What causes "Could not find old mapping file %s" in shwenzhang/AndResGuard?

Re-run the build ensuring the mapping file still exists and is a regular readable file at the configured path

Could not find old mapping file

Error message

Could not find old mapping file %s

What it means

processOldMappingFile wraps its FileReader construction and, if the file cannot be opened (FileNotFoundException), rethrows this IOException naming the absolute path. This is a second, defensive check after readOldMapping's exists() test — it covers races and permission/open failures between the exists() check and the open, or when exists() passed but the path is a directory.

Solutions

Re-run the build ensuring the mapping file still exists and is a regular readable file at the configured path
Check that the path is a file, not a directory, and that the running user has read permission
If the file is generated by a prior task, serialize the pipeline so nothing deletes it mid-run

Example fix

// before
mOldMappingFile = new File("build/outputs/mapping"); // directory, not the file
// after
mOldMappingFile = new File("build/outputs/mapping/release/mapping.txt");

Defensive patterns

Strategy: try-catch

Validate before calling

java.io.File f = new java.io.File(mappingPath);
if (!f.exists() || !f.isFile() || !f.canRead()) {
  throw new IllegalStateException("mapping file must be a readable regular file: " + f.getAbsolutePath());
}

Try / catch

try {
  new Configuration(configFile, ...);
} catch (IOException e) {
  if (e.getMessage().startsWith("Could not find old mapping file")) {
    // re-check that the file was not deleted/concurrently modified between config parse and read
  }
  throw e;
}

Prevention

Avoid concurrent build jobs that clean the same output directory
Point keepmapping at mapping.txt, never at its containing directory
Ensure filesystem permissions allow read for the build user

When it happens

Trigger: Opening mOldMappingFile with new FileReader(mOldMappingFile) throws FileNotFoundException — the mapping file was deleted between the exists() check and the read, is actually a directory, or is unreadable due to permissions on some filesystems.

Common situations: Concurrent CI jobs cleaning build outputs while AndResGuard runs; a <keepmapping> path pointing at a directory instead of mapping.txt; sandboxed environments denying read access.

Understand the failure class

Background: "open() failed", "failed to open file", "cannot create file" — what a file open error means and how to fix it — this error's family across 42 libraries.

Related errors

AI-assisted analysis of shwenzhang/AndResGuard@e4df245d82 (2026-09-12). Data as JSON: /api/errors/909f13355bd072f1. Report an issue: GitHub.

Appendix: source

Thrown at AndResGuard-core/src/main/java/com/tencent/mm/resourceproguard/Configuration.java:468

      throw new IOException(String.format("the old mapping file do not exit, raw path= %s\n",
          mOldMappingFile.getAbsolutePath()
      ));
    }
    processOldMappingFile();
    System.out.printf("you are using the keepmapping mode to proguard resouces: old mapping path:%s\n",
        mOldMappingFile.getAbsolutePath()
    );
  }

  private void processOldMappingFile() throws IOException {
    mOldResMapping.clear();
    mOldFileMapping.clear();

    FileReader fr;
    try {
      fr = new FileReader(mOldMappingFile);
    } catch (FileNotFoundException ex) {
      throw new IOException(String.format("Could not find old mapping file %s", mOldMappingFile.getAbsolutePath()));
    }
    BufferedReader br = new BufferedReader(fr);
    try {
      String line = br.readLine();

      while (line != null) {
        if (line.length() > 0) {
          Matcher mat = MAP_PATTERN.matcher(line);

          if (mat.find()) {
            String nameAfter = mat.group(2);
            String nameBefore = mat.group(1);
            nameAfter = nameAfter.trim();
            nameBefore = nameBefore.trim();

            //如果有这个的话，那就是mOldFileMapping
            if (line.contains("/")) {
              mOldFileMapping.put(nameBefore, nameAfter);

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