refactor: extract out sloppy imports resolution from CLI crate (#25920)

This is slow progress towards creating a `deno_resolver`  crate.

Waiting on:

* https://github.com/denoland/deno/pull/25918
* https://github.com/denoland/deno/pull/25916

Cargo.lock

@@ -1150,7 +1150,6 @@ version = "2.0.0-rc.7"
 dependencies = [
  "anstream",
  "async-trait",
- "base32",
  "base64 0.21.7",
  "bincode",
  "bytes",
@@ -1175,6 +1174,7 @@ dependencies = [
  "deno_npm",
  "deno_package_json",
  "deno_path_util",
+ "deno_resolver",
  "deno_runtime",
  "deno_semver",
  "deno_task_shell",
@@ -1949,6 +1949,16 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "deno_resolver"
+version = "0.0.1"
+dependencies = [
+ "deno_media_type",
+ "deno_path_util",
+ "test_server",
+ "url",
+]
+
 [[package]]
 name = "deno_runtime"
 version = "0.177.0"

Cargo.toml

@@ -21,13 +21,14 @@ members = [
   "ext/napi",
   "ext/net",
   "ext/node",
-  "ext/node_resolver",
   "ext/url",
   "ext/web",
   "ext/webgpu",
   "ext/webidl",
   "ext/websocket",
   "ext/webstorage",
+  "resolvers/deno",
+  "resolvers/node",
   "runtime",
   "runtime/permissions",
   "tests",
@@ -50,6 +51,7 @@ deno_core = { version = "0.311.0" }
 deno_bench_util = { version = "0.162.0", path = "./bench_util" }
 deno_lockfile = "=0.23.1"
 deno_media_type = { version = "0.1.4", features = ["module_specifier"] }
+deno_npm = "=0.25.2"
 deno_path_util = "=0.1.1"
 deno_permissions = { version = "0.28.0", path = "./runtime/permissions" }
 deno_runtime = { version = "0.177.0", path = "./runtime" }
@@ -86,7 +88,10 @@ deno_webgpu = { version = "0.135.0", path = "./ext/webgpu" }
 deno_webidl = { version = "0.168.0", path = "./ext/webidl" }
 deno_websocket = { version = "0.173.0", path = "./ext/websocket" }
 deno_webstorage = { version = "0.163.0", path = "./ext/webstorage" }
-node_resolver = { version = "0.7.0", path = "./ext/node_resolver" }
+
+# resolvers
+deno_resolver = { version = "0.0.1", path = "./resolvers/deno" }
+node_resolver = { version = "0.7.0", path = "./resolvers/node" }
 
 aes = "=0.8.3"
 anyhow = "1.0.57"
@@ -102,6 +107,7 @@ cbc = { version = "=0.1.2", features = ["alloc"] }
 #       Instead use util::time::utc_now()
 chrono = { version = "0.4", default-features = false, features = ["std", "serde"] }
 console_static_text = "=0.8.1"
+dashmap = "5.5.3"
 data-encoding = "2.3.3"
 data-url = "=0.3.0"
 deno_cache_dir = "=0.12.0"

cli/Cargo.toml

@@ -71,9 +71,10 @@ deno_doc = { version = "0.150.0", features = ["html", "syntect"] }
 deno_graph = { version = "=0.82.3" }
 deno_lint = { version = "=0.67.0", features = ["docs"] }
 deno_lockfile.workspace = true
-deno_npm = "=0.25.2"
+deno_npm.workspace = true
 deno_package_json.workspace = true
 deno_path_util.workspace = true
+deno_resolver.workspace = true
 deno_runtime = { workspace = true, features = ["include_js_files_for_snapshotting"] }
 deno_semver.workspace = true
 deno_task_shell = "=0.17.0"
@@ -85,7 +86,6 @@ node_resolver.workspace = true
 
 anstream = "0.6.14"
 async-trait.workspace = true
-base32.workspace = true
 base64.workspace = true
 bincode = "=1.3.3"
 bytes.workspace = true
@@ -96,7 +96,7 @@ clap_complete = "=4.5.24"
 clap_complete_fig = "=4.5.2"
 color-print = "0.3.5"
 console_static_text.workspace = true
-dashmap = "5.5.3"
+dashmap.workspace = true
 data-encoding.workspace = true
 dissimilar = "=1.0.4"
 dotenvy = "0.15.7"

cli/factory.rs

@@ -41,8 +41,9 @@ use crate::resolver::CjsResolutionStore;
 use crate::resolver::CliGraphResolver;
 use crate::resolver::CliGraphResolverOptions;
 use crate::resolver::CliNodeResolver;
+use crate::resolver::CliSloppyImportsResolver;
 use crate::resolver::NpmModuleLoader;
-use crate::resolver::SloppyImportsResolver;
+use crate::resolver::SloppyImportsCachedFs;
 use crate::standalone::DenoCompileBinaryWriter;
 use crate::tools::check::TypeChecker;
 use crate::tools::coverage::CoverageCollector;
@@ -186,7 +187,7 @@ struct CliFactoryServices {
   npm_resolver: Deferred<Arc<dyn CliNpmResolver>>,
   permission_desc_parser: Deferred<Arc<RuntimePermissionDescriptorParser>>,
   root_permissions_container: Deferred<PermissionsContainer>,
-  sloppy_imports_resolver: Deferred<Option<Arc<SloppyImportsResolver>>>,
+  sloppy_imports_resolver: Deferred<Option<Arc<CliSloppyImportsResolver>>>,
   text_only_progress_bar: Deferred<ProgressBar>,
   type_checker: Deferred<Arc<TypeChecker>>,
   cjs_resolutions: Deferred<Arc<CjsResolutionStore>>,
@@ -404,17 +405,16 @@ impl CliFactory {
 
   pub fn sloppy_imports_resolver(
     &self,
-  ) -> Result<Option<&Arc<SloppyImportsResolver>>, AnyError> {
+  ) -> Result<Option<&Arc<CliSloppyImportsResolver>>, AnyError> {
     self
       .services
       .sloppy_imports_resolver
       .get_or_try_init(|| {
-        Ok(
+        Ok(self.cli_options()?.unstable_sloppy_imports().then(|| {
-          self
+          Arc::new(CliSloppyImportsResolver::new(SloppyImportsCachedFs::new(
-            .cli_options()?
+            self.fs().clone(),
-            .unstable_sloppy_imports()
+          )))
-            .then(|| Arc::new(SloppyImportsResolver::new(self.fs().clone()))),
+        }))
-        )
       })
       .map(|maybe| maybe.as_ref())
   }

