Fix for windows policy-pack install (#3837)

* Fix for windows policy-pack install

* Add test for npm install

pkg/npm/npm.go

@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"strings"
 
 	uuid "github.com/satori/go.uuid"
@@ -75,7 +76,8 @@ func Install(dir string, stdout, stderr io.Writer) (string, error) {
 	}
 
 	// Ensure the "node_modules" directory exists.
-	if _, err := os.Stat("node_modules"); os.IsNotExist(err) {
+	nodeModulesPath := filepath.Join(dir, "node_modules")
+	if _, err := os.Stat(nodeModulesPath); os.IsNotExist(err) {
 		return bin, errors.Errorf("%s install reported success, but node_modules directory is missing", bin)
 	}
 

pkg/npm/npm_test.go

@@ -0,0 +1,65 @@
+// Copyright 2016-2020, Pulumi Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package npm
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNPMInstall(t *testing.T) {
+	testInstall(t, "npm")
+}
+
+func TestYarnInstall(t *testing.T) {
+	os.Setenv("PULUMI_PREFER_YARN", "true")
+	testInstall(t, "yarn")
+}
+
+func testInstall(t *testing.T, expectedBin string) {
+	// Skip during short test runs since this test involves downloading dependencies.
+	if testing.Short() {
+		t.Skip("Skipped in short test run")
+	}
+
+	// Create a new empty test directory and change the current working directory to it.
+	tempdir, _ := ioutil.TempDir("", "test-env")
+	defer os.RemoveAll(tempdir)
+	assert.NoError(t, os.Chdir(tempdir))
+
+	// Create a package directory to install dependencies into.
+	pkgdir := filepath.Join(tempdir, "package")
+	assert.NoError(t, os.Mkdir(pkgdir, 0700))
+
+	// Write out a minimal package.json file that has at least one dependency.
+	packageJSONFilename := filepath.Join(pkgdir, "package.json")
+	packageJSON := []byte(`{
+	    "name": "test-package",
+	    "dependencies": {
+	        "@pulumi/pulumi": "^1.0.0"
+	    }
+	}`)
+	assert.NoError(t, ioutil.WriteFile(packageJSONFilename, packageJSON, 0644))
+
+	// Install dependencies, passing nil for stdout and stderr, which connects
+	// them to the file descriptor for the null device (os.DevNull).
+	bin, err := Install(pkgdir, nil, nil)
+	assert.NoError(t, err)
+	assert.Equal(t, expectedBin, bin)
+}