feat(resolver): resolve extension alias (#7565)

Author: siketyan

.changeset/petite-waves-love.md

@@ -0,0 +1,19 @@
+---
+"@biomejs/biome": patch
+---
+
+The resolver can now correctly resolve `.ts`, `.tsx`, `.d.ts`, `.js` files by `.js` extension if exists, based on [the file extension substitution in TypeScript](https://www.typescriptlang.org/docs/handbook/modules/reference.html#file-extension-substitution).
+
+For example, the linter can now detect the floating promise in the following situation, if you have enabled the `noFloatingPromises` rule.
+
+**`foo.ts`**
+```ts
+export async function doSomething(): Promise<void> {}
+```
+
+**`bar.ts`**
+```ts
+import { doSomething } from "./foo.js"; // doesn't exist actually, but it is resolved to `foo.ts`
+
+doSomething(); // floating promise!
+```

.changeset/silent-insects-flow.md

@@ -0,0 +1,5 @@
+---
+"@biomejs/biome": patch
+---
+
+The [`useImportExtensions`](https://biomejs.dev/linter/rules/use-import-extensions/) rule now correctly detects imports with an invalid extension. For example, importing `.ts` file with `.js` extension is flagged by default. If you are using TypeScript with neither the `allowImportingTsExtensions` option nor the `rewriteRelativeImportExtensions` option, it's recommended to turn on the `forceJsExtensions` option of the rule.

crates/biome_js_analyze/src/lint/correctness/use_import_extensions.rs

@@ -229,7 +229,6 @@ fn get_extensionless_import(
         (Some(_), _) if path.file_name()?.starts_with(resolved_path.file_name()?) => {
             return None; // For cases like `./foo.css` -> `./foo.css.ts`
         }
-        (None, Some(_)) => return None,
         _ => {}
     }
 
@@ -250,8 +249,17 @@ fn get_extensionless_import(
         resolved_extension?
     };
 
+    // Check if the existing extension matches the desired one.
+    if existing_extension.is_some_and(|ext| ext == extension) {
+        return None;
+    }
+
     let is_index_file = resolved_stem.is_some_and(|stem| stem == "index");
-    let import_path_ends_with_index = path.file_name().is_some_and(|name| name == "index");
+    let import_path_ends_with_index = path.file_name().is_some_and(|name| name == "index")
+        || path
+            .with_extension("")
+            .file_name()
+            .is_some_and(|name| name == "index");
 
     let new_path = if is_index_file && !import_path_ends_with_index {
         let mut path_parts = path.as_str().split('/');

crates/biome_js_analyze/tests/specs/correctness/useImportExtensions/invalid.ts

@@ -24,4 +24,8 @@ require("./sub/foo")
 
 import "./sub/styles.css"
 import "./sub/component.svg.svelte";
-import "./sub/component.svg.svelte?query=string&query2#hash";
+import "./sub/component.svg.svelte?query=string&query2#hash";
+
+// Invalid extension
+import "./sub/foo.js";
+import "./sub/bar/index.js";

crates/biome_js_analyze/tests/specs/correctness/useImportExtensions/invalid.ts.snap

@@ -31,6 +31,11 @@ require("./sub/foo")
 import "./sub/styles.css"
 import "./sub/component.svg.svelte";
 import "./sub/component.svg.svelte?query=string&query2#hash";
+
+// Invalid extension
+import "./sub/foo.js";
+import "./sub/bar/index.js";
+
 ```
 
 # Diagnostics
@@ -445,6 +450,7 @@ invalid.ts:26:8 lint/correctness/useImportExtensions  FIXABLE  ━━━━━
   > 26 │ import "./sub/component.svg.svelte";
        │        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     27 │ import "./sub/component.svg.svelte?query=string&query2#hash";
+    28 │ 
   
   i Explicit import improves compatibility with browsers and makes file resolution in tooling faster.
   
@@ -455,6 +461,7 @@ invalid.ts:26:8 lint/correctness/useImportExtensions  FIXABLE  ━━━━━
     26    │ - import·"./sub/component.svg.svelte";
        26 │ + import·"./sub/component.svg.svelte.ts";
     27 27 │   import "./sub/component.svg.svelte?query=string&query2#hash";
+    28 28 │   
   
 
 ```
@@ -468,8 +475,59 @@ invalid.ts:27:8 lint/correctness/useImportExtensions ━━━━━━━━━
     26 │ import "./sub/component.svg.svelte";
   > 27 │ import "./sub/component.svg.svelte?query=string&query2#hash";
        │        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    28 │ 
+    29 │ // Invalid extension
   
   i Explicit import improves compatibility with browsers and makes file resolution in tooling faster.
   