cli/graph_util.rs

@@ -14,7 +14,8 @@ use crate::errors::get_error_class_name;
 use crate::file_fetcher::FileFetcher;
 use crate::npm::CliNpmResolver;
 use crate::resolver::CliGraphResolver;
-use crate::resolver::SloppyImportsResolver;
+use crate::resolver::CliSloppyImportsResolver;
+use crate::resolver::SloppyImportsCachedFs;
 use crate::tools::check;
 use crate::tools::check::TypeChecker;
 use crate::util::file_watcher::WatcherCommunicator;
@@ -31,7 +32,6 @@ use deno_core::error::AnyError;
 use deno_core::parking_lot::Mutex;
 use deno_core::ModuleSpecifier;
 use deno_graph::source::Loader;
-use deno_graph::source::ResolutionMode;
 use deno_graph::source::ResolveError;
 use deno_graph::GraphKind;
 use deno_graph::ModuleError;
@@ -40,6 +40,7 @@ use deno_graph::ModuleGraphError;
 use deno_graph::ResolutionError;
 use deno_graph::SpecifierError;
 use deno_path_util::url_to_file_path;
+use deno_resolver::sloppy_imports::SloppyImportsResolutionMode;
 use deno_runtime::deno_fs::FileSystem;
 use deno_runtime::deno_node;
 use deno_runtime::deno_permissions::PermissionsContainer;
@@ -765,8 +766,8 @@ fn enhanced_sloppy_imports_error_message(
   match error {
     ModuleError::LoadingErr(specifier, _, ModuleLoadError::Loader(_)) // ex. "Is a directory" error
     | ModuleError::Missing(specifier, _) => {
-      let additional_message = SloppyImportsResolver::new(fs.clone())
+      let additional_message = CliSloppyImportsResolver::new(SloppyImportsCachedFs::new(fs.clone()))
-        .resolve(specifier, ResolutionMode::Execution)?
+        .resolve(specifier, SloppyImportsResolutionMode::Execution)?
         .as_suggestion_message();
       Some(format!(
         "{} {} or run with --unstable-sloppy-imports",

cli/lsp/config.rs

@@ -59,7 +59,8 @@ use crate::args::LintOptions;
 use crate::cache::FastInsecureHasher;
 use crate::file_fetcher::FileFetcher;
 use crate::lsp::logging::lsp_warn;
-use crate::resolver::SloppyImportsResolver;
+use crate::resolver::CliSloppyImportsResolver;
+use crate::resolver::SloppyImportsCachedFs;
 use crate::tools::lint::CliLinter;
 use crate::tools::lint::CliLinterOptions;
 use crate::tools::lint::LintRuleProvider;
@@ -1181,7 +1182,7 @@ pub struct ConfigData {
   pub lockfile: Option<Arc<CliLockfile>>,
   pub npmrc: Option<Arc<ResolvedNpmRc>>,
   pub resolver: Arc<WorkspaceResolver>,
-  pub sloppy_imports_resolver: Option<Arc<SloppyImportsResolver>>,
+  pub sloppy_imports_resolver: Option<Arc<CliSloppyImportsResolver>>,
   pub import_map_from_settings: Option<ModuleSpecifier>,
   watched_files: HashMap<ModuleSpecifier, ConfigWatchedFileType>,
 }
@@ -1584,9 +1585,11 @@ impl ConfigData {
       .is_ok()
       || member_dir.workspace.has_unstable("sloppy-imports");
     let sloppy_imports_resolver = unstable_sloppy_imports.then(|| {
-      Arc::new(SloppyImportsResolver::new_without_stat_cache(Arc::new(
+      Arc::new(CliSloppyImportsResolver::new(
-        deno_runtime::deno_fs::RealFs,
+        SloppyImportsCachedFs::new_without_stat_cache(Arc::new(
-      )))
+          deno_runtime::deno_fs::RealFs,
+        )),
+      ))
     });
     let resolver = Arc::new(resolver);
     let lint_rule_provider = LintRuleProvider::new(

cli/lsp/diagnostics.rs

@@ -19,8 +19,8 @@ use super::urls::LspUrlMap;
 use crate::graph_util;
 use crate::graph_util::enhanced_resolution_error_message;
 use crate::lsp::lsp_custom::DiagnosticBatchNotificationParams;
-use crate::resolver::SloppyImportsResolution;
+use crate::resolver::CliSloppyImportsResolver;
-use crate::resolver::SloppyImportsResolver;
+use crate::resolver::SloppyImportsCachedFs;
 use crate::tools::lint::CliLinter;
 use crate::tools::lint::CliLinterOptions;
 use crate::tools::lint::LintRuleProvider;
@@ -40,11 +40,12 @@ use deno_core::unsync::spawn_blocking;
 use deno_core::unsync::JoinHandle;
 use deno_core::url::Url;
 use deno_core::ModuleSpecifier;
-use deno_graph::source::ResolutionMode;
 use deno_graph::source::ResolveError;
 use deno_graph::Resolution;
 use deno_graph::ResolutionError;
 use deno_graph::SpecifierError;
+use deno_resolver::sloppy_imports::SloppyImportsResolution;
+use deno_resolver::sloppy_imports::SloppyImportsResolutionMode;
 use deno_runtime::deno_fs;
 use deno_runtime::deno_node;
 use deno_runtime::tokio_util::create_basic_runtime;
@@ -1263,7 +1264,9 @@ impl DenoDiagnostic {
       Self::NotInstalledJsr(pkg_req, specifier) => (lsp::DiagnosticSeverity::ERROR, format!("JSR package \"{pkg_req}\" is not installed or doesn't exist."), Some(json!({ "specifier": specifier }))),
       Self::NotInstalledNpm(pkg_req, specifier) => (lsp::DiagnosticSeverity::ERROR, format!("NPM package \"{pkg_req}\" is not installed or doesn't exist."), Some(json!({ "specifier": specifier }))),
       Self::NoLocal(specifier) => {
-        let maybe_sloppy_resolution = SloppyImportsResolver::new(Arc::new(deno_fs::RealFs)).resolve(specifier, ResolutionMode::Execution);
+        let maybe_sloppy_resolution = CliSloppyImportsResolver::new(
+          SloppyImportsCachedFs::new(Arc::new(deno_fs::RealFs))
+        ).resolve(specifier, SloppyImportsResolutionMode::Execution);
         let data = maybe_sloppy_resolution.as_ref().map(|res| {
           json!({
             "specifier": specifier,

cli/resolver.rs

@@ -22,7 +22,8 @@ use deno_graph::NpmLoadError;
 use deno_graph::NpmResolvePkgReqsResult;
 use deno_npm::resolution::NpmResolutionError;
 use deno_package_json::PackageJsonDepValue;
-use deno_path_util::url_to_file_path;
+use deno_resolver::sloppy_imports::SloppyImportsResolutionMode;
+use deno_resolver::sloppy_imports::SloppyImportsResolver;
 use deno_runtime::colors;
 use deno_runtime::deno_fs;
 use deno_runtime::deno_fs::FileSystem;
@@ -421,13 +422,16 @@ impl CjsResolutionStore {
   }
 }
 
