Try getting dependencies if needed to run pub run build_runner

webdev/bin/webdev.dart

@@ -1,7 +1,13 @@
 import 'dart:async';
 
 import 'package:webdev/webdev.dart';
+import 'package:build_runner/src/logging/std_io_logging.dart';
+import 'package:logging/logging.dart';
 
 Future main(List<String> args) async {
+  // TODO(nshahan) See if build_runner wants to expose their listener.
+  // Using log listener from build_runner to match output format.
+  final logListener = Logger.root.onRecord.listen(stdIOLogListener);
   await webdevCommandRunner().run(args);
+  await logListener?.cancel();
 }

webdev/example/pubspec.yaml

@@ -14,12 +14,22 @@ dev_dependencies:
     path: ../
   ##############################################################################
   # Temporary until build_runner exposes a function to generate it's script.
-  build_runner:
-    git:
-      url: https://github.com/dart-lang/build.git
-      path: build_runner
+  build_runner: ^0.7.5+1
   ##############################################################################
 
 dependency_overrides:
   # Necessary with angular: ^5.0.0-alpha+1 dependency.
   analyzer: ^0.31.0-alpha.1
+  ##############################################################################
+  # Temporary until updated packages are published.
+  build:
+    git:
+      url: https://github.com/dart-lang/build.git
+      ref: ffbba7fc74a1262c958a63fb31c146995f0a3a99
+      path: build
+  build_runner:
+    git:
+      url: https://github.com/dart-lang/build.git
+      ref: ffbba7fc74a1262c958a63fb31c146995f0a3a99
+      path: build_runner
+  ##############################################################################

webdev/lib/src/command/build_command.dart

@@ -1,5 +1,4 @@
 import 'dart:async';
-import 'dart:isolate';
 
 import 'build_runner_command_base.dart';
 
@@ -15,9 +14,6 @@ class BuildCommand extends BuildRunnerCommandBase {
   Future run() async {
     final arguments = ['build'];
     arguments.addAll(argResults.arguments);
-    var exitPort = new ReceivePort();
-    await Isolate.spawnUri(await buildRunnerScript, arguments, null,
-        onExit: exitPort.sendPort, automaticPackageResolution: true);
-    await exitPort.first;
+    await runBuildRunner(arguments);
   }
 }

webdev/lib/src/command/build_runner_command_base.dart

@@ -1,7 +1,12 @@
 import 'dart:async';
 import 'dart:io';
+import 'dart:isolate';
 
 import 'package:args/command_runner.dart';
+import 'package:build_runner/src/logging/logging.dart';
+import 'package:logging/logging.dart';
+
+var _logger = new Logger('webdev');
 
 /// Extend to get a command with the arguments common to all build_runner
 /// commands.
@@ -19,13 +24,89 @@ abstract class BuildRunnerCommandBase extends Command {
           help: 'Enables verbose logging.');
   }
 
-  Future<Uri> get buildRunnerScript async {
+  /// Runs `pub run build_runner` with [arguments] as an isolate.
+  ///
+  /// Attempts to run `pub get` and `pub upgrade` if needed and will retry
+  /// running build_runner after.
+  Future runBuildRunner(List<String> arguments) async {
+    var exitPort = new ReceivePort();
+    var errorPort = new ReceivePort();
+    var errorListener =
+        errorPort.listen((e) => stderr.writeAll(e as List, '\n'));
+    try {
+      await Isolate.spawnUri(await _buildRunnerScript, arguments, null,
+          onExit: exitPort.sendPort,
+          onError: errorPort.sendPort,
+          automaticPackageResolution: true);
+      await exitPort.first;
+    } on _PubDependenciesError catch (_) {
+      exitPort.close();
+    } finally {
+      await errorListener.cancel();
+    }
+  }
+
+  Future<Uri> get _buildRunnerScript async {
+    return await logTimedAsync(
+        _logger, 'Generating build script', _runBuildRunnerGenerate);
+  }
+
+  /// Generates a build script and returns it's location.
+  ///
+  /// Will attempt to run `pub get` or `pub update` if needed.
+  Future<Uri> _runBuildRunnerGenerate() async {
     // TODO(nshahan) build_runner will expose this as a function call that will
     // be imported to avoid running a binary in a transitive dependency with
     // pub run.
     final executable = 'pub';
     final arguments = ['run', 'build_runner', 'generate-build-script'];
-    final results = await Process.run(executable, arguments);
-    return new Uri.file(results.stdout.toString().trim());
+    var result = await Process.run(executable, arguments);
+
+    if (_needPubGet(result)) {
+      _logger.warning('Generating build script failed.');
+      result = await logTimedAsync(_logger, 'Getting dependencies', _runPubGet);
+
+      // Try running build_runner again.
+      result = await Process.run(executable, arguments);
+
+      if (_needPubGet(result)) {
+        _logger.warning('Getting dependencies failed.');
+        result = await logTimedAsync(
+            _logger, 'Upgrading dependencies', _runPubUpgrade);
+
+        if (result.exitCode != 0) {
+          _logger.severe(
+              'Could not retrieve dependencies. webdev must be able to run `pub'
+              ' get`.'
+              '\nPlease fix the dependencies and retry.'
+              '\n\n${result.stderr}');
+          throw new _PubDependenciesError();
+        }
+
+        // Try running build_runner one last time.
+        result = await Process.run(executable, arguments);
+      }
+    }
+
+    return new Uri.file(result.stdout.toString().trim());
+  }
+
+  /// Checks [result] for errors to see if a `pub get` is needed.
+  bool _needPubGet(ProcessResult result) =>
+      result.exitCode != 0 &&
+      result.stderr.toString().contains('please run "pub get"');
+
+  /// Runs `pub get` as a Process.
+  Future<ProcessResult> _runPubGet() async {
+    return await Process.run('pub', ['get', '--no-precompile']);
+  }
+
+  /// Runs `pub upgrade` as a Process.
+  Future<ProcessResult> _runPubUpgrade() async {
+    return await Process.run('pub', ['upgrade', '--no-precompile']);
   }
 }
+
+/// Private error class used to report back an error when attempting to run
+/// `pub get` and `pub upgrade`.
+class _PubDependenciesError extends Error {}

webdev/lib/src/command/serve_command.dart

@@ -1,5 +1,4 @@
 import 'dart:async';
-import 'dart:isolate';
 
 import 'build_runner_command_base.dart';
 
@@ -24,9 +23,6 @@ class ServeCommand extends BuildRunnerCommandBase {
   Future run() async {
     final arguments = ['serve'];
     arguments.addAll(argResults.arguments);
-    var exitPort = new ReceivePort();
-    await Isolate.spawnUri(await buildRunnerScript, arguments, null,
-        onExit: exitPort.sendPort, automaticPackageResolution: true);
-    await exitPort.first;
+    await runBuildRunner(arguments);
   }
 }

webdev/pubspec.yaml

@@ -12,7 +12,22 @@ dependencies:
     git:
       url: https://github.com/dart-lang/build.git
       path: build_runner
-  build_web_compilers: ^0.1.1
+  build_web_compilers: ^0.2.0
 
 dev_dependencies:
   test: "^0.12.0"
+
+################################################################################
+# Temporary until updated packages are published.
+dependency_overrides:
+  build:
+    git:
+      url: https://github.com/dart-lang/build.git
+      ref: ffbba7fc74a1262c958a63fb31c146995f0a3a99
+      path: build
+  build_runner:
+    git:
+      url: https://github.com/dart-lang/build.git
+      ref: ffbba7fc74a1262c958a63fb31c146995f0a3a99
+      path: build_runner
+################################################################################