1 files changed, 39 insertions, 0 deletions
diff --git a/cli/util/path.rs b/cli/util/path.rs
index 69c52bf6e..39ba96d6d 100644
--- a/cli/util/path.rs
+++ b/cli/util/path.rs
@@ -4,6 +4,7 @@ use std::borrow::Cow;
 use std::path::Path;
 use std::path::PathBuf;
 
+use deno_ast::MediaType;
 use deno_ast::ModuleSpecifier;
 use deno_core::error::uri_error;
 use deno_core::error::AnyError;
@@ -28,6 +29,44 @@ pub fn get_extension(file_path: &Path) -> Option<String> {
     .map(|e| e.to_lowercase());
 }
 
+/// TypeScript figures out the type of file based on the extension, but we take
+/// other factors into account like the file headers. The hack here is to map the
+/// specifier passed to TypeScript to a new specifier with the file extension.
+pub fn mapped_specifier_for_tsc(
+  specifier: &ModuleSpecifier,
+  media_type: MediaType,
+) -> Option<String> {
+  let ext_media_type = MediaType::from_specifier(specifier);
+  if media_type != ext_media_type {
+    // we can't just add on the extension because typescript considers
+    // all .d.*.ts files as declaration files in TS 5.0+
+    if media_type != MediaType::Dts
+      && media_type == MediaType::TypeScript
+      && specifier
+        .path()
+        .split('/')
+        .last()
+        .map(|last| last.contains(".d."))
+        .unwrap_or(false)
+    {
+      let mut path_parts = specifier
+        .path()
+        .split('/')
+        .map(ToOwned::to_owned)
+        .collect::<Vec<_>>();
+      let last_part = path_parts.last_mut().unwrap();
+      *last_part = last_part.replace(".d.", "$d$");
+      let mut specifier = specifier.clone();
+      specifier.set_path(&path_parts.join("/"));
+      Some(format!("{}{}", specifier, media_type.as_ts_extension()))
+    } else {
+      Some(format!("{}{}", specifier, media_type.as_ts_extension()))
+    }
+  } else {
+    None
+  }
+}
+
 /// Attempts to convert a specifier to a file path. By default, uses the Url
 /// crate's `to_file_path()` method, but falls back to try and resolve unix-style
 /// paths on Windows.