feat(unstable): `--unstable-detect-cjs` for respecting explicit `"type": "commonjs"` (#26149)

When using the `--unstable-detect-cjs` flag or adding `"unstable":
["detect-cjs"]` to a deno.json, it will make a JS file CJS if the
closest package.json contains `"type": "commonjs"` and the file is not
an ESM module (no TLA, no `import.meta`, no `import`/`export`).

47 files changed, 519 insertions, 154 deletions

diff --git a/cli/args/flags.rs b/cli/args/flags.rs
index d59e5ac1a..acaf74a67 100644
--- a/cli/args/flags.rs
+++ b/cli/args/flags.rs
@@ -575,7 +575,8 @@ fn parse_packages_allowed_scripts(s: &str) -> Result<String, AnyError> {
 pub struct UnstableConfig {
   // TODO(bartlomieju): remove in Deno 2.5
   pub legacy_flag_enabled: bool, // --unstable
-  pub bare_node_builtins: bool,  // --unstable-bare-node-builts
+  pub bare_node_builtins: bool,
+  pub detect_cjs: bool,
   pub sloppy_imports: bool,
   pub features: Vec<String>, // --unstabe-kv --unstable-cron
 }
@@ -1528,7 +1529,7 @@ pub fn clap_root() -> Command {
   );
 
   run_args(Command::new("deno"), true)
-    .args(unstable_args(UnstableArgsConfig::ResolutionAndRuntime))
+    .with_unstable_args(UnstableArgsConfig::ResolutionAndRuntime)
     .next_line_help(false)
     .bin_name("deno")
     .styles(
@@ -1630,7 +1631,7 @@ fn command(
 ) -> Command {
   Command::new(name)
     .about(about)
-    .args(unstable_args(unstable_args_config))
+    .with_unstable_args(unstable_args_config)
 }
 
 fn help_subcommand(app: &Command) -> Command {
@@ -4142,23 +4143,29 @@ enum UnstableArgsConfig {
   ResolutionAndRuntime,
 }
 
-struct UnstableArgsIter {
-  idx: usize,
-  cfg: UnstableArgsConfig,
+trait CommandExt {
+  fn with_unstable_args(self, cfg: UnstableArgsConfig) -> Self;
 }
 
-impl Iterator for UnstableArgsIter {
-  type Item = Arg;
+impl CommandExt for Command {
+  fn with_unstable_args(self, cfg: UnstableArgsConfig) -> Self {
+    let mut next_display_order = {
+      let mut value = 1000;
+      move || {
+        value += 1;
+        value
+      }
+    };
 
-  fn next(&mut self) -> Option<Self::Item> {
-    let arg = if self.idx == 0 {
+    let mut cmd = self.arg(
       Arg::new("unstable")
-        .long("unstable")
-        .help(cstr!("Enable all unstable features and APIs. Instead of using this flag, consider enabling individual unstable features
+      .long("unstable")
+      .help(cstr!("Enable all unstable features and APIs. Instead of using this flag, consider enabling individual unstable features
   <p(245)>To view the list of individual unstable feature flags, run this command again with --help=unstable</>"))
-        .action(ArgAction::SetTrue)
-        .hide(matches!(self.cfg, UnstableArgsConfig::None))
-    } else if self.idx == 1 {
+      .action(ArgAction::SetTrue)
+      .hide(matches!(cfg, UnstableArgsConfig::None))
+      .display_order(next_display_order())
+    ).arg(
       Arg::new("unstable-bare-node-builtins")
         .long("unstable-bare-node-builtins")
         .help("Enable unstable bare node builtins feature")
@@ -4166,20 +4173,36 @@ impl Iterator for UnstableArgsIter {
         .value_parser(FalseyValueParser::new())
         .action(ArgAction::SetTrue)
         .hide(true)
-        .long_help(match self.cfg {
+        .long_help(match cfg {
+          UnstableArgsConfig::None => None,
+          UnstableArgsConfig::ResolutionOnly
+          | UnstableArgsConfig::ResolutionAndRuntime => Some("true"),
+        })
+        .help_heading(UNSTABLE_HEADING)
+        .display_order(next_display_order()),
+    ).arg(
+      Arg::new("unstable-detect-cjs")
+        .long("unstable-detect-cjs")
+        .help("Reads the package.json type field in a project to treat .js files as .cjs")
+        .value_parser(FalseyValueParser::new())
+        .action(ArgAction::SetTrue)
+        .hide(true)
+        .long_help(match cfg {
           UnstableArgsConfig::None => None,
           UnstableArgsConfig::ResolutionOnly
           | UnstableArgsConfig::ResolutionAndRuntime => Some("true"),
         })
         .help_heading(UNSTABLE_HEADING)
-    } else if self.idx == 2 {
+        .display_order(next_display_order())
+    ).arg(
       Arg::new("unstable-byonm")
         .long("unstable-byonm")
         .value_parser(FalseyValueParser::new())
         .action(ArgAction::SetTrue)
         .hide(true)
         .help_heading(UNSTABLE_HEADING)
-    } else if self.idx == 3 {
+        .display_order(next_display_order()),
+    ).arg(
       Arg::new("unstable-sloppy-imports")
       .long("unstable-sloppy-imports")
       .help("Enable unstable resolving of specifiers by extension probing, .js to .ts, and directory probing")
@@ -4187,40 +4210,39 @@ impl Iterator for UnstableArgsIter {
       .value_parser(FalseyValueParser::new())
       .action(ArgAction::SetTrue)
       .hide(true)
-      .long_help(match self.cfg {
+      .long_help(match cfg {
         UnstableArgsConfig::None => None,
         UnstableArgsConfig::ResolutionOnly | UnstableArgsConfig::ResolutionAndRuntime => Some("true")
       })
       .help_heading(UNSTABLE_HEADING)
-    } else if self.idx > 3 {
-      let granular_flag = crate::UNSTABLE_GRANULAR_FLAGS.get(self.idx - 4)?;
-      Arg::new(format!("unstable-{}", granular_flag.name))
-        .long(format!("unstable-{}", granular_flag.name))
-        .help(granular_flag.help_text)
-        .action(ArgAction::SetTrue)
-        .hide(true)
-        .help_heading(UNSTABLE_HEADING)
-        // we don't render long help, so using it here as a sort of metadata
-        .long_help(if granular_flag.show_in_help {
-          match self.cfg {
-            UnstableArgsConfig::None | UnstableArgsConfig::ResolutionOnly => {
-              None
+      .display_order(next_display_order())
+    );
+
+    for granular_flag in crate::UNSTABLE_GRANULAR_FLAGS.iter() {
+      cmd = cmd.arg(
+        Arg::new(format!("unstable-{}", granular_flag.name))
+          .long(format!("unstable-{}", granular_flag.name))
+          .help(granular_flag.help_text)
+          .action(ArgAction::SetTrue)
+          .hide(true)
+          .help_heading(UNSTABLE_HEADING)
+          // we don't render long help, so using it here as a sort of metadata
+          .long_help(if granular_flag.show_in_help {
+            match cfg {
+              UnstableArgsConfig::None | UnstableArgsConfig::ResolutionOnly => {
+                None
+              }
+              UnstableArgsConfig::ResolutionAndRuntime => Some("true"),
             }
-            UnstableArgsConfig::ResolutionAndRuntime => Some("true"),
-          }
-        } else {
-          None
-        })
-    } else {
-      return None;
-    };
-    self.idx += 1;
-    Some(arg.display_order(self.idx + 1000))
-  }
-}
+          } else {
+            None
+          })
+          .display_order(next_display_order()),
+      );
+    }
 
