FileUtil: getRelativePath should return relative the path from the base to the file regardless existence or the type of the base file.

platform/util-rt/src/com/intellij/openapi/util/io/FileUtilRt.java

@@ -234,15 +234,19 @@ public class FileUtilRt {
     return fileName.replace('\\', '/');
   }
 
+  /**
+   * Gets the relative path from the {@code base} to the {@code file} regardless existence or the type of the {@code base}.
+   * <p>
+   * NOTE: if the file(not directory) passed as the {@code base} the result can not be used as a relative path from the {@code base} parent directory to the {@code file}
+   *
+   * @param base the base
+   * @param file the file
+   * @return the relative path from the {@code base} to the {@code file} or {@code null}
+   */
   @Nullable
   public static String getRelativePath(File base, File file) {
     if (base == null || file == null) return null;
 
-    if (base.exists() && !base.isDirectory()) {
-      base = base.getParentFile();
-      if (base == null) return null;
-    }
-
     //noinspection FileEqualsUsage
     if (base.equals(file)) return ".";
 

platform/util/src/com/intellij/openapi/util/io/FileUtil.java

@@ -78,6 +78,15 @@ public class FileUtil extends FileUtilRt {
     return StringUtil.join(parts, File.separator);
   }
 
+  /**
+   * Gets the relative path from the {@code base} to the {@code file} regardless existence or the type of the {@code base}.
+   * <p>
+   * NOTE: if the file(not directory) passed as the {@code base} the result can not be used as a relative path from the {@code base} parent directory to the {@code file}
+   *
+   * @param base the base
+   * @param file the file
+   * @return the relative path from the {@code base} to the {@code file} or {@code null}
+   */
   @Nullable
   public static String getRelativePath(File base, File file) {
     return FileUtilRt.getRelativePath(base, file);

platform/util/testSrc/com/intellij/openapi/util/io/FileUtilHeavyTest.java

@@ -324,4 +324,20 @@ public class FileUtilHeavyTest {
     String path = myFindTestFirstFile.getPath();
     assertEquals(SystemInfo.isFileSystemCaseSensitive, FileUtil.isFileSystemCaseSensitive(path));
   }
+
+  @Test
+  public void testFileRelativePath() {
+    String relativePath = FileUtil.toSystemDependentName("relative/path.file");
+
+    File existingDir = myTempDirectory;
+    assertEquals(relativePath, FileUtil.getRelativePath(existingDir, new File(existingDir, relativePath)));
+
+    File notExistingDirOrFile = new File("not/existing/path");
+    assertEquals(relativePath, FileUtil.getRelativePath(notExistingDirOrFile, new File(notExistingDirOrFile, relativePath)));
+
+    // FileUtil.getRelativePath(File, File) should have the same behavior then FileUtil.getRelativePath(String, String, char)
+    File existingFile = IoTestUtil.createTestFile(existingDir, "foo.file");
+    assertEquals(".." + File.separatorChar + relativePath,
+                 FileUtil.getRelativePath(existingFile, new File(existingFile.getParent(), relativePath)));
+  }
 }

platform/util/testSrc/com/intellij/openapi/util/io/FileUtilLightTest.java

@@ -24,10 +24,12 @@ import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.containers.Convertor;
 import org.junit.Test;
 
-import java.io.File;
 import java.io.IOException;
 import java.io.StringReader;
-import java.util.*;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.*;
@@ -190,20 +192,6 @@ public class FileUtilLightTest {
     }
   }
 
-  @Test
-  public void testFileRelativePath() {
-    String relativePath = FileUtil.toSystemDependentName("relative/path.file");
-
-    File existingDir = IoTestUtil.createTestDir(UUID.randomUUID().toString());
-    assertEquals(relativePath, FileUtil.getRelativePath(existingDir, new File(existingDir, relativePath)));
-
-    File notExistingDir = new File("not/existing/path");
-    assertEquals(relativePath, FileUtil.getRelativePath(notExistingDir, new File(notExistingDir, relativePath)));
-
-    File existingFile = IoTestUtil.createTestFile(existingDir, "foo.file");
-    assertEquals(relativePath, FileUtil.getRelativePath(existingFile, new File(existingFile.getParent(), relativePath)));
-  }
-
   @Test
   public void testRelativeToUserHome() {
     assertEquals(SystemProperties.getUserHome(), FileUtil.getLocationRelativeToUserHome(SystemProperties.getUserHome(), false));