Fix web app installation logic (#105)

-Fixed issue with using incorrect home directory as default web directory.
-Print actual docker error messages during launch, if any.
-Updated readme.

README.md

@@ -200,7 +200,9 @@ $ oauth2l reset
 
 ### web
 
-Runs the web application and opens a new window to show it. If the web application is not installed it is installed in `~/.oauth2l-web` by default.
+Locally deploys and launches the OAuth2l Playground web application in a browser. If the web application packages are not yet installed, it will be installed under `~/.oauth2l-web` by default. See Command Options section for all supported options for the web command.
+
+Note that a local installation of Docker and docker-compose tool is required in order to support this feature. For most platforms, Docker can be installed by following the instructions [here](https://docs.docker.com/get-docker/). For Google workstations, follow special installation procedures at "go/installdocker". The web feature is currently experimental and will be improved in the future.
 
 ```bash
 $ oauth2l web
@@ -389,17 +391,17 @@ Path to Curl CLI. For optional use with "curl" command.
 $ oauth2l curl --curlcli /usr/bin/curl --type sso --email [email protected] --scope cloud-platform --url https://pubsub.googleapis.com/v1/projects/my-project-id/topics
 ```
 
-## web --stop
+### web --stop
 
-Stops the OAuth2l Playground.
+Stops the OAuth2l Playground web app.
 
 ```bash
 $ oauth2l web --stop
 ```
 
-## web --directory
+### web --directory
 
-Downloads OAuth2l-web in a specfic directory.
+Installs OAuth2l-web packages to a specfic directory. If this option is used, it should be provided again for future executions of the web command, such as stopping and restarting the web app.
 
 ```
 $ oauth2l web --directory your/new/directory

main.go

@@ -162,6 +162,13 @@ func setCacheLocation(cache *string) {
 	}
 }
 
+// Overrides default web directory if configured.
+func setWebDirectory(directory string) {
+	if directory != "" {
+		util.WebDirectory = directory
+	}
+}
+
 // Extracts the common fetch options based on chosen command.
 func getCommonFetchOptions(cmdOpts commandOptions, cmd string) commonFetchOptions {
 	var commonOpts commonFetchOptions
@@ -378,14 +385,11 @@ func main() {
 
 		os.Exit(task(token))
 	} else if cmd == "web" {
-		var directory string = "~/.oauth2l-web"
-		if len(opts.Web.Directory) > 0 {
-			directory = opts.Web.Directory
-		}
+		setWebDirectory(opts.Web.Directory)
 		if opts.Web.Stop {
-			util.WebStop(directory)
+			util.WebStop()
 		} else {
-			util.Web(directory)
+			util.Web()
 		}
 
 	} else if cmd == "reset" {

util/web.go

@@ -1,5 +1,5 @@
 //
-// Copyright 2018 Google Inc.
+// Copyright 2020 Google Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -15,44 +15,55 @@
 package util
 
 import (
+	"bytes"
 	"fmt"
 	"log"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"runtime"
+
+	"github.com/google/oauth2l/sgauth"
 )
 
 const (
-	defaultServer = "http://localhost:3000/"
+	defaultServer         = "http://localhost:3000/"
+	defaultWebPackageName = ".oauth2l-web"
 )
 
+var WebDirectory string = filepath.Join(sgauth.GuessUnixHomeDir(), defaultWebPackageName)
+
 // Runs the frontend/backend for OAuth2l Playground
-func Web(directory string) {
-	_, err := os.Stat(directory)
+func Web() {
+	_, err := os.Stat(WebDirectory)
 	if os.IsNotExist(err) {
 		fmt.Println("Installing...")
-		cmd := exec.Command("git", "clone", "https://github.com/googleinterns/oauth2l-web.git", directory)
-		clonErr := cmd.Run()
-		if clonErr != nil {
-			fmt.Println("Please enter a valid directory")
-			log.Fatal(clonErr.Error())
+		cmd := exec.Command("git", "clone", "https://github.com/googleinterns/oauth2l-web.git", WebDirectory)
+		cmdErr := cmd.Run()
+		if cmdErr != nil {
+			fmt.Println("Failed to install web feature.")
+			log.Fatal(cmdErr.Error())
 		} else {
 			fmt.Println("Web feature installed")
 		}
 	}
 	cmd := exec.Command("docker-compose", "up", "-d", "--build")
-	cmd.Dir = directory
-	dockErr := cmd.Run()
-	if dockErr != nil {
-		fmt.Println("Please ensure that Docker is installed.")
-		log.Fatal(dockErr.Error())
+	cmd.Dir = WebDirectory
+
+	// Capture actual error message from docker command, if there is any
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
 
+	cmdErr := cmd.Run()
+	if cmdErr != nil {
+		fmt.Println(stderr.String())
+		log.Fatal(cmdErr.Error())
 	} else {
 		openWeb()
 	}
 }
 
-// opens the website on the default browser
+// Opens the website on the default browser
 func openWeb() error {
 	var cmd string
 
@@ -70,17 +81,17 @@ func openWeb() error {
 	return exec.Command(cmd, defaultServer).Start()
 }
 
-// closes the containers and removes stopped containers
-func WebStop(directory string) {
+// Closes the containers and removes stopped containers
+func WebStop() {
 	cmd := exec.Command("docker-compose", "stop")
-	cmd.Dir = directory
+	cmd.Dir = WebDirectory
 	err := cmd.Run()
 	if err != nil {
 		log.Fatal(err.Error())
 	}
 
 	remContainer := exec.Command("docker-compose", "rm", "-f")
-	remContainer.Dir = directory
+	remContainer.Dir = WebDirectory
 	remErr := remContainer.Run()
 	if remErr != nil {
 		log.Fatal(err.Error())