1 files changed, 58 insertions, 1 deletions

diff --git a/cli/tsc.rs b/cli/tsc.rs
index 7f90dd7b2..bcaeaaeb6 100644
--- a/cli/tsc.rs
+++ b/cli/tsc.rs
@@ -22,6 +22,7 @@ use deno_core::Snapshot;
 use serde::Deserialize;
 use std::cell::RefCell;
 use std::collections::HashMap;
+use std::path::PathBuf;
 use std::rc::Rc;
 
 /// Provide static assets that are not preloaded in the compiler snapshot.
@@ -63,6 +64,41 @@ fn get_maybe_hash(
   }
 }
 
+/// tsc only supports `.ts`, `.tsx`, `.d.ts`, `.js`, or `.jsx` as root modules
+/// and so we have to detect the apparent media type based on extensions it
+/// supports.
+fn get_tsc_media_type(specifier: &ModuleSpecifier) -> MediaType {
+  let url = specifier.as_url();
+  let path = if url.scheme() == "file" {
+    if let Ok(path) = url.to_file_path() {
+      path
+    } else {
+      PathBuf::from(url.path())
+    }
+  } else {
+    PathBuf::from(url.path())
+  };
+  match path.extension() {
+    None => MediaType::Unknown,
+    Some(os_str) => match os_str.to_str() {
+      Some("ts") => {
+        if let Some(os_str) = path.file_stem() {
+          if let Some(file_name) = os_str.to_str() {
+            if file_name.ends_with(".d") {
+              return MediaType::Dts;
+            }
+          }
+        }
+        MediaType::TypeScript
+      }
+      Some("tsx") => MediaType::TSX,
+      Some("js") => MediaType::JavaScript,
+      Some("jsx") => MediaType::JSX,
+      _ => MediaType::Unknown,
+    },
+  }
+}
+
 #[derive(Debug, Clone, Default, Eq, PartialEq)]
 pub struct EmittedFile {
   pub data: String,
@@ -337,7 +373,7 @@ pub fn exec(
     .root_names
     .iter()
     .map(|(s, mt)| {
-      let ext_media_type = MediaType::from(&s.as_str().to_owned());
+      let ext_media_type = get_tsc_media_type(s);
       if mt != &ext_media_type {
         let new_specifier = format!("{}{}", s, mt.as_ts_extension());
         root_map.insert(new_specifier.clone(), s.clone());
@@ -490,6 +526,27 @@ mod tests {
     );
   }
 
+  #[test]
+  fn test_get_tsc_media_type() {
+    let fixtures = vec![
+      ("file:///a.ts", MediaType::TypeScript),
+      ("file:///a.tsx", MediaType::TSX),
+      ("file:///a.d.ts", MediaType::Dts),
+      ("file:///a.js", MediaType::JavaScript),
+      ("file:///a.jsx", MediaType::JSX),
+      ("file:///a.cjs", MediaType::Unknown),
+      ("file:///a.mjs", MediaType::Unknown),
+      ("file:///a.json", MediaType::Unknown),
+      ("file:///a.wasm", MediaType::Unknown),
+      ("file:///a.js.map", MediaType::Unknown),
+      ("file:///.tsbuildinfo", MediaType::Unknown),
+    ];
+    for (specifier, media_type) in fixtures {
+      let specifier = ModuleSpecifier::resolve_url_or_path(specifier).unwrap();
+      assert_eq!(get_tsc_media_type(&specifier), media_type);
+    }
+  }
+
   #[tokio::test]
   async fn test_emit() {
     let mut state = setup(None, None, None).await;