-fn unstable_args(cfg: UnstableArgsConfig) -> impl IntoIterator<Item = Arg> {
-  UnstableArgsIter { idx: 0, cfg }
+    cmd
+  }
 }
 
 fn allow_scripts_arg_parse(
@@ -5678,6 +5700,7 @@ fn unstable_args_parse(
 
   flags.unstable_config.bare_node_builtins =
     matches.get_flag("unstable-bare-node-builtins");
+  flags.unstable_config.detect_cjs = matches.get_flag("unstable-detect-cjs");
   flags.unstable_config.sloppy_imports =
     matches.get_flag("unstable-sloppy-imports");
 
diff --git a/cli/args/mod.rs b/cli/args/mod.rs
index 07906a86a..f905e186b 100644
--- a/cli/args/mod.rs
+++ b/cli/args/mod.rs
@@ -1576,6 +1576,11 @@ impl CliOptions {
       || self.workspace().has_unstable("bare-node-builtins")
   }
 
+  pub fn unstable_detect_cjs(&self) -> bool {
+    self.flags.unstable_config.detect_cjs
+      || self.workspace().has_unstable("detect-cjs")
+  }
+
   fn byonm_enabled(&self) -> bool {
     // check if enabled via unstable
     self.node_modules_dir().ok().flatten() == Some(NodeModulesDirMode::Manual)
@@ -1620,21 +1625,17 @@ impl CliOptions {
       });
 
     if !from_config_file.is_empty() {
-      // collect unstable granular flags
-      let mut all_valid_unstable_flags: Vec<&str> =
-        crate::UNSTABLE_GRANULAR_FLAGS
-          .iter()
-          .map(|granular_flag| granular_flag.name)
-          .collect();
-
-      let mut another_unstable_flags = Vec::from([
-        "sloppy-imports",
-        "byonm",
-        "bare-node-builtins",
-        "fmt-component",
-      ]);
-      // add more unstable flags to the same vector holding granular flags
-      all_valid_unstable_flags.append(&mut another_unstable_flags);
+      let all_valid_unstable_flags: Vec<&str> = crate::UNSTABLE_GRANULAR_FLAGS
+        .iter()
+        .map(|granular_flag| granular_flag.name)
+        .chain([
+          "sloppy-imports",
+          "byonm",
+          "bare-node-builtins",
+          "fmt-component",
+          "detect-cjs",
+        ])
+        .collect();
 
       // check and warn if the unstable flag of config file isn't supported, by
       // iterating through the vector holding the unstable flags
diff --git a/cli/cache/mod.rs b/cli/cache/mod.rs
index 628502c50..ded163b4e 100644
--- a/cli/cache/mod.rs
+++ b/cli/cache/mod.rs
@@ -9,10 +9,13 @@ use crate::file_fetcher::FetchPermissionsOptionRef;
 use crate::file_fetcher::FileFetcher;
 use crate::file_fetcher::FileOrRedirect;
 use crate::npm::CliNpmResolver;
+use crate::resolver::CliNodeResolver;
 use crate::util::fs::atomic_write_file_with_retries;
 use crate::util::fs::atomic_write_file_with_retries_and_fs;
 use crate::util::fs::AtomicWriteFileFsAdapter;
 use crate::util::path::specifier_has_extension;
+use crate::util::text_encoding::arc_str_to_bytes;
+use crate::util::text_encoding::from_utf8_lossy_owned;
 
 use deno_ast::MediaType;
 use deno_core::futures;
@@ -57,6 +60,7 @@ pub use fast_check::FastCheckCache;
 pub use incremental::IncrementalCache;
 pub use module_info::ModuleInfoCache;
 pub use node::NodeAnalysisCache;
+pub use parsed_source::EsmOrCjsChecker;
 pub use parsed_source::LazyGraphSourceParser;
 pub use parsed_source::ParsedSourceCache;
 
@@ -177,37 +181,46 @@ pub struct FetchCacherOptions {
   pub permissions: PermissionsContainer,
   /// If we're publishing for `deno publish`.
   pub is_deno_publish: bool,
+  pub unstable_detect_cjs: bool,
 }
 
 /// A "wrapper" for the FileFetcher and DiskCache for the Deno CLI that provides
 /// a concise interface to the DENO_DIR when building module graphs.
 pub struct FetchCacher {
-  file_fetcher: Arc<FileFetcher>,
   pub file_header_overrides: HashMap<ModuleSpecifier, HashMap<String, String>>,
+  esm_or_cjs_checker: Arc<EsmOrCjsChecker>,
+  file_fetcher: Arc<FileFetcher>,
   global_http_cache: Arc<GlobalHttpCache>,
+  node_resolver: Arc<CliNodeResolver>,
   npm_resolver: Arc<dyn CliNpmResolver>,
   module_info_cache: Arc<ModuleInfoCache>,
   permissions: PermissionsContainer,
-  cache_info_enabled: bool,
   is_deno_publish: bool,
+  unstable_detect_cjs: bool,
+  cache_info_enabled: bool,
 }
 
 impl FetchCacher {
   pub fn new(
+    esm_or_cjs_checker: Arc<EsmOrCjsChecker>,
     file_fetcher: Arc<FileFetcher>,
     global_http_cache: Arc<GlobalHttpCache>,
+    node_resolver: Arc<CliNodeResolver>,
     npm_resolver: Arc<dyn CliNpmResolver>,
     module_info_cache: Arc<ModuleInfoCache>,
     options: FetchCacherOptions,
   ) -> Self {
     Self {
       file_fetcher,
+      esm_or_cjs_checker,
       global_http_cache,
+      node_resolver,
       npm_resolver,
       module_info_cache,
       file_header_overrides: options.file_header_overrides,
       permissions: options.permissions,
       is_deno_publish: options.is_deno_publish,
+      unstable_detect_cjs: options.unstable_detect_cjs,
       cache_info_enabled: false,
     }
   }
@@ -282,6 +295,46 @@ impl Loader for FetchCacher {
           },
         ))));
       }
+
+      if self.unstable_detect_cjs && specifier_has_extension(specifier, "js") {
+        if let Ok(Some(pkg_json)) =
+          self.node_resolver.get_closest_package_json(specifier)
+        {
+          if pkg_json.typ == "commonjs" {
+            if let Ok(path) = specifier.to_file_path() {
+              if let Ok(bytes) = std::fs::read(&path) {
+                let text: Arc<str> = from_utf8_lossy_owned(bytes).into();
+                let is_es_module = match self.esm_or_cjs_checker.is_esm(
+                  specifier,
+                  text.clone(),
+                  MediaType::JavaScript,
+                ) {
+                  Ok(value) => value,
+                  Err(err) => {
+                    return Box::pin(futures::future::ready(Err(err.into())));
+                  }
+                };
+                if !is_es_module {
+                  self.node_resolver.mark_cjs_resolution(specifier.clone());
+                  return Box::pin(futures::future::ready(Ok(Some(
+                    LoadResponse::External {
+                      specifier: specifier.clone(),
+                    },
+                  ))));
+                } else {
+                  return Box::pin(futures::future::ready(Ok(Some(
+                    LoadResponse::Module {
+                      specifier: specifier.clone(),
+                      content: arc_str_to_bytes(text),
+                      maybe_headers: None,
+                    },
+                  ))));
+                }
+              }
+            }
+          }
+        }
+      }
     }
 
     if self.is_deno_publish
diff --git a/cli/cache/parsed_source.rs b/cli/cache/parsed_source.rs
index e956361f4..df6e45c35 100644
--- a/cli/cache/parsed_source.rs
+++ b/cli/cache/parsed_source.rs
@@ -5,6 +5,7 @@ use std::sync::Arc;
 
