Rationalize arg handling for pub build and serve.

sdk/lib/_internal/pub/test/barback/utils.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS d.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.
+
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../../lib/src/exit_codes.dart' as exit_codes;
+import '../test_pub.dart';
+
+/// Runs separate integration tests for "pub build", "pub serve", and
+/// "pub build --format json" and validates that in all cases, it fails with
+/// an expected error message and exits with [exitCode].
+///
+/// The integrations assume set up is already done, so you will likely want to
+/// call [setUp] before this.
+///
+/// If [error] is provided, then both pub build and pub serve should exit with
+/// that message. Otherwise, [buildError] is the expected error from pub build
+/// and [serveError] from pub serve.
+void pubBuildAndServeShouldFail(String description, {List<String> args,
+    String error, String buildError, String serveError, int exitCode}) {
+
+  if (error != null) {
+    assert(buildError == null);
+    buildError = error;
+
+    assert(serveError == null);
+    serveError = error;
+  }
+
+  // Usage errors also print the usage, so validate that.
+  var buildExpectation = buildError;
+  var serveExpectation = serveError;
+  if (exitCode == exit_codes.USAGE) {
+    buildExpectation = allOf(
+        startsWith(buildExpectation), contains("Usage: pub build"));
+    serveExpectation = allOf(
+        startsWith(serveExpectation), contains("Usage: pub serve"));
+  }
+
+  integration("build fails $description", () {
+    schedulePub(args: ["build"]..addAll(args),
+        error: buildExpectation,
+        exitCode: exitCode);
+  });
+
+  integration("build --format json fails $description", () {
+    schedulePub(args: ["build", "--format", "json"]..addAll(args),
+        outputJson: {
+          "error": buildError // No usage in JSON output.
+        },
+        exitCode: exitCode);
+  });
+
+  integration("serve fails $description", () {
+    schedulePub(args: ["serve"]..addAll(args),
+        error: serveExpectation,
+        exitCode: exitCode);
+  });
+}