.cjs_resolutions {
                  if let NodeResolution::CommonJs(specifier) = &resolution {
                    // remember that this was a common js resolution
                    cjs_resolutions.insert(specifier.clone());
                  }
                }

                return Ok(resolution.into_url());
              }
              None => {
                return Err(ResolveError::Other(anyhow!(
                  "Failed resolving package subpath for '{}' in '{}'.",
                  npm_req_ref,
                  package_folder.display()
                )));
              }
            }
          }
        }
        Err(_) => {
          if referrer.scheme() == "file" {
            if let Some(node_resolver) = &self.node_resolver {
              let node_result = node_resolver.resolve(
                specifier,
                referrer,
                to_node_mode(mode),
                &PermissionsContainer::allow_all(),
              );
              match node_result {
                Ok(Some(resolution)) => {
                  if let Some(cjs_resolutions) = &self.cjs_resolutions {
                    if let NodeResolution::CommonJs(specifier) = &resolution {
                      // remember that this was a common js resolution
                      cjs_resolutions.insert(specifier.clone());
                    }
                  }
                  return Ok(resolution.into_url());
                }
                Ok(None) => {
                  self
                    .check_surface_byonm_node_error(
                      specifier,
                      referrer,
                      to_node_mode(mode),
                      anyhow!("Cannot find \"{}\"", specifier),
                      resolver,
                    )
                    .map_err(ResolveError::Other)?;
                }
                Err(err) => {
                  self
                    .check_surface_byonm_node_error(
                      specifier,
                      referrer,
                      to_node_mode(mode),
                      err,
                      resolver,
                    )
                    .map_err(ResolveError::Other)?;
                }
              }
            }
          }
        }
      }
    }

    result
  }
}

fn sloppy_imports_resolve(
  resolver: &UnstableSloppyImportsResolver,
  specifier: ModuleSpecifier,
  referrer_range: &deno_graph::Range,
) -> ModuleSpecifier {
  let resolution = resolver.resolve(&specifier);
  let hint_message = match &resolution {
    UnstableSloppyImportsResolution::JsToTs(to_specifier) => {
      let from_media_type = MediaType::from_specifier(&specifier);
      let to_media_type = MediaType::from_specifier(to_specifier);
      format!(
        "update {} extension to {}",
        from_media_type.as_ts_extension(),
        to_media_type.as_ts_extension()
      )
    }
    UnstableSloppyImportsResolution::NoExtension(to_specifier) => {
      let to_media_type = MediaType::from_specifier(to_specifier);
      format!("add {} extension", to_media_type.as_ts_extension())
    }
    UnstableSloppyImportsResolution::Directory(to_specifier) => {
      let file_name = to_specifier
        .path()
        .rsplit_once('/')
        .map(|(_, file_name)| file_name)
        .unwrap_or(to_specifier.path());
      format!("specify path to {} file in directory instead", file_name)
    }
    UnstableSloppyImportsResolution::None(_) => return specifier,
  };
  // show a warning when this happens in order to drive
  // the user towards correcting these specifiers
  log::warn!(
    "{} Sloppy import resolution {}\n    at {}",
    crate::colors::yellow("Warning"),
    crate::colors::gray(format!("(hint: {})", hint_message)),
    if referrer_range.end == deno_graph::Position::zeroed() {
      // not worth showing the range in this case
      crate::colors::cyan(referrer_range.specifier.as_str()).to_string()
    } else {
      format_range_with_colors(referrer_range)
    },
  );
  resolution.into_owned_specifier()
}

fn resolve_package_json_dep(
  specifier: &str,
  deps: &PackageJsonDeps,
) -> Result<Option<ModuleSpecifier>, AnyError> {
  for (bare_specifier, req_result) in deps {
    if specifier.starts_with(bare_specifier) {
      let path = &specifier[bare_specifier.len()..];
      if path.is_empty() || path.starts_with('/') {
        let req = req_result.as_ref().map_err(|err| {
          anyhow!(
            "Parsing version constraints in the application-level package.json is more strict at the moment.\n\n{:#}",
            err.clone()
          )
        })?;
        return Ok(Some(ModuleSpecifier::parse(&format!("npm:{req}{path}"))?));
      }
    }
  }

