new TestStringSetGenerator() {
              @Override
              public Set<String> create(String[] elements) {
                Set<String> unfiltered = Sets.newLinkedHashSet();
                unfiltered.add("yyy");
                Collections.addAll(unfiltered, elements);
                unfiltered.add("zzz");
                return Sets.filter(unfiltered, Collections2Test.NOT_YYY_ZZZ);
              }
            })

            new TestStringSetGenerator() {
              @Override
              public Set<String> create(String[] elements) {
                Set<String> unfiltered = Sets.newLinkedHashSet();
                unfiltered.add("yyy");
                Collections.addAll(unfiltered, elements);
                unfiltered.add("zzz");
                return Sets.filter(unfiltered, Collections2Test.NOT_YYY_ZZZ);
              }
            })

// Or until cancelled by parent context
func getCNIConfigFilepath(ctx context.Context, cniConfName, mountedCNINetDir string, chained bool) (string, error) {
	if !chained {
		if len(cniConfName) == 0 {
			cniConfName = "YYY-istio-cni.conf"
		}
		return filepath.Join(mountedCNINetDir, cniConfName), nil
	}

	watcher, err := util.CreateFileWatcher(mountedCNINetDir)
	if err != nil {
		return "", err
	}
	defer watcher.Close()

	if err := os.Mkdir(instdir, 0777); err != nil {
		t.Fatal(err)
	}
	mdir := filepath.Join(dir, "meta2")
	if err := os.Mkdir(mdir, 0777); err != nil {
		t.Fatal(err)
	}
	mpath := filepath.Join(mdir, "covmeta.yyy")
	incfg := writePkgConfig(t, instdir, tag, ppath, pname, gran, mpath)
	_, _, errmsg := runPkgCover(t, instdir, tag, incfg, mode,
		pkgfiles, false)
	if errmsg != "" {
		t.Fatalf("runPkgCover err: %q", errmsg)
	}

// Test that panic message is not clobbered.
// See issue 30150.
func TestDoublePanic(t *testing.T) {
	output := runTestProg(t, "testprog", "DoublePanic", "GODEBUG=clobberfree=1")
	wants := []string{"panic: XXX", "panic: YYY"}
	for _, want := range wants {
		if !strings.Contains(output, want) {
			t.Errorf("output:\n%s\n\nwant output containing: %s", output, want)
		}
	}
}

You can have attributes on both the requested dependency _or_ the substitute and the substitution is not limited to `platform`: you can actually specify the whole set of dependency attributes using the `variant` notation.

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