+pub type CliSloppyImportsResolver =
+  SloppyImportsResolver<SloppyImportsCachedFs>;
+
 /// A resolver that takes care of resolution, taking into account loaded
 /// import map, JSX settings.
 #[derive(Debug)]
 pub struct CliGraphResolver {
   node_resolver: Option<Arc<CliNodeResolver>>,
   npm_resolver: Option<Arc<dyn CliNpmResolver>>,
-  sloppy_imports_resolver: Option<Arc<SloppyImportsResolver>>,
+  sloppy_imports_resolver: Option<Arc<CliSloppyImportsResolver>>,
   workspace_resolver: Arc<WorkspaceResolver>,
   maybe_default_jsx_import_source: Option<String>,
   maybe_default_jsx_import_source_types: Option<String>,
@@ -441,7 +445,7 @@ pub struct CliGraphResolver {
 pub struct CliGraphResolverOptions<'a> {
   pub node_resolver: Option<Arc<CliNodeResolver>>,
   pub npm_resolver: Option<Arc<dyn CliNpmResolver>>,
-  pub sloppy_imports_resolver: Option<Arc<SloppyImportsResolver>>,
+  pub sloppy_imports_resolver: Option<Arc<CliSloppyImportsResolver>>,
   pub workspace_resolver: Arc<WorkspaceResolver>,
   pub bare_node_builtins_enabled: bool,
   pub maybe_jsx_import_source_config: Option<JsxImportSourceConfig>,
@@ -565,7 +569,15 @@ impl Resolver for CliGraphResolver {
           if let Some(sloppy_imports_resolver) = &self.sloppy_imports_resolver {
             Ok(
               sloppy_imports_resolver
-                .resolve(&specifier, mode)
+                .resolve(
+                  &specifier,
+                  match mode {
+                    ResolutionMode::Execution => {
+                      SloppyImportsResolutionMode::Execution
+                    }
+                    ResolutionMode::Types => SloppyImportsResolutionMode::Types,
+                  },
+                )
                 .map(|s| s.into_specifier())
                 .unwrap_or(specifier),
             )
@@ -847,96 +859,18 @@ impl<'a> deno_graph::source::NpmResolver for WorkerCliNpmGraphResolver<'a> {
   }
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum SloppyImportsFsEntry {
-  File,
-  Dir,
-}
-
-impl SloppyImportsFsEntry {
-  pub fn from_fs_stat(
-    stat: &deno_runtime::deno_io::fs::FsStat,
-  ) -> Option<SloppyImportsFsEntry> {
-    if stat.is_file {
-      Some(SloppyImportsFsEntry::File)
-    } else if stat.is_directory {
-      Some(SloppyImportsFsEntry::Dir)
-    } else {
-      None
-    }
-  }
-}
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum SloppyImportsResolution {
-  /// Ex. `./file.js` to `./file.ts`
-  JsToTs(ModuleSpecifier),
-  /// Ex. `./file` to `./file.ts`
-  NoExtension(ModuleSpecifier),
-  /// Ex. `./dir` to `./dir/index.ts`
-  Directory(ModuleSpecifier),
-}
-
-impl SloppyImportsResolution {
-  pub fn as_specifier(&self) -> &ModuleSpecifier {
-    match self {
-      Self::JsToTs(specifier) => specifier,
-      Self::NoExtension(specifier) => specifier,
-      Self::Directory(specifier) => specifier,
-    }
-  }
-
-  pub fn into_specifier(self) -> ModuleSpecifier {
-    match self {
-      Self::JsToTs(specifier) => specifier,
-      Self::NoExtension(specifier) => specifier,
-      Self::Directory(specifier) => specifier,
-    }
-  }
-
-  pub fn as_suggestion_message(&self) -> String {
-    format!("Maybe {}", self.as_base_message())
-  }
-
-  pub fn as_quick_fix_message(&self) -> String {
-    let message = self.as_base_message();
-    let mut chars = message.chars();
-    format!(
-      "{}{}.",
-      chars.next().unwrap().to_uppercase(),
-      chars.as_str()
-    )
-  }
-
-  fn as_base_message(&self) -> String {
-    match self {
-      SloppyImportsResolution::JsToTs(specifier) => {
-        let media_type = MediaType::from_specifier(specifier);
-        format!("change the extension to '{}'", media_type.as_ts_extension())
-      }
-      SloppyImportsResolution::NoExtension(specifier) => {
-        let media_type = MediaType::from_specifier(specifier);
-        format!("add a '{}' extension", media_type.as_ts_extension())
-      }
-      SloppyImportsResolution::Directory(specifier) => {
-        let file_name = specifier
-          .path()
-          .rsplit_once('/')
-          .map(|(_, file_name)| file_name)
-          .unwrap_or(specifier.path());
-        format!("specify path to '{}' file in directory instead", file_name)
-      }
-    }
-  }
-}
-
 #[derive(Debug)]
-pub struct SloppyImportsResolver {
+pub struct SloppyImportsCachedFs {
-  fs: Arc<dyn FileSystem>,
+  fs: Arc<dyn deno_fs::FileSystem>,
-  cache: Option<DashMap<PathBuf, Option<SloppyImportsFsEntry>>>,
+  cache: Option<
+    DashMap<
+      PathBuf,
+      Option<deno_resolver::sloppy_imports::SloppyImportsFsEntry>,
+    >,
+  >,
 }
 
-impl SloppyImportsResolver {
+impl SloppyImportsCachedFs {
   pub fn new(fs: Arc<dyn FileSystem>) -> Self {
     Self {
       fs,
@@ -947,409 +881,34 @@ impl SloppyImportsResolver {
   pub fn new_without_stat_cache(fs: Arc<dyn FileSystem>) -> Self {
     Self { fs, cache: None }
   }
+}
 
