feat(resolver): add a realpath to package.json (#1634)

Using the `realpath` for resolving browser field will lead to missing
queries.

This fixes a cases where `browserField` fails to read.

---

`styled-components` is using a trick for loading browser modules:

---

https://github.com/styled-components/styled-components/blob/7c065e0b6f890760d7a6759ec5e4a95775b6e688/packages/styled-components/package.json#L6C1-L12C5

```json
  "main": "dist/styled-components.cjs.js",
  "module": "./dist/styled-components.esm.js",
  "browser": {
    "./dist/styled-components.esm.js": "./dist/styled-components.browser.esm.js",
    "./dist/styled-components.cjs.js": "./dist/styled-components.browser.cjs.js"
  },
```

Module resolution has to go from `"module":
"./dist/styled-components.esm.js"`, then to `browser`'s
`"./dist/styled-components.esm.js":
"./dist/styled-components.browser.esm.js"` part in order for things to
get resolved correctly.

---

Fixtures are hard to setup for this test case due to needing symlinks,
I've created https://github.com/oxc-project/oxc_resolver for tacking
such cases.

crates/oxc_resolver/examples/resolver.rs

@@ -18,6 +18,7 @@ fn main() {
     println!("request: {request}");
 
     let options = ResolveOptions {
+        alias_fields: vec![vec!["browser".into()]],
         alias: vec![("/asdf".into(), vec![AliasValue::Path("./test.js".into())])],
         ..ResolveOptions::default()
     };

crates/oxc_resolver/src/cache.rs

@@ -277,15 +277,20 @@ impl CachedPathImpl {
                 let Ok(package_json_string) = fs.read_to_string(&package_json_path) else {
                     return Ok(None);
                 };
-                let package_json_path = if options.symlinks {
+                let real_path = if options.symlinks {
                     self.realpath(fs)?.join("package.json")
                 } else {
-                    package_json_path
+                    package_json_path.clone()
                 };
-                PackageJson::parse(package_json_path.clone(), &package_json_string, options)
-                    .map(Arc::new)
-                    .map(Some)
-                    .map_err(|error| ResolveError::from_serde_json_error(package_json_path, &error))
+                PackageJson::parse(
+                    package_json_path.clone(),
+                    real_path,
+                    &package_json_string,
+                    options,
+                )
+                .map(Arc::new)
+                .map(Some)
+                .map_err(|error| ResolveError::from_serde_json_error(package_json_path, &error))
             })
             .cloned()
     }

crates/oxc_resolver/src/package_json.rs

@@ -21,6 +21,10 @@ pub struct PackageJson {
     #[serde(skip)]
     pub path: PathBuf,
 
+    /// Realpath to `package.json`. Contains the `package.json` filename.
+    #[serde(skip)]
+    pub realpath: PathBuf,
+
     #[serde(skip)]
     #[serde(default)]
     pub raw_json: Arc<serde_json::Value>,
@@ -117,6 +121,7 @@ impl PackageJson {
     /// # Errors
     pub fn parse(
         path: PathBuf,
+        realpath: PathBuf,
         json: &str,
         options: &ResolveOptions,
     ) -> Result<Self, serde_json::Error> {
@@ -171,6 +176,7 @@ impl PackageJson {
         }
 
         package_json.path = path;
+        package_json.realpath = realpath;
         package_json.raw_json = Arc::new(package_json_value);
         Ok(package_json)
     }
@@ -193,7 +199,7 @@ impl PackageJson {
         Some(value)
     }
 
-    /// Directory to `package.json`
+    /// Raw json of `package.json`
     pub fn raw_json(&self) -> &serde_json::Value {
         self.raw_json.as_ref()
     }
@@ -204,8 +210,8 @@ impl PackageJson {
     ///
     /// * When the package.json path is misconfigured.
     pub fn directory(&self) -> &Path {
-        debug_assert!(self.path.file_name().is_some_and(|x| x == "package.json"));
-        self.path.parent().unwrap()
+        debug_assert!(self.realpath.file_name().is_some_and(|x| x == "package.json"));
+        self.realpath.parent().unwrap()
     }
 
     /// Resolve the request string for this package.json by looking at the `browser` field.