 use deno_ast::MediaType;
 use deno_ast::ModuleSpecifier;
+use deno_ast::ParseDiagnostic;
 use deno_ast::ParsedSource;
 use deno_core::parking_lot::Mutex;
 use deno_graph::CapturingModuleParser;
@@ -149,3 +150,42 @@ impl deno_graph::ParsedSourceStore for ParsedSourceCache {
     }
   }
 }
+
+pub struct EsmOrCjsChecker {
+  parsed_source_cache: Arc<ParsedSourceCache>,
+}
+
+impl EsmOrCjsChecker {
+  pub fn new(parsed_source_cache: Arc<ParsedSourceCache>) -> Self {
+    Self {
+      parsed_source_cache,
+    }
+  }
+
+  pub fn is_esm(
+    &self,
+    specifier: &ModuleSpecifier,
+    source: Arc<str>,
+    media_type: MediaType,
+  ) -> Result<bool, ParseDiagnostic> {
+    // todo(dsherret): add a file cache here to avoid parsing with swc on each run
+    let source = match self.parsed_source_cache.get_parsed_source(specifier) {
+      Some(source) => source.clone(),
+      None => {
+        let source = deno_ast::parse_program(deno_ast::ParseParams {
+          specifier: specifier.clone(),
+          text: source,
+          media_type,
+          capture_tokens: true, // capture because it's used for cjs export analysis
+          scope_analysis: false,
+          maybe_syntax: None,
+        })?;
+        self
+          .parsed_source_cache
+          .set_parsed_source(specifier.clone(), source.clone());
+        source
+      }
+    };
+    Ok(source.is_module())
+  }
+}
diff --git a/cli/factory.rs b/cli/factory.rs
index b96a133e9..25f355110 100644
--- a/cli/factory.rs
+++ b/cli/factory.rs
@@ -14,6 +14,7 @@ use crate::cache::CodeCache;
 use crate::cache::DenoDir;
 use crate::cache::DenoDirProvider;
 use crate::cache::EmitCache;
+use crate::cache::EsmOrCjsChecker;
 use crate::cache::GlobalHttpCache;
 use crate::cache::HttpCache;
 use crate::cache::LocalHttpCache;
@@ -171,6 +172,7 @@ struct CliFactoryServices {
   http_client_provider: Deferred<Arc<HttpClientProvider>>,
   emit_cache: Deferred<Arc<EmitCache>>,
   emitter: Deferred<Arc<Emitter>>,
+  esm_or_cjs_checker: Deferred<Arc<EsmOrCjsChecker>>,
   fs: Deferred<Arc<dyn deno_fs::FileSystem>>,
   main_graph_container: Deferred<Arc<MainModuleGraphContainer>>,
   maybe_inspector_server: Deferred<Option<Arc<InspectorServer>>>,
@@ -298,6 +300,12 @@ impl CliFactory {
       .get_or_init(|| ProgressBar::new(ProgressBarStyle::TextOnly))
   }
 
+  pub fn esm_or_cjs_checker(&self) -> &Arc<EsmOrCjsChecker> {
+    self.services.esm_or_cjs_checker.get_or_init(|| {
+      Arc::new(EsmOrCjsChecker::new(self.parsed_source_cache().clone()))
+    })
+  }
+
   pub fn global_http_cache(&self) -> Result<&Arc<GlobalHttpCache>, AnyError> {
     self.services.global_http_cache.get_or_try_init(|| {
       Ok(Arc::new(GlobalHttpCache::new(
@@ -579,6 +587,7 @@ impl CliFactory {
           node_analysis_cache,
           self.fs().clone(),
           node_resolver,
+          Some(self.parsed_source_cache().clone()),
         );
 
         Ok(Arc::new(NodeCodeTranslator::new(
@@ -619,8 +628,10 @@ impl CliFactory {
         Ok(Arc::new(ModuleGraphBuilder::new(
           cli_options.clone(),
           self.caches()?.clone(),
+          self.esm_or_cjs_checker().clone(),
           self.fs().clone(),
           self.resolver().await?.clone(),
+          self.cli_node_resolver().await?.clone(),
           self.npm_resolver().await?.clone(),
           self.module_info_cache()?.clone(),
           self.parsed_source_cache().clone(),
@@ -792,6 +803,7 @@ impl CliFactory {
 
     Ok(CliMainWorkerFactory::new(
       self.blob_store().clone(),
+      self.cjs_resolutions().clone(),
       if cli_options.code_cache_enabled() {
         Some(self.code_cache()?.clone())
       } else {
@@ -896,6 +908,7 @@ impl CliFactory {
       node_ipc: cli_options.node_ipc_fd(),
       serve_port: cli_options.serve_port(),
       serve_host: cli_options.serve_host(),
+      unstable_detect_cjs: cli_options.unstable_detect_cjs(),
     })
   }
 }
diff --git a/cli/graph_util.rs b/cli/graph_util.rs
index e2f6246e7..e67ae7821 100644
--- a/cli/graph_util.rs
+++ b/cli/graph_util.rs
@@ -6,6 +6,7 @@ use crate::args::CliLockfile;
 use crate::args::CliOptions;
 use crate::args::DENO_DISABLE_PEDANTIC_NODE_WARNINGS;
 use crate::cache;
+use crate::cache::EsmOrCjsChecker;
 use crate::cache::GlobalHttpCache;
 use crate::cache::ModuleInfoCache;
 use crate::cache::ParsedSourceCache;
@@ -14,6 +15,7 @@ use crate::errors::get_error_class_name;
 use crate::file_fetcher::FileFetcher;
 use crate::npm::CliNpmResolver;
 use crate::resolver::CliGraphResolver;
+use crate::resolver::CliNodeResolver;
 use crate::resolver::CliSloppyImportsResolver;
 use crate::resolver::SloppyImportsCachedFs;
 use crate::tools::check;
@@ -379,8 +381,10 @@ pub struct BuildFastCheckGraphOptions<'a> {
 pub struct ModuleGraphBuilder {
   options: Arc<CliOptions>,
   caches: Arc<cache::Caches>,
+  esm_or_cjs_checker: Arc<EsmOrCjsChecker>,
   fs: Arc<dyn FileSystem>,
   resolver: Arc<CliGraphResolver>,
+  node_resolver: Arc<CliNodeResolver>,
   npm_resolver: Arc<dyn CliNpmResolver>,
   module_info_cache: Arc<ModuleInfoCache>,
   parsed_source_cache: Arc<ParsedSourceCache>,
@@ -396,8 +400,10 @@ impl ModuleGraphBuilder {
   pub fn new(
     options: Arc<CliOptions>,
     caches: Arc<cache::Caches>,
+    esm_or_cjs_checker: Arc<EsmOrCjsChecker>,
     fs: Arc<dyn FileSystem>,
     resolver: Arc<CliGraphResolver>,
+    node_resolver: Arc<CliNodeResolver>,
     npm_resolver: Arc<dyn CliNpmResolver>,
     module_info_cache: Arc<ModuleInfoCache>,
     parsed_source_cache: Arc<ParsedSourceCache>,
@@ -410,8 +416,10 @@ impl ModuleGraphBuilder {
     Self {
       options,
       caches,
+      esm_or_cjs_checker,
       fs,
       resolver,
+      node_resolver,
       npm_resolver,
       module_info_cache,
       parsed_source_cache,
@@ -691,8 +699,10 @@ impl ModuleGraphBuilder {
     permissions: PermissionsContainer,
   ) -> cache::FetchCacher {
     cache::FetchCacher::new(
+      self.esm_or_cjs_checker.clone(),
       self.file_fetcher.clone(),
       self.global_http_cache.clone(),
+      self.node_resolver.clone(),
       self.npm_resolver.clone(),
       self.module_info_cache.clone(),
       cache::FetchCacherOptions {
@@ -702,6 +712,7 @@ impl ModuleGraphBuilder {
           self.options.sub_command(),
           crate::args::DenoSubcommand::Publish { .. }
         ),
+        unstable_detect_cjs: self.options.unstable_detect_cjs(),
       },
     )
   }
diff --git a/cli/module_loader.rs b/cli/module_loader.rs
index 293f41dda..37d42f78e 100644
--- a/cli/module_loader.rs
+++ b/cli/module_loader.rs
@@ -331,15 +331,23 @@ impl<TGraphContainer: ModuleGraphContainer>
     maybe_referrer: Option<&ModuleSpecifier>,
     requested_module_type: RequestedModuleType,
   ) -> Result<ModuleSource, AnyError> {
-    let code_source = if let Some(result) = self
-      .shared
-      .npm_module_loader
-      .load_if_in_npm_package(specifier, maybe_referrer)
-      .await
-    {
-      result?
-    } else {
-      self.load_prepared_module(specifier, maybe_referrer).await?
+    let code_source = match self.load_prepared_module(specifier).await? {
+      Some(code_source) => code_source,
+      None => {
+        if self.shared.npm_module_loader.if_in_npm_package(specifier) {
+          self
+            .shared
+            .npm_module_loader
+            .load(specifier, maybe_referrer)
+            .await?
+        } else {
+          let mut msg = format!("Loading unprepared module: {specifier}");
+          if let Some(referrer) = maybe_referrer {
+            msg = format!("{}, imported from: {}", msg, referrer.as_str());
+          }
+          return Err(anyhow!(msg));
+        }
+      }
     };
     let code = if self.shared.is_inspecting {
       // we need the code with the source map in order for
@@ -514,17 +522,12 @@ impl<TGraphContainer: ModuleGraphContainer>
   async fn load_prepared_module(
     &self,
     specifier: &ModuleSpecifier,
-    maybe_referrer: Option<&ModuleSpecifier>,
-  ) -> Result<ModuleCodeStringSource, AnyError> {
+  ) -> Result<Option<ModuleCodeStringSource>, AnyError> {
     // Note: keep this in sync with the sync version below
     let graph = self.graph_container.graph();
-    match self.load_prepared_module_or_defer_emit(
-      &graph,
-      specifier,
-      maybe_referrer,
-    ) {
-      Ok(CodeOrDeferredEmit::Code(code_source)) => Ok(code_source),
-      Ok(CodeOrDeferredEmit::DeferredEmit {
+    match self.load_prepared_module_or_defer_emit(&graph, specifier)? {
+      Some(CodeOrDeferredEmit::Code(code_source)) => Ok(Some(code_source)),
+      Some(CodeOrDeferredEmit::DeferredEmit {
         specifier,
         media_type,
         source,
@@ -537,30 +540,25 @@ impl<TGraphContainer: ModuleGraphContainer>
         // at this point, we no longer need the parsed source in memory, so free it
         self.parsed_source_cache.free(specifier);
 
