tsparser: fall back to junction points on windows

Windows requires Developer Mode to be enabled to use
symlinks without admin permissions. This isn't always enabled,
so fall back to using junction points if symlink creation fails.

This is for example what rustup does already.
See rust-lang/rustup#3687 for example.

tsparser/Cargo.toml

@@ -41,6 +41,7 @@ serde_yaml = "0.9.32"
 symlink = "0.1.0"
 tracing = "0.1.40"
 tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }
+junction = "1.2.0"
 
 [build-dependencies]
 prost-build = { version = "0.12.1" }

tsparser/src/builder/package_mgmt.rs

@@ -4,6 +4,7 @@ use std::path::{Path, PathBuf};
 use anyhow::{Context, Result};
 use duct::cmd;
 use serde::Deserialize;
+use std::io;
 
 use crate::builder::compile::CmdSpec;
 
@@ -279,22 +280,20 @@ fn symlink_encore_dev(app_root: &Path, encore_dev_path: &Path) -> Result<()> {
     let node_mod_dst = node_modules.join("encore.dev");
 
     // If the node_modules directory exists, symlink the encore.dev package.
-    if let Ok(meta) = node_mod_dst.symlink_metadata() {
-        // Is this a symlink?
-        if meta.is_symlink() {
-            // If the symlink is already pointing to our desired target, we're done.
-            if let Ok(target) = std::fs::read_link(&node_mod_dst) {
-                if target == encore_dev_path {
-                    log::info!("encore.dev symlink already points to the local runtime, skipping.");
-                    return Ok(());
-                }
+    if let Ok(target) = read_symlink(&node_mod_dst) {
+        if let Some(target) = target {
+            if target == encore_dev_path {
+                log::info!("encore.dev symlink already points to the local runtime, skipping.");
+                return Ok(());
             }
 
             // It's a symlink pointing elsewhere. Remove it.
-            symlink::remove_symlink_auto(&node_mod_dst).with_context(|| {
+            delete_symlink(&node_mod_dst).with_context(|| {
                 format!("remove existing encore.dev symlink at {:?}", node_mod_dst)
             })?;
-        } else {
+        }
+
+        if node_mod_dst.exists() {
             // It's not a symlink. Remove the directory so we can add a symlink.
             std::fs::remove_dir_all(&node_mod_dst).with_context(|| {
                 format!("remove existing encore.dev directory at {:?}", node_mod_dst)
@@ -304,9 +303,58 @@ fn symlink_encore_dev(app_root: &Path, encore_dev_path: &Path) -> Result<()> {
 
     // Create the symlink if the node_modules directory exists.
     if node_modules.exists() {
-        symlink::symlink_dir(encore_dev_path, &node_mod_dst)
+        create_symlink(encore_dev_path, &node_mod_dst)
             .with_context(|| format!("symlink encore.dev directory at {:?}", node_mod_dst))?;
     }
-
     Ok(())
 }
+
+#[cfg(not(windows))]
+fn create_symlink(src: &Path, dst: &Path) -> io::Result<()> {
+    symlink::symlink_dir(src, dst)
+}
+
+#[cfg(windows)]
+fn create_symlink(src: &Path, dst: &Path) -> io::Result<()> {
+    symlink::symlink_dir(src, dst).or_else(|_| junction::create(src, &dst))
+}
+
+#[cfg(not(windows))]
+fn read_symlink(src: &Path) -> io::Result<Option<PathBuf>> {
+    if let Ok(meta) = src.symlink_metadata() {
+        if meta.is_symlink() {
+            return std::fs::read_link(src).map(Some);
+        }
+    }
+    Ok(None)
+}
+
+#[cfg(windows)]
+fn read_symlink(src: &Path) -> io::Result<Option<PathBuf>> {
+    if let Ok(meta) = src.symlink_metadata() {
+        // Is this a symlink?
+        if meta.is_symlink() {
+            return std::fs::read_link(src).map(Some);
+        }
+    }
+
+    // Check if it's a junction.
+    if junction::exists(src)? {
+        return junction::get_target(src).map(Some);
+    }
+
+    Ok(None)
+}
+
+#[cfg(not(windows))]
+fn delete_symlink(src: &Path) -> io::Result<()> {
+    symlink::remove_symlink_auto(src)
+}
+
+#[cfg(windows)]
+fn delete_symlink(src: &Path) -> io::Result<()> {
+    if let Ok(_) = symlink::remove_symlink_auto(src) {
+        return Ok(());
+    }
+    junction::delete(src)
+}