  Ok(None)
}

impl NpmResolver for CliGraphResolver {
  fn resolve_builtin_node_module(
    &self,
    specifier: &ModuleSpecifier,
  ) -> Result<Option<String>, UnknownBuiltInNodeModuleError> {
    if specifier.scheme() != "node" {
      return Ok(None);
    }

    let module_name = specifier.path().to_string();
    if is_builtin_node_module(&module_name) {
      Ok(Some(module_name))
    } else {
      Err(UnknownBuiltInNodeModuleError { module_name })
    }
  }

  fn on_resolve_bare_builtin_node_module(
    &self,
    module_name: &str,
    range: &deno_graph::Range,
  ) {
    let deno_graph::Range {
      start, specifier, ..
    } = range;
    let line = start.line + 1;
    let column = start.character + 1;
    log::warn!("Warning: Resolving \"{module_name}\" as \"node:{module_name}\" at {specifier}:{line}:{column}. If you want to use a built-in Node module, add a \"node:\" prefix.")
  }

  fn load_and_cache_npm_package_info(
    &self,
    package_name: &str,
  ) -> LocalBoxFuture<'static, Result<(), AnyError>> {
    match &self.npm_resolver {
      Some(npm_resolver) if npm_resolver.as_managed().is_some() => {
        let package_name = package_name.to_string();
        let npm_resolver = npm_resolver.clone();
        async move {
          if let Some(managed) = npm_resolver.as_managed() {
            managed.cache_package_info(&package_name).await?;
          }
          Ok(())
        }
        .boxed()
      }
      _ => {
        // return it succeeded and error at the import site below
        Box::pin(future::ready(Ok(())))
      }
    }
  }

  fn resolve_npm(&self, package_req: &PackageReq) -> NpmPackageReqResolution {
    match &self.npm_resolver {
      Some(npm_resolver) => match npm_resolver.as_inner() {
        InnerCliNpmResolverRef::Managed(npm_resolver) => {
          npm_resolver.resolve_npm_for_deno_graph(package_req)
        }
        // if we are using byonm, then this should never be called because
        // we don't use deno_graph's npm resolution in this case
        InnerCliNpmResolverRef::Byonm(_) => unreachable!(),
      },
      None => NpmPackageReqResolution::Err(anyhow!(
        "npm specifiers were requested; but --no-npm is specified"
      )),
    }
  }

  fn enables_bare_builtin_node_module(&self) -> bool {
    self.bare_node_builtins_enabled
  }
}

#[derive(Debug)]
struct UnstableSloppyImportsStatCache {
  fs: Arc<dyn FileSystem>,
  cache: Mutex<HashMap<PathBuf, Option<UnstableSloppyImportsFsEntry>>>,
}

impl UnstableSloppyImportsStatCache {
  pub fn new(fs: Arc<dyn FileSystem>) -> Self {
    Self {
      fs,
      cache: Default::default(),
    }
  }

  pub fn stat_sync(&self, path: &Path) -> Option<UnstableSloppyImportsFsEntry> {
    // there will only ever be one thread in here at a
    // time, so it's ok to hold the lock for so long
    let mut cache = self.cache.lock();
    if let Some(entry) = cache.get(path) {
      return *entry;
    }

    let entry = self.fs.stat_sync(path).ok().and_then(|stat| {
      if stat.is_file {
        Some(UnstableSloppyImportsFsEntry::File)
      } else if stat.is_directory {
        Some(UnstableSloppyImportsFsEntry::Dir)
      } else {
        None
      }
    });
    cache.insert(path.to_owned(), entry);
    entry
  }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum UnstableSloppyImportsFsEntry {
  File,
  Dir,
}

#[derive(Debug, PartialEq, Eq)]
pub enum UnstableSloppyImportsResolution<'a> {
  /// No sloppy resolution was found.
  None(&'a ModuleSpecifier),
  /// Ex. `./file.js` to `./file.ts`
  JsToTs(ModuleSpecifier),
  /// Ex. `./file` to `./file.ts`
  NoExtension(ModuleSpecifier),
  /// Ex. `./dir` to `./dir/index.ts`
  Directory(ModuleSpecifier),
}

impl<'a> UnstableSloppyImportsResolution<'a> {
  pub fn into_specifier(self) -> Cow<'a, ModuleSpecifier> {
    match self {
      Self::None(specifier) => Cow::Borrowed(specifier),
      Self::JsToTs(specifier) => Cow::Owned(specifier),
      Self::NoExtension(specifier) => Cow::Owned(specifier),
      Self::Directory(specifier) => Cow::Owned(specifier),
    }
  }

  pub fn into_owned_specifier(self) -> ModuleSpecifier {
    match self {
      Self::None(specifier) => specifier.clone(),
      Self::JsToTs(specifier) => specifier,
      Self::NoExtension(specifier) => specifier,
      Self::Directory(specifier) => specifier,
    }
  }
}