-        Ok(ModuleCodeStringSource {
+        Ok(Some(ModuleCodeStringSource {
           code: ModuleSourceCode::Bytes(transpile_result),
           found_url: specifier.clone(),
           media_type,
-        })
+        }))
       }
-      Err(err) => Err(err),
+      None => Ok(None),
     }
   }
 
   fn load_prepared_module_sync(
     &self,
     specifier: &ModuleSpecifier,
-    maybe_referrer: Option<&ModuleSpecifier>,
-  ) -> Result<ModuleCodeStringSource, AnyError> {
+  ) -> Result<Option<ModuleCodeStringSource>, AnyError> {
     // Note: keep this in sync with the async version above
     let graph = self.graph_container.graph();
-    match self.load_prepared_module_or_defer_emit(
-      &graph,
-      specifier,
-      maybe_referrer,
-    ) {
-      Ok(CodeOrDeferredEmit::Code(code_source)) => Ok(code_source),
-      Ok(CodeOrDeferredEmit::DeferredEmit {
+    match self.load_prepared_module_or_defer_emit(&graph, specifier)? {
+      Some(CodeOrDeferredEmit::Code(code_source)) => Ok(Some(code_source)),
+      Some(CodeOrDeferredEmit::DeferredEmit {
         specifier,
         media_type,
         source,
@@ -572,13 +570,13 @@ impl<TGraphContainer: ModuleGraphContainer>
         // at this point, we no longer need the parsed source in memory, so free it
         self.parsed_source_cache.free(specifier);
 
-        Ok(ModuleCodeStringSource {
+        Ok(Some(ModuleCodeStringSource {
           code: ModuleSourceCode::Bytes(transpile_result),
           found_url: specifier.clone(),
           media_type,
-        })
+        }))
       }
-      Err(err) => Err(err),
+      None => Ok(None),
     }
   }
 
@@ -586,8 +584,7 @@ impl<TGraphContainer: ModuleGraphContainer>
     &self,
     graph: &'graph ModuleGraph,
     specifier: &ModuleSpecifier,
-    maybe_referrer: Option<&ModuleSpecifier>,
-  ) -> Result<CodeOrDeferredEmit<'graph>, AnyError> {
+  ) -> Result<Option<CodeOrDeferredEmit<'graph>>, AnyError> {
     if specifier.scheme() == "node" {
       // Node built-in modules should be handled internally.
       unreachable!("Deno bug. {} was misconfigured internally.", specifier);
@@ -599,11 +596,11 @@ impl<TGraphContainer: ModuleGraphContainer>
         media_type,
         specifier,
         ..
-      })) => Ok(CodeOrDeferredEmit::Code(ModuleCodeStringSource {
+      })) => Ok(Some(CodeOrDeferredEmit::Code(ModuleCodeStringSource {
         code: ModuleSourceCode::String(source.clone().into()),
         found_url: specifier.clone(),
         media_type: *media_type,
-      })),
+      }))),
       Some(deno_graph::Module::Js(JsModule {
         source,
         media_type,
@@ -624,11 +621,11 @@ impl<TGraphContainer: ModuleGraphContainer>
           | MediaType::Cts
           | MediaType::Jsx
           | MediaType::Tsx => {
-            return Ok(CodeOrDeferredEmit::DeferredEmit {
+            return Ok(Some(CodeOrDeferredEmit::DeferredEmit {
               specifier,
               media_type: *media_type,
               source,
-            });
+            }));
           }
           MediaType::TsBuildInfo | MediaType::Wasm | MediaType::SourceMap => {
             panic!("Unexpected media type {media_type} for {specifier}")
@@ -638,24 +635,18 @@ impl<TGraphContainer: ModuleGraphContainer>
         // at this point, we no longer need the parsed source in memory, so free it
         self.parsed_source_cache.free(specifier);
 