-  pub fn resolve(
+impl deno_resolver::sloppy_imports::SloppyImportResolverFs
+  for SloppyImportsCachedFs
+{
+  fn stat_sync(
     &self,
-    specifier: &ModuleSpecifier,
+    path: &Path,
-    mode: ResolutionMode,
+  ) -> Option<deno_resolver::sloppy_imports::SloppyImportsFsEntry> {
-  ) -> Option<SloppyImportsResolution> {
-    fn path_without_ext(
-      path: &Path,
-      media_type: MediaType,
-    ) -> Option<Cow<str>> {
-      let old_path_str = path.to_string_lossy();
-      match media_type {
-        MediaType::Unknown => Some(old_path_str),
-        _ => old_path_str
-          .strip_suffix(media_type.as_ts_extension())
-          .map(|s| Cow::Owned(s.to_string())),
-      }
-    }
-
-    fn media_types_to_paths(
-      path_no_ext: &str,
-      original_media_type: MediaType,
-      probe_media_type_types: Vec<MediaType>,
-      reason: SloppyImportsResolutionReason,
-    ) -> Vec<(PathBuf, SloppyImportsResolutionReason)> {
-      probe_media_type_types
-        .into_iter()
-        .filter(|media_type| *media_type != original_media_type)
-        .map(|media_type| {
-          (
-            PathBuf::from(format!(
-              "{}{}",
-              path_no_ext,
-              media_type.as_ts_extension()
-            )),
-            reason,
-          )
-        })
-        .collect::<Vec<_>>()
-    }
-
-    if specifier.scheme() != "file" {
-      return None;
-    }
-
-    let path = url_to_file_path(specifier).ok()?;
-
-    #[derive(Clone, Copy)]
-    enum SloppyImportsResolutionReason {
-      JsToTs,
-      NoExtension,
-      Directory,
-    }
-
-    let probe_paths: Vec<(PathBuf, SloppyImportsResolutionReason)> =
-      match self.stat_sync(&path) {
-        Some(SloppyImportsFsEntry::File) => {
-          if mode.is_types() {
-            let media_type = MediaType::from_specifier(specifier);
-            // attempt to resolve the .d.ts file before the .js file
-            let probe_media_type_types = match media_type {
-              MediaType::JavaScript => {
-                vec![(MediaType::Dts), MediaType::JavaScript]
-              }
-              MediaType::Mjs => {
-                vec![MediaType::Dmts, MediaType::Dts, MediaType::Mjs]
-              }
-              MediaType::Cjs => {
-                vec![MediaType::Dcts, MediaType::Dts, MediaType::Cjs]
-              }
-              _ => return None,
-            };
-            let path_no_ext = path_without_ext(&path, media_type)?;
-            media_types_to_paths(
-              &path_no_ext,
-              media_type,
-              probe_media_type_types,
-              SloppyImportsResolutionReason::JsToTs,
-            )
-          } else {
-            return None;
-          }
-        }
-        entry @ None | entry @ Some(SloppyImportsFsEntry::Dir) => {
-          let media_type = MediaType::from_specifier(specifier);
-          let probe_media_type_types = match media_type {
-            MediaType::JavaScript => (
-              if mode.is_types() {
-                vec![MediaType::TypeScript, MediaType::Tsx, MediaType::Dts]
-              } else {
-                vec![MediaType::TypeScript, MediaType::Tsx]
-              },
-              SloppyImportsResolutionReason::JsToTs,
-            ),
-            MediaType::Jsx => {
-              (vec![MediaType::Tsx], SloppyImportsResolutionReason::JsToTs)
-            }
-            MediaType::Mjs => (
-              if mode.is_types() {
-                vec![MediaType::Mts, MediaType::Dmts, MediaType::Dts]
-              } else {
-                vec![MediaType::Mts]
-              },
-              SloppyImportsResolutionReason::JsToTs,
-            ),
-            MediaType::Cjs => (
-              if mode.is_types() {
-                vec![MediaType::Cts, MediaType::Dcts, MediaType::Dts]
-              } else {
-                vec![MediaType::Cts]
-              },
-              SloppyImportsResolutionReason::JsToTs,
-            ),
-            MediaType::TypeScript
-            | MediaType::Mts
-            | MediaType::Cts
-            | MediaType::Dts
-            | MediaType::Dmts
-            | MediaType::Dcts
-            | MediaType::Tsx
-            | MediaType::Json
-            | MediaType::Wasm
-            | MediaType::TsBuildInfo
-            | MediaType::SourceMap => {
-              return None;
-            }
-            MediaType::Unknown => (
-              if mode.is_types() {
-                vec![
-                  MediaType::TypeScript,
-                  MediaType::Tsx,
-                  MediaType::Mts,
-                  MediaType::Dts,
-                  MediaType::Dmts,
-                  MediaType::Dcts,
-                  MediaType::JavaScript,
-                  MediaType::Jsx,
-                  MediaType::Mjs,
-                ]
-              } else {
-                vec![
-                  MediaType::TypeScript,
-                  MediaType::JavaScript,
-                  MediaType::Tsx,
-                  MediaType::Jsx,
-                  MediaType::Mts,
-                  MediaType::Mjs,
-                ]
-              },
-              SloppyImportsResolutionReason::NoExtension,
-            ),
-          };
-          let mut probe_paths = match path_without_ext(&path, media_type) {
-            Some(path_no_ext) => media_types_to_paths(
-              &path_no_ext,
-              media_type,
-              probe_media_type_types.0,
-              probe_media_type_types.1,
-            ),
-            None => vec![],
-          };
-
-          if matches!(entry, Some(SloppyImportsFsEntry::Dir)) {
-            // try to resolve at the index file
-            if mode.is_types() {
-              probe_paths.push((
-                path.join("index.ts"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-
-              probe_paths.push((
-                path.join("index.mts"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.d.ts"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.d.mts"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.js"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.mjs"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.tsx"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.jsx"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-            } else {
-              probe_paths.push((
-                path.join("index.ts"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.mts"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.tsx"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.js"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.mjs"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-              probe_paths.push((
-                path.join("index.jsx"),
-                SloppyImportsResolutionReason::Directory,
-              ));
-            }
-          }
-          if probe_paths.is_empty() {
-            return None;
-          }
-          probe_paths
-        }
-      };
-
-    for (probe_path, reason) in probe_paths {
-      if self.stat_sync(&probe_path) == Some(SloppyImportsFsEntry::File) {
-        if let Ok(specifier) = ModuleSpecifier::from_file_path(probe_path) {
-          match reason {
-            SloppyImportsResolutionReason::JsToTs => {
-              return Some(SloppyImportsResolution::JsToTs(specifier));
-            }
-            SloppyImportsResolutionReason::NoExtension => {
-              return Some(SloppyImportsResolution::NoExtension(specifier));
-            }
-            SloppyImportsResolutionReason::Directory => {
-              return Some(SloppyImportsResolution::Directory(specifier));
-            }
-          }
-        }
-      }
-    }
-
-    None
-  }
-
-  fn stat_sync(&self, path: &Path) -> Option<SloppyImportsFsEntry> {
     if let Some(cache) = &self.cache {
       if let Some(entry) = cache.get(path) {
         return *entry;
       }
     }
 
