Java: support LGTM alert suppression using @SuppressWarnings annotations

[yh-semmle]

Supports alert suppression of the form @SuppressWarnings("lgtm[query-id]").

[yh-semmle]

Testing using a full LGTM distribution build revealed no performance (or other) issues.

[yh-semmle]

@Semmle/doc this affects documentation of alert suppression:

In addition to alert suppression using comments, LGTM now supports alert suppression for Java analysis using @SuppressWarnings annotations. For example, a @SuppressWarnings("lgtm[query-id]") annotation on a method would suppress all alerts for query query-id within that method.

[mchammer01]

@yh-semmle - can you clarify what a method is? An example might help me here (to be included in the help, with an example of annotation for a method, and an existing Java query). Thanks.
That's the topic I'll be updating: https://help.semmle.com/lgtm-enterprise/user/help/alert-suppression.html

[jf205]

Thanks for the mention @yh-semmle
I'll update the QL command-line tools docs for this change (https://help.semmle.com/wiki/display/SD/Suppressing+alerts)
@mchammer01 will update the LGTM topic

[yh-semmle]

can you clarify what a method is? An example might help me here (to be included in the help, with an example of annotation for a method, and an existing Java query).

The existing alert suppression documentation at https://lgtm.com/help/lgtm/alert-suppression#java gives the following example for suppression comments:

void test(int length) {
    int firstIndex = length * 0; // lgtm[java/evaluation-to-constant]
    int secondIndex = length * 1;
    int thirdIndex = length * 2;
    ...
}

The alert can now also be suppressed as follows:

@SuppressWarnings("lgtm[java/evaluation-to-constant]")
void test(int length) {
    int firstIndex = length * 0;
    int secondIndex = length * 1;
    int thirdIndex = length * 2;
    ...
}

Note that this will suppress all alerts for this query in the above method (Java terminology for "function" in other languages), not just on the line where the suppression comment was located.

Note that @SuppressWarnings annotations are a standard feature of the Java language, so should not need any explanation for Java developers (see the Javadoc or this tutorial).

[mchammer01]

Thanks for the info @yh-semmle 👍