Adding support for symbolic links.

jib-core/src/main/java/com/google/cloud/tools/jib/image/ReproducibleLayerBuilder.java

@@ -25,6 +25,7 @@
 import com.google.common.collect.ImmutableList;
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
@@ -33,6 +34,7 @@
 import java.util.List;
 import java.util.Set;
 import org.apache.commons.compress.archivers.tar.TarArchiveEntry;
+import org.apache.commons.compress.archivers.tar.TarConstants;
 
 /**
  * Builds a reproducible layer {@link Blob} from files. The reproducibility is implemented by strips
@@ -147,12 +149,21 @@ public Blob build() throws IOException {
 
     // Adds all the layer entries as tar entries.
     for (FileEntry layerEntry : layerEntries) {
-      // Adds the entries to uniqueTarArchiveEntries, which makes sure all entries are unique and
-      // adds parent directories for each extraction path.
-      TarArchiveEntry entry =
-          new TarArchiveEntry(
-              layerEntry.getSourceFile(), layerEntry.getExtractionPath().toString());
 
+      TarArchiveEntry entry;
+      if (Files.isSymbolicLink(layerEntry.getSourceFile())) {
+        entry =
+                new TarArchiveEntry(
+                        layerEntry.getExtractionPath().toString(), TarConstants.LF_SYMLINK );
+        Path targetPath = Files.readSymbolicLink(layerEntry.getSourceFile());
+        entry.setLinkName(targetPath.toString());
+      } else {
+        // Adds the entries to uniqueTarArchiveEntries, which makes sure all entries are unique and
+        // adds parent directories for each extraction path.
+        entry =
+                new TarArchiveEntry(
+                        layerEntry.getSourceFile(), layerEntry.getExtractionPath().toString());
+      }
       // Sets the entry's permissions by masking out the permission bits from the entry's mode (the
       // lowest 9 bits) then using a bitwise OR to set them to the layerEntry's permissions.
       entry.setMode((entry.getMode() & ~0777) | layerEntry.getPermissions().getPermissionBits());

jib-core/src/main/java/com/google/cloud/tools/jib/tar/TarStreamBuilder.java

@@ -63,7 +63,7 @@ public void writeAsTarArchiveTo(OutputStream out) throws IOException {
    */
   public void addTarArchiveEntry(TarArchiveEntry entry) {
     archiveMap.put(
-        entry, entry.isFile() ? Blobs.from(entry.getPath()) : Blobs.from(ignored -> {}, true));
+        entry, (entry.isFile() && ! entry.isSymbolicLink()) ? Blobs.from(entry.getPath()) : Blobs.from(ignored -> {}, true));
   }
 
   /**

jib-core/src/test/java/com/google/cloud/tools/jib/image/ReproducibleLayerBuilderTest.java

@@ -38,15 +38,45 @@
 import java.nio.file.StandardOpenOption;
 import java.nio.file.attribute.FileTime;
 import java.time.Instant;
+import java.util.ArrayList;
+import java.util.List;
+
 import org.apache.commons.compress.archivers.tar.TarArchiveEntry;
 import org.apache.commons.compress.archivers.tar.TarArchiveInputStream;
+import org.junit.After;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 
 /** Tests for {@link ReproducibleLayerBuilder}. */
 public class ReproducibleLayerBuilderTest {
 
+
+
+  @After
+  public void cleanUp() throws IOException, URISyntaxException {
+    removeLinks(getLinks());
+  }
+
+  private List<Path> getLinks() throws URISyntaxException {
+    List<Path> linksList = new ArrayList<>();
+    Path blobA = Paths.get(Resources.getResource("core/blobA").toURI());
+    String resourceDir = blobA.getParent().toString();
+    Path link1 = Paths.get(   resourceDir,   "blob-link1");
+    linksList.add(link1);
+    Path link2 = Paths.get(resourceDir + "/layer/a/b/", "blob-link2");
+    linksList.add(link2);
+    return linksList;
+  }
+
+  private void removeLinks(List<Path> linksList) throws IOException {
+    for (Path path: linksList) {
+      if (Files.exists(path)) {
+        Files.delete(path);
+      }
+    }
+  }
+
   /**
    * Verifies the correctness of the next {@link TarArchiveEntry} in the {@link
    * TarArchiveInputStream}.
@@ -67,6 +97,24 @@ private static void verifyNextTarArchiveEntry(
     assertThat(extractedBytes).isEqualTo(expectedBytes);
   }
 