-    let entry = self
+    let entry = self.fs.stat_sync(path).ok().and_then(|stat| {
-      .fs
+      if stat.is_file {
-      .stat_sync(path)
+        Some(deno_resolver::sloppy_imports::SloppyImportsFsEntry::File)
-      .ok()
+      } else if stat.is_directory {
-      .and_then(|stat| SloppyImportsFsEntry::from_fs_stat(&stat));
+        Some(deno_resolver::sloppy_imports::SloppyImportsFsEntry::Dir)
+      } else {
+        None
+      }
+    });
+
     if let Some(cache) = &self.cache {
       cache.insert(path.to_owned(), entry);
     }
     entry
   }
 }
-
-#[cfg(test)]
-mod test {
-  use test_util::TestContext;
-
-  use super::*;
-
-  #[test]
-  fn test_unstable_sloppy_imports() {
-    fn resolve(specifier: &ModuleSpecifier) -> Option<SloppyImportsResolution> {
-      resolve_with_mode(specifier, ResolutionMode::Execution)
-    }
-
-    fn resolve_types(
-      specifier: &ModuleSpecifier,
-    ) -> Option<SloppyImportsResolution> {
-      resolve_with_mode(specifier, ResolutionMode::Types)
-    }
-
-    fn resolve_with_mode(
-      specifier: &ModuleSpecifier,
-      mode: ResolutionMode,
-    ) -> Option<SloppyImportsResolution> {
-      SloppyImportsResolver::new(Arc::new(deno_fs::RealFs))
-        .resolve(specifier, mode)
-    }
-
-    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("");
-      assert_eq!(resolve(&ts_file.url_file()), None);
-      assert_eq!(
-        resolve(
-          &temp_dir
-            .url_dir()
-            .join(&format!("file.{}", ext_from))
-            .unwrap()
-        ),
-        Some(SloppyImportsResolution::JsToTs(ts_file.url_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
-            .url_dir()
-            .join("file") // no ext
-            .unwrap()
-        ),
-        Some(SloppyImportsResolution::NoExtension(file.url_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("");
-      assert_eq!(resolve(&js_file.url_file()), None);
-    }
-
-    // only js exists, .js specified
-    {
-      let js_only_file = temp_dir.join("js_only.js");
-      js_only_file.write("");
-      assert_eq!(resolve(&js_only_file.url_file()), None);
-      assert_eq!(resolve_types(&js_only_file.url_file()), None);
-    }
-
-    // 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.url_file()),
-        Some(SloppyImportsResolution::Directory(index_file.url_file())),
-      );
-    }
-
-    // both a directory and a file with specifier is present
-    {
-      let api_dir = temp_dir.join("api");
-      api_dir.create_dir_all();
-      let bar_file = api_dir.join("bar.ts");
-      bar_file.write("");
-      let api_file = temp_dir.join("api.ts");
-      api_file.write("");
-      assert_eq!(
-        resolve(&api_dir.url_file()),
-        Some(SloppyImportsResolution::NoExtension(api_file.url_file())),
-      );
-    }
-  }
-
-  #[test]
-  fn test_sloppy_import_resolution_suggestion_message() {
-    // directory
-    assert_eq!(
-      SloppyImportsResolution::Directory(
-        ModuleSpecifier::parse("file:///dir/index.js").unwrap()
-      )
-      .as_suggestion_message(),
-      "Maybe specify path to 'index.js' file in directory instead"
-    );
-    // no ext
-    assert_eq!(
-      SloppyImportsResolution::NoExtension(
-        ModuleSpecifier::parse("file:///dir/index.mjs").unwrap()
-      )
-      .as_suggestion_message(),
-      "Maybe add a '.mjs' extension"
-    );
-    // js to ts
-    assert_eq!(
-      SloppyImportsResolution::JsToTs(
-        ModuleSpecifier::parse("file:///dir/index.mts").unwrap()
-      )
-      .as_suggestion_message(),
-      "Maybe change the extension to '.mts'"
-    );
-  }
-}

cli/tools/lint/rules/mod.rs

@@ -14,7 +14,7 @@ use deno_graph::ModuleGraph;
 use deno_lint::diagnostic::LintDiagnostic;
 use deno_lint::rules::LintRule;
 
-use crate::resolver::SloppyImportsResolver;
+use crate::resolver::CliSloppyImportsResolver;
 
 mod no_sloppy_imports;
 mod no_slow_types;
@@ -144,13 +144,13 @@ impl ConfiguredRules {
 }
 
 pub struct LintRuleProvider {
-  sloppy_imports_resolver: Option<Arc<SloppyImportsResolver>>,
+  sloppy_imports_resolver: Option<Arc<CliSloppyImportsResolver>>,
   workspace_resolver: Option<Arc<WorkspaceResolver>>,
 }
 
 impl LintRuleProvider {
   pub fn new(
-    sloppy_imports_resolver: Option<Arc<SloppyImportsResolver>>,
+    sloppy_imports_resolver: Option<Arc<CliSloppyImportsResolver>>,
     workspace_resolver: Option<Arc<WorkspaceResolver>>,
   ) -> Self {
     Self {

cli/tools/lint/rules/no_sloppy_imports.rs

@@ -16,24 +16,25 @@ use deno_lint::diagnostic::LintDiagnosticRange;
 use deno_lint::diagnostic::LintFix;
 use deno_lint::diagnostic::LintFixChange;
 use deno_lint::rules::LintRule;
+use deno_resolver::sloppy_imports::SloppyImportsResolution;
+use deno_resolver::sloppy_imports::SloppyImportsResolutionMode;
 use text_lines::LineAndColumnIndex;
 
 use crate::graph_util::CliJsrUrlProvider;
-use crate::resolver::SloppyImportsResolution;
+use crate::resolver::CliSloppyImportsResolver;
-use crate::resolver::SloppyImportsResolver;
 
 use super::ExtendedLintRule;
 
