Try a different approach for loading TS config files

aryaemami59 · aryaemami59 · commit 209c79169b68 · 2024-05-31T09:15:11.000-05:00
- This is done for mainly 2 reasons:

  1. We don't know how many runtime environments are going to support loading TS files natively in the future, so this saves us having to check for every single one.
  2. This also ensures that we give the user the option of passing their own TS loader of choice through `NODE_OPTIONS` in CLI for example: `NODE_OPTIONS=--import=tsx/esm`, without ESLint getting in the way and potentially causing conflicts between multiple loaders.
diff --git a/lib/eslint/eslint.js b/lib/eslint/eslint.js
@@ -291,20 +291,22 @@ function isFileTS(filePath) {
     return fileExtension.endsWith("ts");
 }
 
-/**
- * Check if ESLint is running in Bun.
- * @returns {boolean} `true` if the ESLint is running Bun, `false` if it's not.
- */
-function isRunningInBun() {
-    return !!globalThis.Bun || !!globalThis.process?.versions?.bun;
-}
+const unableToLoadTSFile = Symbol("Unable to load TS file");
 
 /**
- * Check if ESLint is running in Deno.
- * @returns {boolean} `true` if the ESLint is running in Deno, `false` if it's not.
+ * Load the TypeScript config file.
+ * @param {string} filePath The file path to check.
+ * @returns {Promise<{ default?: any } | typeof unableToLoadTSFile>} The loaded TypeScript file or `false` if it's not loaded.
  */
-function isRunningInDeno() {
-    return !!globalThis.Deno;
+async function loadTSFile(filePath) {
+    try {
+        return await import(filePath);
+    } catch (error) {
+
+        debug(`${error}`);
+
+        return unableToLoadTSFile;
+    }
 }
 
 /**
@@ -350,30 +352,35 @@ async function loadFlatConfigFile(filePath) {
         delete require.cache[filePath];
     }
 
+    let config;
+
     const isTS = isFileTS(filePath);
 
-    const isBun = isRunningInBun();
+    if (isTS) {
 
-    const isDeno = isRunningInDeno();
+        const loadedTSFile = await loadTSFile(fileURL.href);
 
-    if (isTS && !isDeno && !isBun) {
+        if (loadedTSFile === unableToLoadTSFile) {
+            try {
+                require.resolve("jiti");
+            } catch (error) {
+                debug(`${error}`);
 
-        try {
-            require.resolve("jiti");
-        } catch {
-            throw new Error("'jiti' is required for loading TypeScript configuration files. Make sure to install it.");
-        }
+                throw new Error("'jiti' is required for loading TypeScript configuration files. Make sure to install it.");
+            }
 
-        const jiti = (await import("jiti")).default(__filename, { interopDefault: true, esmResolve: true });
+            const jiti = (await import("jiti")).default(__filename, { interopDefault: true, esmResolve: true });
 
-        const config = jiti(fileURL.href);
+            config = jiti(fileURL.href);
 
-        importedConfigFileModificationTime.set(filePath, mtime);
+        } else {
+            config = loadedTSFile?.default ?? loadedTSFile;
+        }
 
-        return config;
-    }
+    } else {
+        config = (await import(fileURL.href)).default;
 
-    const config = (await import(fileURL.href)).default;
+    }
 
     importedConfigFileModificationTime.set(filePath, mtime);
 