-        Ok(CodeOrDeferredEmit::Code(ModuleCodeStringSource {
+        Ok(Some(CodeOrDeferredEmit::Code(ModuleCodeStringSource {
           code: ModuleSourceCode::String(code),
           found_url: specifier.clone(),
           media_type: *media_type,
-        }))
+        })))
       }
       Some(
         deno_graph::Module::External(_)
         | deno_graph::Module::Node(_)
         | deno_graph::Module::Npm(_),
       )
-      | None => {
-        let mut msg = format!("Loading unprepared module: {specifier}");
-        if let Some(referrer) = maybe_referrer {
-          msg = format!("{}, imported from: {}", msg, referrer.as_str());
-        }
-        Err(anyhow!(msg))
-      }
+      | None => Ok(None),
     }
   }
 }
@@ -828,7 +819,7 @@ impl<TGraphContainer: ModuleGraphContainer> ModuleLoader
       "wasm" | "file" | "http" | "https" | "data" | "blob" => (),
       _ => return None,
     }
-    let source = self.0.load_prepared_module_sync(&specifier, None).ok()?;
+    let source = self.0.load_prepared_module_sync(&specifier).ok()??;
     source_map_from_code(source.code.as_bytes())
   }
 
diff --git a/cli/node.rs b/cli/node.rs
index a3cee8dde..733d5f871 100644
--- a/cli/node.rs
+++ b/cli/node.rs
@@ -5,6 +5,7 @@ use std::sync::Arc;
 use deno_ast::MediaType;
 use deno_ast::ModuleSpecifier;
 use deno_core::error::AnyError;
+use deno_graph::ParsedSourceStore;
 use deno_runtime::deno_fs;
 use deno_runtime::deno_node::DenoFsNodeResolverEnv;
 use node_resolver::analyze::CjsAnalysis as ExtNodeCjsAnalysis;
@@ -16,6 +17,7 @@ use serde::Serialize;
 
 use crate::cache::CacheDBHash;
 use crate::cache::NodeAnalysisCache;
+use crate::cache::ParsedSourceCache;
 use crate::resolver::CliNodeResolver;
 use crate::util::fs::canonicalize_path_maybe_not_exists;
 
@@ -56,6 +58,7 @@ pub struct CliCjsCodeAnalyzer {
   cache: NodeAnalysisCache,
   fs: deno_fs::FileSystemRc,
   node_resolver: Arc<CliNodeResolver>,
+  parsed_source_cache: Option<Arc<ParsedSourceCache>>,
 }
 
 impl CliCjsCodeAnalyzer {
@@ -63,11 +66,13 @@ impl CliCjsCodeAnalyzer {
     cache: NodeAnalysisCache,
     fs: deno_fs::FileSystemRc,
     node_resolver: Arc<CliNodeResolver>,
+    parsed_source_cache: Option<Arc<ParsedSourceCache>>,
   ) -> Self {
     Self {
       cache,
       fs,
       node_resolver,
+      parsed_source_cache,
     }
   }
 
@@ -107,18 +112,26 @@ impl CliCjsCodeAnalyzer {
       }
     }
 
+    let maybe_parsed_source = self
+      .parsed_source_cache
+      .as_ref()
+      .and_then(|c| c.remove_parsed_source(specifier));
+
     let analysis = deno_core::unsync::spawn_blocking({
       let specifier = specifier.clone();
       let source: Arc<str> = source.into();
       move || -> Result<_, deno_ast::ParseDiagnostic> {
-        let parsed_source = deno_ast::parse_program(deno_ast::ParseParams {
-          specifier,
-          text: source,
-          media_type,
-          capture_tokens: true,
-          scope_analysis: false,
-          maybe_syntax: None,
-        })?;
+        let parsed_source =
+          maybe_parsed_source.map(Ok).unwrap_or_else(|| {
+            deno_ast::parse_program(deno_ast::ParseParams {
+              specifier,
+              text: source,
+              media_type,
+              capture_tokens: true,
+              scope_analysis: false,
+              maybe_syntax: None,
+            })
+          })?;
         if parsed_source.is_script() {
           let analysis = parsed_source.analyze_cjs();
           Ok(CliCjsAnalysis::Cjs {
diff --git a/cli/resolver.rs b/cli/resolver.rs
index 7804261b8..84c671268 100644
--- a/cli/resolver.rs
+++ b/cli/resolver.rs
@@ -43,7 +43,6 @@ use node_resolver::NodeModuleKind;
 use node_resolver::NodeResolution;
 use node_resolver::NodeResolutionMode;
 use node_resolver::PackageJson;
-use std::borrow::Cow;
 use std::path::Path;
 use std::path::PathBuf;
 use std::sync::Arc;
@@ -53,7 +52,9 @@ use crate::args::DENO_DISABLE_PEDANTIC_NODE_WARNINGS;
 use crate::node::CliNodeCodeTranslator;
 use crate::npm::CliNpmResolver;
 use crate::npm::InnerCliNpmResolverRef;
+use crate::util::path::specifier_has_extension;
 use crate::util::sync::AtomicFlag;
+use crate::util::text_encoding::from_utf8_lossy_owned;
 
 pub struct ModuleCodeStringSource {
   pub code: ModuleSourceCode,
@@ -215,7 +216,7 @@ impl CliNodeResolver {
     referrer: &ModuleSpecifier,
     mode: NodeResolutionMode,
   ) -> Result<NodeResolution, NodeResolveError> {
-    let referrer_kind = if self.cjs_resolutions.contains(referrer) {
+    let referrer_kind = if self.cjs_resolutions.is_known_cjs(referrer) {
       NodeModuleKind::Cjs
     } else {
       NodeModuleKind::Esm
@@ -310,9 +311,7 @@ impl CliNodeResolver {
       if self.in_npm_package(&specifier) {
         let resolution =
           self.node_resolver.url_to_node_resolution(specifier)?;
-        if let NodeResolution::CommonJs(specifier) = &resolution {
-          self.cjs_resolutions.insert(specifier.clone());
-        }
+        let resolution = self.handle_node_resolution(resolution);
         return Ok(Some(resolution.into_url()));
       }
     }
@@ -333,12 +332,17 @@ impl CliNodeResolver {
   ) -> NodeResolution {
     if let NodeResolution::CommonJs(specifier) = &resolution {
       // remember that this was a common js resolution
-      self.cjs_resolutions.insert(specifier.clone());
+      self.mark_cjs_resolution(specifier.clone());
     }
     resolution
   }
+
+  pub fn mark_cjs_resolution(&self, specifier: ModuleSpecifier) {
+    self.cjs_resolutions.insert(specifier);
+  }
 }
 
+// todo(dsherret): move to module_loader.rs
 #[derive(Clone)]
 pub struct NpmModuleLoader {
   cjs_resolutions: Arc<CjsResolutionStore>,
@@ -362,18 +366,9 @@ impl NpmModuleLoader {
     }
   }
 
-  pub async fn load_if_in_npm_package(
-    &self,
-    specifier: &ModuleSpecifier,
-    maybe_referrer: Option<&ModuleSpecifier>,
-  ) -> Option<Result<ModuleCodeStringSource, AnyError>> {
-    if self.node_resolver.in_npm_package(specifier)
-      || (specifier.scheme() == "file" && specifier.path().ends_with(".cjs"))
-    {
-      Some(self.load(specifier, maybe_referrer).await)
-    } else {
-      None
-    }
+  pub fn if_in_npm_package(&self, specifier: &ModuleSpecifier) -> bool {
+    self.node_resolver.in_npm_package(specifier)
+      || self.cjs_resolutions.is_known_cjs(specifier)
   }
 
   pub async fn load(
@@ -418,16 +413,9 @@ impl NpmModuleLoader {
         }
       })?;
 
