fix(install): auto-create package.json when missing in vp install / vp add

Running `vp install` or `vp add` in a directory without package.json previously
failed with "Package not found in workspace". Now a minimal `{ "type": "module" }`
package.json is created automatically, allowing PM detection and install to proceed.

Author: fengmk2

crates/vite_global_cli/src/commands/add.rs

@@ -36,6 +36,7 @@ impl AddCommand {
         pass_through_args: Option<&[String]>,
     ) -> Result<ExitStatus, Error> {
         prepend_js_runtime_to_path_env(&self.cwd).await?;
+        super::ensure_package_json(&self.cwd).await?;
 
         let add_command_options = AddCommandOptions {
             packages,

crates/vite_global_cli/src/commands/install.rs

@@ -18,6 +18,7 @@ impl InstallCommand {
 
     pub async fn execute(self, options: &InstallCommandOptions<'_>) -> Result<ExitStatus, Error> {
         prepend_js_runtime_to_path_env(&self.cwd).await?;
+        super::ensure_package_json(&self.cwd).await?;
 
         let package_manager = PackageManager::builder(&self.cwd).build_with_default().await?;
 
@@ -83,6 +84,42 @@ mod tests {
         assert!(result.is_ok());
     }
 
+    #[tokio::test]
+    async fn test_ensure_package_json_creates_when_missing() {
+        let temp_dir = TempDir::new().unwrap();
+        let dir_path = AbsolutePathBuf::new(temp_dir.path().to_path_buf()).unwrap();
+        let package_json_path = dir_path.join("package.json");
+
+        // Verify no package.json exists
+        assert!(!package_json_path.as_path().exists());
+
+        // Call ensure_package_json
+        crate::commands::ensure_package_json(&dir_path).await.unwrap();
+
+        // Verify package.json was created with correct content
+        let content = fs::read_to_string(&package_json_path).unwrap();
+        let parsed: serde_json::Value = serde_json::from_str(&content).unwrap();
+        assert_eq!(parsed["type"], "module");
+    }
+
+    #[tokio::test]
+    async fn test_ensure_package_json_does_not_overwrite_existing() {
+        let temp_dir = TempDir::new().unwrap();
+        let dir_path = AbsolutePathBuf::new(temp_dir.path().to_path_buf()).unwrap();
+        let package_json_path = dir_path.join("package.json");
+
+        // Create an existing package.json
+        let existing_content = r#"{"name": "existing-package"}"#;
+        fs::write(&package_json_path, existing_content).unwrap();
+
+        // Call ensure_package_json
+        crate::commands::ensure_package_json(&dir_path).await.unwrap();
+
+        // Verify existing package.json was NOT overwritten
+        let content = fs::read_to_string(&package_json_path).unwrap();
+        assert_eq!(content, existing_content);
+    }
+
     #[tokio::test]
     async fn test_install_command_execute_with_invalid_workspace() {
         let temp_dir = TempDir::new().unwrap();

crates/vite_global_cli/src/commands/mod.rs

@@ -28,6 +28,20 @@ use vite_shared::{PrependOptions, prepend_to_path_env};
 
 use crate::{error::Error, js_executor::JsExecutor};
 
+/// Ensure a package.json exists in the given directory.
+/// If it doesn't exist, create a minimal one with `{ "type": "module" }`.
+pub async fn ensure_package_json(project_path: &AbsolutePath) -> Result<(), Error> {
+    let package_json_path = project_path.join("package.json");
+    if !package_json_path.as_path().exists() {
+        let content = serde_json::to_string_pretty(&serde_json::json!({
+            "type": "module"
+        }))?;
+        tokio::fs::write(&package_json_path, format!("{content}\n")).await?;
+        tracing::info!("Created package.json in {:?}", project_path);
+    }
+    Ok(())
+}
+
 /// Ensure the JS runtime is downloaded and prepend its bin directory to PATH.
 /// This should be called before executing any package manager command.
 ///

packages/global/snap-tests/command-install-auto-create-package-json/snap.txt

@@ -0,0 +1,24 @@
+> test ! -f package.json && echo 'no package.json' # verify no package.json exists
+no package.json
+
+> vp install --silent && cat package.json # should auto-create package.json and install
+{
+  "type": "module",
+  "packageManager": "pnpm@<semver>"
+}
+> vp add testnpm2 -D && cat package.json # should add package to auto-created package.json
+Packages: +<variable>
++<repeat>
+Progress: resolved <variable>, reused <variable>, downloaded <variable>, added <variable>, done
+
+devDependencies:
++ testnpm2 <semver>
+
+Done in <variable>ms using pnpm v<semver>
+{
+  "type": "module",
+  "packageManager": "pnpm@<semver>",
+  "devDependencies": {
+    "testnpm2": "^1.0.1"
+  }
+}

packages/global/snap-tests/command-install-auto-create-package-json/steps.json

@@ -0,0 +1,11 @@
+{
+  "ignoredPlatforms": ["win32"],
+  "env": {
+    "VITE_DISABLE_AUTO_INSTALL": "1"
+  },
+  "commands": [
+    "test ! -f package.json && echo 'no package.json' # verify no package.json exists",
+    "vp install --silent && cat package.json # should auto-create package.json and install",
+    "vp add testnpm2 -D && cat package.json # should add package to auto-created package.json"
+  ]
+}