Avoid warning if traceparent not present

[quaff]

TextMapCodec.extract() return null with no warning if SPAN_CONTEXT_KEY not present, TraceContextCodec should align with it.
After switch TextMapCodec to TraceContextCodec, my application show lots of warning .
I have to change my code to suppress it.

SpanContext parent = tracer.extract(Format.Builtin.HTTP_HEADERS, new HttpServletRequestTextMap(request));

add ugly null check

SpanContext parent = request.getHeader("traceparent") != null ? tracer.extract(Format.Builtin.HTTP_HEADERS, new HttpServletRequestTextMap(request)) : null;

[codecov]

Codecov Report

Merging #698 into master will decrease coverage by 0.17%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #698      +/-   ##
============================================
- Coverage     89.70%   89.53%   -0.18%     
+ Complexity      587      586       -1     
============================================
  Files            70       70              
  Lines          2157     2159       +2     
  Branches        281      282       +1     
============================================
- Hits           1935     1933       -2     
- Misses          134      136       +2     
- Partials         88       90       +2     

Impacted Files	Coverage Δ	Complexity Δ
...racing/internal/propagation/TraceContextCodec.java	77.41% <100.00%> (-5.92%)	15.00 <0.00> (-1.00)

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[yurishkuro]

please add a unit test

[quaff]

please add a unit test

It's already covered by unit test.
https://github.com/jaegertracing/jaeger-client-java/blob/master/jaeger-core/src/test/java/io/jaegertracing/internal/propagation/TraceContextCodecTest.java#L96

[yurishkuro]

Yes, but you are adding new behavior and a new expectation that no logs are produced on missing traceparent. That's not covered by the existing unit test.

[pavolloffay]

@quaff could you please fix the CI?

[pavolloffay]

thanks @quaff

[quaff]

I admit the unit test is a bit fragile, It depends gradle, since gradle reassigned System.out, maybe there is a better way to detect log message, please improve it. @pavolloffay