Create ServerDescriptor#isHiddenServiceDir.

Turns out that Tor has never supported versions in the
hidden-service-dir descriptor line.

This commit replaces ServerDescriptor#getHiddenServiceDirVersions with
ServerDescriptor#isHiddenServiceDir.

Fixes #25712.

CHANGELOG.md

 # Changes in version 2.3.0 - 2018-0?-??
 
- * Minor changes.
+ * Medium changes
+   - Replace ServerDescriptor#getHiddenServiceDirVersions with
+     ServerDescriptor#isHiddenServiceDir, because Tor has never
+     supported versions in the hidden-service-dir descriptor line.
+
+ * Minor changes
    - Override logLines() method from LogDescriptor in
      WebServerAccessLog.
    - Use 1-minute connect and read timeouts for fetching CollecTor's

src/main/java/org/torproject/descriptor/ServerDescriptor.java

@@ -318,10 +318,20 @@ public interface ServerDescriptor extends Descriptor {
    * this server stores and serves, or null if it doesn't store and serve
    * any hidden service descriptors.
    *
+   * @deprecated Replaced with {@link #isHiddenServiceDir}, because Tor has
+   *     never supported versions in the hidden-service-dir descriptor line.
+   *
    * @since 1.0.0
    */
   public List<Integer> getHiddenServiceDirVersions();
 
+  /**
+   * Return whether this server stores and serves hidden service descriptors.
+   *
+   * @since 2.3.0
+   */
+  public boolean isHiddenServiceDir();
+
   /**
    * Return the list of link protocol versions that this server
    * supports.

src/main/java/org/torproject/descriptor/impl/ServerDescriptorImpl.java

@@ -10,6 +10,7 @@ import org.torproject.descriptor.ServerDescriptor;
 import java.io.File;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Scanner;
@@ -462,21 +463,8 @@ public abstract class ServerDescriptorImpl extends DescriptorImpl
   }
 
   private void parseHiddenServiceDirLine(String line, String lineNoOpt,
-      String[] partsNoOpt) throws DescriptorParseException {
-    if (partsNoOpt.length == 1) {
-      this.hiddenServiceDirVersions = new Integer[] { 2 };
-    } else {
-      try {
-        Integer[] result = new Integer[partsNoOpt.length - 1];
-        for (int i = 1; i < partsNoOpt.length; i++) {
-          result[i - 1] = Integer.parseInt(partsNoOpt[i]);
-        }
-        this.hiddenServiceDirVersions = result;
-      } catch (NumberFormatException e) {
-        throw new DescriptorParseException("Illegal value in line '"
-            + line + "'.");
-      }
-    }
+      String[] partsNoOpt) {
+    this.hiddenServiceDir = true;
   }
 
   private void parseProtocolsLine(String line, String lineNoOpt,
@@ -854,12 +842,17 @@ public abstract class ServerDescriptorImpl extends DescriptorImpl
     return this.extraInfoDigestSha256;
   }
 
-  private Integer[] hiddenServiceDirVersions;
+  private boolean hiddenServiceDir;
+
+  @Override
+  public boolean isHiddenServiceDir() {
+    return this.hiddenServiceDir;
+  }
 
   @Override
+  @SuppressWarnings("deprecation")
   public List<Integer> getHiddenServiceDirVersions() {
-    return this.hiddenServiceDirVersions == null ? null
-        : Arrays.asList(this.hiddenServiceDirVersions);
+    return this.hiddenServiceDir ? null : Collections.singletonList(2);
   }
 
   private Integer[] linkProtocolVersions;

src/test/java/org/torproject/descriptor/impl/ServerDescriptorImplTest.java

@@ -482,8 +482,7 @@ public class ServerDescriptorImplTest {
     assertEquals(53470, (int) descriptor.getBandwidthObserved());
     assertEquals("1469D1550738A25B1E7B47CDDBCD7B2899F51B74",
         descriptor.getExtraInfoDigestSha1Hex());
-    assertEquals(Arrays.asList(new Integer[] {2}),
-        descriptor.getHiddenServiceDirVersions());
+    assertTrue(descriptor.isHiddenServiceDir());
     assertEquals("Random Person <nobody AT example dot com>",
         descriptor.getContact());
     assertEquals(Arrays.asList(new String[] {"reject *:*"}),
@@ -1014,7 +1013,7 @@ public class ServerDescriptorImplTest {
       throws DescriptorParseException {
     ServerDescriptor descriptor = DescriptorBuilder
         .createWithHiddenServiceDirLine(null);
-    assertNull(descriptor.getHiddenServiceDirVersions());
+    assertFalse(descriptor.isHiddenServiceDir());
   }
 
   @Test
@@ -1022,8 +1021,7 @@ public class ServerDescriptorImplTest {
       throws DescriptorParseException {
     ServerDescriptor descriptor = DescriptorBuilder
         .createWithHiddenServiceDirLine("hidden-service-dir");
-    assertEquals(Arrays.asList(new Integer[] {2}),
-        descriptor.getHiddenServiceDirVersions());
+    assertTrue(descriptor.isHiddenServiceDir());
   }
 
   @Test
@@ -1031,8 +1029,7 @@ public class ServerDescriptorImplTest {
       throws DescriptorParseException {
     ServerDescriptor descriptor = DescriptorBuilder
         .createWithHiddenServiceDirLine("hidden-service-dir 2 3");
-    assertEquals(Arrays.asList(new Integer[] {2, 3}),
-        descriptor.getHiddenServiceDirVersions());
+    assertTrue(descriptor.isHiddenServiceDir());
   }
 
   @Test