Add an initial "pub lish" command.

utils/pub/oauth2.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library oauth2;
+
+import 'dart:io';
+import 'dart:uri';
+
+import '../../pkg/oauth2/lib/oauth2.dart';

[Bob Nystrom, 2012/11/26 23:39:52]

Add a TODO here to do... something... better than this path at some point. Not
sure what.

[nweiz, 2012/11/27 20:15:54]

Done.

+import 'curl_client.dart';
+import 'io.dart';
+import 'system_cache.dart';
+import 'utils.dart';
+
+export '../../pkg/oauth2/lib/oauth2.dart';
+
+/// The pub client's OAuth2 identifier.
+final String _identifier = '818368855108-8grd2eg9tj9f38os6f1urbcvsq399u8n.apps.'

[Bob Nystrom, 2012/11/26 23:39:52]

You don't need to type annotate final top-level variables, since it's always
obvious from the initializer.

[nweiz, 2012/11/27 20:15:54]

Done.

+    'googleusercontent.com';
+
+/// The pub client's OAuth2 secret. This isn't actually meant to be kept a
+/// secret.
+final String _secret = 'SWeqj8seoJW0w7_CpEPFLX0K';
+
+/// The URL to which the user will be directed to authorize the pub client to
+/// get an OAuth2 access token.
+///
+/// `access_type=offline` and `approval_prompt=force` ensures that we always get
+/// a refresh token from the server. See the [Google OAuth2 documentation][].
+///
+/// [Google OAuth2 documentation]: https://developers.google.com/accounts/docs/OAuth2WebServer#offline
+final Uri _authorizationEndpoint = new Uri.fromString(
+    'https://accounts.google.com/o/oauth2/auth?access_type=offline'
+    '&approval_prompt=force');
+
+/// The URL from which the pub client will request an access token once it's
+/// been authorized by the user.
+final Uri _tokenEndpoint = new Uri.fromString(
+    'https://accounts.google.com/o/oauth2/token');
+
+/// The OAuth2 scopes that the pub client needs. Currently the client only needs
+/// the user's email so that the server can verify their identity.
+final List<String> _scopes = ['https://www.googleapis.com/auth/userinfo.email'];
+
+/// An in-memory cache of the user's OAuth2 credentials. This should always be
+/// the same as the credentials file stored in the system cache.
+Credentials _credentials;
+
+/// Asynchronously passes an OAuth2 [Client] to [fn], and closes the client when
+/// the [Future] returned by [fn] completes.
+///
+/// This takes care of loading and saving the client's credentials, as well as
+/// prompting the user for their authorization.
+Future withClient(SystemCache cache, Future fn(Client client)) {
+  return _getClient(cache).chain((client) {
+    var completer = new Completer();
+    var future = fn(client);
+    future.onComplete((_) {
+      try {
+        client.close();
+        // Be sure to save the credentials even when an error happens. Also be
+        // sure to pipe the exception from `future` to `completer`.
+        chainToCompleter(
+            _saveCredentials(cache, client.credentials).chain((_) => future),
+            completer);
+      } catch (e, stackTrace) {
+        // onComplete will drop exceptions on the floor. We want to ensure that
+        // any programming errors here don't go un-noticed. See issue 4127.
+        completer.completeException(e, stackTrace);
+      }
+    });
+    return completer.future;
+  });
+}
+
+/// Gets a new OAuth2 client. If saved credentials are available, those are
+/// used; otherwise, the user is prompted to authorize the pub client.
+Future<Client> _getClient(SystemCache cache) {
+  var httpClient = new CurlClient();
+
+  return _loadCredentials(cache).chain((credentials) {
+    if (credentials != null) {
+      return new Future.immediate(new Client(
+          _identifier, _secret, credentials, httpClient: httpClient));
+    }
+
+    // Allow the tests to inject their own token endpoint URL.
+    var tokenEndpoint = Platform.environment['_PUB_TEST_TOKEN_ENDPOINT'];
+    if (tokenEndpoint != null) {
+      tokenEndpoint = new Uri.fromString(tokenEndpoint);
+    } else {
+      tokenEndpoint = _tokenEndpoint;
+    }
+
+    var grant = new AuthorizationCodeGrant(
+        _identifier,
+        _secret,
+        _authorizationEndpoint,
+        tokenEndpoint,
+        httpClient: httpClient);
+
+    // TODO(nweiz): spin up a server on localhost and redirect the user there so
+    // they don't have to copy/paste the authorization code.
+    var authUrl = grant.getAuthorizationUrl(
+        new Uri.fromString('urn:ietf:wg:oauth:2.0:oob'), scopes: _scopes);
+
+    stdout.writeString(
+        'Pub needs your authorization to upload packages on your behalf.\n'
+        'Go to $authUrl\n'
+        'Then click "Allow access" and paste the code below:\n'
+        '> ');
+    return readLine().chain(grant.handleAuthorizationCode);
+  }).chain((client) {
+    return _saveCredentials(cache, client.credentials).transform((_) => client);
+  });
+}
+
+/// Loads the user's OAuth2 credentials from the in-memory cache or the
+/// filesystem if possible. If the credentials can't be loaded for any reason,
+/// the returned [Future] will complete to null.
+Future<Credentials> _loadCredentials(SystemCache cache) {
+  if (_credentials != null) return new Future.immediate(_credentials);
+  return fileExists(_credentialsFile(cache)).chain((credentialsExist) {
+    if (!credentialsExist) return new Future.immediate(null);
+
+    return readTextFile(_credentialsFile(cache)).transform((credentialsJson) {
+      var credentials = new Credentials.fromJson(credentialsJson);
+      if (credentials.isExpired && !credentials.canRefresh) {
+        printError("Pub's authorization to upload packages has expired and "
+            "can't be automatically refreshed.");