-    let code = if self.cjs_resolutions.contains(specifier)
-      || (specifier.scheme() == "file" && specifier.path().ends_with(".cjs"))
-    {
+    let code = if self.cjs_resolutions.is_known_cjs(specifier) {
       // translate cjs to esm if it's cjs and inject node globals
-      let code = match String::from_utf8_lossy(&code) {
-        Cow::Owned(code) => code,
-        // SAFETY: `String::from_utf8_lossy` guarantees that the result is valid
-        // UTF-8 if `Cow::Borrowed` is returned.
-        Cow::Borrowed(_) => unsafe { String::from_utf8_unchecked(code) },
-      };
+      let code = from_utf8_lossy_owned(code);
       ModuleSourceCode::String(
         self
           .node_code_translator
@@ -452,8 +440,12 @@ impl NpmModuleLoader {
 pub struct CjsResolutionStore(DashSet<ModuleSpecifier>);
 
 impl CjsResolutionStore {
-  pub fn contains(&self, specifier: &ModuleSpecifier) -> bool {
-    self.0.contains(specifier)
+  pub fn is_known_cjs(&self, specifier: &ModuleSpecifier) -> bool {
+    if specifier.scheme() != "file" {
+      return false;
+    }
+
+    specifier_has_extension(specifier, "cjs") || self.0.contains(specifier)
   }
 
   pub fn insert(&self, specifier: ModuleSpecifier) {
diff --git a/cli/schemas/config-file.v1.json b/cli/schemas/config-file.v1.json
index af18e6f21..4a6239f0d 100644
--- a/cli/schemas/config-file.v1.json
+++ b/cli/schemas/config-file.v1.json
@@ -528,6 +528,7 @@
           "bare-node-builtins",
           "byonm",
           "cron",
+          "detect-cjs",
           "ffi",
           "fs",
           "http",
diff --git a/cli/standalone/binary.rs b/cli/standalone/binary.rs
index 1290a238f..6e747bed4 100644
--- a/cli/standalone/binary.rs
+++ b/cli/standalone/binary.rs
@@ -622,6 +622,7 @@ impl<'a> DenoCompileBinaryWriter<'a> {
       unstable_config: UnstableConfig {
         legacy_flag_enabled: false,
         bare_node_builtins: cli_options.unstable_bare_node_builtins(),
+        detect_cjs: cli_options.unstable_detect_cjs(),
         sloppy_imports: cli_options.unstable_sloppy_imports(),
         features: cli_options.unstable_features(),
       },
diff --git a/cli/standalone/mod.rs b/cli/standalone/mod.rs
index 258de0dad..60018228b 100644
--- a/cli/standalone/mod.rs
+++ b/cli/standalone/mod.rs
@@ -586,6 +586,7 @@ pub async fn run(
     node_analysis_cache,
     fs.clone(),
     cli_node_resolver.clone(),
+    None,
   );
   let node_code_translator = Arc::new(NodeCodeTranslator::new(
     cjs_esm_code_analyzer,
@@ -651,7 +652,7 @@ pub async fn run(
       workspace_resolver,
       node_resolver: cli_node_resolver.clone(),
       npm_module_loader: Arc::new(NpmModuleLoader::new(
-        cjs_resolutions,
+        cjs_resolutions.clone(),
         node_code_translator,
         fs.clone(),
         cli_node_resolver,
@@ -696,6 +697,7 @@ pub async fn run(
   });
   let worker_factory = CliMainWorkerFactory::new(
     Arc::new(BlobStore::default()),
+    cjs_resolutions,
     // Code cache is not supported for standalone binary yet.
     None,
     feature_checker,
@@ -738,6 +740,7 @@ pub async fn run(
       node_ipc: None,
       serve_port: None,
       serve_host: None,
+      unstable_detect_cjs: metadata.unstable_config.detect_cjs,
     },
   );
 
diff --git a/cli/tools/compile.rs b/cli/tools/compile.rs
index c1f98bc08..3cc4414fc 100644
--- a/cli/tools/compile.rs
+++ b/cli/tools/compile.rs
@@ -54,6 +54,16 @@ pub async fn compile(
     );
   }
 
+  if cli_options.unstable_detect_cjs() {
+    log::warn!(
+      concat!(
+        "{} --unstable-detect-cjs is not properly supported in deno compile. ",
+        "The compiled executable may encounter runtime errors.",
+      ),
+      crate::colors::yellow("Warning"),
+    );
+  }
+
   let output_path = resolve_compile_executable_output_path(
     http_client,
     &compile_flags,
diff --git a/cli/util/text_encoding.rs b/cli/util/text_encoding.rs
index d2e0832c9..0b7601cb9 100644
--- a/cli/util/text_encoding.rs
+++ b/cli/util/text_encoding.rs
@@ -1,6 +1,8 @@
 // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
 
+use std::borrow::Cow;
 use std::ops::Range;
+use std::sync::Arc;
 
 use base64::prelude::BASE64_STANDARD;
 use base64::Engine;
@@ -9,6 +11,15 @@ use deno_core::ModuleSourceCode;
 static SOURCE_MAP_PREFIX: &[u8] =
   b"//# sourceMappingURL=data:application/json;base64,";
 
+pub fn from_utf8_lossy_owned(bytes: Vec<u8>) -> String {
+  match String::from_utf8_lossy(&bytes) {
+    Cow::Owned(code) => code,
+    // SAFETY: `String::from_utf8_lossy` guarantees that the result is valid
+    // UTF-8 if `Cow::Borrowed` is returned.
+    Cow::Borrowed(_) => unsafe { String::from_utf8_unchecked(bytes) },
+  }
+}
+
 pub fn source_map_from_code(code: &[u8]) -> Option<Vec<u8>> {
   let range = find_source_map_range(code)?;
   let source_map_range = &code[range];
@@ -85,6 +96,13 @@ fn find_source_map_range(code: &[u8]) -> Option<Range<usize>> {
   }
 }
 
+/// Converts an `Arc<str>` to an `Arc<[u8]>`.
+pub fn arc_str_to_bytes(arc_str: Arc<str>) -> Arc<[u8]> {
+  let raw = Arc::into_raw(arc_str);
+  // SAFETY: This is safe because they have the same memory layout.
+  unsafe { Arc::from_raw(raw as *const [u8]) }
+}
+
 #[cfg(test)]
 mod tests {
   use std::sync::Arc;
diff --git a/cli/worker.rs b/cli/worker.rs
index cc18c0d15..489b2dd93 100644
--- a/cli/worker.rs
+++ b/cli/worker.rs
@@ -51,9 +51,11 @@ use crate::args::DenoSubcommand;
 use crate::args::StorageKeyResolver;
 use crate::errors;
 use crate::npm::CliNpmResolver;
+use crate::resolver::CjsResolutionStore;
 use crate::util::checksum;
 use crate::util::file_watcher::WatcherCommunicator;
 use crate::util::file_watcher::WatcherRestartMode;
+use crate::util::path::specifier_has_extension;
 use crate::version;
 
 pub struct ModuleLoaderAndSourceMapGetter {
@@ -120,11 +122,13 @@ pub struct CliMainWorkerOptions {
   pub node_ipc: Option<i64>,
   pub serve_port: Option<u16>,
   pub serve_host: Option<String>,
+  pub unstable_detect_cjs: bool,
 }
 
