Create static factory methods for creating Matchers

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

@@ -1,5 +1,7 @@
 package org.hamcrest;
 
+import java.util.function.Function;
+
 import org.hamcrest.internal.ReflectiveTypeFinder;
 
 /**
@@ -29,6 +31,20 @@ public FeatureMatcher(Matcher<? super U> subMatcher, String featureDescription,
     this.featureName = featureName;
   }
 
+  /**
+   * Constructor
+   * @param subMatcher The matcher to apply to the feature
+   * @param featureDescription Descriptive text to use in describeTo
+   * @param featureName Identifying text for mismatch message
+   * @param expectedType expected type of the feature value
+   */
+private FeatureMatcher(Matcher<? super U> subMatcher, String featureDescription, String featureName, Class<?> expectedType) {
+    super(expectedType);
+    this.subMatcher = subMatcher;
+    this.featureDescription = featureDescription;
+    this.featureName = featureName;
+  }
+
   /**
    * Implement this to extract the interesting feature.
    * @param actual the target object
@@ -53,4 +69,20 @@ public final void describeTo(Description description) {
                .appendDescriptionOf(subMatcher);
   }
 
+	/**
+	 * Create a matcher that matches a feature of an object.
+	 *
+	 * @param expected              the matcher for the expected feature value
+	 * @param extractor             function to extract the feature from the object
+	 * @param featureDescription    descriptive text to use in describeTo
+	 * @param featureName           identifying text for mismatch message
+	 * @param expectedType 			expected type to match against
+	 * @return a matcher that matches the feature of the object
+	 */
+  public static <T,F> Matcher<T> matcher(final Matcher<F> expected, final Function<T, F> extractor, String featureDescription, String featureName, Class<T> expectedType) {
+      return new FeatureMatcher<T, F>(expected, featureDescription, featureName, expectedType) {
+          @Override protected F featureValueOf(T actual) { return extractor.apply(actual); }
+      };
+  }
+
 }

hamcrest/src/main/java/org/hamcrest/TypeSafeDiagnosingMatcher.java

@@ -1,5 +1,7 @@
 package org.hamcrest;
 
+import java.util.function.Predicate;
+
 import org.hamcrest.internal.ReflectiveTypeFinder;
 
 /**
@@ -82,4 +84,31 @@ public final void describeMismatch(Object item, Description mismatchDescription)
       }
     }
 
+    /**
+     * Creates a TypeSafeDiagnosingMatcher that matches an item based on a predicate.
+     * 
+     * @param <T> Type of the item to match
+     * @param predicate Predicate to test the item
+     * @param successDescription Description to use when the predicate matches
+     * @param failureDescription Description to use when the predicate does not match
+     * @param expectedType Expected type of the item to match
+     * @return Matcher that matches the item based on the predicate
+     */
+    public static <T> Matcher<T> matcher(Predicate<T> predicate, final String successDescription, final String failureDescription, Class<T> expectedType) {
+        return new TypeSafeDiagnosingMatcher<T>(expectedType) {
+            public boolean matchesSafely(T actual, Description mismatchDescription) {
+                final boolean result = predicate.test(actual);
+                if (!result) {
+                    mismatchDescription.appendText(String.format("'%s' %s", actual, failureDescription));
+                }
+                return result;
+            }
+
+            public void describeTo(Description description) {
+                description.appendText(successDescription);
+            }
+        };
+    }
+
+
 }

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

@@ -9,23 +9,41 @@
 public final class FeatureMatcherTest {
 
     private final FeatureMatcher<Thingy, String> resultMatcher = resultMatcher();
+	private final Matcher<Thingy> resultMatcherStaticCtr = 
+			FeatureMatcher.matcher(new Match("bar"), t->t.getResult(), "Thingy with result", "result", Thingy.class);
 
     @Test public void
     matchesPartOfAnObject() {
         assertMatches("feature", resultMatcher, new Thingy("bar"));
         assertDescription("Thingy with result \"bar\"", resultMatcher);
     }
 
+    @Test public void
+    matchesPartOfAnObject_staticConstructor() {
+        assertMatches("feature", resultMatcherStaticCtr, new Thingy("bar"));
+        assertDescription("Thingy with result \"bar\"", resultMatcherStaticCtr);
+    }
+
     @Test public void
     mismatchesPartOfAnObject() {
         assertMismatchDescription("result mismatch-description", resultMatcher, new Thingy("foo"));
     }
 