#[derive(Debug)]
pub struct UnstableSloppyImportsResolver {
  stat_cache: UnstableSloppyImportsStatCache,
}

impl UnstableSloppyImportsResolver {
  pub fn new(fs: Arc<dyn FileSystem>) -> Self {
    Self {
      stat_cache: UnstableSloppyImportsStatCache::new(fs),
    }
  }

  pub fn resolve_with_stat_sync(
    specifier: &ModuleSpecifier,
    stat_sync: impl Fn(&Path) -> Option<UnstableSloppyImportsFsEntry>,
  ) -> UnstableSloppyImportsResolution {
    if specifier.scheme() != "file" {
      return UnstableSloppyImportsResolution::None(specifier);
    }

    let Ok(path) = specifier_to_file_path(specifier) else {
      return UnstableSloppyImportsResolution::None(specifier);
    };
    let mut is_dir_resolution = false;
    let mut is_no_ext_resolution = false;
    let probe_paths = match (stat_sync)(&path) {
      Some(UnstableSloppyImportsFsEntry::File) => {
        return UnstableSloppyImportsResolution::None(specifier);
      }
      Some(UnstableSloppyImportsFsEntry::Dir) => {
        is_dir_resolution = true;
        // try to resolve at the index file
        vec![
          path.join("index.ts"),
          path.join("index.js"),
          path.join("index.mts"),
          path.join("index.mjs"),
          path.join("index.tsx"),
          path.join("index.jsx"),
        ]
      }
      None => {
        let media_type = MediaType::from_specifier(specifier);
        let probe_media_type_types = match media_type {
          MediaType::JavaScript => vec![MediaType::TypeScript, MediaType::Tsx],
          MediaType::Jsx => vec![MediaType::Tsx],
          MediaType::Mjs => vec![MediaType::Mts],
          MediaType::Cjs => vec![MediaType::Cts],
          MediaType::TypeScript
          | MediaType::Mts
          | MediaType::Cts
          | MediaType::Dts
          | MediaType::Dmts
          | MediaType::Dcts
          | MediaType::Tsx
          | MediaType::Json
          | MediaType::Wasm
          | MediaType::TsBuildInfo
          | MediaType::SourceMap => {
            return UnstableSloppyImportsResolution::None(specifier)
          }
          MediaType::Unknown => {
            is_no_ext_resolution = true;
            vec![
              MediaType::TypeScript,
              MediaType::JavaScript,
              MediaType::Tsx,
              MediaType::Jsx,
              MediaType::Mts,
              MediaType::Mjs,
            ]
          }
        };
        let old_path_str = path.to_string_lossy();
        let old_path_str = match media_type {
          MediaType::Unknown => old_path_str,
          _ => match old_path_str.strip_suffix(media_type.as_ts_extension()) {
            Some(s) => Cow::Borrowed(s),
            None => return UnstableSloppyImportsResolution::None(specifier),
          },
        };
        probe_media_type_types
          .into_iter()
          .map(|media_type| {
            PathBuf::from(format!(
              "{}{}",
              old_path_str,
              media_type.as_ts_extension()
            ))
          })
          .collect::<Vec<_>>()
      }
    };

    for probe_path in probe_paths {
      if (stat_sync)(&probe_path) == Some(UnstableSloppyImportsFsEntry::File) {
        if let Ok(specifier) = ModuleSpecifier::from_file_path(probe_path) {
          if is_dir_resolution {
            return UnstableSloppyImportsResolution::Directory(specifier);
          } else if is_no_ext_resolution {
            return UnstableSloppyImportsResolution::NoExtension(specifier);
          } else {
            return UnstableSloppyImportsResolution::JsToTs(specifier);
          }
        }
      }
    }

    UnstableSloppyImportsResolution::None(specifier)
  }

  pub fn resolve<'a>(
    &self,
    specifier: &'a ModuleSpecifier,
  ) -> UnstableSloppyImportsResolution<'a> {
    Self::resolve_with_stat_sync(specifier, |path| {
      self.stat_cache.stat_sync(path)
    })
  }
}

#[cfg(test)]
mod test {
  use std::collections::BTreeMap;

  use deno_runtime::deno_fs::RealFs;
  use test_util::TestContext;

  use super::*;