 
 ```
+
+```
+invalid.ts:30:8 lint/correctness/useImportExtensions  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! Add a file extension for relative imports.
+  
+    29 │ // Invalid extension
+  > 30 │ import "./sub/foo.js";
+       │        ^^^^^^^^^^^^^^
+    31 │ import "./sub/bar/index.js";
+    32 │ 
+  
+  i Explicit import improves compatibility with browsers and makes file resolution in tooling faster.
+  
+  i Safe fix: Add import extension .ts.
+  
+    28 28 │   
+    29 29 │   // Invalid extension
+    30    │ - import·"./sub/foo.js";
+       30 │ + import·"./sub/foo.ts";
+    31 31 │   import "./sub/bar/index.js";
+    32 32 │   
+  
+
+```
+
+```
+invalid.ts:31:8 lint/correctness/useImportExtensions  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! Add a file extension for relative imports.
+  
+    29 │ // Invalid extension
+    30 │ import "./sub/foo.js";
+  > 31 │ import "./sub/bar/index.js";
+       │        ^^^^^^^^^^^^^^^^^^^^
+    32 │ 
+  
+  i Explicit import improves compatibility with browsers and makes file resolution in tooling faster.
+  
+  i Safe fix: Add import extension .ts.
+  
+    29 29 │   // Invalid extension
+    30 30 │   import "./sub/foo.js";
+    31    │ - import·"./sub/bar/index.js";
+       31 │ + import·"./sub/bar/index.ts";
+    32 32 │   
+  
+
+```

crates/biome_js_analyze/tests/specs/correctness/useImportExtensions/invalidWithForcedJsExtensions.ts

@@ -23,4 +23,8 @@ require("./sub/foo")
 
 import "./sub/styles.css"
 import "./sub/component.svg.svelte";
-import "./sub/component.svg.svelte?query=string&query2#hash";
+import "./sub/component.svg.svelte?query=string&query2#hash";
+
+// Invalid extension
+import "./sub/foo.ts";
+import "./sub/bar/index.ts";

crates/biome_js_analyze/tests/specs/correctness/useImportExtensions/invalidWithForcedJsExtensions.ts.snap

@@ -30,6 +30,11 @@ require("./sub/foo")
 import "./sub/styles.css"
 import "./sub/component.svg.svelte";
 import "./sub/component.svg.svelte?query=string&query2#hash";
+
+// Invalid extension
+import "./sub/foo.ts";
+import "./sub/bar/index.ts";
+
 ```
 
 # Diagnostics
@@ -418,6 +423,7 @@ invalidWithForcedJsExtensions.ts:25:8 lint/correctness/useImportExtensions  FIXA
   > 25 │ import "./sub/component.svg.svelte";
        │        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     26 │ import "./sub/component.svg.svelte?query=string&query2#hash";
+    27 │ 
   
   i Explicit import improves compatibility with browsers and makes file resolution in tooling faster.
   
@@ -428,6 +434,7 @@ invalidWithForcedJsExtensions.ts:25:8 lint/correctness/useImportExtensions  FIXA
     25    │ - import·"./sub/component.svg.svelte";
        25 │ + import·"./sub/component.svg.svelte.js";
     26 26 │   import "./sub/component.svg.svelte?query=string&query2#hash";
+    27 27 │   
   
 
 ```
@@ -441,8 +448,59 @@ invalidWithForcedJsExtensions.ts:26:8 lint/correctness/useImportExtensions ━
     25 │ import "./sub/component.svg.svelte";
   > 26 │ import "./sub/component.svg.svelte?query=string&query2#hash";
        │        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    27 │ 
+    28 │ // Invalid extension
   
   i Explicit import improves compatibility with browsers and makes file resolution in tooling faster.
   
 
 ```
+
+```
+invalidWithForcedJsExtensions.ts:29:8 lint/correctness/useImportExtensions  FIXABLE  ━━━━━━━━━━━━━━━
+
+  ! Add a file extension for relative imports.
+  
+    28 │ // Invalid extension
+  > 29 │ import "./sub/foo.ts";
+       │        ^^^^^^^^^^^^^^
+    30 │ import "./sub/bar/index.ts";
+    31 │ 
+  
+  i Explicit import improves compatibility with browsers and makes file resolution in tooling faster.
+  
+  i Safe fix: Add import extension .js.
+  
+    27 27 │   
+    28 28 │   // Invalid extension
+    29    │ - import·"./sub/foo.ts";
+       29 │ + import·"./sub/foo.js";
+    30 30 │   import "./sub/bar/index.ts";
+    31 31 │   
+  
+
+```
+
+```
+invalidWithForcedJsExtensions.ts:30:8 lint/correctness/useImportExtensions  FIXABLE  ━━━━━━━━━━━━━━━
+
+  ! Add a file extension for relative imports.
+  
+    28 │ // Invalid extension
+    29 │ import "./sub/foo.ts";
+  > 30 │ import "./sub/bar/index.ts";
+       │        ^^^^^^^^^^^^^^^^^^^^
+    31 │ 
+  
+  i Explicit import improves compatibility with browsers and makes file resolution in tooling faster.
+  
+  i Safe fix: Add import extension .js.
+  
+    28 28 │   // Invalid extension
+    29 29 │   import "./sub/foo.ts";
+    30    │ - import·"./sub/bar/index.ts";
+       30 │ + import·"./sub/bar/index.js";
+    31 31 │   
+  
+
+```

crates/biome_module_graph/src/js_module_info/visitor.rs

@@ -18,6 +18,14 @@ use crate::{
 
 use super::{ResolvedPath, collector::JsModuleInfoCollector};
 
+/// Extensions to try to resolve based on the extension in the import specifier.
+/// ref: https://www.typescriptlang.org/docs/handbook/modules/reference.html#the-moduleresolution-compiler-option
+const EXTENSION_ALIASES: &[(&str, &[&str])] = &[
+    ("js", &["ts", "tsx", "d.ts", "js", "jsx"]),
+    ("mjs", &["mts", "d.mts", "mjs"]),
+    ("cjs", &["cts", "d.cts", "cjs"]),
+];
+
 pub(crate) struct JsModuleVisitor<'a> {
     root: AnyJsRoot,
     directory: &'a Utf8Path,
@@ -401,7 +409,7 @@ impl<'a> JsModuleVisitor<'a> {
                             if let Ok(binding) = node.pattern() {
                                 self.visit_binding_pattern(
                                     binding,
-                                   collector,
+                                    collector,
                                 );
                             }
                         }
@@ -450,6 +458,7 @@ impl<'a> JsModuleVisitor<'a> {
             condition_names: &["types", "import", "default"],
             default_files: &["index"],
             extensions: SUPPORTED_EXTENSIONS,
+            extension_aliases: EXTENSION_ALIASES,
             resolve_node_builtins: true,
             resolve_types: true,
             ..Default::default()