fix(npm/types): resolve main entrypoint declaration file when no types entry (#16791)

Closes #16782

cli/tests/integration/npm_tests.rs

@@ -306,6 +306,14 @@ itest!(types_entry_value_not_exists {
   exit_code: 0,
 });
 
+itest!(types_no_types_entry {
+  args: "run --check=all npm/types_no_types_entry/main.ts",
+  output: "npm/types_no_types_entry/main.out",
+  envs: env_vars(),
+  http_server: true,
+  exit_code: 0,
+});
+
 #[test]
 fn parallel_downloading() {
   let (out, _err) = util::run_and_collect_output_with_args(

cli/tests/testdata/npm/registry/@denotest/types-no-types-entry/1.0.0/dist/main.d.ts

@@ -0,0 +1 @@
+export function getValue(): 5;

cli/tests/testdata/npm/registry/@denotest/types-no-types-entry/1.0.0/dist/main.js

@@ -0,0 +1 @@
+module.exports.getValue = () => 5;

cli/tests/testdata/npm/registry/@denotest/types-no-types-entry/1.0.0/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "@denotest/types-no-types-entry",
+  "version": "1.0.0",
+  "main": "./dist/main.js"
+}

cli/tests/testdata/npm/types_no_types_entry/main.out

@@ -0,0 +1,4 @@
+Download http://localhost:4545/npm/registry/@denotest/types-no-types-entry
+Download http://localhost:4545/npm/registry/@denotest/types-no-types-entry/1.0.0.tgz
+Check file://[WILDCARD]/types_no_types_entry/main.ts
+5

cli/tests/testdata/npm/types_no_types_entry/main.ts

@@ -0,0 +1,4 @@
+import { getValue } from "npm:@denotest/types-no-types-entry";
+
+const result: 5 = getValue();
+console.log(result);

ext/node/resolution.rs

@@ -806,19 +806,31 @@ pub fn legacy_main_resolve(
 ) -> Result<Option<PathBuf>, AnyError> {
   let is_types = conditions == TYPES_CONDITIONS;
   let maybe_main = if is_types {
-    package_json.types.as_ref()
+    match package_json.types.as_ref() {
+      Some(types) => Some(types),
+      None => {
+        // fallback to checking the main entrypoint for
+        // a corresponding declaration file
+        if let Some(main) = package_json.main(referrer_kind) {
+          let main = package_json.path.parent().unwrap().join(main).clean();
+          let path = path_to_declaration_path(main, referrer_kind);
+          if path.exists() {
+            return Ok(Some(path));
+          }
+        }
+        None
+      }
+    }
   } else {
     package_json.main(referrer_kind)
   };
-  let mut guess;
 
   if let Some(main) = maybe_main {
-    guess = package_json.path.parent().unwrap().join(main).clean();
+    let guess = package_json.path.parent().unwrap().join(main).clean();
     if file_exists(&guess) {
       return Ok(Some(guess));
     }
 
-    let mut found = false;
     // todo(dsherret): investigate exactly how node and typescript handles this
     let endings = if is_types {
       match referrer_kind {
@@ -838,22 +850,17 @@ pub fn legacy_main_resolve(
       vec![".js", "/index.js"]
     };
     for ending in endings {
-      guess = package_json
+      let guess = package_json
         .path
         .parent()
         .unwrap()
         .join(&format!("{}{}", main, ending))
         .clean();
       if file_exists(&guess) {
-        found = true;
-        break;
+        // TODO(bartlomieju): emitLegacyIndexDeprecation()
+        return Ok(Some(guess));
       }
     }
-
-    if found {
-      // TODO(bartlomieju): emitLegacyIndexDeprecation()
-      return Ok(Some(guess));
-    }
   }
 
   let index_file_names = if is_types {
@@ -866,7 +873,7 @@ pub fn legacy_main_resolve(
     vec!["index.js"]
   };
   for index_file_name in index_file_names {
-    guess = package_json
+    let guess = package_json
       .path
       .parent()
       .unwrap()