Don't assume that a transform node is consistently deferred or not.

pkg/barback/test/package_graph/declaring_transformer_test.dart

Index: pkg/barback/test/package_graph/declaring_transformer_test.dart
diff --git a/pkg/barback/test/package_graph/declaring_transformer_test.dart b/pkg/barback/test/package_graph/declaring_transformer_test.dart
index 638aeb304b50e142c9d9db11e0e66cf515554e66..dc180aee2151009b4dd7800b556320f97686b714 100644
--- a/pkg/barback/test/package_graph/declaring_transformer_test.dart
+++ b/pkg/barback/test/package_graph/declaring_transformer_test.dart
@@ -220,38 +220,36 @@ main() {
     expect(declaring.numRuns, completion(equals(2)));
   });
 
-  // TODO(nweiz): Re-enable these when barback is capable of dealing with a
-  // changing [TransformNode.deferred] value.
-  // group("with an error in declareOutputs", () {
-  //   test("still runs apply", () {
-  //     initGraph(["app|foo.txt"], {"app": [[
-  //       new DeclaringBadTransformer("app|out.txt",
-  //           declareError: true, applyError: false)
-  //     ]]});
-  //
-  //     updateSources(["app|foo.txt"]);
-  //     expectAsset("app|out.txt", "bad out");
-  //     expectAsset("app|foo.txt", "foo");
-  //     buildShouldFail([isTransformerException(BadTransformer.ERROR)]);
-  //   });
-  //
-  //   test("waits for apply to complete before passing through the input even if "
-  //       "consumePrimary was called", () {
-  //     var transformer = new DeclaringBadTransformer("app|out.txt",
-  //           declareError: true, applyError: false)..consumePrimary = true;
-  //     initGraph(["app|foo.txt"], {"app": [[transformer]]});
-  //
-  //     transformer.pauseApply();
-  //     updateSources(["app|foo.txt"]);
-  //     expectAssetDoesNotComplete("app|out.txt");
-  //     expectAssetDoesNotComplete("app|foo.txt");
-  //
-  //     transformer.resumeApply();
-  //     expectAsset("app|out.txt", "bad out");
-  //     expectNoAsset("app|foo.txt");
-  //     buildShouldFail([isTransformerException(BadTransformer.ERROR)]);
-  //   });
-  // });
+  group("with an error in declareOutputs", () {
+    test("still runs apply", () {

[Bob Nystrom, 2014/04/29 23:46:22]

This seems like a perverse edge case to add complexity to support. If a
transformer fails when declaring its outputs, why apply it?

[nweiz, 2014/04/30 00:36:57]

Why not apply it? As far as we know, it'll still function perfectly well as an
eager transformer.

The complexity in this CL is necessary for aggregate transformers regardless.

[Bob Nystrom, 2014/04/30 19:21:24]

Maybe, but it's also likely to be broken if it couldn't even declare its
outputs. The main reason I'd say we shouldn't support it would be just to keep
things simpler.
Ah, that's fine then.

+      initGraph(["app|foo.txt"], {"app": [[
+        new DeclaringBadTransformer("app|out.txt",
+            declareError: true, applyError: false)
+      ]]});
+
+      updateSources(["app|foo.txt"]);
+      expectAsset("app|out.txt", "bad out");
+      expectAsset("app|foo.txt", "foo");
+      buildShouldFail([isTransformerException(BadTransformer.ERROR)]);
+    });
+
+    test("waits for apply to complete before passing through the input even if "
+        "consumePrimary was called", () {
+      var transformer = new DeclaringBadTransformer("app|out.txt",
+            declareError: true, applyError: false)..consumePrimary = true;
+      initGraph(["app|foo.txt"], {"app": [[transformer]]});
+
+      transformer.pauseApply();
+      updateSources(["app|foo.txt"]);
+      expectAssetDoesNotComplete("app|out.txt");
+      expectAssetDoesNotComplete("app|foo.txt");
+
+      transformer.resumeApply();
+      expectAsset("app|out.txt", "bad out");
+      expectNoAsset("app|foo.txt");
+      buildShouldFail([isTransformerException(BadTransformer.ERROR)]);
+    });
+  });
 
   test("with an error in apply still passes through the input", () {
    initGraph(["app|foo.txt"], {"app": [[