 #[derive(Debug)]
 pub struct NoSloppyImportsRule {
-  sloppy_imports_resolver: Option<Arc<SloppyImportsResolver>>,
+  sloppy_imports_resolver: Option<Arc<CliSloppyImportsResolver>>,
   // None for making printing out the lint rules easy
   workspace_resolver: Option<Arc<WorkspaceResolver>>,
 }
 
 impl NoSloppyImportsRule {
   pub fn new(
-    sloppy_imports_resolver: Option<Arc<SloppyImportsResolver>>,
+    sloppy_imports_resolver: Option<Arc<CliSloppyImportsResolver>>,
     workspace_resolver: Option<Arc<WorkspaceResolver>>,
   ) -> Self {
     NoSloppyImportsRule {
@@ -172,7 +173,7 @@ impl LintRule for NoSloppyImportsRule {
 #[derive(Debug)]
 struct SloppyImportCaptureResolver<'a> {
   workspace_resolver: &'a WorkspaceResolver,
-  sloppy_imports_resolver: &'a SloppyImportsResolver,
+  sloppy_imports_resolver: &'a CliSloppyImportsResolver,
   captures: RefCell<HashMap<Range, SloppyImportsResolution>>,
 }
 
@@ -194,7 +195,13 @@ impl<'a> deno_graph::source::Resolver for SloppyImportCaptureResolver<'a> {
       }
       | deno_config::workspace::MappedResolution::ImportMap {
         specifier, ..
-      } => match self.sloppy_imports_resolver.resolve(&specifier, mode) {
+      } => match self.sloppy_imports_resolver.resolve(
+        &specifier,
+        match mode {
+          ResolutionMode::Execution => SloppyImportsResolutionMode::Execution,
+          ResolutionMode::Types => SloppyImportsResolutionMode::Types,
+        },
+      ) {
         Some(res) => {
           self
             .captures

cli/tools/registry/mod.rs

@@ -43,7 +43,8 @@ use crate::cache::ParsedSourceCache;
 use crate::factory::CliFactory;
 use crate::graph_util::ModuleGraphCreator;
 use crate::http_util::HttpClient;
-use crate::resolver::SloppyImportsResolver;
+use crate::resolver::CliSloppyImportsResolver;
+use crate::resolver::SloppyImportsCachedFs;
 use crate::tools::check::CheckOptions;
 use crate::tools::lint::collect_no_slow_type_diagnostics;
 use crate::tools::registry::diagnostics::PublishDiagnostic;
@@ -108,7 +109,9 @@ pub async fn publish(
   }
   let specifier_unfurler = Arc::new(SpecifierUnfurler::new(
     if cli_options.unstable_sloppy_imports() {
-      Some(SloppyImportsResolver::new(cli_factory.fs().clone()))
+      Some(CliSloppyImportsResolver::new(SloppyImportsCachedFs::new(
+        cli_factory.fs().clone(),
+      )))
     } else {
       None
     },

cli/tools/registry/unfurl.rs

@@ -12,9 +12,10 @@ use deno_graph::DynamicTemplatePart;
 use deno_graph::ParserModuleAnalyzer;
 use deno_graph::TypeScriptReference;
 use deno_package_json::PackageJsonDepValue;
+use deno_resolver::sloppy_imports::SloppyImportsResolutionMode;
 use deno_runtime::deno_node::is_builtin_node_module;
 
-use crate::resolver::SloppyImportsResolver;
+use crate::resolver::CliSloppyImportsResolver;
 
 #[derive(Debug, Clone)]
 pub enum SpecifierUnfurlerDiagnostic {
@@ -42,14 +43,14 @@ impl SpecifierUnfurlerDiagnostic {
 }
 
 pub struct SpecifierUnfurler {
-  sloppy_imports_resolver: Option<SloppyImportsResolver>,
+  sloppy_imports_resolver: Option<CliSloppyImportsResolver>,
   workspace_resolver: WorkspaceResolver,
   bare_node_builtins: bool,
 }
 
 impl SpecifierUnfurler {
   pub fn new(
-    sloppy_imports_resolver: Option<SloppyImportsResolver>,
+    sloppy_imports_resolver: Option<CliSloppyImportsResolver>,
     workspace_resolver: WorkspaceResolver,
     bare_node_builtins: bool,
   ) -> Self {
@@ -179,7 +180,7 @@ impl SpecifierUnfurler {
     let resolved =
       if let Some(sloppy_imports_resolver) = &self.sloppy_imports_resolver {
         sloppy_imports_resolver
-          .resolve(&resolved, deno_graph::source::ResolutionMode::Execution)
+          .resolve(&resolved, SloppyImportsResolutionMode::Execution)
           .map(|res| res.into_specifier())
           .unwrap_or(resolved)
       } else {
@@ -388,6 +389,8 @@ fn to_range(
 mod tests {
   use std::sync::Arc;
 
+  use crate::resolver::SloppyImportsCachedFs;
+
   use super::*;
   use deno_ast::MediaType;
   use deno_ast::ModuleSpecifier;
@@ -455,7 +458,9 @@ mod tests {
     );
     let fs = Arc::new(RealFs);
     let unfurler = SpecifierUnfurler::new(
-      Some(SloppyImportsResolver::new(fs)),
+      Some(CliSloppyImportsResolver::new(SloppyImportsCachedFs::new(
+        fs,
+      ))),
       workspace_resolver,
       true,
     );

resolvers/deno/Cargo.toml

@@ -0,0 +1,24 @@
+# Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+[package]
+name = "deno_resolver"
+version = "0.0.1"
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+readme = "README.md"
+repository.workspace = true
+description = "Deno resolution algorithm"
+
+[lib]
+path = "lib.rs"
+
+[features]
+
+[dependencies]
+deno_media_type.workspace = true
+deno_path_util.workspace = true
+url.workspace = true
+
+[dev-dependencies]
+test_util.workspace = true

resolvers/deno/README.md

@@ -0,0 +1,3 @@
+# deno_resolver
+
+Deno resolution algorithm.

