TeamCityProvider.BuildProblem method should conform to TeamCity API

[kcamp]

What You Are Seeing?

Cake is failing to successfully write TeamCity buildProblem service messages

What is Expected?

Cake should validate arguments to methods to conform with documented TeamCity API and either omit them or provide sane defaults as necessary. In my opinion, for this case, it should be an omission rather than an string.Empty.

Per the docs

##teamcity[buildProblem description='<description>' identity='<identity>']
where
description - (mandatory) a human-readable plain text describing the build problem. 
By default, the description appears in the build status text and in the list of build's problems. 
The text is limited to 4000 symbols, and will be truncated if the limit is exceeded.

identity - (optional) a unique problem id. 
Different problems must have different identity, same problems - same identity, which should not change throughout builds if the same problem occurs, e.g. the same compilation error. 
It should be a valid Java id up to 60 characters. If omitted, the identity is calculated based on the description text.

If the caller has omitted the identity parameter, it should't be passed as a KeyValuePair<string, string> with a null value to the WriteServiceMessage method.

What version of Cake are you using?

0.29.0 (but have validated that the problematic code main/0.32.1)

Are you running on a 32 or 64 bit system?

x64

What environment are you running on? Windows? Linux? Mac?

Windows

Are you running on a CI Server? If so, which one?

TeamCity

How Did You Get This To Happen? (Steps to Reproduce)

I have this in my error deferral mechanism, being invoked in a custom teardown method.

// in this case, problem.Identity is null, which creates the issue.
if(_context.TeamCity().IsRunningOnTeamCity)
{
    _context.TeamCity().BuildProblem(problem.Message, problem.Identity);
}

(I have since amended the script for problem.Identity ?? "" to successfully work around this issue.

Output Log

[08:47:57]W:	 [Step 1/1] An error occurred in a custom teardown action.
[08:47:57]W:	 [Step 1/1] Error: System.AggregateException: One or more errors occurred. ---> System.NullReferenceException: Object reference not set to an instance of an object.
[08:47:57]W:	 [Step 1/1]    at Cake.Common.Build.TeamCity.TeamCityProvider.Sanitize(String source)
[08:47:57]W:	 [Step 1/1]    at Cake.Common.Build.TeamCity.TeamCityProvider.<>c.<WriteServiceMessage>b__28_0(KeyValuePair`2 keypair)
[08:47:57]W:	 [Step 1/1]    at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
[08:47:57]W:	 [Step 1/1]    at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
[08:47:57]W:	 [Step 1/1]    at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
[08:47:57]W:	 [Step 1/1]    at Cake.Common.Build.TeamCity.TeamCityProvider.WriteServiceMessage(String messageName, Dictionary`2 values)

[kcamp]

I can have a PR for this issue in the next day or so. Easy adjustment to make.

[devlead]

Fixed by #2475