 struct SharedWorkerState {
   blob_store: Arc<BlobStore>,
   broadcast_channel: InMemoryBroadcastChannel,
+  cjs_resolution_store: Arc<CjsResolutionStore>,
   code_cache: Option<Arc<dyn code_cache::CodeCache>>,
   compiled_wasm_module_store: CompiledWasmModuleStore,
   feature_checker: Arc<FeatureChecker>,
@@ -422,6 +426,7 @@ impl CliMainWorkerFactory {
   #[allow(clippy::too_many_arguments)]
   pub fn new(
     blob_store: Arc<BlobStore>,
+    cjs_resolution_store: Arc<CjsResolutionStore>,
     code_cache: Option<Arc<dyn code_cache::CodeCache>>,
     feature_checker: Arc<FeatureChecker>,
     fs: Arc<dyn deno_fs::FileSystem>,
@@ -441,6 +446,7 @@ impl CliMainWorkerFactory {
       shared: Arc::new(SharedWorkerState {
         blob_store,
         broadcast_channel: Default::default(),
+        cjs_resolution_store,
         code_cache,
         compiled_wasm_module_store: Default::default(),
         feature_checker,
@@ -486,6 +492,9 @@ impl CliMainWorkerFactory {
     stdio: deno_runtime::deno_io::Stdio,
   ) -> Result<CliMainWorker, AnyError> {
     let shared = &self.shared;
+    let ModuleLoaderAndSourceMapGetter { module_loader } = shared
+      .module_loader_factory
+      .create_for_main(permissions.clone());
     let (main_module, is_main_cjs) = if let Ok(package_ref) =
       NpmPackageReqReference::from_specifier(&main_module)
     {
@@ -526,13 +535,28 @@ impl CliMainWorkerFactory {
       let is_main_cjs = matches!(node_resolution, NodeResolution::CommonJs(_));
       (node_resolution.into_url(), is_main_cjs)
     } else {
-      let is_cjs = main_module.path().ends_with(".cjs");
+      let is_maybe_cjs_js_ext = self.shared.options.unstable_detect_cjs
+        && specifier_has_extension(&main_module, "js")
+        && self
+          .shared
+          .node_resolver
+          .get_closest_package_json(&main_module)
+          .ok()
+          .flatten()
+          .map(|pkg_json| pkg_json.typ == "commonjs")
+          .unwrap_or(false);
+      let is_cjs = if is_maybe_cjs_js_ext {
+        // fill the cjs resolution store by preparing the module load
+        module_loader
+          .prepare_load(&main_module, None, false)
+          .await?;
+        self.shared.cjs_resolution_store.is_known_cjs(&main_module)
+      } else {
+        specifier_has_extension(&main_module, "cjs")
+      };
       (main_module, is_cjs)
     };
 
-    let ModuleLoaderAndSourceMapGetter { module_loader } = shared
-      .module_loader_factory
-      .create_for_main(permissions.clone());
     let maybe_inspector_server = shared.maybe_inspector_server.clone();
 
