[ZEPPELIN-6247] Fix flag parsing bug in FileInterpreter

[renechoi]

[MINOR] Fix flag parsing bug in FileInterpreter

What is this PR for?

This PR fixes a bug in the FileInterpreter class where the dash character (-) was incorrectly included as a flag when parsing command arguments.

What type of PR is it?

Bug Fix

What is the Jira issue?

https://issues.apache.org/jira/browse/ZEPPELIN-6247

How should this be tested?

1. Run the new unit tests: FileInterpreterTest.java
2. Verify that flag parsing works correctly:
   • Command: ls -l should only have flag 'l', not '-' and 'l'
   • Command: ls -lah should have flags 'l', 'a', 'h', without '-'

Screenshots (if appropriate)

N/A

Questions:

• Does the license files need update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No

Description

Problem

The current implementation of parseArg() method in FileInterpreter.java incorrectly includes the dash character as a flag:

// Before (line 73)
for (int i = 0; i < arg.length(); i++) {

When parsing -l, this adds both '-' and 'l' to the flags HashSet.

Solution

Start the loop from index 1 to skip the dash character:

// After
for (int i = 1; i < arg.length(); i++) {

Impact Analysis

• Current behavior is not affected because the existing code (HDFSFileInterpreter) only checks for specific flag characters like 'l' and 'h'
• However, this is a correctness issue that could cause problems in future implementations
• The fix ensures that only actual flag characters are stored in the flags set

Test Coverage

Added comprehensive unit tests in FileInterpreterTest.java to verify:

• Single flags (-l)
• Multiple flags (-la, -lah)
• Separate flags (-l -h)
• Edge cases (empty flag -)
• Verification that dash is not included in the flags set

[Reamer]

LGTM, but please create a JIRA ticket for this.

[renechoi]

@Reamer Thank you for the review! I've created a JIRA ticket as requested: ZEPPELIN-6247

I'll update the PR title to include the JIRA issue number.

[Reamer]

@renechoi Two Checkstyle errors

[INFO] --- checkstyle:3.4.0:check (checkstyle-fail-build) @ zeppelin-file ---
[INFO] There are 2 errors reported by Checkstyle 9.3 with zeppelin/checkstyle.xml ruleset.
Error:  src/test/java/org/apache/zeppelin/file/FileInterpreterTest.java:[1] (misc) NewlineAtEndOfFile: File does not end with a newline.
Error:  src/test/java/org/apache/zeppelin/file/FileInterpreterTest.java:[39,5] (modifier) RedundantModifier: Redundant 'public' modifier.

[renechoi]

@Reamer Thank you for catching those checkstyle errors! I've fixed both issues:

1. Added the missing newline at the end of FileInterpreterTest.java
2. Removed the redundant 'public' modifier from the TestFileInterpreter constructor

The changes have been applied and the code should now pass all checkstyle checks.

[Reamer]

Let's wait for CI.

[Reamer]

Merged into master and branch-0.12