chore: check nested tsconfigs

src/utils.ts

@@ -1,7 +1,8 @@
 import type { DtsGenerationConfig } from './types'
 import { readdir } from 'node:fs/promises'
-import { extname, join } from 'node:path'
+import { dirname, extname, isAbsolute, join, resolve } from 'node:path'
 import process from 'node:process'
+import { pathToFileURL } from 'node:url'
 import { config } from './config'
 
 export async function writeToFile(filePath: string, content: string): Promise<void> {
@@ -20,17 +21,67 @@ export async function getAllTypeScriptFiles(directory?: string): Promise<string[
   return Array.prototype.concat(...files).filter(file => extname(file) === '.ts')
 }
 
+// only checks for 2 potentially nested levels
 export async function checkIsolatedDeclarations(options?: DtsGenerationConfig): Promise<boolean> {
   try {
     const cwd = options?.cwd || process.cwd()
     const tsconfigPath = options?.tsconfigPath || join(cwd, 'tsconfig.json')
-    const tsconfig = await import(tsconfigPath)
 
-    return tsconfig.compilerOptions?.isolatedDeclarations === true
+    // Convert to file URL for import()
+    const baseConfigPath = pathToFileURL(tsconfigPath).href
+    const baseConfig = await import(baseConfigPath)
+
+    if (baseConfig.compilerOptions?.isolatedDeclarations === true) {
+      return true
+    }
+
+    // If there's an extends property, we need to check the extended config
+    if (baseConfig.extends) {
+      // Make the extended path absolute relative to the base config
+      const extendedPath = makeAbsolute(tsconfigPath, baseConfig.extends)
+      // Add .json if not present
+      const fullExtendedPath = extendedPath.endsWith('.json') ? extendedPath : `${extendedPath}.json`
+      const extendedConfigPath = pathToFileURL(fullExtendedPath).href
+      const extendedConfig = await import(extendedConfigPath)
+
+      // Recursively check extended configs
+      if (extendedConfig.compilerOptions?.isolatedDeclarations === true) {
+        return true
+      }
+
+      // If the extended config also extends another config, check that too
+      if (extendedConfig.extends) {
+        // Make the next extended path absolute relative to the previous extended config
+        const nextExtendedPath = makeAbsolute(fullExtendedPath, extendedConfig.extends)
+        const fullNextExtendedPath = nextExtendedPath.endsWith('.json') ? nextExtendedPath : `${nextExtendedPath}.json`
+        const extendedExtendedConfigPath = pathToFileURL(fullNextExtendedPath).href
+        const extendedExtendedConfig = await import(extendedExtendedConfigPath)
+
+        if (extendedExtendedConfig.compilerOptions?.isolatedDeclarations === true) {
+          return true
+        }
+      }
+    }
+
+    return false
   }
+  // eslint-disable-next-line unused-imports/no-unused-vars
   catch (error) {
-    // eslint-disable-next-line no-console
-    console.log('Error reading tsconfig.json:', error)
     return false
   }
 }
+
+function makeAbsolute(basePath: string, configPath: string): string {
+  // If it's already absolute, return as is
+  if (isAbsolute(configPath)) {
+    return configPath
+  }
+
+  // If it starts with a dot, resolve relative to base path
+  if (configPath.startsWith('.')) {
+    return resolve(dirname(basePath), configPath)
+  }
+
+  // For node_modules paths, resolve from cwd
+  return resolve(process.cwd(), 'node_modules', configPath)
+}