feat: add realpath function and update resolver to use it

- Introduced a new `realpath` function to resolve symlinks and normalize paths, providing a fallback to normalization on error.
- Updated the resolver to utilize `realpath` for directory and file path handling, improving accuracy in path resolution.
- Added test fixtures for symlink resolution, including configuration and example files to validate the new functionality.

Author: benpsnyder

src/path.ts

@@ -1,3 +1,4 @@
+import * as fs from 'node:fs'
 import * as os from 'node:os'
 import * as path from 'node:path'
 import * as vite from 'vite'
@@ -47,4 +48,13 @@ export const basename = (p: NormalizedPath, suffix?: string): NormalizedPath =>
 export const dirname = (p: NormalizedPath): NormalizedPath =>
   path.dirname(p) as NormalizedPath
 
+/** Resolve symlinks and normalize. Falls back to normalize on error. */
+export const realpath = (p: string): NormalizedPath => {
+  try {
+    return normalize(fs.realpathSync(p))
+  } catch {
+    return normalize(p)
+  }
+}
+
 export const relativeImportRE: RegExp = /^\.\.?(\/|$)/

src/resolver.ts

@@ -111,7 +111,7 @@ export function createTsconfigResolvers({
 
   const addProject = (project: Project, data?: Directory) => {
     const tsconfigFile = project.tsconfigFile
-    const dir = path.normalize(path.dirname(tsconfigFile))
+    const dir = path.realpath(path.dirname(tsconfigFile))
     data ??= directoryCache.get(dir)
 
     // Sanity check
@@ -247,7 +247,7 @@ export function createTsconfigResolvers({
   ): AsyncIterable<Resolver> {
     await initializing
 
-    let dir = path.normalize(importer)
+    let dir = path.realpath(importer)
     const { root } = path.parse(dir)
     while (dir !== (dir = path.dirname(dir)) && dir !== root) {
       let data = directoryCache.get(dir)
@@ -292,7 +292,7 @@ export function createTsconfigResolvers({
       watcher.add(tsconfigFile)
     }
     watcher.on('all', (event, file) => {
-      const normalizedFile = path.normalize(file)
+      const normalizedFile = path.realpath(file)
       if (
         !normalizedFile.endsWith('.json') ||
         !path.isAbsolute(normalizedFile)

test/__fixtures__/symlink-resolve/config.json

@@ -0,0 +1,3 @@
+{
+  "root": "link"
+}

test/__fixtures__/symlink-resolve/link

@@ -0,0 +1 @@
+real

test/__fixtures__/symlink-resolve/real/index.ts

@@ -0,0 +1,3 @@
+import { log } from '~/log'
+
+log('Hello, world!')

test/__fixtures__/symlink-resolve/real/log.ts

@@ -0,0 +1 @@
+export const log = console.log.bind(console)

test/__fixtures__/symlink-resolve/real/tsconfig.json

@@ -0,0 +1,12 @@
+{
+  "exclude": ["dist"],
+  "compilerOptions": {
+    "module": "esnext",
+    "moduleResolution": "bundler",
+    "skipLibCheck": true,
+    "rootDir": ".",
+    "paths": {
+      "~/*": ["./*"]
+    }
+  }
+}