JPlag fails to generate report when input and working directories are on different drives (Windows path relativize error)

[YashParmar05]

Bug Description

When running JPlag on Windows, the report generation fails if the JPlag execution directory and the dataset directory are located on different drives (e.g., C: vs E:).

Although submission parsing and comparison complete successfully, the tool throws an exception while writing the report JSON. As a result, the generated report is corrupted, and the web viewer shows:

There was an Error!
Unexpected end of JSON input

JPlag Version

6.3.0

Operating System

Windows 10

Java Version

Java 25

[Kr0nox]

I could not reproduce this issue. I ran jplag with this command: java -jar .\jplag-6.3.0-SNAPSHOT-jar-with-dependencies.jar .\Progpedia\ACCEPTED -r D:/result.jplag and it provided a working result file.

Could you maybe provide us with the exact command you ran?

Do you get a correct result file, if the file is written to the same drive?

[YashParmar05]

I used this command : java -jar jplag-6.3.0-jar-with-dependencies.jar -l cpp -r result_p1 "E:\Mtech AI\sem 3\Dataset\Dataset_Junior\jp"

here jp folder is my main folder having p1->s1.cpp, p2->s2.cpp so on...
pi : folder name
si : solution file

[Kr0nox]

Yes this way I could reproduce the issue. It seams to only happen in the case you mentioned (report on same disc as jar, submissions on other) and not when the result is written to another disk.

But: The different disk between submissions and report is not the issue. The problem is that the jar is not on the same drive as the submission folder.

I quickly checked the contents of the generated report and the only file that is not correct is the options file (which is completly empty).
From the error below my guess is that the issue lies in the FileSerializer (which is only used in the options). There we try to get a relative path to the submission directory. Due to the jar being on a different disk this relativization fails.
Here are the relevant code pieces we should look at to fix this

JPlag/core/src/main/java/de/jplag/reporting/jsonfactory/serializer/FileSerializer.java

Lines 37 to 39 in 2ede0e4

	public void serialize(File file, JsonGenerator generator, SerializerProvider provider) throws IOException {
	generator.writeString(FilePathUtil.forceRelativePath(file.toPath()).toString());
	}

JPlag/core/src/main/java/de/jplag/reporting/FilePathUtil.java

Lines 39 to 44 in 2ede0e4

	public static Path forceRelativePath(Path path) {
	if (path.isAbsolute()) {
	return Path.of("./").toAbsolutePath().relativize(path);
	}
	return path;
	}

Complete error log

2026-05-07-09:35:49_994 [ERROR] ZipWriter - Failed to write JSON entry options.json
com.fasterxml.jackson.databind.JsonMappingException: 'other' has different root (through reference chain: de.jplag.options.JPlagOptions["submissionDirectories"]->java.util.Collections$UnmodifiableSet[0])
        at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:400)
        at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:371)
        at com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:346)
        at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContentsUsing(CollectionSerializer.java:186)
        at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:120)
        at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:111)
        at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:25)
        at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:732)
        at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:760)
        at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:183)
        at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:503)
        at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:342)
        at com.fasterxml.jackson.databind.ObjectMapper._writeValueAndClose(ObjectMapper.java:4926)
        at com.fasterxml.jackson.databind.ObjectMapper.writeValueAsBytes(ObjectMapper.java:4171)
        at de.jplag.reporting.reportobject.writer.ZipWriter.addJsonEntry(ZipWriter.java:48)
        at de.jplag.reporting.reportobject.ReportObjectFactory.writeOptionsFiles(ReportObjectFactory.java:202)
        at de.jplag.reporting.reportobject.ReportObjectFactory.createAndSaveReport(ReportObjectFactory.java:108)
        at de.jplag.cli.OutputFileGenerator.generateJPlagResultFile(OutputFileGenerator.java:50)
        at de.jplag.cli.CLI.runJPlag(CLI.java:120)
        at de.jplag.cli.CLI.runAndView(CLI.java:132)
        at de.jplag.cli.CLI.selectModeAutomatically(CLI.java:160)
        at de.jplag.cli.CLI.executeCli(CLI.java:79)
        at de.jplag.cli.CLI.executeCliAndHandleErrors(CLI.java:92)
        at de.jplag.cli.CLI.main(CLI.java:233)
Caused by: java.lang.IllegalArgumentException: 'other' has different root
        at java.base/sun.nio.fs.WindowsPath.relativize(WindowsPath.java:415)
        at java.base/sun.nio.fs.WindowsPath.relativize(WindowsPath.java:42)
        at de.jplag.reporting.FilePathUtil.forceRelativePath(FilePathUtil.java:41)
        at de.jplag.reporting.jsonfactory.serializer.FileSerializer.serialize(FileSerializer.java:38)
        at de.jplag.reporting.jsonfactory.serializer.FileSerializer.serialize(FileSerializer.java:17)
        at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContentsUsing(CollectionSerializer.java:179)
        ... 20 more