HBASE-28660 list_namespace not working after an incorrect user input

[arvindKandpal-ksolves]

Why are the changes needed?

As reported in HBASE-28660, when a user enters an incorrect command like list_namespace, 'ns.*', the JRuby parser mistakenly creates a local variable named list_namespace initialized to nil before throwing a SyntaxError. Because Ruby prioritizes local variables over method calls, subsequent valid list_namespace commands return empty/nil instead of executing the actual shell command.

How does this PR fix the problem?

• Added a cleanup mechanism inside hirb.rb's eval_input loop.
• After evaluating a line, it checks if any newly created local variables match the names of registered HBase shell commands.
• If a collision (shadowing) is detected, it outputs a warning message to the user (WARN: '<command>' is a reserved HBase command. Local variable assignment ignored.).
• It then safely discards the polluted binding, creates a fresh workspace binding, and restores only the non-conflicting user variables.
• Added comprehensive test cases in general_test_cluster.rb to cover direct assignments, syntax errors, and safe variable preservations.

Tests run

Ran the shell tests locally and verified that the behavior works as expected without regressions.
mvn test -Dtest=TestShell -pl hbase-shell (All tests passed).

[vaijosh]

LGTM.

I have tested this features and verified that it works fine.

[Copilot]

Pull request overview

This PR addresses HBASE-28660 by preventing HBase shell commands (e.g., list, list_namespace) from being shadowed by local variables created during IRB evaluation, and adds a regression test to ensure reserved command names cannot persist as locals.

Changes:

• Add an ensure block in IRB::HIRB#eval_input to detect and remove local variables that conflict with HBase command names, rehydrating a clean workspace binding.
• Emit warnings when reserved command names are detected as locals.
• Add a shell test that simulates IRB input and asserts reserved command locals are not preserved while normal locals are preserved.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
hbase-shell/src/test/ruby/shell/general_test_cluster.rb	Adds a regression test using a mock IRB input method to validate reserved-command shadowing prevention.
hbase-shell/src/main/ruby/irb/hirb.rb	Implements the reserved-command local-variable detection/removal logic inside HIRB#eval_input.

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[arvindKandpal-ksolves]

Hi @liuxiaocs7 , I have applied copilot suggestions , Please take a look.

[arvindKandpal-ksolves]

Just a gentle follow-up on this PR. I have addressed all the review comments and verified that the local tests are passing. Please let me know if anything else is needed or if this is good to go.

cc @liuxiaocs7 @vaijosh @Apache9