resolvers/deno/lib.rs

@@ -0,0 +1,3 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+pub mod sloppy_imports;

resolvers/deno/sloppy_imports.rs

@@ -0,0 +1,511 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+use std::borrow::Cow;
+use std::path::Path;
+use std::path::PathBuf;
+
+use deno_media_type::MediaType;
+use deno_path_util::url_to_file_path;
+use url::Url;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum SloppyImportsFsEntry {
+  File,
+  Dir,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum SloppyImportsResolution {
+  /// Ex. `./file.js` to `./file.ts`
+  JsToTs(Url),
+  /// Ex. `./file` to `./file.ts`
+  NoExtension(Url),
+  /// Ex. `./dir` to `./dir/index.ts`
+  Directory(Url),
+}
+
+impl SloppyImportsResolution {
+  pub fn as_specifier(&self) -> &Url {
+    match self {
+      Self::JsToTs(specifier) => specifier,
+      Self::NoExtension(specifier) => specifier,
+      Self::Directory(specifier) => specifier,
+    }
+  }
+
+  pub fn into_specifier(self) -> Url {
+    match self {
+      Self::JsToTs(specifier) => specifier,
+      Self::NoExtension(specifier) => specifier,
+      Self::Directory(specifier) => specifier,
+    }
+  }
+
+  pub fn as_suggestion_message(&self) -> String {
+    format!("Maybe {}", self.as_base_message())
+  }
+
+  pub fn as_quick_fix_message(&self) -> String {
+    let message = self.as_base_message();
+    let mut chars = message.chars();
+    format!(
+      "{}{}.",
+      chars.next().unwrap().to_uppercase(),
+      chars.as_str()
+    )
+  }
+
+  fn as_base_message(&self) -> String {
+    match self {
+      SloppyImportsResolution::JsToTs(specifier) => {
+        let media_type = MediaType::from_specifier(specifier);
+        format!("change the extension to '{}'", media_type.as_ts_extension())
+      }
+      SloppyImportsResolution::NoExtension(specifier) => {
+        let media_type = MediaType::from_specifier(specifier);
+        format!("add a '{}' extension", media_type.as_ts_extension())
+      }
+      SloppyImportsResolution::Directory(specifier) => {
+        let file_name = specifier
+          .path()
+          .rsplit_once('/')
+          .map(|(_, file_name)| file_name)
+          .unwrap_or(specifier.path());
+        format!("specify path to '{}' file in directory instead", file_name)
+      }
+    }
+  }
+}
+
+/// The kind of resolution currently being done.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum SloppyImportsResolutionMode {
+  /// Resolving for code that will be executed.
+  Execution,
+  /// Resolving for code that will be used for type information.
+  Types,
+}
+
+impl SloppyImportsResolutionMode {
+  pub fn is_types(&self) -> bool {
+    *self == SloppyImportsResolutionMode::Types
+  }
+}
+
+pub trait SloppyImportResolverFs {
+  fn stat_sync(&self, path: &Path) -> Option<SloppyImportsFsEntry>;
+
+  fn is_file(&self, path: &Path) -> bool {
+    self.stat_sync(path) == Some(SloppyImportsFsEntry::File)
+  }
+}
+
+#[derive(Debug)]
+pub struct SloppyImportsResolver<Fs: SloppyImportResolverFs> {
+  fs: Fs,
+}
+
+impl<Fs: SloppyImportResolverFs> SloppyImportsResolver<Fs> {
+  pub fn new(fs: Fs) -> Self {
+    Self { fs }
+  }
+
+  pub fn resolve(
+    &self,
+    specifier: &Url,
+    mode: SloppyImportsResolutionMode,
+  ) -> Option<SloppyImportsResolution> {
+    fn path_without_ext(
+      path: &Path,
+      media_type: MediaType,
+    ) -> Option<Cow<str>> {
+      let old_path_str = path.to_string_lossy();
+      match media_type {
+        MediaType::Unknown => Some(old_path_str),
+        _ => old_path_str
+          .strip_suffix(media_type.as_ts_extension())
+          .map(|s| Cow::Owned(s.to_string())),
+      }
+    }
+
+    fn media_types_to_paths(
+      path_no_ext: &str,
+      original_media_type: MediaType,
+      probe_media_type_types: Vec<MediaType>,
+      reason: SloppyImportsResolutionReason,
+    ) -> Vec<(PathBuf, SloppyImportsResolutionReason)> {
+      probe_media_type_types
+        .into_iter()
+        .filter(|media_type| *media_type != original_media_type)
+        .map(|media_type| {
+          (
+            PathBuf::from(format!(
+              "{}{}",
+              path_no_ext,
+              media_type.as_ts_extension()
+            )),
+            reason,
+          )
+        })
+        .collect::<Vec<_>>()
+    }
+
+    if specifier.scheme() != "file" {
+      return None;
+    }
+
+    let path = url_to_file_path(specifier).ok()?;
+
+    #[derive(Clone, Copy)]
+    enum SloppyImportsResolutionReason {
+      JsToTs,
+      NoExtension,
+      Directory,
+    }
+
+    let probe_paths: Vec<(PathBuf, SloppyImportsResolutionReason)> =
+      match self.fs.stat_sync(&path) {
+        Some(SloppyImportsFsEntry::File) => {
+          if mode.is_types() {
+            let media_type = MediaType::from_specifier(specifier);
+            // attempt to resolve the .d.ts file before the .js file
+            let probe_media_type_types = match media_type {
+              MediaType::JavaScript => {
+                vec![(MediaType::Dts), MediaType::JavaScript]
+              }
+              MediaType::Mjs => {
+                vec![MediaType::Dmts, MediaType::Dts, MediaType::Mjs]
+              }
+              MediaType::Cjs => {
+                vec![MediaType::Dcts, MediaType::Dts, MediaType::Cjs]
+              }
+              _ => return None,
+            };
+            let path_no_ext = path_without_ext(&path, media_type)?;
+            media_types_to_paths(
+              &path_no_ext,
+              media_type,
+              probe_media_type_types,
+              SloppyImportsResolutionReason::JsToTs,
+            )
+          } else {
+            return None;
+          }
+        }
+        entry @ None | entry @ Some(SloppyImportsFsEntry::Dir) => {
+          let media_type = MediaType::from_specifier(specifier);
+          let probe_media_type_types = match media_type {
+            MediaType::JavaScript => (
+              if mode.is_types() {
+                vec![MediaType::TypeScript, MediaType::Tsx, MediaType::Dts]
+              } else {
+                vec![MediaType::TypeScript, MediaType::Tsx]
+              },
+              SloppyImportsResolutionReason::JsToTs,
+            ),
+            MediaType::Jsx => {
+              (vec![MediaType::Tsx], SloppyImportsResolutionReason::JsToTs)
+            }
+            MediaType::Mjs => (
+              if mode.is_types() {
+                vec![MediaType::Mts, MediaType::Dmts, MediaType::Dts]
+              } else {
+                vec![MediaType::Mts]
+              },
+              SloppyImportsResolutionReason::JsToTs,
+            ),
+            MediaType::Cjs => (
+              if mode.is_types() {
+                vec![MediaType::Cts, MediaType::Dcts, MediaType::Dts]
+              } else {
+                vec![MediaType::Cts]
+              },
+              SloppyImportsResolutionReason::JsToTs,
+            ),
+            MediaType::TypeScript
+            | MediaType::Mts
+            | MediaType::Cts
