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https://issues.apache.org/jira/browse/FLINK-32128?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17723871#comment-17723871
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Seungchul Lee commented on FLINK-32128:
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Can I get a ticket for this?
> Unmodifiable implementation for getter method in test function
> --------------------------------------------------------------
>
> Key: FLINK-32128
> URL: https://issues.apache.org/jira/browse/FLINK-32128
> Project: Flink
> Issue Type: Improvement
> Components: Tests
> Affects Versions: 1.17.0
> Reporter: Seungchul Lee
> Priority: Minor
> Labels: test-stability
> Fix For: 1.18.0
>
> Original Estimate: 2h
> Remaining Estimate: 2h
>
> While using the Flink in our company, I would like to share a small
> suggestion in the test code. I understand that it may be a minor issue, but I
> would like to raise it and share my thoughts as one of the Flink's user.
>
> As you already know, ArrayList is a mutable container class.
> To prevent callers from being able to mutable its internal data, the current
> code copies the entires data into new ArrayList as below.
>
>
> {code:java}
> public class TestingReaderContext implements SourceReaderContext {
> private final SourceReaderMetricGroup metrics;
> private final Configuration config;
> private final ArrayList<SourceEvent> sentEvents = new ArrayList<>();
> ....
> public List<SourceEvent> getSentEvents() {
> return new ArrayList<>(sentEvents);
> }
> ....
> } {code}
>
> I would like to suggest that alternatively, if possible, it is better to
> return some other implementation that the class can use to enforce its
> invariants.
> For example, rather than copying its entire dataset in the current test code,
> I would like to use an unmodifiable implementation as shown in below.
>
>
> {code:java}
> public class TestingReaderContext implements SourceReaderContext {
> private final SourceReaderMetricGroup metrics;
> private final Configuration config;
> private final ArrayList<SourceEvent> sentEvents = new ArrayList<>();
> ....
> public List<SourceEvent> getSentEvents() {
> return Collections.unmodifiableList(sentEvents);
> }
> ....
> } {code}
>
>
> Since the callers that uses the sentEvents list are only used for reading its
> internal data in the test code, it would be better to use an unmodifiable
> implementation.
>
> The entire code can be found in the TestingReaderContext class.
>
> While it may be a small suggestion, I raised the issue with the intention of
> making the current test code more robust.
>
> Thanks.
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