Fix old JabRef linked files containing the file directory as element in the filename

CHANGELOG.md

@@ -89,6 +89,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 
 ### Fixed
 
+- We fixed an issue where linked fails containing parts of the main file directory could not be opened [#8991](https://github.com/JabRef/jabref/issues/8991)
 - We fixed an issue where the user could not rate an entry in the main table when an entry was not yet ranked. [#5842](https://github.com/JabRef/jabref/issues/5842)
 - We fixed an issue that caused JabRef to sometimes open multiple instances when "Remote Operation" is enabled. [#8653](https://github.com/JabRef/jabref/issues/8653)
 - We fixed an issue where linked files with the filetype "application/pdf" in an entry were not shown with the correct PDF-Icon in the main table [8930](https://github.com/JabRef/jabref/issues/8930)

src/main/java/org/jabref/model/util/FileHelper.java

@@ -151,8 +151,12 @@ public static boolean isCharLegal(char c) {
     }
 
     /**
-     * Converts a relative filename to an absolute one, if necessary. Returns
-     * an empty optional if the file does not exist.
+     * Converts a relative filename to an absolute one, if necessary.
+     *
+     * @param fileName the filename (e.g., a .pdf file), may contain path separators
+     * @param directory the directory which should be search starting point
+     *
+     * @returns an empty optional if the file does not exist, otherwise, the absolute path
      */
     public static Optional<Path> find(String fileName, Path directory) {
         Objects.requireNonNull(fileName);
@@ -168,6 +172,17 @@ public static Optional<Path> find(String fileName, Path directory) {
         }
 
         Path resolvedFile = directory.resolve(fileName);
+        if (Files.exists(resolvedFile)) {
+            return Optional.of(resolvedFile);
+        }
+
+        // get the furthest path element from root and check if our filename starts with the same name
+        // workaround for old JabRef behavior
+        String furthestDirFromRoot = directory.getFileName().toString();
+        if (fileName.startsWith(furthestDirFromRoot)) {
+            resolvedFile = directory.resolveSibling(fileName);
+        }
+
         if (Files.exists(resolvedFile)) {
             return Optional.of(resolvedFile);
         } else {

src/test/java/org/jabref/model/util/FileHelperTest.java

@@ -1,15 +1,18 @@
 package org.jabref.model.util;
 
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Optional;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 class FileHelperTest {
+
     @Test
     public void extractFileExtension() {
         final String filePath = FileHelperTest.class.getResource("pdffile.pdf").getPath();
@@ -24,14 +27,42 @@ public void fileExtensionFromUrl() {
 
     @Test
     public void testFileNameEmpty() {
-      Path path = Path.of("/");
-      assertEquals(Optional.of(path), FileHelper.find("", path));
+        Path path = Path.of("/");
+        assertEquals(Optional.of(path), FileHelper.find("", path));
     }
 
     @ParameterizedTest
-    @ValueSource(strings = { "*", "?", ">", "\"" })
+    @ValueSource(strings = {"*", "?", ">", "\""})
     public void testFileNameIllegal(String fileName) {
         Path path = Path.of("/");
         assertEquals(Optional.empty(), FileHelper.find(fileName, path));
     }
+
+    @Test
+    public void testFindsFileInDirectory(@TempDir Path temp) throws Exception {
+        Path firstFilePath = temp.resolve("files");
+        Files.createDirectories(firstFilePath);
+        Path firstFile = Files.createFile(firstFilePath.resolve("test.pdf"));
+
+        assertEquals(Optional.of(firstFile), FileHelper.find("test.pdf", temp.resolve("files")));
+    }
+
+    @Test
+    public void testFindsFileStartingWithTheSameDirectory(@TempDir Path temp) throws Exception {
+        Path firstFilePath = temp.resolve("files");
+        Files.createDirectories(firstFilePath);
+        Path firstFile = Files.createFile(firstFilePath.resolve("test.pdf"));
+
+        assertEquals(Optional.of(firstFile), FileHelper.find("files/test.pdf", temp.resolve("files")));
+    }
+
+    @Test
+    public void testDoesNotFindsFileStartingWithTheSameDirectoryHasASubdirectory(@TempDir Path temp) throws Exception {
+        Path firstFilesPath = temp.resolve("files");
+        Path secondFilesPath = firstFilesPath.resolve("files");
+        Files.createDirectories(secondFilesPath);
+        Path testFile = secondFilesPath.resolve("test.pdf");
+        Files.createFile(testFile);
+        assertEquals(Optional.of(testFile.toAbsolutePath()), FileHelper.find("files/test.pdf", firstFilesPath));
+    }
 }