Respect link deps when calculating peerDep sets

lib/arborist/build-ideal-tree.js

@@ -883,6 +883,8 @@ This is a one-time fix-up, please be patient...
     // create a virtual root node with the same deps as the node that
     // is requesting this one, so that we can get all the peer deps in
     // a context where they're likely to be resolvable.
+    // Note that the virtual root will also have virtual copies of the
+    // targets of any child Links, so that they resolve appropriately.
     const parent = parent_ || this[_virtualRoot](edge.from)
     const realParent = edge.peer ? edge.from.resolveParent : edge.from
 
@@ -936,11 +938,23 @@ This is a one-time fix-up, please be patient...
       return this[_virtualRoots].get(node)
 
     const vr = new Node({
-      path: '/virtual-root',
+      path: node.realpath,
       sourceReference: node,
       legacyPeerDeps: this.legacyPeerDeps,
     })
 
+    // also need to set up any targets from any link deps, so that
+    // they are properly reflected in the virtual environment
+    for (const child of node.children.values()) {
+      if (child.isLink) {
+        new Node({
+          path: child.realpath,
+          sourceReference: child.target,
+          root: vr,
+        })
+      }
+    }
+
     this[_virtualRoots].set(node, vr)
     return vr
   }

lib/printable.js

@@ -63,6 +63,13 @@ class ArboristNode {
   }
 }
 
+class ArboristVirtualNode extends ArboristNode {
+  constructor (tree, path) {
+    super(tree, path)
+    this.sourceReference = printableTree(tree.sourceReference, path)
+  }
+}
+
 class ArboristLink extends ArboristNode {
   constructor (tree, path) {
     super(tree, path)
@@ -119,10 +126,14 @@ class EdgeIn extends Edge {
 }
 
 const printableTree = (tree, path = []) => {
-  if (path.includes(tree))
-    return { location: tree.location }
+  const Cls = tree.isLink ? ArboristLink
+    : tree.sourceReference ? ArboristVirtualNode
+    : ArboristNode
+  if (path.includes(tree)) {
+    const obj = Object.create(Cls.prototype)
+    return Object.assign(obj, { location: tree.location })
+  }
   path.push(tree)
-  const Cls = tree.isLink ? ArboristLink : ArboristNode
   return new Cls(tree, path)
 }
 

lib/shrinkwrap.js

@@ -41,6 +41,7 @@ const readFile = promisify(fs.readFile)
 const writeFile = promisify(fs.writeFile)
 const stat = promisify(fs.stat)
 const readdir_ = promisify(fs.readdir)
+const readlink = promisify(fs.readlink)
 
 // XXX remove when drop support for node v10
 const lstat = promisify(fs.lstat)
@@ -176,10 +177,19 @@ const assertNoNewer = async (path, data, lockTime, dir = path, seen = null) => {
     : readdir(parent, { withFileTypes: true })
 
   return children.catch(() => [])
-    .then(ents => Promise.all(
-      ents.filter(ent => ent.isDirectory() && !/^\./.test(ent.name))
-        .map(ent => assertNoNewer(path, data, lockTime, resolve(parent, ent.name), seen))
-    )).then(() => {
+    .then(ents => Promise.all(ents.map(async ent => {
+      const child = resolve(parent, ent.name)
+      if (ent.isDirectory() && !/^\./.test(ent.name))
+        await assertNoNewer(path, data, lockTime, child, seen)
+      else if (ent.isSymbolicLink()) {
+        const target = resolve(parent, await readlink(child))
+        const tstat = await stat(target).catch(() => null)
+        seen.add(relpath(path, child))
+        if (tstat && tstat.isDirectory() && !seen.has(relpath(path, target)))
+          await assertNoNewer(path, data, lockTime, target, seen)
+      }
+    })))
+    .then(() => {
       if (dir !== path)
         return