  #[test]
  fn test_resolve_package_json_dep() {
    fn resolve(
      specifier: &str,
      deps: &BTreeMap<String, PackageReq>,
    ) -> Result<Option<String>, String> {
      let deps = deps
        .iter()
        .map(|(key, value)| (key.to_string(), Ok(value.clone())))
        .collect();
      resolve_package_json_dep(specifier, &deps)
        .map(|s| s.map(|s| s.to_string()))
        .map_err(|err| err.to_string())
    }

    let deps = BTreeMap::from([
      (
        "package".to_string(),
        PackageReq::from_str("package@1.0").unwrap(),
      ),
      (
        "package-alias".to_string(),
        PackageReq::from_str("package@^1.2").unwrap(),
      ),
      (
        "@deno/test".to_string(),
        PackageReq::from_str("@deno/test@~0.2").unwrap(),
      ),
    ]);

    assert_eq!(
      resolve("package", &deps).unwrap(),
      Some("npm:package@1.0".to_string()),
    );
    assert_eq!(
      resolve("package/some_path.ts", &deps).unwrap(),
      Some("npm:package@1.0/some_path.ts".to_string()),
    );

    assert_eq!(
      resolve("@deno/test", &deps).unwrap(),
      Some("npm:@deno/test@~0.2".to_string()),
    );
    assert_eq!(
      resolve("@deno/test/some_path.ts", &deps).unwrap(),
      Some("npm:@deno/test@~0.2/some_path.ts".to_string()),
    );
    // matches the start, but doesn't have the same length or a path
    assert_eq!(resolve("@deno/testing", &deps).unwrap(), None,);

    // alias
    assert_eq!(
      resolve("package-alias", &deps).unwrap(),
      Some("npm:package@^1.2".to_string()),
    );

    // non-existent bare specifier
    assert_eq!(resolve("non-existent", &deps).unwrap(), None);
  }

  #[test]
  fn test_unstable_sloppy_imports() {
    fn resolve(specifier: &ModuleSpecifier) -> UnstableSloppyImportsResolution {
      UnstableSloppyImportsResolver::resolve_with_stat_sync(specifier, |path| {
        RealFs.stat_sync(path).ok().and_then(|stat| {
          if stat.is_file {
            Some(UnstableSloppyImportsFsEntry::File)
          } else if stat.is_directory {
            Some(UnstableSloppyImportsFsEntry::Dir)
          } else {
            None
          }
        })
      })
    }

    let context = TestContext::default();
    let temp_dir = context.temp_dir().path();

    // scenarios like resolving ./example.js to ./example.ts
    for (ext_from, ext_to) in [("js", "ts"), ("js", "tsx"), ("mjs", "mts")] {
      let ts_file = temp_dir.join(format!("file.{}", ext_to));
      ts_file.write("");
      let ts_file_uri = ts_file.uri_file();
      assert_eq!(
        resolve(&ts_file.uri_file()),
        UnstableSloppyImportsResolution::None(&ts_file_uri),
      );
      assert_eq!(
        resolve(
          &temp_dir
            .uri_dir()
            .join(&format!("file.{}", ext_from))
            .unwrap()
        ),
        UnstableSloppyImportsResolution::JsToTs(ts_file.uri_file()),
      );
      ts_file.remove_file();
    }

    // no extension scenarios
    for ext in ["js", "ts", "js", "tsx", "jsx", "mjs", "mts"] {
      let file = temp_dir.join(format!("file.{}", ext));
      file.write("");
      assert_eq!(
        resolve(
          &temp_dir
            .uri_dir()
            .join("file") // no ext
            .unwrap()
        ),
        UnstableSloppyImportsResolution::NoExtension(file.uri_file()),
      );
      file.remove_file();
    }

    // .ts and .js exists, .js specified (goes to specified)
    {
      let ts_file = temp_dir.join("file.ts");
      ts_file.write("");
      let js_file = temp_dir.join("file.js");
      js_file.write("");
      let js_file_uri = js_file.uri_file();
      assert_eq!(
        resolve(&js_file.uri_file()),
        UnstableSloppyImportsResolution::None(&js_file_uri),
      );
    }

    // resolving a directory to an index file
    {
      let routes_dir = temp_dir.join("routes");
      routes_dir.create_dir_all();
      let index_file = routes_dir.join("index.ts");
      index_file.write("");
      assert_eq!(
        resolve(&routes_dir.uri_file()),
        UnstableSloppyImportsResolution::Directory(index_file.uri_file()),
      );
    }
  }
}