From 99606ea4dfe66e6a26925cc6cc48311ab8255d98 Mon Sep 17 00:00:00 2001
From: Pooya Parsa <pooya@pi0.io>
Date: Wed, 21 Feb 2024 14:01:45 +0100
Subject: [PATCH] perf(resolver): stat absolute paths once in fast path (#229)

* test: add test for links

* add test for non js modules

* perf(resolver): stat absolute paths once in fast path
---
 src/resolve.ts              | 26 ++++++++++++++++----------
 test.mjs                    |  1 +
 test/fixture/hello.link.mjs |  1 +
 test/fixture/test.link.txt  |  1 +
 test/fixture/test.txt       |  1 +
 test/resolve.test.ts        | 12 ++++++++++++
 6 files changed, 32 insertions(+), 10 deletions(-)
 create mode 100644 test.mjs
 create mode 120000 test/fixture/hello.link.mjs
 create mode 120000 test/fixture/test.link.txt
 create mode 100644 test/fixture/test.txt

diff --git a/src/resolve.ts b/src/resolve.ts
index df18f56..24bcdac 100644
--- a/src/resolve.ts
+++ b/src/resolve.ts
@@ -1,4 +1,4 @@
-import { existsSync, realpathSync } from "node:fs";
+import { statSync } from "node:fs";
 import { pathToFileURL } from "node:url";
 import { joinURL } from "ufo";
 import { isAbsolute, normalize } from "pathe";
@@ -27,7 +27,7 @@ function _tryModuleResolve(
   id: string,
   url: URL,
   conditions: any,
-): any | undefined {
+): URL | undefined {
   try {
     return moduleResolve(id, url, conditions);
   } catch (error) {
@@ -49,10 +49,17 @@ function _resolve(id: string, options: ResolveOptions = {}): string {
   }
 
   // Skip resolve for absolute paths
-  if (isAbsolute(id) && existsSync(id)) {
-    // Resolve realPath and normalize slash
-    const realPath = realpathSync(fileURLToPath(id));
-    return pathToFileURL(realPath).toString();
+  if (isAbsolute(id)) {
+    try {
+      const stat = statSync(id);
+      if (stat.isFile()) {
+        return pathToFileURL(id).toString();
+      }
+    } catch (error) {
+      if (error.code !== "ENOENT") {
+        throw error;
+      }
+    }
   }
 
   // Condition set
@@ -82,7 +89,7 @@ function _resolve(id: string, options: ResolveOptions = {}): string {
     }
   }
 
-  let resolved;
+  let resolved: URL | undefined;
   for (const url of urls) {
     // Try simple resolve
     resolved = _tryModuleResolve(id, url, conditionsSet);
@@ -120,9 +127,8 @@ function _resolve(id: string, options: ResolveOptions = {}): string {
     throw error;
   }
 
-  // Resolve realPath and normalize slash
-  const realPath = realpathSync(fileURLToPath(resolved));
-  return pathToFileURL(realPath).toString();
+  // Normalize (TODO: simplify)
+  return pathToFileURL(fileURLToPath(resolved)).toString();
 }
 
 export function resolveSync(id: string, options?: ResolveOptions): string {
diff --git a/test.mjs b/test.mjs
new file mode 100644
index 0000000..11f474e
--- /dev/null
+++ b/test.mjs
@@ -0,0 +1 @@
+console.log(import.meta.resolve.toString())
diff --git a/test/fixture/hello.link.mjs b/test/fixture/hello.link.mjs
new file mode 120000
index 0000000..5d12f6b
--- /dev/null
+++ b/test/fixture/hello.link.mjs
@@ -0,0 +1 @@
+hello.mjs
\ No newline at end of file
diff --git a/test/fixture/test.link.txt b/test/fixture/test.link.txt
new file mode 120000
index 0000000..541cb64
--- /dev/null
+++ b/test/fixture/test.link.txt
@@ -0,0 +1 @@
+test.txt
\ No newline at end of file
diff --git a/test/fixture/test.txt b/test/fixture/test.txt
new file mode 100644
index 0000000..524acff
--- /dev/null
+++ b/test/fixture/test.txt
@@ -0,0 +1 @@
+Test file
diff --git a/test/resolve.test.ts b/test/resolve.test.ts
index 75e5a02..c1a2d50 100644
--- a/test/resolve.test.ts
+++ b/test/resolve.test.ts
@@ -36,6 +36,18 @@ describe("resolveSync", () => {
       }
     });
   }
+
+  it("follows symlinks", () => {
+    const resolved = resolveSync("./fixture/hello.link", {
+      url: import.meta.url,
+    });
+    expect(fileURLToPath(resolved)).match(/fixture\/hello\.mjs$/);
+
+    const resolved2 = resolveSync("./fixture/test.link.txt", {
+      url: import.meta.url,
+    });
+    expect(fileURLToPath(resolved2)).match(/fixture\/test.txt$/);
+  });
 });
 
 describe("resolvePathSync", () => {