Throw NoSuchElementException for non-existent certificates/keys

Fixes #2

pgp-cert-d-java/src/main/java/pgp/cert_d/PGPCertificateDirectory.java

@@ -15,6 +15,8 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.util.Iterator;
 import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.Objects;
 import java.util.Set;
 import java.util.regex.Pattern;
 
@@ -46,13 +48,17 @@ public class PGPCertificateDirectory
         if (!openPgpV4FingerprintPattern.matcher(fingerprint).matches()) {
             throw new BadNameException();
         }
-        return backend.readByFingerprint(fingerprint);
+        Certificate certificate = backend.readByFingerprint(fingerprint);
+        if (certificate == null) {
+            throw new NoSuchElementException();
+        }
+        return certificate;
     }
 
     @Override
     public Certificate getByFingerprintIfChanged(String fingerprint, long tag)
             throws IOException, BadNameException, BadDataException {
-        if (tag != backend.getTagForFingerprint(fingerprint)) {
+        if (!Objects.equals(tag, backend.getTagForFingerprint(fingerprint))) {
             return getByFingerprint(fingerprint);
         }
         return null;
@@ -66,13 +72,13 @@ public class PGPCertificateDirectory
         if (keyMaterial != null) {
             return keyMaterial.asCertificate();
         }
-        return null;
+        throw new NoSuchElementException();
     }
 
     @Override
     public Certificate getBySpecialNameIfChanged(String specialName, long tag)
             throws IOException, BadNameException, BadDataException {
-        if (tag != backend.getTagForSpecialName(specialName)) {
+        if (!Objects.equals(tag, backend.getTagForSpecialName(specialName))) {
             return getBySpecialName(specialName);
         }
         return null;
@@ -121,7 +127,11 @@ public class PGPCertificateDirectory
     @Override
     public KeyMaterial getTrustRoot() throws IOException, BadDataException {
         try {
-            return backend.readBySpecialName(SpecialNames.TRUST_ROOT);
+            KeyMaterial keyMaterial = backend.readBySpecialName(SpecialNames.TRUST_ROOT);
+            if (keyMaterial == null) {
+                throw new NoSuchElementException();
+            }
+            return keyMaterial;
         } catch (BadNameException e) {
             throw new AssertionError("'" + SpecialNames.TRUST_ROOT + "' is implementation MUST");
         }

pgp-cert-d-java/src/main/java/pgp/cert_d/backend/FileBasedCertificateDirectoryBackend.java

@@ -33,6 +33,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
+import java.util.NoSuchElementException;
 import java.util.regex.Pattern;
 
 /**
@@ -348,7 +349,7 @@ public class FileBasedCertificateDirectoryBackend implements PGPCertificateDirec
 
     private Long getTag(File file) throws IOException {
         if (!file.exists()) {
-            throw new IllegalArgumentException("File MUST exist.");
+            throw new NoSuchElementException();
         }
         Path path = file.toPath();
         BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);

pgp-cert-d-java/src/test/java/pgp/cert_d/PGPCertificateDirectoryTest.java

@@ -31,6 +31,7 @@ import java.nio.file.Files;
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Iterator;
+import java.util.NoSuchElementException;
 import java.util.Set;
 import java.util.stream.Stream;
 
@@ -68,6 +69,55 @@ public class PGPCertificateDirectoryTest {
                 Arguments.of(Named.of("FileBasedCertificateDirectory", fileBased)));
     }
 