+            | MediaType::Dts
+            | MediaType::Dmts
+            | MediaType::Dcts
+            | MediaType::Tsx
+            | MediaType::Json
+            | MediaType::Wasm
+            | MediaType::TsBuildInfo
+            | MediaType::SourceMap => {
+              return None;
+            }
+            MediaType::Unknown => (
+              if mode.is_types() {
+                vec![
+                  MediaType::TypeScript,
+                  MediaType::Tsx,
+                  MediaType::Mts,
+                  MediaType::Dts,
+                  MediaType::Dmts,
+                  MediaType::Dcts,
+                  MediaType::JavaScript,
+                  MediaType::Jsx,
+                  MediaType::Mjs,
+                ]
+              } else {
+                vec![
+                  MediaType::TypeScript,
+                  MediaType::JavaScript,
+                  MediaType::Tsx,
+                  MediaType::Jsx,
+                  MediaType::Mts,
+                  MediaType::Mjs,
+                ]
+              },
+              SloppyImportsResolutionReason::NoExtension,
+            ),
+          };
+          let mut probe_paths = match path_without_ext(&path, media_type) {
+            Some(path_no_ext) => media_types_to_paths(
+              &path_no_ext,
+              media_type,
+              probe_media_type_types.0,
+              probe_media_type_types.1,
+            ),
+            None => vec![],
+          };
+
+          if matches!(entry, Some(SloppyImportsFsEntry::Dir)) {
+            // try to resolve at the index file
+            if mode.is_types() {
+              probe_paths.push((
+                path.join("index.ts"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+
+              probe_paths.push((
+                path.join("index.mts"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.d.ts"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.d.mts"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.js"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.mjs"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.tsx"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.jsx"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+            } else {
+              probe_paths.push((
+                path.join("index.ts"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.mts"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.tsx"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.js"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.mjs"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+              probe_paths.push((
+                path.join("index.jsx"),
+                SloppyImportsResolutionReason::Directory,
+              ));
+            }
+          }
+          if probe_paths.is_empty() {
+            return None;
+          }
+          probe_paths
+        }
+      };
+
+    for (probe_path, reason) in probe_paths {
+      if self.fs.is_file(&probe_path) {
+        if let Ok(specifier) = Url::from_file_path(probe_path) {
+          match reason {
+            SloppyImportsResolutionReason::JsToTs => {
+              return Some(SloppyImportsResolution::JsToTs(specifier));
+            }
+            SloppyImportsResolutionReason::NoExtension => {
+              return Some(SloppyImportsResolution::NoExtension(specifier));
+            }
+            SloppyImportsResolutionReason::Directory => {
+              return Some(SloppyImportsResolution::Directory(specifier));
+            }
+          }
+        }
+      }
+    }
+
+    None
+  }
+}
+
+#[cfg(test)]
+mod test {
+  use test_util::TestContext;
+
+  use super::*;
+
+  #[test]
+  fn test_unstable_sloppy_imports() {
+    fn resolve(specifier: &Url) -> Option<SloppyImportsResolution> {
+      resolve_with_mode(specifier, SloppyImportsResolutionMode::Execution)
+    }
+
+    fn resolve_types(specifier: &Url) -> Option<SloppyImportsResolution> {
+      resolve_with_mode(specifier, SloppyImportsResolutionMode::Types)
+    }
+
+    fn resolve_with_mode(
+      specifier: &Url,
+      mode: SloppyImportsResolutionMode,
+    ) -> Option<SloppyImportsResolution> {
+      struct RealSloppyImportsResolverFs;
+      impl SloppyImportResolverFs for RealSloppyImportsResolverFs {
+        fn stat_sync(&self, path: &Path) -> Option<SloppyImportsFsEntry> {
+          let stat = std::fs::metadata(path).ok()?;
+          if stat.is_dir() {
+            Some(SloppyImportsFsEntry::Dir)
+          } else if stat.is_file() {
+            Some(SloppyImportsFsEntry::File)
+          } else {
+            None
+          }
+        }
+      }
+
+      SloppyImportsResolver::new(RealSloppyImportsResolverFs)
+        .resolve(specifier, mode)
+    }
+
+    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("");
+      assert_eq!(resolve(&ts_file.url_file()), None);
+      assert_eq!(
+        resolve(
+          &temp_dir
+            .url_dir()
+            .join(&format!("file.{}", ext_from))
+            .unwrap()
+        ),
+        Some(SloppyImportsResolution::JsToTs(ts_file.url_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
+            .url_dir()
+            .join("file") // no ext
+            .unwrap()
+        ),
+        Some(SloppyImportsResolution::NoExtension(file.url_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("");
+      assert_eq!(resolve(&js_file.url_file()), None);
+    }
+
+    // only js exists, .js specified
+    {
+      let js_only_file = temp_dir.join("js_only.js");
+      js_only_file.write("");
+      assert_eq!(resolve(&js_only_file.url_file()), None);
+      assert_eq!(resolve_types(&js_only_file.url_file()), None);
+    }
+
+    // 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.url_file()),
+        Some(SloppyImportsResolution::Directory(index_file.url_file())),
+      );
+    }
+
+    // both a directory and a file with specifier is present
+    {
+      let api_dir = temp_dir.join("api");
+      api_dir.create_dir_all();
+      let bar_file = api_dir.join("bar.ts");
+      bar_file.write("");
+      let api_file = temp_dir.join("api.ts");
+      api_file.write("");
+      assert_eq!(
+        resolve(&api_dir.url_file()),
+        Some(SloppyImportsResolution::NoExtension(api_file.url_file())),
+      );
+    }
+  }
+
+  #[test]
+  fn test_sloppy_import_resolution_suggestion_message() {
+    // directory
+    assert_eq!(
+      SloppyImportsResolution::Directory(
+        Url::parse("file:///dir/index.js").unwrap()
+      )
+      .as_suggestion_message(),
+      "Maybe specify path to 'index.js' file in directory instead"
+    );
+    // no ext
+    assert_eq!(
+      SloppyImportsResolution::NoExtension(
+        Url::parse("file:///dir/index.mjs").unwrap()
+      )
+      .as_suggestion_message(),
+      "Maybe add a '.mjs' extension"
+    );
+    // js to ts
+    assert_eq!(
+      SloppyImportsResolution::JsToTs(
+        Url::parse("file:///dir/index.mts").unwrap()
+      )
+      .as_suggestion_message(),
+      "Maybe change the extension to '.mts'"
+    );
+  }
+}