Added file content matchers to PathMatchers.

These correspond to the recently added FileMatchers matchers.

Author: rmcdouga

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

@@ -9,6 +9,7 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.function.Predicate;
+import java.util.stream.Collectors;
 
 import static org.hamcrest.TypeSafeDiagnosingMatcher.matcher;
 import static org.hamcrest.core.IsEqual.equalTo;
@@ -207,6 +208,39 @@ public static Matcher<Path> hasFileSystem(final Matcher<FileSystem> expected) {
         };
     }
 
+    /**
+     * Matcher for matching file content with given file path
+     * 
+     * Note: line endings in the file are preserved in their platform dependent form, 
+     * so both files must contain the same line endings to match.
+     * 
+     * @param expected The file with the expected content
+     * @return A FeatureMatcher that takes the content of a file path as feature
+     */
+    public static Matcher<Path> matchesContentOf(Path expected) {
+        String expectedContent =  toUncheckedEx(()->Files.readString(expected));
+        return new FeatureMatcher<Path, String>(equalTo(expectedContent), "A file with content", "content") {
+            @Override protected String featureValueOf(Path actual) { return toUncheckedEx(()->Files.readString(actual));}
+        };
+    }
+
+    /**
+     * Matcher for matching file content with given String Matcher
+     * 
+     * Note: line endings in the file are converted to '\n' to avoid platform dependent test results
+     * 
+     * @param expected The expected content Matcher
+     * @return A FeatureMatcher that takes the content of a file as feature
+     */
+    public static Matcher<Path> hasContent(Matcher<String> expected) {
+        return new FeatureMatcher<Path, String>(expected, "A file with content", "content") {
+            @Override protected String featureValueOf(Path actual) {
+                // use collector to avoid platform dependent line endings
+                return toUncheckedEx(()->Files.lines(actual).collect(Collectors.joining("\n")));
+                }
+        };
+    }
+
     // Possible additions:
     // - hasParent(Matcher<Path>)
     // - hasRoot(Matcher<Path>)
@@ -221,7 +255,6 @@ public static Matcher<Path> hasFileSystem(final Matcher<FileSystem> expected) {
     // - hasFileAttribute(String, Matcher<Object>)
     // - hasProvider(Matcher<FileSystemProvider>)
 
-    // - hasContent(Matcher<String>)
     // - containsStrings(String...)
 
     // Workaround for JDK 8 not supporting Files.isHidden(Path) for directories

hamcrest/src/test/java/org/hamcrest/io/PathMatchersTest.java

@@ -23,13 +23,16 @@ public class PathMatchersTest extends AbstractMatcherTest {
     @TempDir Path tempDir;
     private Path directory;
     private Path file;
+    private Path anotherFile;
     private Path symbolicLink;
 
     @BeforeEach
     protected void setUp() throws IOException {
         directory = Files.createDirectory(tempDir.resolve("myDir"));
         file = directory.resolve("myFile");
+        anotherFile = directory.resolve("myAnotherFile");
         Files.createFile(file);
+        Files.writeString(anotherFile, "world");
         Files.createFile(directory.resolve("mydirFile")); // Makes sure myDir is not empty.
         if (!OS.WINDOWS.isCurrentOs()) { // Can't do symbolic links on Windows unless admin privileges are available.
             symbolicLink = tempDir.resolve("mySymbolicLink");
@@ -193,7 +196,29 @@ public void testHasFileSystem() {
 //      assertDoesNotMatch("doesn't match incorrect file system",PathMatchers.hasFileSystem(equalTo(Paths.get("foo").getFileSystem())), file);
     }
 
-    @Override
+    @Test
+    public void testFileContentMatcher() {
+        assertMatches("matches file content with a file", PathMatchers.matchesContentOf(file), file);
+        assertDoesNotMatch("content of two files with different content won't match", PathMatchers.matchesContentOf(anotherFile), file);
+    }
+
+    @Test
+    public void testFileContentMatcherDescription() {
+        assertMismatchDescription("content was \"\"", PathMatchers.matchesContentOf(anotherFile), file);
+    }
+
+    @Test
+    public void testAFileWithContent() {
+        assertMatches("matches file content", PathMatchers.hasContent(equalTo("")), file);
+        assertDoesNotMatch("doesn't match incorrect content", PathMatchers.hasContent(equalTo("world")), file);
+    }
+
+    @Test
+    public void testAFileWithContentDescription() {
+        assertMismatchDescription("content was \"\"", PathMatchers.hasContent(equalTo("world")), file);
+    }
+
+   @Override
     protected Matcher<?> createMatcher() {
         return PathMatchers.hasSizeEqualTo(1L);
 //        return PathMatchers.isSymbolicLink();