     let create_web_worker_cb =
diff --git a/tests/specs/compile/detect_cjs/__test__.jsonc b/tests/specs/compile/detect_cjs/__test__.jsonc
new file mode 100644
index 000000000..32bebb7a5
--- /dev/null
+++ b/tests/specs/compile/detect_cjs/__test__.jsonc
@@ -0,0 +1,24 @@
+{
+  "tempDir": true,
+  "steps": [{
+    "if": "unix",
+    "args": "compile --allow-read --output main main.js",
+    "output": "compile.out"
+  }, {
+    "if": "unix",
+    "commandName": "./main",
+    "args": [],
+    "output": "output.out",
+    "exitCode": 1
+  }, {
+    "if": "windows",
+    "args": "compile --allow-read --output main.exe main.js",
+    "output": "compile.out"
+  }, {
+    "if": "windows",
+    "commandName": "./main.exe",
+    "args": [],
+    "output": "output.out",
+    "exitCode": 1
+  }]
+}
diff --git a/tests/specs/compile/detect_cjs/add.js b/tests/specs/compile/detect_cjs/add.js
new file mode 100644
index 000000000..2a886fbc1
--- /dev/null
+++ b/tests/specs/compile/detect_cjs/add.js
@@ -0,0 +1,3 @@
+module.exports.add = function (a, b) {
+  return a + b;
+};
diff --git a/tests/specs/compile/detect_cjs/compile.out b/tests/specs/compile/detect_cjs/compile.out
new file mode 100644
index 000000000..6509b7f29
--- /dev/null
+++ b/tests/specs/compile/detect_cjs/compile.out
@@ -0,0 +1,3 @@
+Warning --unstable-detect-cjs is not properly supported in deno compile. The compiled executable may encounter runtime errors.
+Check file:///[WILDLINE]/main.js
+Compile file:///[WILDLINE]
diff --git a/tests/specs/compile/detect_cjs/deno.json b/tests/specs/compile/detect_cjs/deno.json
new file mode 100644
index 000000000..35f64c86f
--- /dev/null
+++ b/tests/specs/compile/detect_cjs/deno.json
@@ -0,0 +1,5 @@
+{
+  "unstable": [
+    "detect-cjs"
+  ]
+}
diff --git a/tests/specs/compile/detect_cjs/main.js b/tests/specs/compile/detect_cjs/main.js
new file mode 100644
index 000000000..8c55f673b
--- /dev/null
+++ b/tests/specs/compile/detect_cjs/main.js
@@ -0,0 +1,3 @@
+import { add } from "./add.js";
+
+console.log(add(1, 2));
diff --git a/tests/specs/compile/detect_cjs/output.out b/tests/specs/compile/detect_cjs/output.out
new file mode 100644
index 000000000..b53c44369
--- /dev/null
+++ b/tests/specs/compile/detect_cjs/output.out
@@ -0,0 +1 @@
+error: Module not found: file:///[WILDLINE]/add.js
diff --git a/tests/specs/compile/detect_cjs/package.json b/tests/specs/compile/detect_cjs/package.json
new file mode 100644
index 000000000..5bbefffba
--- /dev/null
+++ b/tests/specs/compile/detect_cjs/package.json
@@ -0,0 +1,3 @@
+{
+  "type": "commonjs"
+}
diff --git a/tests/specs/run/package_json_type/commonjs/__test__.jsonc b/tests/specs/run/package_json_type/commonjs/__test__.jsonc
new file mode 100644
index 000000000..85b7219fa
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/__test__.jsonc
@@ -0,0 +1,34 @@
+{
+  "tests": {
+    "main_cjs": {
+      "args": "run --allow-read=. main_cjs.js",
+      "output": "3\n"
+    },
+    "main_esm": {
+      "args": "run --allow-read=. main_esm.js",
+      "output": "3\n"
+    },
+    "main_mix": {
+      "args": "run --allow-read=. main_mix.js",
+      "output": "main_mix.out",
+      "exitCode": 1
+    },
+    "import_import_meta": {
+      "args": "run import_import_meta.js",
+      "output": "[WILDLINE]/import_meta.js\n"
+    },
+    "main_import_meta": {
+      "args": "run main_esm_import_meta.js",
+      "output": "main_esm_import_meta.out",
+      "exitCode": 1
+    },
+    "not_import_meta": {
+      "args": "run --allow-read=. not_import_meta.js",
+      "output": "3\n"
+    },
+    "tla": {
+      "args": "run --allow-read=. tla.js",
+      "output": "loaded\n"
+    }
+  }
+}
diff --git a/tests/specs/run/package_json_type/commonjs/add.js b/tests/specs/run/package_json_type/commonjs/add.js
new file mode 100644
index 000000000..2a886fbc1
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/add.js
@@ -0,0 +1,3 @@
+module.exports.add = function (a, b) {
+  return a + b;
+};
diff --git a/tests/specs/run/package_json_type/commonjs/deno.jsonc b/tests/specs/run/package_json_type/commonjs/deno.jsonc
new file mode 100644
index 000000000..35f64c86f
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/deno.jsonc
@@ -0,0 +1,5 @@
+{
+  "unstable": [
+    "detect-cjs"
+  ]
+}
diff --git a/tests/specs/run/package_json_type/commonjs/import_import_meta.js b/tests/specs/run/package_json_type/commonjs/import_import_meta.js
new file mode 100644
index 000000000..f07518985
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/import_import_meta.js
@@ -0,0 +1,3 @@
+import { value } from "./import_meta.js";
+
+console.log(value);
diff --git a/tests/specs/run/package_json_type/commonjs/import_meta.js b/tests/specs/run/package_json_type/commonjs/import_meta.js
new file mode 100644
index 000000000..2bdbc30fe
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/import_meta.js
@@ -0,0 +1 @@
+export const value = import.meta.url;
diff --git a/tests/specs/run/package_json_type/commonjs/main_cjs.js b/tests/specs/run/package_json_type/commonjs/main_cjs.js
new file mode 100644
index 000000000..365e8e06f
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/main_cjs.js
@@ -0,0 +1,2 @@
+const { add } = require("./add");
+console.log(add(1, 2));
diff --git a/tests/specs/run/package_json_type/commonjs/main_esm.js b/tests/specs/run/package_json_type/commonjs/main_esm.js
new file mode 100644
index 000000000..8c55f673b
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/main_esm.js
@@ -0,0 +1,3 @@
+import { add } from "./add.js";
+
+console.log(add(1, 2));
diff --git a/tests/specs/run/package_json_type/commonjs/main_esm_import_meta.js b/tests/specs/run/package_json_type/commonjs/main_esm_import_meta.js
new file mode 100644
index 000000000..f1dff20b5
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/main_esm_import_meta.js
@@ -0,0 +1,2 @@
+console.log(import.meta.url);
+console.log(require("./add"));
diff --git a/tests/specs/run/package_json_type/commonjs/main_esm_import_meta.out b/tests/specs/run/package_json_type/commonjs/main_esm_import_meta.out
new file mode 100644
index 000000000..e177defff
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/main_esm_import_meta.out
@@ -0,0 +1,2 @@
+[WILDLINE]main_esm_import_meta.js
+error: Uncaught (in promise) ReferenceError: require is not defined[WILDCARD]
diff --git a/tests/specs/run/package_json_type/commonjs/main_mix.js b/tests/specs/run/package_json_type/commonjs/main_mix.js
new file mode 100644
index 000000000..2a2c2c62a
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/main_mix.js
@@ -0,0 +1,6 @@
+import { add } from "./add.js";
+
+console.log(add(1, 2));
+
+// will error
+console.log(require("./add").add(1, 2));
diff --git a/tests/specs/run/package_json_type/commonjs/main_mix.out b/tests/specs/run/package_json_type/commonjs/main_mix.out
new file mode 100644
index 000000000..d6123d48b
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/main_mix.out
@@ -0,0 +1,5 @@
+3
+error: Uncaught (in promise) ReferenceError: require is not defined
+console.log(require("./add").add(1, 2));
+        ^
+    at file:///[WILDLINE]main_mix.js:[WILDLINE]
diff --git a/tests/specs/run/package_json_type/commonjs/not_import_meta.js b/tests/specs/run/package_json_type/commonjs/not_import_meta.js
new file mode 100644
index 000000000..216b900df
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/not_import_meta.js
@@ -0,0 +1,8 @@
+try {
+  console.log(test.import.meta.url);
+} catch {
+  // ignore
+}
+
+// should work because this is not an ESM file
+console.log(require("./add").add(1, 2));
diff --git a/tests/specs/run/package_json_type/commonjs/package.json b/tests/specs/run/package_json_type/commonjs/package.json
new file mode 100644
index 000000000..5bbefffba
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/package.json
@@ -0,0 +1,3 @@
+{
+  "type": "commonjs"
+}
diff --git a/tests/specs/run/package_json_type/commonjs/tla.js b/tests/specs/run/package_json_type/commonjs/tla.js
new file mode 100644
index 000000000..978578de4
--- /dev/null
+++ b/tests/specs/run/package_json_type/commonjs/tla.js
@@ -0,0 +1,2 @@
+await new Promise((r) => r());
+console.log("loaded");
diff --git a/tests/specs/run/package_json_type/none/__test__.jsonc b/tests/specs/run/package_json_type/none/__test__.jsonc
new file mode 100644
index 000000000..fa1d22ca1
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/__test__.jsonc
@@ -0,0 +1,18 @@
+{
+  "tests": {
+    "main_cjs": {
+      "args": "run --allow-read=. main_cjs.js",
+      "output": "main_cjs.out",
+      "exitCode": 1
+    },
+    "main_esm": {
+      "args": "run --allow-read=. main_esm.js",
+      "output": "main_esm.out",
+      "exitCode": 1
+    },
+    "sub_folder_cjs": {
+      "args": "run --allow-read=. sub_folder_cjs.js",
+      "output": "3\n"
+    }
+  }
+}
diff --git a/tests/specs/run/package_json_type/none/add.js b/tests/specs/run/package_json_type/none/add.js
new file mode 100644
index 000000000..2a886fbc1
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/add.js
@@ -0,0 +1,3 @@
+module.exports.add = function (a, b) {
+  return a + b;
+};
diff --git a/tests/specs/run/package_json_type/none/commonjs/add.js b/tests/specs/run/package_json_type/none/commonjs/add.js
new file mode 100644
index 000000000..2a886fbc1
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/commonjs/add.js
@@ -0,0 +1,3 @@
+module.exports.add = function (a, b) {
+  return a + b;
+};
diff --git a/tests/specs/run/package_json_type/none/commonjs/package.json b/tests/specs/run/package_json_type/none/commonjs/package.json
new file mode 100644
index 000000000..5bbefffba
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/commonjs/package.json
@@ -0,0 +1,3 @@
+{
+  "type": "commonjs"
+}
diff --git a/tests/specs/run/package_json_type/none/deno.jsonc b/tests/specs/run/package_json_type/none/deno.jsonc
new file mode 100644
index 000000000..35f64c86f
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/deno.jsonc
@@ -0,0 +1,5 @@
+{
+  "unstable": [
+    "detect-cjs"
+  ]
+}
diff --git a/tests/specs/run/package_json_type/none/main_cjs.js b/tests/specs/run/package_json_type/none/main_cjs.js
new file mode 100644
index 000000000..365e8e06f
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/main_cjs.js
@@ -0,0 +1,2 @@
+const { add } = require("./add");
+console.log(add(1, 2));
diff --git a/tests/specs/run/package_json_type/none/main_cjs.out b/tests/specs/run/package_json_type/none/main_cjs.out
new file mode 100644
index 000000000..fe9acf009
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/main_cjs.out
@@ -0,0 +1,4 @@
+error: Uncaught (in promise) ReferenceError: require is not defined
+const { add } = require("./add");
+                ^
+    at file:///[WILDLINE]
diff --git a/tests/specs/run/package_json_type/none/main_esm.js b/tests/specs/run/package_json_type/none/main_esm.js
new file mode 100644
index 000000000..8c55f673b
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/main_esm.js
@@ -0,0 +1,3 @@
+import { add } from "./add.js";
+
+console.log(add(1, 2));
diff --git a/tests/specs/run/package_json_type/none/main_esm.out b/tests/specs/run/package_json_type/none/main_esm.out
new file mode 100644
index 000000000..5f16c5f35
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/main_esm.out
@@ -0,0 +1,4 @@
+error: Uncaught SyntaxError: The requested module './add.js' does not provide an export named 'add'
+import { add } from "./add.js";
+         ^
+    at <anonymous> (file:///[WILDLINE])
diff --git a/tests/specs/run/package_json_type/none/package.json b/tests/specs/run/package_json_type/none/package.json
new file mode 100644
index 000000000..2c63c0851
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/package.json
@@ -0,0 +1,2 @@
+{
+}
diff --git a/tests/specs/run/package_json_type/none/sub_folder_cjs.js b/tests/specs/run/package_json_type/none/sub_folder_cjs.js
new file mode 100644
index 000000000..ad04e6730
--- /dev/null
+++ b/tests/specs/run/package_json_type/none/sub_folder_cjs.js
@@ -0,0 +1,3 @@
+import { add } from "./commonjs/add.js";
+
+console.log(add(1, 2));