+    @ParameterizedTest
+    @MethodSource("provideTestSubjects")
+    public void getNonExistentCertByFingerprintThrowsNoSuchElementException(PGPCertificateDirectory directory) {
+        assertThrows(NoSuchElementException.class, () ->
+                directory.getByFingerprint("0000000000000000000000000000000000000000"));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestSubjects")
+    public void getNonExistentCertByFingerprintIfChangedThrowsNoSuchElementException(PGPCertificateDirectory directory) {
+        assertThrows(NoSuchElementException.class, () ->
+                directory.getByFingerprintIfChanged("0000000000000000000000000000000000000000", 12));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestSubjects")
+    public void getNonExistentCertBySpecialNameThrowsNoSuchElementException(PGPCertificateDirectory directory) {
+        assertThrows(NoSuchElementException.class, () ->
+                directory.getBySpecialName(SpecialNames.TRUST_ROOT));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestSubjects")
+    public void getNonExistentCertBySpecialNameIfChangedThrowsNoSuchElementException(PGPCertificateDirectory directory) {
+        assertThrows(NoSuchElementException.class, () ->
+                directory.getBySpecialNameIfChanged(SpecialNames.TRUST_ROOT, 12));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestSubjects")
+    public void getNonExistentTrustRootThrowsNoSuchElementException(PGPCertificateDirectory directory) {
+        assertThrows(NoSuchElementException.class, () ->
+                directory.getTrustRoot());
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestSubjects")
+    public void getNonExistentTrustRootIfChangedThrowsNoSuchElementException(PGPCertificateDirectory directory) {
+        assertThrows(NoSuchElementException.class, () ->
+                directory.getTrustRootCertificateIfChanged(12));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestSubjects")
+    public void getNonExistentTrustRootCertificateThrowsNoSuchElementException(PGPCertificateDirectory directory) {
+        assertThrows(NoSuchElementException.class, () ->
+                directory.getTrustRootCertificate());
+    }
+
     @ParameterizedTest
     @MethodSource("provideTestSubjects")
     public void lockDirectoryAndTryInsertWillFail(PGPCertificateDirectory directory)
@@ -130,7 +180,7 @@ public class PGPCertificateDirectoryTest {
     @MethodSource("provideTestSubjects")
     public void testInsertAndGetSingleCert(PGPCertificateDirectory directory)
             throws BadDataException, IOException, InterruptedException, BadNameException {
-        assertNull(directory.getByFingerprint(CEDRIC_FP), "Empty directory MUST NOT contain certificate");
+        assertThrows(NoSuchElementException.class, () -> directory.getByFingerprint(CEDRIC_FP), "Empty directory MUST NOT contain certificate");
 
         Certificate certificate = directory.insert(TestKeys.getCedricCert(), merger);
         assertEquals(CEDRIC_FP, certificate.getFingerprint(), "Fingerprint of inserted cert MUST match");
@@ -148,7 +198,7 @@ public class PGPCertificateDirectoryTest {
     @MethodSource("provideTestSubjects")
     public void testInsertAndGetTrustRootAndCert(PGPCertificateDirectory directory)
             throws BadDataException, IOException, InterruptedException {
-        assertNull(directory.getTrustRoot());
+        assertThrows(NoSuchElementException.class, () -> directory.getTrustRoot());
 
         KeyMaterial trustRootMaterial = directory.insertTrustRoot(
                 TestKeys.getHarryKey(), merger);
@@ -188,6 +238,7 @@ public class PGPCertificateDirectoryTest {
         assertNotNull(directory.getTrustRootCertificateIfChanged(tag + 1));
 
         Long oldTag = tag;
+        Thread.sleep(10);
         // "update" key
         trustRootMaterial = directory.insertTrustRoot(
                 TestKeys.getHarryKey(), merger);
@@ -241,10 +292,12 @@ public class PGPCertificateDirectoryTest {
 
         Long oldTag = tag;
 
+        Thread.sleep(10);
         // Change the file on disk directly, this invalidates the tag due to changed modification date
         File certFile = resolver.getCertFileByFingerprint(certificate.getFingerprint());
         FileOutputStream fileOut = new FileOutputStream(certFile);
         Streams.pipeAll(certificate.getInputStream(), fileOut);
+        fileOut.write("\n".getBytes());
         fileOut.close();
 
         // Old invalidated tag indicates a change, so the modified certificate is returned

pgp-cert-d-java/src/test/java/pgp/cert_d/PGPCertificateStoreAdapterTest.java

@@ -17,6 +17,7 @@ import pgp.certificate_store.exception.BadNameException;
 import java.io.IOException;
 import java.util.Iterator;
 import java.util.List;
+import java.util.NoSuchElementException;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
@@ -52,7 +53,7 @@ public class PGPCertificateStoreAdapterTest {
     @Test
     public void testInsertGetCertificate()
             throws BadDataException, IOException, InterruptedException, BadNameException {
-        assertNull(adapter.getCertificate(TestKeys.CEDRIC_FP));
+        assertThrows(NoSuchElementException.class, () -> adapter.getCertificate(TestKeys.CEDRIC_FP));
         assertFalse(adapter.getCertificates().hasNext());
 
         Certificate certificate = adapter.insertCertificate(TestKeys.getCedricCert(), merger);
@@ -70,7 +71,7 @@ public class PGPCertificateStoreAdapterTest {
     @Test
     public void testInsertGetTrustRoot()
             throws BadDataException, BadNameException, IOException, InterruptedException {
-        assertNull(adapter.getCertificate(SpecialNames.TRUST_ROOT));
+        assertThrows(NoSuchElementException.class, () -> adapter.getCertificate(SpecialNames.TRUST_ROOT));
 
         Certificate certificate = adapter.insertCertificateBySpecialName(
                 SpecialNames.TRUST_ROOT, TestKeys.getHarryKey(), merger);