fix: error handling in Iterator.Next() method

[DeVikingMark]

This PR fixes the error handling in the Iterator.Next() method by properly storing the error in the iter.err field, similar to how it's done in FastIterator.

The TODO comment "double-check if this error is correctly handled" has been addressed by adding code to store the error in the iter.err field when an error occurs during the traversal.next() call.

This ensures that the error can be properly retrieved later via the Error() method, maintaining consistency with other iterator implementations in the codebase.

Summary by CodeRabbit

• Bug Fixes
  • Improved error handling during data iteration to ensure errors are properly detected and reported, enhancing reliability.
• Tests
  • Added tests to verify that errors during data traversal are correctly captured and handled, ensuring robustness.

[coderabbitai[bot]]

Walkthrough

The changes update the Next method in iterator.go by adding explicit error handling. After calling iter.t.next(), the code now checks if an error is returned and, if so, assigns it to iter.err. This ensures that any errors during iteration are captured properly. A new test in iterator_test.go verifies that iterator errors propagate correctly when underlying node data is corrupted. There are no modifications to the public API.

Changes

File	Change Summary
iterator.go	Updated the Next method: introduced a conditional check for errors returned from iter.t.next(), storing any encountered error in iter.err.
iterator_test.go	Added TestIterator_ErrorPropagation to verify that errors during iteration are properly captured and reported when node data is corrupted.

Sequence Diagram(s)

sequenceDiagram
    participant Client as Client
    participant Iterator as Iterator
    participant T as iter.t
    Client->>Iterator: Call Next()
    Iterator->>T: Call next()
    alt Error encountered
        T-->>Iterator: Return error
        Iterator->>Iterator: Set iter.err with error, set iter.t=nil, iter.valid=false
        Iterator-->>Client: Return error state
    else No error
        T-->>Iterator: Return next item
        Iterator-->>Client: Return next item
    end

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Chasing bugs in the pale moonlight,
Now errors, once sly, have been tamed with care,
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Error: you are using a configuration file for golangci-lint v2 with golangci-lint v1: please use golangci-lint v2 Failed executing command with error: you are using a configuration file for golangci-lint v2 with golangci-lint v1: please use golangci-lint v2

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[technicallyty]

This PR fixes the error handling in the Iterator.Next() method by properly storing the error in the iter.err field, similar to how it's done in FastIterator.

what do you mean here? What is FastIterator?

[DeVikingMark]

FastIterator is another iterator implementation in this project (in fast_iterator.go) that properly stores errors in iter.err field. My PR makes Iterator.Next() handle errors the same way for consistency across all iterators in the codebase.

This PR fixes the error handling in the Iterator.Next() method by properly storing the error in the iter.err field, similar to how it's done in FastIterator.

what do you mean here? What is FastIterator?

@technicallyty Hey, FastIterator is another iterator in this codebase (in fast_iterator.go) that already handles errors correctly by storing them in iter.err. I just made Iterator.Next() follow the same pattern for consistency.