handle case where arg is an object but not an npa instance (#29)

Author: zkat

npa.js

@@ -18,6 +18,15 @@ const isFilename = /[.](?:tgz|tar.gz|tar)$/i
 function npa (arg, where) {
   let name
   let spec
+  if (typeof arg === 'object') {
+    if (arg instanceof Result && (!where || where === arg.where)) {
+      return arg
+    } else if (arg.name && arg.rawSpec) {
+      return npa.resolve(arg.name, arg.rawSpec, where || arg.where)
+    } else {
+      return npa(arg.raw, where || arg.where)
+    }
+  }
   const nameEndsAt = arg[0] === '@' ? arg.slice(1).indexOf('@') + 1 : arg.indexOf('@')
   const namePart = nameEndsAt > 0 ? arg.slice(0, nameEndsAt) : arg
   if (isURL.test(arg)) {

test/basic.js

@@ -420,6 +420,22 @@ require('tap').test('basic', function (t) {
 //    t.has(res, tests[arg], arg + ' matches expectations')
   })
 
+  var objSpec = {name: 'foo', rawSpec: '1.2.3'}
+  t.equal(npa(objSpec, '/whatnot').toString(), 'foo@1.2.3', 'parsed object')
+
+  objSpec = {raw: './foo/bar', where: '/here'}
+  t.equal(npa(objSpec).fetchSpec, '/here/foo/bar', '`where` is reused')
+
+  objSpec = {raw: './foo/bar', where: '/here'}
+  t.equal(npa(objSpec, '/whatnot').fetchSpec, '/whatnot/foo/bar', '`where` arg overrides the one in the spec object')
+
+  t.equal(npa(npa('foo@1.2.3')).toString(), 'foo@1.2.3', 'spec is passthrough')
+
+  var parsedSpec = npa('./foo', './here')
+  t.equal(npa(parsedSpec), parsedSpec, 'reused if no where')
+  t.equal(npa(parsedSpec, './here'), parsedSpec, 'reused if where matches')
+  t.notEqual(npa(parsedSpec, './there'), parsedSpec, 'new instance if where does not match')
+  t.notEqual(npa(parsedSpec, './there').fetchSpec, '/there/foo', 'new instance has new where')
   // Completely unreasonable invalid garbage throws an error
   t.throws(function () {
     t.comment(npa('this is not a \0 valid package name or url'))