+  /**
+   * Verifies the correctness of the next {@link TarArchiveEntry} in the {@link
+   * TarArchiveInputStream}.
+   *
+   * @param tarArchiveInputStream the {@link TarArchiveInputStream} to read from
+   * @param expectedExtractionPath the expected extraction path of the next entry
+   * @param expectedLinkName the expected link name of the next entry
+   * @throws IOException if an I/O exception occurs
+   */
+  private static void verifyNextTarArchiveEntryIsLink(
+      TarArchiveInputStream tarArchiveInputStream, String expectedExtractionPath, String expectedLinkName)
+      throws IOException {
+    TarArchiveEntry header = tarArchiveInputStream.getNextTarEntry();
+    assertThat(header.getName()).isEqualTo(expectedExtractionPath);
+    assertThat(header.getLinkName()).isEqualTo(expectedLinkName);
+    assertThat(header.isSymbolicLink()).isTrue();
+  }
+
   /**
    * Verifies that the next {@link TarArchiveEntry} in the {@link TarArchiveInputStream} is a
    * directory with correct permissions.
@@ -94,11 +142,22 @@ private static FileEntry defaultLayerEntry(Path source, AbsoluteUnixPath destina
 
   @Rule public final TemporaryFolder temporaryFolder = new TemporaryFolder();
 
+  private String getExtractPath(String parent, Path layerDirectory, Path target) {
+
+    return parent + target.getParent().toString().replaceAll(layerDirectory.getParent().toString(), "") + "/" + target.getFileName().toString();
+  }
+
   @Test
   public void testBuild() throws URISyntaxException, IOException {
     Path layerDirectory = Paths.get(Resources.getResource("core/layer").toURI());
     Path blobA = Paths.get(Resources.getResource("core/blobA").toURI());
 
+    List<Path> linksList = getLinks();
+    removeLinks(linksList);
+    for (Path path: linksList) {
+      Files.createSymbolicLink(path, path.getParent().relativize(blobA));
+    }
+
     ReproducibleLayerBuilder layerBuilder =
         new ReproducibleLayerBuilder(
             ImmutableList.copyOf(
@@ -107,6 +166,8 @@ public void testBuild() throws URISyntaxException, IOException {
                         layerDirectory, AbsoluteUnixPath.get("/extract/here/apple/layer"))
                     .addEntry(blobA, AbsoluteUnixPath.get("/extract/here/apple/blobA"))
                     .addEntry(blobA, AbsoluteUnixPath.get("/extract/here/banana/blobA"))
+                    .addEntry(linksList.get(0), AbsoluteUnixPath.get(getExtractPath("/extract/here/apple/", layerDirectory, linksList.get(0) )))
+                    .addEntry(linksList.get(1), AbsoluteUnixPath.get(getExtractPath("/extract/here/apple/", layerDirectory, linksList.get(1) )))
                     .build()
                     .getEntries()));
 
@@ -124,6 +185,7 @@ public void testBuild() throws URISyntaxException, IOException {
       verifyNextTarArchiveEntryIsDirectory(tarArchiveInputStream, "extract/");
       verifyNextTarArchiveEntryIsDirectory(tarArchiveInputStream, "extract/here/");
       verifyNextTarArchiveEntryIsDirectory(tarArchiveInputStream, "extract/here/apple/");
+      verifyNextTarArchiveEntryIsLink(tarArchiveInputStream, "extract/here/apple/blob-link1", "blobA");
       verifyNextTarArchiveEntry(tarArchiveInputStream, "extract/here/apple/blobA", blobA);
       verifyNextTarArchiveEntryIsDirectory(tarArchiveInputStream, "extract/here/apple/layer/");
       verifyNextTarArchiveEntryIsDirectory(tarArchiveInputStream, "extract/here/apple/layer/a/");
@@ -132,6 +194,7 @@ public void testBuild() throws URISyntaxException, IOException {
           tarArchiveInputStream,
           "extract/here/apple/layer/a/b/bar",
           Paths.get(Resources.getResource("core/layer/a/b/bar").toURI()));
+      verifyNextTarArchiveEntryIsLink(tarArchiveInputStream, "extract/here/apple/layer/a/b/blob-link2", "../../../blobA");
       verifyNextTarArchiveEntryIsDirectory(tarArchiveInputStream, "extract/here/apple/layer/c/");
       verifyNextTarArchiveEntry(
           tarArchiveInputStream,