+    @Test public void
+    mismatchesPartOfAnObject_staticConstructor() {
+        assertMismatchDescription("result mismatch-description", resultMatcherStaticCtr, new Thingy("foo"));
+    }
+
     @Test public void
     doesNotThrowNullPointerException() {
         assertMismatchDescription("was null", resultMatcher, null);
     }
 
+    @Test public void
+    doesNotThrowNullPointerException_staticConstructor() {
+        assertMismatchDescription("was null", resultMatcherStaticCtr, null);
+    }
+
     @Test public void
     doesNotThrowClassCastException() {
         resultMatcher.matches(new ShouldNotMatch());
@@ -34,6 +52,14 @@ public final class FeatureMatcherTest {
         assertEquals("was ShouldNotMatch <ShouldNotMatch>", mismatchDescription.toString());
     }
 
+    @Test public void
+    doesNotThrowClassCastException_staticConstructor() {
+        resultMatcherStaticCtr.matches(new ShouldNotMatch());
+        StringDescription mismatchDescription = new StringDescription();
+        resultMatcherStaticCtr.describeMismatch(new ShouldNotMatch(), mismatchDescription);
+        assertEquals("was ShouldNotMatch <ShouldNotMatch>", mismatchDescription.toString());
+    }
+
     public static class Match extends IsEqual<String> {
         public Match(String equalArg) { super(equalArg); }
         @Override public void describeMismatch(Object item, Description description) {

hamcrest/src/test/java/org/hamcrest/TypeSafeDiagnosingMatcherTest.java

@@ -17,6 +17,15 @@ public class TypeSafeDiagnosingMatcherTest {
         assertMismatchDescription("mismatching", STRING_MATCHER, "other");
     }
 
+    @Test public void
+    describesMismatches_staticConstructor() {
+    	Matcher<String> stringMatcher = 
+    			TypeSafeDiagnosingMatcher.matcher(item->false,"matches","mismatching",String.class);        
+    	assertMismatchDescription("was null", STRING_MATCHER, null);
+        assertMismatchDescription("was Character \"c\"", STRING_MATCHER, 'c');
+        assertMismatchDescription("mismatching", STRING_MATCHER, "other");
+    }
+
     @Test public void
     detects_non_builtin_types() {
       final Matcher<NotBuiltIn> matcher = new TypeSafeDiagnosingMatcher<NotBuiltIn>() {
@@ -32,13 +41,30 @@ protected boolean matchesSafely(NotBuiltIn item, Description mismatchDescription
       assertDoesNotMatch("other not built in", (Matcher)matcher, new OtherNotBuiltIn());
     }
 
+    @Test public void
+    detects_non_builtin_types_static_constructor() {
+        final Matcher<NotBuiltIn> matcher = 
+        		TypeSafeDiagnosingMatcher.matcher(item->true,"a builtin","a not builtin",NotBuiltIn.class);        
+
+      assertMatches("not built in", matcher, new NotBuiltIn());
+      assertDoesNotMatch("other not built in", (Matcher)matcher, new OtherNotBuiltIn());
+    }
+
     @Test public void
     filters_type_for_subclassed_matcher_when_expected_type_passed_in() {
       final Matcher<NotBuiltIn> matcher = new SubMatcher<>(new NotBuiltIn());
 
       assertMatches("not built in", matcher, new NotBuiltIn());
       assertDoesNotMatch("other not built in", (Matcher)matcher, new OtherNotBuiltIn());
-  }
+    }
+
+    @Test public void
+    filters_type_for_subclassed_matcher_when_expected_type_passed_in_staticConstructor() {
+        final Matcher<NotBuiltIn> matcher = SubMatcher.matcher(new NotBuiltIn());
+
+        assertMatches("not built in", matcher, new NotBuiltIn());
+        assertDoesNotMatch("other not built in", (Matcher)matcher, new OtherNotBuiltIn());
+    }
 
     @Test public void
     but_cannot_detect_generic_type_in_subclassed_matcher_using_reflection() {
@@ -59,6 +85,7 @@ protected boolean matchesSafely(String item, Description mismatchDescription) {
         public void describeTo(Description description) { }
     };
 
+
     public static class SubMatcher<T> extends TypeSafeDiagnosingMatcher<T> {
       public SubMatcher() {
           super();
@@ -68,6 +95,12 @@ public SubMatcher(T expectedObject) {
       }
       @Override protected boolean matchesSafely(T item, Description mismatchDescription) { return true; }
       @Override public void describeTo(Description description) { description.appendText("sub type"); }
+
+      static <T> Matcher<T> matcher(T expectedObject) {
+    	  return new SubMatcher<T>(expectedObject) {
+
+    	  };
+      }
     }
 
     public static class NotBuiltIn {