[Bob Nystrom, 2012/11/26 23:39:52]

We should tell the user what they need to do here.

[nweiz, 2012/11/27 20:15:54]

Returning null here will trigger the re-authorization process.

+        return null;
+      }
+
+      return credentials;
+    });
+  }).transformException((e) {
+    printError('Warning: could not load the saved OAuth2 credentials:'
+        '  $e\n'
+        'Obtaining new credentials...');

[Bob Nystrom, 2012/11/26 23:39:52]

I don't understand this bit. Where is it obtaining the new credentials?

Also, we should really guard this by checking that "e" is some expected type.

[nweiz, 2012/11/27 20:15:54]

The "null" return value is a signal that the credentials should be reloaded.
This is one case where I sort of feel like it makes sense to have a broad catch.
There are a wide variety of exceptions that could be thrown in this bit of code,
up to and including crazy things like dart:io bugs, and we want to recover from
almost all of them. Rather than try to enumerate everything that could possibly
go wrong in the previous block of code and risk missing a case and breaking
someone's ability to upload, it seems safer to catch everything and risk trying
to recover an unrecoverable condition.

[Bob Nystrom, 2012/11/27 21:00:53]

Can you add a comment with that?
I'm fine with broadly catching runtime exceptions. What I'm not crazy about is
that this will also catch system and programmatic errors. This will swallow
NoSuchMethodError, ArgumentError, StackOverflowError, etc. which seems pretty
wrong to me.

It would be nice if our exception hierarchy had a single type (Exception) that
was the supertype of all runtime errors but not programmatic ones, but we don't
currently.

[nweiz, 2012/11/27 22:07:34]

Done.
It's not like those errors will be swallowed silently; they'll still print the
warning message. This will just allow the user to continue if such an error
occurs in this non-essential bit of code.

+    return null;
+  });
+}
+
+/// Save the user's OAuth2 credentials to the in-memory cache and the
+/// filesystem.
+Future _saveCredentials(SystemCache cache, Credentials credentials) {
+  _credentials = credentials;
+  var credentialsFile = _credentialsFile(cache);
+  return ensureDir(dirname(credentialsFile)).chain((_) =>
+      writeTextFile(credentialsFile, credentials.toJson()));
+}
+
+/// The path to the file in which the user's OAuth2 credentials are stored.
+String _credentialsFile(SystemCache cache) =>
+  join(cache.rootDir, 'credentials.json');