147         this.tree.forEach((dep, next) => {
188     return tree.forEachAsync((dep, next) => {
189       if (!this.checkDepEnv(dep)) { return }
190       const depPath = dep.path(this.prefix)
191       const spec = npa.resolve(dep.name, dep.version, this.prefix)
192       if (dep.isRoot) {
196         this.log.silly('extractTree', `${dep.name}@${spec.fetchSpec} -> ${depPath} (symlink)`)
208         this.log.silly('extractTree', `${dep.name}@${dep.version} -> ${depPath}`)
210           dep.bundled
223                 dep.name, dep, depPath, this.opts
235   checkDepEnv (dep) {  argument
248     return (dep.dev && includeDev) ||
249       (dep.optional && includeOptional) ||
250       (!dep.dev && !dep.optional && includeProd)
256     return tree.forEachAsync((dep, next) => {
257       if (!this.checkDepEnv(dep)) { return }
258       const spec = npa.resolve(dep.name, dep.version)
259       const depPath = dep.path(this.prefix)
264           : this.updateFromField(dep, pkg).then(() => pkg)
268           : this.updateInstallScript(dep, pkg).then(() => pkg)
270         .tap(pkg => { pkgJsons.set(dep, pkg) })
277     return tree.forEachAsync((dep, next) => {
278       if (!this.checkDepEnv(dep)) { return }
279       const spec = npa.resolve(dep.name, dep.version)
280       const depPath = dep.path(this.prefix)
281       const pkg = pkgJsons.get(dep)
288             dep.isRoot ||
313           if (dep.optional) {
314             this.failedDeps.add(dep)
322   updateFromField (dep, pkg) {  argument
323     const depPath = dep.path(this.prefix)
325     const parent = dep.requiredBy.values().next().value
328         (ppkg.dependencies && ppkg.dependencies[dep.name]) ||
329       (ppkg.devDependencies && ppkg.devDependencies[dep.name]) ||
330       (ppkg.optionalDependencies && ppkg.optionalDependencies[dep.name])
332       .then(from => npa.resolve(dep.name, from))
338   updateInstallScript (dep, pkg) {  argument
339     const depPath = dep.path(this.prefix)
391   tree.forEach((dep, next) => {
392     if (!failed.has(dep)) {
393       liveDeps.add(dep)
402   return tree.forEachAsync((dep, next) => {
405         !dep.isRoot && // never purge root! ��
406         !liveDeps.has(dep) &&
407         !purged.has(dep)
409         purged.add(dep)
410         return rimraf(dep.path(prefix))