Fix FeatureMacther: featureValueOf may throw

Right now, that may happen in:
- HasToString, if the actual object has a custom toString method which may throw
- FileMatchers.aFileWithCanonicalPath and siblings

hamcrest/src/main/java/org/hamcrest/FeatureMatcher.java

@@ -33,17 +33,23 @@ public FeatureMatcher(Matcher<? super U> subMatcher, String featureDescription,
  * @param actual the target object
  * @return the feature to be matched
  */
- protected abstract U featureValueOf(T actual);
+ protected abstract U featureValueOf(T actual) throws Exception;
 
  @Override
  protected boolean matchesSafely(T actual, Description mismatch) {
- final U featureValue = featureValueOf(actual);
- if (!subMatcher.matches(featureValue)) {
- mismatch.appendText(featureName).appendText(" ");
- subMatcher.describeMismatch(featureValue, mismatch);
+ try {
+ final U featureValue = featureValueOf(actual);
+ if (!subMatcher.matches(featureValue)) {
+ mismatch.appendText(featureName).appendText(" ");
+ subMatcher.describeMismatch(featureValue, mismatch);
+ return false;
+ }
+ return true;
+ } catch (Exception e) { // catches exceptions thrown by featureValueOf(), if any
+ mismatch.appendText("an exception was thrown: ");
+ mismatch.appendText(e.toString()); //TODO + stacktrace (?)
  return false;
  }
- return true;
  }
 
  @Override

hamcrest/src/main/java/org/hamcrest/io/FileMatchers.java

@@ -50,12 +50,8 @@ public static Matcher<File> aFileNamed(final Matcher<String> expected) {
 
  public static Matcher<File> aFileWithCanonicalPath(final Matcher<String> expected) {
  return new FeatureMatcher<File, String>(expected, "A file with canonical path", "path") {
- @Override protected String featureValueOf(File actual) {
- try {
- return actual.getCanonicalPath();
- } catch (IOException e) {
- return "Exception: " + e.getMessage();
- }
+ @Override protected String featureValueOf(File actual) throws IOException {
+ return actual.getCanonicalPath();
  }
  };
  }

hamcrest/src/test/java/org/hamcrest/FeatureMatcherTest.java

@@ -33,6 +33,14 @@ public final class FeatureMatcherTest {
  assertEquals("was ShouldNotMatch <ShouldNotMatch>", mismatchDescription.toString());
  }
 
+ @Test public void
+ canRecoverFromFaultyFeature() {
+ assertMismatchDescription(
+ "an exception was thrown: java.lang.UnsupportedOperationException: make the feature fail!",
+ resultMatcher, new FaultyThingy());
+ }
+
+
  public static class Match extends IsEqual<String> {
  public Match(String equalArg) { super(equalArg); }
  @Override public void describeMismatch(Object item, Description description) {
@@ -52,6 +60,17 @@ public String getResult() {
  }
  }
 
+ public static class FaultyThingy extends Thingy {
+ public FaultyThingy() {
+ super("thingy with failing feature");
+ }
+
+ @Override
+ public String getResult() {
+ throw new UnsupportedOperationException("make the feature fail!");
+ }
+ }
+
  public static class ShouldNotMatch {
  @Override public String toString() { return "ShouldNotMatch"; }
  }